Merge pull request 'Impl analyzer' (#5) from impl-analyzer into v1.1

Reviewed-on: #5

.gitignore

@@ -5,6 +5,7 @@
 !/exl
 !/include
 !/src
+!/tests
 
 # Files
 !/.clang-format

CMakeLists.txt

@@ -14,17 +14,39 @@ include_directories(include)
 
 # Compiler
 add_executable(fzc
-	src/compiler/fzl_token.c
-	src/compiler/fzl_reader.c
-	src/compiler/fzl_parser.c
-	src/compiler/fzl_debug.c
-	src/compiler/fzl_walker.c
-	src/compiler/fzl_writer.c
 	src/compiler/utils/fzl_const_pool.c
 	src/compiler/utils/fzl_symtable.c
 	src/compiler/utils/fzl_linked.c
 	src/compiler/utils/fzl_options.c
 	src/compiler/utils/fzl_ctable.c
+	src/compiler/checkers/fzl_loop_check.c
+	src/compiler/analyzer/utility.c
+	src/compiler/analyzer/context.c
+	src/compiler/analyzer/an_assign.c
+	src/compiler/analyzer/an_binmath.c
+	src/compiler/analyzer/an_block.c
+	src/compiler/analyzer/an_break.c
+	src/compiler/analyzer/an_call.c
+	src/compiler/analyzer/an_class.c
+	src/compiler/analyzer/an_common.c
+	src/compiler/analyzer/an_condition.c
+	src/compiler/analyzer/an_conditional.c
+	src/compiler/analyzer/an_construct.c
+	src/compiler/analyzer/an_declaration.c
+	src/compiler/analyzer/an_field.c
+	src/compiler/analyzer/an_function.c
+	src/compiler/analyzer/an_identifier.c
+	src/compiler/analyzer/an_loop.c
+	src/compiler/analyzer/an_return.c
+	src/compiler/analyzer/an_unarycond.c
+	src/compiler/analyzer/an_unarymath.c
+	src/compiler/fzl_analyzer.c
+	src/compiler/fzl_debug.c
+	src/compiler/fzl_parser.c
+	src/compiler/fzl_reader.c
+	src/compiler/fzl_token.c
+	src/compiler/fzl_walker.c
+	src/compiler/fzl_writer.c
 	src/compiler/main.c)
 
 # Virtual machine
@@ -35,108 +57,31 @@ add_executable(fz
 	src/vm/main.c)
 
 #
-# ========== Compilation tests ==========
+# ========== Tests ==========
 #
 
 enable_testing()
 
-add_test(
+file(GLOB TEST_PROGS RELATIVE "${CMAKE_CURRENT_SOURCE_DIR}" "tests/programs/*.fzs")
-	NAME compile_hw
+foreach (TEST_FILE IN LISTS TEST_PROGS)
-	COMMAND fzc -o "${CMAKE_CURRENT_BINARY_DIR}/hw.fzb" "${CMAKE_CURRENT_SOURCE_DIR}/exl/hw.fzs"
+	get_filename_component(TEST_NAME "${TEST_FILE}" NAME_WE)
-)
-add_test(
-	NAME compile_print_empty
-	COMMAND fzc -o "${CMAKE_CURRENT_BINARY_DIR}/print_empty.fzb" "${CMAKE_CURRENT_SOURCE_DIR}/exl/print_empty.fzs"
-)
-add_test(
-	NAME compile_problematic_hw
-	COMMAND fzc -o "${CMAKE_CURRENT_BINARY_DIR}/problematic_hw.fzb" "${CMAKE_CURRENT_SOURCE_DIR}/exl/problematic_hw.fzs"
-)
-add_test(
-	NAME compile_base_math
-	COMMAND fzc -o "${CMAKE_CURRENT_BINARY_DIR}/base_math.fzb" "${CMAKE_CURRENT_SOURCE_DIR}/exl/base_math.fzs"
-)
-add_test(
-	NAME compile_variables
-	COMMAND fzc -o "${CMAKE_CURRENT_BINARY_DIR}/variables.fzb" "${CMAKE_CURRENT_SOURCE_DIR}/exl/variables.fzs"
-)
-add_test(
-	NAME compile_conditions
-	COMMAND fzc -o "${CMAKE_CURRENT_BINARY_DIR}/conditions.fzb" "${CMAKE_CURRENT_SOURCE_DIR}/exl/conditions.fzs"
-)
-add_test(
-	NAME compile_fn
-	COMMAND fzc -o "${CMAKE_CURRENT_BINARY_DIR}/fn.fzb" "${CMAKE_CURRENT_SOURCE_DIR}/exl/fn.fzs"
-)
-add_test(
-	NAME compile_comment
-	COMMAND fzc -o "${CMAKE_CURRENT_BINARY_DIR}/comment.fzb" "${CMAKE_CURRENT_SOURCE_DIR}/exl/comment.fzs"
-)
-add_test(
-	NAME compile_class
-	COMMAND fzc -o "${CMAKE_CURRENT_BINARY_DIR}/class.fzb" "${CMAKE_CURRENT_SOURCE_DIR}/exl/class.fzs"
-)
-add_test(
-	NAME compile_raii
-	COMMAND fzc -o "${CMAKE_CURRENT_BINARY_DIR}/raii.fzb" "${CMAKE_CURRENT_SOURCE_DIR}/exl/raii.fzs"
-)
-add_test(
-	NAME compile_borrow
-	COMMAND fzc -o "${CMAKE_CURRENT_BINARY_DIR}/borrow.fzb" "${CMAKE_CURRENT_SOURCE_DIR}/exl/borrow.fzs"
-)
-add_test(
-	NAME compile_hard_1
-	COMMAND fzc -o "${CMAKE_CURRENT_BINARY_DIR}/hard-1.fzb" "${CMAKE_CURRENT_SOURCE_DIR}/exl/hard-1.fzs"
-)
 	
-set_tests_properties(compile_problematic_hw PROPERTIES WILL_FAIL TRUE)
+	add_test(
+		NAME "progs_compile_${TEST_NAME}"
+		COMMAND fzc -o "${CMAKE_CURRENT_BINARY_DIR}/p_${TEST_NAME}.fzb" "${CMAKE_CURRENT_SOURCE_DIR}/${TEST_FILE}"
+	)
+	add_test(
+		NAME "progs_runtime_${TEST_NAME}"
+		COMMAND fz "${CMAKE_CURRENT_BINARY_DIR}/p_${TEST_NAME}.fzb"
+	)
 
-#
+	if (TEST_NAME MATCHES "neg_")
-# ========== Runtime tests ==========
+		set_tests_properties("progs_compile_${TEST_NAME}" PROPERTIES WILL_FAIL TRUE)
-#
+		set_tests_properties("progs_runtime_${TEST_NAME}" PROPERTIES WILL_FAIL TRUE)
+	endif()
 
-add_test(
+	if (TEST_NAME MATCHES "negr_")
-	NAME runtime_hw
+		set_tests_properties("progs_runtime_${TEST_NAME}" PROPERTIES WILL_FAIL TRUE)
-	COMMAND fz "${CMAKE_CURRENT_BINARY_DIR}/hw.fzb"
+	endif()
-)
+endforeach()
-add_test(
-	NAME runtime_print_empty
-	COMMAND fz "${CMAKE_CURRENT_BINARY_DIR}/print_empty.fzb"
-)
-add_test(
-	NAME runtime_base_math
-	COMMAND fz "${CMAKE_CURRENT_BINARY_DIR}/base_math.fzb"
-)
-add_test(
-	NAME runtime_variables
-	COMMAND fz "${CMAKE_CURRENT_BINARY_DIR}/variables.fzb"
-)
-add_test(
-	NAME runtime_conditions
-	COMMAND fz "${CMAKE_CURRENT_BINARY_DIR}/conditions.fzb"
-)
-add_test(
-	NAME runtime_fn
-	COMMAND fz "${CMAKE_CURRENT_BINARY_DIR}/fn.fzb"
-)
-add_test(
-	NAME runtime_comment
-	COMMAND fz "${CMAKE_CURRENT_BINARY_DIR}/comment.fzb"
-)
-add_test(
-	NAME runtime_class
-	COMMAND fz "${CMAKE_CURRENT_BINARY_DIR}/class.fzb"
-)
-add_test(
-	NAME runtime_raii
-	COMMAND fz "${CMAKE_CURRENT_BINARY_DIR}/raii.fzb"
-)
-add_test(
-	NAME runtime_borrow
-	COMMAND fz "${CMAKE_CURRENT_BINARY_DIR}/borrow.fzb"
-)
-add_test(
-	NAME runtime_hard_1
-	COMMAND fz "${CMAKE_CURRENT_BINARY_DIR}/hard-1.fzb"
-)
 

Makefile

@@ -1,9 +1,11 @@
-.PHONY: configure build debug-c debug-vm test
+.PHONY: build debug-c debug-vm test
 
-configure:
+build:
 	cmake -S . -B build -DCMAKE_BUILD_TYPE=Debug
+	cmake --build build
 
-build: configure
+build-release:
+	cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
 	cmake --build build
 
 debug-c: build

README.md

@@ -27,7 +27,7 @@ Working examples of code can be found in `exl/` directory.
 ## Building
 
 1. Clone the repository: `git clone https://git.samsonium.dev/samsonium/fz-lang.git`
-2. Build: `make build`
+2. Build: `make build-release`
 
 After this, a "build" directory will appear in the project root. It will contain two executable files:
 

README.ru.md

@@ -27,7 +27,7 @@
 ## Инструкции по сборке
 
 1. Склонировать проект: `git clone https://git.samsonium.dev/samsonium/fz-lang.git`
-2. Собрать проект: `make build`
+2. Собрать проект: `make build-release`
 
 После этого в корне появится директория **"build"**. В ней будут лежать два скомпилированных бинарных файла:
 

exl/00_variables.fzs

@@ -0,0 +1,32 @@
+// There are two ways to work with variables
+// 1. Declare variable:
+str someString = "world, hello!";
+
+// 2. Change variable value:
+someString = "hello, world!";
+
+// Variables help you store values to use it later
+int a = 2;
+int b = a + a * a;
+int c = a * b;
+
+printline("Now we got 12:");
+printline(c);
+
+// Also, there are many different variable types to help your program
+//  work with many things:
+int signedInteger;
+uint unsignedInteger;
+str string;
+bool boolean;
+
+i8  integer1; // 8-byte int
+i16 integer2; // 16-byte int
+i32 integer3; // 32-byte int
+i64 integer4; // 64-byte int
+
+u8  integer5; // unsigned 8-byte integer
+u16 integer6; // unsigned 16-byte integer
+u32 integer7; // unsigned 32-byte integer
+u64 integer8; // unsigned 64-byte integer
+

exl/01_conditions.fzs

@@ -0,0 +1,30 @@
+// When you need to check some value
+//  a conditional statement might help you
+
+int valueToCheck = 2 + 2;
+if (valueToCheck == 4)
+{
+  printline("Yay! 2 + 2 = 4");
+}
+
+// Conditional statement uses condition in parenthesis
+//  after `if` keyword and executes command(s) after
+//  if condition turns out to be true
+
+// Otherwise, to execute block when condition turns
+//  out to be false, you can use `else` keyword:
+
+int age = 30;
+
+if (age <= 20)
+  printline("You're too young");
+else
+{
+  age = 20;
+  printline("You look too young!");
+}
+
+// NOTE: If you need to execute only one statement
+//  inside `if` or `else` block, then the curly
+//  braces can be omitted.
+

exl/02_functions.fzs

@@ -0,0 +1,30 @@
+// If you have some code section which is
+//  duplicated in program several times
+//  then it means your program needs some
+//  functions!
+
+fn doSomeWork()
+{
+  printline("Some work");
+}
+
+// If the function makes some kind of
+//  calculations then you should specify
+//  the result type
+
+fn sum(int a, int b) int
+{
+  return a + b;
+}
+
+// The `return` keyword can be used to
+//  actually return the value from the
+//  function. Also, you can specify list
+//  of arguments that you will use inside
+//  the function
+
+int first = 5;
+int second = 6;
+int result = sum(first, second);
+printline(result);
+

exl/borrow.fzs

@@ -1,46 +0,0 @@
-class A
-{
-  uint some;
-}
-
-fn doSome(A a) A
-{
-  // NOTE: section below won't change `a.some` value
-
-  if (a.some < 1)
-  {
-    a.some = 1;
-    return a;
-  }
-
-  return a;
-}
-
-fn doSomeNew() A
-{
-  if (1 == 1)
-  {
-    return new A;
-  }
-}
-
-A a = new A;
-a.some = 0;
-if (a.some != 0)
-{
-  printline("Test failed (first a.some != 0)");
-  exit(1);
-}
-else printline(a);
-
-a = doSome(a);
-if (a.some != 1)
-{
-  printline("Test failed (2nd a.some != 1)");
-  exit(1);
-}
-else printline(a);
-
-A b = doSomeNew();
-printline(b);
-

exl/class.fzs

@@ -1,36 +0,0 @@
-class Point
-{
-  int x;
-  int y;
-
-  // Move point by [dx,dy]
-  fn move(int dx, int dy) {
-    this.x = this.x + dx;
-    this.y = this.y + dy;
-  }
-}
-
-Point obj = new Point;
-obj.x = 1;
-obj.y = 2;
-
-printline("Current X,Y:");
-printline(obj.x);
-printline(obj.y);
-
-// NOTE: WHY THE FUCK THIS FUCKING COMPILER REQUIRES ';' AFTER '='?!
-//      |
-//      v
-obj.move(9, 8);
-printline("X,Y after move:");
-printline(obj.x);
-printline(obj.y);
-
-if (obj.x == 10 && obj.y == 10)
-  printline("Test passed");
-else
-{
-  printline("Test failed");
-  exit(1);
-}
-

exl/comment.fzs

@@ -1,3 +0,0 @@
-// I'm a comment
-printline("Comment is skipped");;;;;
-

exl/conditions.fzs

@@ -1,20 +0,0 @@
-bool flag = true;
-
-if (!flag)
-{
-  printline("buhhh, flag is not true");
-  exit(1);
-}
-else if (2 + 2 >= 4)
-{
-  printline ("two plus two is four");
-}
-else {
-  printline("gotcha");
-  exit(1);
-}
-
-{
-  printline("block after");
-}
-

exl/fn.fzs

@@ -1,32 +0,0 @@
-fn fib(int n) int
-{
-  if (n <= 1)
-    return n;
-
-  return fib(n - 1) + fib(n - 2);
-}
-
-fn sum(uint a, uint b) uint
-{
-  return a + b;
-}
-
-printline("Test #1: fibonacci");
-int result = fib(7);
-if (result == 13)
-  printline("Recurse test passed");
-else
-{
-  printline("Recurse test failed");
-  exit(1);
-}
-
-printline("Test #2: sum");
-if (sum(2, 2) == 4)
-  printline("Sum test passed");
-else
-{
-  printline("Sum test failed");
-  exit(1);
-}
-

exl/hw.fzs

@@ -1,2 +0,0 @@
-printline('hello, world');
-

exl/print_empty.fzs

@@ -1 +0,0 @@
-printline("");

exl/problematic_hw.fzs

@@ -1 +0,0 @@
-printline("hello);

exl/raii.fzs

@@ -1,46 +0,0 @@
-class Animal
-{
-  str type;
-  str name;
-  int age;
-
-  fn copy() Animal
-  {
-    Animal cp = new Animal;
-    cp.type = this.type;
-    cp.name = this.name;
-    cp.age = this.age;
-
-    return cp;
-  }
-}
-
-Animal a = new Animal;
-a.type = "Cow";
-a.name = "Buryatka";
-a.age = 5;
-
-Animal b = a.copy();
-b.name = "Gavryusha";
-b.age = 10;
-
-printline(a);
-printline(b);
-
-printline("Types are same:");
-printline(a.type == b.type);
-
-printline("Names are NOT the same");
-printline(a.name != b.name);
-
-printline("1st age less than 2nd");
-printline(a.age < b.age);
-
-if (a.type == b.type && a.name != b.name && a.age < b.age)
-  printline("Test passed");
-else
-{
-  printline("Test failed");
-  exit(1);
-}
-

include/compiler/fzl_analyzer.h

@@ -0,0 +1,107 @@
+#ifndef FZL_ANALYZER_H
+#define FZL_ANALYZER_H
+
+#include <common/fzl_types.h>
+#include <compiler/fzl_parser.h>
+#include <compiler/fzl_token.h>
+#include <compiler/utils/fzl_symtable.h>
+#include <stdbool.h>
+#include <stddef.h>
+
+// Analyzing context type
+typedef enum
+{
+  FZL_AN_CTX_TYPE_UNNECESSARY, // default type
+  FZL_AN_CTX_TYPE_FUNCTION,    // when analyzing function
+  FZL_AN_CTX_TYPE_LOOP,        // when analyzing loop
+  FZL_AN_CTX_TYPE_CLASS,       // when analyzing class
+} fzl_an_ctx_type_t;
+
+// Inner node analyzing result descriptor
+typedef struct
+{
+  bool error;
+
+  fzl_type_t type;
+  char *classname;
+} fzl_an_res_t;
+
+// Current node context descriptor
+typedef struct fzl_an_ctx
+{
+  struct fzl_an_ctx *parent;
+
+  fzl_an_ctx_type_t type;
+  fzl_symtable_t *symbols;
+  size_t symbols_level;
+
+  union
+  {
+    fzl_node_t *fn;
+    char *classname;
+  };
+} fzl_an_ctx_t;
+
+// Analyzer descriptor
+typedef struct
+{
+  char *warnings[256];
+  size_t warnings_top;
+
+  char *errors[256];
+  size_t errors_top;
+
+  fzl_symtable_t *symbols[256];
+  size_t symbols_top;
+
+  char *alloc_names[256];
+  size_t alloc_names_top;
+
+  fzl_node_t *root;
+  fzl_an_ctx_t *ctx;
+} fzl_analyzer_t;
+
+// Allocate analyzer
+fzl_analyzer_t *fzl_mkanalyzer(fzl_node_t *node);
+
+// Push error to errors list
+bool an_push_error(fzl_analyzer_t *analyzer, fzl_token_t *tok, char *error);
+
+// Push warning to warnings list
+bool an_push_warning(fzl_analyzer_t *analyzer, fzl_token_t *tok, char *warning);
+
+// Analyze AST
+void fzl_analyze(fzl_analyzer_t *analyzer);
+
+// Free analyzer
+void fzl_freeanalyzer(fzl_analyzer_t *analyzer);
+
+extern char an_problem[256];
+
+bool an_is_compatible(fzl_type_t a, fzl_type_t b, char *ac, char *bc);
+char *an_typetostr(fzl_type_t type, char *classname);
+fzl_type_t an_toktotype(fzl_token_t *tok);
+
+fzl_an_res_t analyze_common(fzl_analyzer_t *analyzer, fzl_node_t *node);
+fzl_an_res_t analyze_call(fzl_analyzer_t *analyzer, fzl_node_t *call_node);
+fzl_an_res_t analyze_identifier(fzl_analyzer_t *analyzer, fzl_node_t *id);
+fzl_an_res_t analyze_conditional(fzl_analyzer_t *analyzer, fzl_node_t *cond);
+fzl_an_res_t analyze_function(fzl_analyzer_t *analyzer, fzl_node_t *fn_node);
+fzl_an_res_t analyze_block(fzl_analyzer_t *analyzer, fzl_node_t *block_node);
+fzl_an_res_t analyze_return(fzl_analyzer_t *analyzer, fzl_node_t *ret_node);
+fzl_an_res_t analyze_class(fzl_analyzer_t *analyzer, fzl_node_t *class_node);
+fzl_an_res_t analyze_field(fzl_analyzer_t *analyzer, fzl_node_t *field);
+fzl_an_res_t analyze_declaration(fzl_analyzer_t *analyzer, fzl_node_t *decl);
+fzl_an_res_t analyze_construct(fzl_analyzer_t *analyzer, fzl_node_t *construct);
+fzl_an_res_t analyze_loop(fzl_analyzer_t *analyzer, fzl_node_t *loop_node);
+fzl_an_res_t analyze_break(fzl_analyzer_t *analyzer, fzl_node_t *break_node);
+fzl_an_res_t analyze_binmath(fzl_analyzer_t *analyzer, fzl_node_t *bin_node);
+fzl_an_res_t analyze_unarymath(fzl_analyzer_t *analyzer, fzl_node_t *unary);
+fzl_an_res_t analyze_condition(fzl_analyzer_t *analyzer, fzl_node_t *cond_node);
+fzl_an_res_t analyze_unarycond(fzl_analyzer_t *analyzer, fzl_node_t *unary);
+fzl_an_res_t analyze_assign(fzl_analyzer_t *analyzer, fzl_node_t *assign_node);
+
+fzl_an_ctx_t *an_nest_ctx(fzl_analyzer_t *analyzer, fzl_an_ctx_type_t type);
+fzl_an_ctx_t *an_fin_ctx(fzl_analyzer_t *analyzer);
+
+#endif // FZL_ANALYZER_H

include/compiler/fzl_parser.h

@@ -18,6 +18,8 @@ typedef enum
   FZL_NODETYPE_CLASS,
   FZL_NODETYPE_FIELD,
   FZL_NODETYPE_CONSTRUCT,
+  FZL_NODETYPE_LOOP,
+  FZL_NODETYPE_BREAK,
 
   FZL_NODETYPE_ADD,
   FZL_NODETYPE_SUB,
@@ -140,6 +142,16 @@ typedef struct fzl_node
     {
       struct fzl_node *name;
     } construct;
+
+    // Loop
+    struct
+    {
+      struct fzl_node *init;
+      struct fzl_node *cond;
+      struct fzl_node *step;
+
+      struct fzl_node *body;
+    } loop;
   };
 } fzl_node_t;
 

include/compiler/fzl_token.h

@@ -14,6 +14,10 @@ typedef enum
   FZL_TOKTYPE_FUNCTION, // fn
   FZL_TOKTYPE_RETURN,   // return
 
+  FZL_TOKTYPE_FOR,   // for
+  FZL_TOKTYPE_WHILE, // while
+  FZL_TOKTYPE_BREAK, // break
+
   FZL_TOKTYPE_IF,   // if
   FZL_TOKTYPE_ELSE, // else
 

include/compiler/fzl_walker.h

@@ -16,7 +16,8 @@ typedef enum
   FZL_WALK_CTX_TYPE_GLOBAL,
   FZL_WALK_CTX_TYPE_FN,
   FZL_WALK_CTX_TYPE_CLASS,
-  FZL_WALK_CTX_TYPE_ASSIGN
+  FZL_WALK_CTX_TYPE_ASSIGN,
+  FZL_WALK_CTX_TYPE_LOOP,
 } fzl_walk_ctx_type_t;
 
 // Internal walk function result
@@ -36,8 +37,23 @@ typedef struct fzl_walk_ctx
   fzl_walk_ctx_type_t type;
   struct fzl_walk_ctx *parent;
 
-  fzl_node_t *fn;
   size_t initial_env_lvl;
+  union
+  {
+    // function info
+    struct
+    {
+      fzl_node_t *fn;
+    };
+
+    // loops `break`s writeback addrs
+    struct
+    {
+      size_t *breaks;
+      size_t breaks_count;
+      size_t breaks_remainder;
+    };
+  };
 } fzl_walk_ctx_t;
 
 // Walker descriptor

include/compiler/utils/fzl_symtable.h

@@ -2,6 +2,7 @@
 #define FZL_SYMTABLE_H
 
 #include <common/fzl_types.h>
+#include <compiler/fzl_parser.h>
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
@@ -19,6 +20,7 @@ typedef struct
 {
   char *name;
   fzl_type_t type;
+  fzl_node_t *node;
   size_t ip;
 
   char *classname;
@@ -37,8 +39,8 @@ typedef struct
 fzl_symtable_t *fzl_mksymt();
 
 // Put new entry into symtable
-fzl_symtable_res_t fzl_symt_put(fzl_symtable_t *symt, char *name,
+fzl_symtable_res_t fzl_symt_put(fzl_symtable_t *symt, fzl_node_t *node,
-                                fzl_type_t type, uint64_t ip);
+                                char *name, fzl_type_t type, uint64_t ip);
 
 // Assign class name to object type
 fzl_symtable_res_t fzl_symt_setobjclass(fzl_symtable_t *symt, char *name,

include/vm/fzl_vm.h

@@ -36,7 +36,7 @@ typedef struct
 fzl_vm_t *fzl_mkvm(const char *filepath);
 
 // Load and run code
-int fzl_vm_run(fzl_vm_t *vm);
+int fzl_vm_run(fzl_vm_t *vm, bool allow_infinite, uint64_t max_iter);
 
 // Get last VM error message
 char *fzl_vm_geterror();

src/compiler/analyzer/an_assign.c

@@ -0,0 +1,50 @@
+#include <common/fzl_types.h>
+#include <compiler/fzl_analyzer.h>
+#include <compiler/fzl_parser.h>
+#include <stdio.h>
+
+// Analyze assigns
+fzl_an_res_t analyze_assign(fzl_analyzer_t *analyzer, fzl_node_t *assign_node)
+{
+  if (!analyzer)
+    return (fzl_an_res_t){.error = true};
+
+  if (!assign_node || assign_node->type != FZL_NODETYPE_ASSIGN)
+  {
+    an_push_error(analyzer, NULL, "node is not assignment");
+    return (fzl_an_res_t){.error = true};
+  }
+
+  fzl_node_t *left      = assign_node->binary_op.left;
+  fzl_an_res_t leftside = analyze_common(analyzer, left);
+  if (leftside.error)
+    return (fzl_an_res_t){.error = true};
+
+  fzl_an_res_t rightside =
+      analyze_common(analyzer, assign_node->binary_op.right);
+  if (rightside.error)
+    return (fzl_an_res_t){.error = true};
+
+  if (left->type != FZL_NODETYPE_DECLARATION &&
+      left->type != FZL_NODETYPE_IDENTIFIER && left->type != FZL_NODETYPE_FIELD)
+  {
+    an_push_error(analyzer, left->token,
+                  "left side must be one of these: declaration, identifier or "
+                  "field access");
+    return (fzl_an_res_t){.error = true};
+  }
+
+  if (!an_is_compatible(leftside.type, rightside.type, leftside.classname,
+                        rightside.classname))
+  {
+    snprintf(an_problem, sizeof(an_problem),
+             "incompatible types - '%s' is expected, got '%s'",
+             an_typetostr(leftside.type, leftside.classname),
+             an_typetostr(rightside.type, rightside.classname));
+    an_push_error(analyzer, assign_node->binary_op.right->token, an_problem);
+    return (fzl_an_res_t){.error = true};
+  }
+
+  return (fzl_an_res_t){
+      .error = false, .type = FZL_TYPE_NULL, .classname = NULL};
+}

src/compiler/analyzer/an_binmath.c

@@ -0,0 +1,50 @@
+#include <common/fzl_types.h>
+#include <compiler/fzl_analyzer.h>
+#include <compiler/fzl_parser.h>
+#include <stdio.h>
+
+// Analyze binary arithmetics
+fzl_an_res_t analyze_binmath(fzl_analyzer_t *analyzer, fzl_node_t *bin_node)
+{
+  if (!analyzer)
+    return (fzl_an_res_t){.error = true};
+
+  if (!bin_node || (bin_node->type != FZL_NODETYPE_ADD &&
+                    bin_node->type != FZL_NODETYPE_SUB &&
+                    bin_node->type != FZL_NODETYPE_MUL &&
+                    bin_node->type != FZL_NODETYPE_DIV &&
+                    bin_node->type != FZL_NODETYPE_POW &&
+                    bin_node->type != FZL_NODETYPE_MOD))
+  {
+    an_push_error(analyzer, NULL, "node is not binary math operator");
+    return (fzl_an_res_t){.error = true};
+  }
+
+  fzl_an_res_t left = analyze_common(analyzer, bin_node->binary_op.left);
+  if (left.error)
+    return (fzl_an_res_t){.error = true};
+
+  fzl_an_res_t right = analyze_common(analyzer, bin_node->binary_op.right);
+  if (right.error)
+    return (fzl_an_res_t){.error = true};
+
+  if (left.type < FZL_TYPE_INT8)
+  {
+    snprintf(an_problem, sizeof(an_problem),
+             "integer type is expected, got '%s'",
+             an_typetostr(left.type, left.classname));
+    an_push_error(analyzer, bin_node->binary_op.left->token, an_problem);
+    return (fzl_an_res_t){.error = true};
+  }
+
+  if (right.type < FZL_TYPE_INT8)
+  {
+    snprintf(an_problem, sizeof(an_problem),
+             "integer type is expected, got '%s'",
+             an_typetostr(right.type, right.classname));
+    an_push_error(analyzer, bin_node->binary_op.right->token, an_problem);
+    return (fzl_an_res_t){.error = true};
+  }
+
+  return (fzl_an_res_t){.error = false, .type = left.type, .classname = NULL};
+}

src/compiler/analyzer/an_block.c

@@ -0,0 +1,88 @@
+#include <common/fzl_types.h>
+#include <compiler/fzl_analyzer.h>
+#include <compiler/fzl_parser.h>
+#include <compiler/fzl_token.h>
+#include <stddef.h>
+#include <stdio.h>
+
+// Analyze block
+fzl_an_res_t analyze_block(fzl_analyzer_t *analyzer, fzl_node_t *block_node)
+{
+  if (!analyzer)
+    return (fzl_an_res_t){.error = true};
+
+  if (!block_node || block_node->type != FZL_NODETYPE_BLOCK)
+  {
+    snprintf(an_problem, sizeof(an_problem), "node is not a block");
+    an_push_error(analyzer, NULL, an_problem);
+    return (fzl_an_res_t){.error = true};
+  }
+
+  an_nest_ctx(analyzer, FZL_AN_CTX_TYPE_UNNECESSARY);
+
+  bool has_return = false;
+  bool error      = false;
+  for (size_t i = 0; i < block_node->list.entry_count; i++)
+  {
+    if (has_return)
+      an_push_warning(analyzer, block_node->list.entries[i]->token,
+                      "this statement will never execute");
+
+    fzl_an_res_t entry_res =
+        analyze_common(analyzer, block_node->list.entries[i]);
+    if (entry_res.error)
+      error = true;
+
+    if (block_node->list.entries[i]->type == FZL_NODETYPE_RETURN)
+      has_return = true;
+  }
+
+  fzl_an_ctx_t *fnctx = analyzer->ctx;
+  while (fnctx != NULL)
+  {
+    if (fnctx && fnctx->type == FZL_AN_CTX_TYPE_FUNCTION)
+      break;
+
+    fnctx = fnctx->parent;
+  }
+
+  if (fnctx && fnctx->type == FZL_AN_CTX_TYPE_FUNCTION)
+  {
+    fzl_type_t rettype = an_toktotype(fnctx->fn->fn.type);
+    char *classname    = NULL;
+    char *rettype_str  = an_typetostr(rettype, classname);
+
+    if (rettype == FZL_TYPE_OBJECT)
+      classname = (char *)fnctx->fn->fn.type->value;
+
+    if (rettype != FZL_TYPE_NULL)
+    {
+      if (!has_return || block_node->list.entry_count < 1)
+      {
+        snprintf(an_problem, sizeof(an_problem),
+                 "'return <%s>' is expected in the function with non-null "
+                 "return type",
+                 rettype_str);
+        an_push_error(analyzer, block_node->token, an_problem);
+        return (fzl_an_res_t){.error = true};
+      }
+
+      fzl_node_t *last_node =
+          block_node->list.entries[block_node->list.entry_count - 1];
+      if (last_node->type != FZL_NODETYPE_RETURN)
+      {
+        // NOTE: replace with ghost walker to check if all branch return an
+        // expected value type
+        snprintf(an_problem, sizeof(an_problem),
+                 "expected last statement in block to be 'return <%s>'",
+                 rettype_str);
+        an_push_error(analyzer, last_node->token, an_problem);
+        return (fzl_an_res_t){.error = true};
+      }
+    }
+  }
+
+  an_fin_ctx(analyzer);
+
+  return (fzl_an_res_t){.error = error, .type = FZL_TYPE_NULL};
+}

src/compiler/analyzer/an_break.c

@@ -0,0 +1,35 @@
+#include <common/fzl_types.h>
+#include <compiler/fzl_analyzer.h>
+#include <compiler/fzl_parser.h>
+
+// Analyze break node
+fzl_an_res_t analyze_break(fzl_analyzer_t *analyzer, fzl_node_t *break_node)
+{
+  if (!analyzer)
+    return (fzl_an_res_t){.error = true};
+
+  if (!break_node || break_node->type != FZL_NODETYPE_BREAK)
+  {
+    an_push_error(analyzer, NULL, "node is not a break statement");
+    return (fzl_an_res_t){.error = true};
+  }
+
+  fzl_an_ctx_t *ctx = analyzer->ctx;
+  while (ctx != NULL)
+  {
+    if (ctx && ctx->type == FZL_AN_CTX_TYPE_LOOP)
+      break;
+
+    ctx = ctx->parent;
+  }
+
+  if (!ctx || ctx->type != FZL_AN_CTX_TYPE_LOOP)
+  {
+    an_push_error(analyzer, break_node->token,
+                  "cannot use 'break' outside the loop");
+    return (fzl_an_res_t){.error = true};
+  }
+
+  return (fzl_an_res_t){
+      .error = false, .type = FZL_TYPE_NULL, .classname = NULL};
+}

src/compiler/analyzer/an_call.c

@@ -0,0 +1,238 @@
+#include <common/fzl_types.h>
+#include <compiler/fzl_analyzer.h>
+#include <compiler/fzl_parser.h>
+#include <compiler/fzl_token.h>
+#include <compiler/utils/fzl_symtable.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+char *tmp_method_name = NULL;
+char *tmp_fnname      = NULL;
+char *tmp_classname   = NULL;
+
+// Try to get symbol name from callee
+char *resolve_callee(fzl_analyzer_t *analyzer, fzl_node_t *callee, bool *method)
+{
+  *method = false;
+
+  if (callee->type == FZL_NODETYPE_IDENTIFIER)
+    return (char *)callee->token->value;
+
+  if (callee->type != FZL_NODETYPE_FIELD)
+  {
+    an_push_error(analyzer, callee->token, "unknown call format");
+    return NULL;
+  }
+
+  *method                 = true;
+  fzl_an_res_t parent_res = analyze_common(analyzer, callee->memb.parent);
+  if (parent_res.type != FZL_TYPE_OBJECT || !parent_res.classname)
+    return NULL;
+
+  char *fn_name         = callee->memb.field->token->value;
+  tmp_fnname            = fn_name;
+  tmp_classname         = parent_res.classname;
+  size_t classname_len  = strlen(parent_res.classname);
+  size_t methodname_len = strlen(fn_name);
+  tmp_method_name       = malloc(classname_len + methodname_len + 2);
+  if (!tmp_method_name)
+  {
+    an_push_error(analyzer, callee->token, "out of memory");
+    return NULL;
+  }
+
+  strcpy(tmp_method_name, parent_res.classname);
+  tmp_method_name[classname_len] = '_';
+  strcpy(tmp_method_name + classname_len + 1, fn_name);
+  tmp_method_name[classname_len + methodname_len + 1] = 0;
+
+  return tmp_method_name;
+}
+
+// Analyze call node
+fzl_an_res_t analyze_call(fzl_analyzer_t *analyzer, fzl_node_t *call_node)
+{
+  if (!call_node || call_node->type != FZL_NODETYPE_CALL)
+  {
+    an_push_error(analyzer, NULL, "node is not call");
+    return (fzl_an_res_t){.error = true};
+  }
+
+  fzl_node_t *callee = call_node->call.callee;
+
+  bool is_method    = false;
+  char *callee_name = resolve_callee(analyzer, callee, &is_method);
+  if (!callee_name)
+  {
+    an_push_error(analyzer, callee->token, "expression is not callable");
+
+    if (tmp_method_name != NULL)
+    {
+      free(tmp_method_name);
+      tmp_method_name = NULL;
+    }
+
+    return (fzl_an_res_t){.error = true};
+  }
+
+  // NOTE: move into `compiler/analyzer/builtins.c`
+  if (strcmp(callee_name, "printline") == 0 || strcmp(callee_name, "exit") == 0)
+  {
+    if (call_node->call.args_count != 1)
+    {
+      snprintf(an_problem, sizeof(an_problem),
+               "'%s' builtin should be called with 1 argument instead of %zu",
+               callee_name, call_node->call.args_count);
+      an_push_error(analyzer, call_node->token, an_problem);
+
+      if (tmp_method_name != NULL)
+      {
+        free(tmp_method_name);
+        tmp_method_name = NULL;
+      }
+
+      return (fzl_an_res_t){.error = true};
+    }
+
+    if (tmp_method_name != NULL)
+    {
+      free(tmp_method_name);
+      tmp_method_name = NULL;
+    }
+
+    return (fzl_an_res_t){
+        .error = false, .type = FZL_TYPE_NULL, .classname = NULL};
+  }
+
+  fzl_sym_t sym;
+  bool sym_found = false;
+  for (ssize_t i = analyzer->symbols_top - 1; i >= 0; i--)
+  {
+    if ((sym_found = fzl_symt_get(analyzer->symbols[i], callee_name, &sym)))
+      break;
+  }
+
+  if (!sym_found)
+  {
+    snprintf(an_problem, sizeof(an_problem), "cannot resolve symbol '%s'",
+             callee_name);
+    an_push_error(analyzer, call_node->token, an_problem);
+
+    if (tmp_method_name != NULL)
+    {
+      free(tmp_method_name);
+      tmp_method_name = NULL;
+    }
+
+    return (fzl_an_res_t){.error = true};
+  }
+
+  if (sym.node->type != FZL_NODETYPE_FUNCTION)
+  {
+    snprintf(an_problem, sizeof(an_problem), "'%s' is not callable",
+             callee_name);
+    an_push_error(analyzer, call_node->token, an_problem);
+
+    if (tmp_method_name != NULL)
+    {
+      free(tmp_method_name);
+      tmp_method_name = NULL;
+    }
+
+    return (fzl_an_res_t){.error = true};
+  }
+
+  size_t offset = is_method ? 1 : 0;
+  if ((sym.node->fn.args_count - offset) != call_node->call.args_count)
+  {
+    if (is_method)
+    {
+      snprintf(an_problem, sizeof(an_problem),
+               "method '%s.%s' is expecting %zu argument(s), got %zu",
+               tmp_classname, tmp_fnname, sym.node->fn.args_count,
+               call_node->call.args_count - offset);
+    }
+    else
+    {
+      snprintf(an_problem, sizeof(an_problem),
+               "function '%s' is expecting %zu argument(s), got %zu",
+               callee_name, sym.node->fn.args_count,
+               call_node->call.args_count - offset);
+    }
+    an_push_error(analyzer, call_node->token, an_problem);
+
+    if (tmp_method_name != NULL)
+    {
+      free(tmp_method_name);
+      tmp_method_name = NULL;
+    }
+
+    return (fzl_an_res_t){.error = true};
+  }
+
+  for (size_t i = offset; i < sym.node->fn.args_count; i++)
+  {
+    fzl_node_t *arg     = sym.node->fn.args[i];
+    fzl_type_t req_type = an_toktotype(arg->var.type);
+    char *req_classname = NULL;
+    if (req_type == FZL_TYPE_OBJECT)
+      req_classname = arg->var.type->value;
+
+    fzl_an_res_t got =
+        analyze_common(analyzer, call_node->call.args[i - offset]);
+    if (got.error)
+    {
+      if (tmp_method_name != NULL)
+      {
+        free(tmp_method_name);
+        tmp_method_name = NULL;
+      }
+      return (fzl_an_res_t){.error = true};
+    }
+
+    if (!an_is_compatible(req_type, got.type, req_classname, got.classname))
+    {
+      if (is_method)
+      {
+        snprintf(an_problem, sizeof(an_problem),
+                 "method '%s.%s' is expecting %zu argument to have type '%s', "
+                 "got '%s'",
+                 tmp_classname, tmp_fnname, i + 1 - offset,
+                 an_typetostr(req_type, req_classname),
+                 an_typetostr(got.type, got.classname));
+      }
+      else
+      {
+        snprintf(an_problem, sizeof(an_problem),
+                 "function '%s' is expecting %zu argument to have type '%s', "
+                 "got '%s'",
+                 callee_name, i + 1 - offset,
+                 an_typetostr(req_type, req_classname),
+                 an_typetostr(got.type, got.classname));
+      }
+      an_push_error(analyzer, call_node->token, an_problem);
+
+      if (tmp_method_name != NULL)
+      {
+        free(tmp_method_name);
+        tmp_method_name = NULL;
+      }
+
+      return (fzl_an_res_t){.error = true};
+    }
+  }
+
+  fzl_type_t type = an_toktotype(sym.node->fn.type);
+  char *classname = sym.classname;
+
+  if (tmp_method_name != NULL)
+  {
+    free(tmp_method_name);
+    tmp_method_name = NULL;
+  }
+
+  return (fzl_an_res_t){.error = false, .type = type, .classname = classname};
+}

src/compiler/analyzer/an_class.c

@@ -0,0 +1,71 @@
+#include <common/fzl_types.h>
+#include <compiler/fzl_analyzer.h>
+#include <compiler/fzl_parser.h>
+#include <compiler/utils/fzl_symtable.h>
+#include <stdio.h>
+
+// Analyze class declaration
+fzl_an_res_t analyze_class(fzl_analyzer_t *analyzer, fzl_node_t *class_node)
+{
+  if (!analyzer)
+    return (fzl_an_res_t){.error = true};
+
+  if (!class_node || class_node->type != FZL_NODETYPE_CLASS)
+  {
+    an_push_error(analyzer, NULL, "node is not class");
+    return (fzl_an_res_t){.error = true};
+  }
+
+  char *classname   = (char *)class_node->class.name->value;
+  fzl_an_ctx_t *ctx = an_nest_ctx(analyzer, FZL_AN_CTX_TYPE_CLASS);
+  ctx->classname    = classname;
+
+  fzl_sym_t sym;
+  bool sym_found = false;
+  for (ssize_t i = analyzer->symbols_top - 1; i >= 0; i--)
+  {
+    if ((sym_found = fzl_symt_get(analyzer->symbols[i], classname, &sym)))
+      break;
+  }
+
+  fzl_symtable_res_t res =
+      fzl_symt_put(analyzer->symbols[analyzer->symbols_top - 2], class_node,
+                   classname, FZL_TYPE_NULL, 0);
+
+  if (res != FZL_SYMTABLE_RESULT_OK)
+  {
+    if (res == FZL_SYMTABLE_RESULT_EXISTS)
+    {
+      snprintf(an_problem, sizeof(an_problem),
+               "name '%s' already has been declared", classname);
+      an_push_error(analyzer, class_node->token, an_problem);
+    }
+    else
+    {
+      snprintf(an_problem, sizeof(an_problem), "cannot store name '%s'",
+               classname);
+      an_push_error(analyzer, class_node->token, an_problem);
+    }
+
+    an_fin_ctx(analyzer);
+    return (fzl_an_res_t){.error = true};
+  }
+
+  bool error = false;
+  for (size_t i = 0; i < class_node->class.fields_count; i++)
+  {
+    fzl_an_res_t res = analyze_common(analyzer, class_node->class.fields[i]);
+    if (res.error)
+      error = true;
+  }
+
+  for (size_t i = 0; i < class_node->class.methods_count; i++)
+  {
+    fzl_an_res_t res = analyze_common(analyzer, class_node->class.methods[i]);
+    if (res.error)
+      error = true;
+  }
+
+  an_fin_ctx(analyzer);
+  return (fzl_an_res_t){.error = error, .type = FZL_TYPE_NULL};
+}

src/compiler/analyzer/an_common.c

@@ -0,0 +1,127 @@
+#include <common/fzl_types.h>
+#include <compiler/fzl_analyzer.h>
+#include <compiler/fzl_parser.h>
+#include <compiler/fzl_token.h>
+#include <stddef.h>
+#include <stdlib.h>
+
+// Analyzer main function
+fzl_an_res_t analyze_common(fzl_analyzer_t *analyzer, fzl_node_t *node)
+{
+  if (!analyzer || !node)
+    return (fzl_an_res_t){.error = true};
+
+  fzl_an_res_t res = {.error = false, .type = FZL_TYPE_NULL, .classname = NULL};
+  switch (node->type)
+  {
+    case FZL_NODETYPE_ASSIGN:
+      res = analyze_assign(analyzer, node);
+      break;
+
+    case FZL_NODETYPE_NOT:
+      res = analyze_unarycond(analyzer, node);
+      break;
+
+    case FZL_NODETYPE_OR:
+    case FZL_NODETYPE_AND:
+    case FZL_NODETYPE_LESS:
+    case FZL_NODETYPE_LESS_EQUAL:
+    case FZL_NODETYPE_GREATER:
+    case FZL_NODETYPE_GREATER_EQUAL:
+    case FZL_NODETYPE_EQUAL:
+    case FZL_NODETYPE_NEQUAL:
+      res = analyze_condition(analyzer, node);
+      break;
+
+    case FZL_NODETYPE_UNARY_MINUS:
+    case FZL_NODETYPE_UNARY_PLUS:
+      res = analyze_unarymath(analyzer, node);
+      break;
+
+    case FZL_NODETYPE_ADD:
+    case FZL_NODETYPE_SUB:
+    case FZL_NODETYPE_MUL:
+    case FZL_NODETYPE_DIV:
+    case FZL_NODETYPE_POW:
+    case FZL_NODETYPE_MOD:
+      res = analyze_binmath(analyzer, node);
+      break;
+
+    case FZL_NODETYPE_BREAK:
+      res = analyze_break(analyzer, node);
+      break;
+
+    case FZL_NODETYPE_LOOP:
+      res = analyze_loop(analyzer, node);
+      break;
+
+    case FZL_NODETYPE_CONSTRUCT:
+      res = analyze_construct(analyzer, node);
+      break;
+
+    case FZL_NODETYPE_DECLARATION:
+      res = analyze_declaration(analyzer, node);
+      break;
+
+    case FZL_NODETYPE_FIELD:
+      res = analyze_field(analyzer, node);
+      break;
+
+    case FZL_NODETYPE_CLASS:
+      res = analyze_class(analyzer, node);
+      break;
+
+    case FZL_NODETYPE_RETURN:
+      res = analyze_return(analyzer, node);
+      break;
+
+    case FZL_NODETYPE_FUNCTION:
+      res = analyze_function(analyzer, node);
+      break;
+
+    case FZL_NODETYPE_CONDITIONAL:
+      res = analyze_conditional(analyzer, node);
+      break;
+
+    case FZL_NODETYPE_IDENTIFIER:
+      res = analyze_identifier(analyzer, node);
+      break;
+
+    case FZL_NODETYPE_BLOCK:
+      res = analyze_block(analyzer, node);
+      break;
+
+    case FZL_NODETYPE_CALL:
+      res = analyze_call(analyzer, node);
+      break;
+
+    case FZL_NODETYPE_LITERAL:
+      switch (node->token->type)
+      {
+        case FZL_TOKTYPE_STR_LITERAL:
+          res.type = FZL_TYPE_STRING;
+          break;
+
+        case FZL_TOKTYPE_NUM_LITERAL:
+          res.type = FZL_TYPE_INT;
+          break;
+
+        case FZL_TOKTYPE_BOOL_LITERAL:
+          res.type = FZL_TYPE_BOOL;
+          break;
+
+        case FZL_TOKTYPE_NULL_LITERAL:
+          res.type      = FZL_TYPE_OBJECT;
+          res.classname = "null";
+          break;
+
+        default:
+          an_push_error(analyzer, node->token, "unknown literal type");
+          res.error = true;
+          break;
+      }
+      break;
+  }
+
+  return res;
+}

src/compiler/analyzer/an_condition.c

@@ -0,0 +1,114 @@
+#include <common/fzl_types.h>
+#include <compiler/fzl_analyzer.h>
+#include <compiler/fzl_parser.h>
+#include <stdio.h>
+
+// Analyze binary conditional nodes
+fzl_an_res_t analyze_condition(fzl_analyzer_t *analyzer, fzl_node_t *cond_node)
+{
+  if (!analyzer)
+    return (fzl_an_res_t){.error = true};
+
+  if (!cond_node || (cond_node->type != FZL_NODETYPE_OR &&
+                     cond_node->type != FZL_NODETYPE_AND &&
+                     cond_node->type != FZL_NODETYPE_LESS &&
+                     cond_node->type != FZL_NODETYPE_LESS_EQUAL &&
+                     cond_node->type != FZL_NODETYPE_GREATER &&
+                     cond_node->type != FZL_NODETYPE_GREATER_EQUAL &&
+                     cond_node->type != FZL_NODETYPE_EQUAL &&
+                     cond_node->type != FZL_NODETYPE_NEQUAL))
+  {
+    an_push_error(analyzer, NULL, "node is not a binary conditional operator");
+    return (fzl_an_res_t){.error = true};
+  }
+
+  fzl_an_res_t left = analyze_common(analyzer, cond_node->binary_op.left);
+  if (left.error)
+    return (fzl_an_res_t){.error = true};
+
+  fzl_an_res_t right = analyze_common(analyzer, cond_node->binary_op.right);
+  if (right.error)
+    return (fzl_an_res_t){.error = true};
+
+  if (cond_node->type == FZL_NODETYPE_OR || cond_node->type == FZL_NODETYPE_AND)
+  {
+    if (left.type != FZL_TYPE_BOOL)
+      an_push_warning(analyzer, cond_node->binary_op.left->token,
+                      "left operand is not resulting with boolean type");
+
+    if (right.type != FZL_TYPE_BOOL)
+      an_push_warning(analyzer, cond_node->binary_op.right->token,
+                      "right operand is not resulting with boolean type");
+  }
+  else if (cond_node->type == FZL_NODETYPE_LESS ||
+           cond_node->type == FZL_NODETYPE_LESS_EQUAL ||
+           cond_node->type == FZL_NODETYPE_GREATER ||
+           cond_node->type == FZL_NODETYPE_GREATER_EQUAL)
+  {
+    if (left.type < FZL_TYPE_INT8)
+    {
+      an_push_error(analyzer, cond_node->binary_op.left->token,
+                    "left operand must have integer type");
+      return (fzl_an_res_t){.error = true};
+    }
+
+    if (left.type < FZL_TYPE_INT8)
+    {
+      an_push_error(analyzer, cond_node->binary_op.left->token,
+                    "right operand must have integer type");
+      return (fzl_an_res_t){.error = true};
+    }
+  }
+  else if (left.type >= FZL_TYPE_INT8)
+  {
+    if (right.type < FZL_TYPE_INT8)
+    {
+      an_push_error(analyzer, cond_node->binary_op.right->token,
+                    "right operand must have integer type");
+      return (fzl_an_res_t){.error = true};
+    }
+
+    return (fzl_an_res_t){
+        .error = false, .type = FZL_TYPE_BOOL, .classname = NULL};
+  }
+  else if (left.type == FZL_TYPE_OBJECT)
+  {
+    if (!left.classname || !right.classname)
+    {
+      an_push_error(analyzer, cond_node->binary_op.left->token,
+                    "unhandled error :(");
+      return (fzl_an_res_t){.error = true};
+    }
+
+    if (!an_is_compatible(left.type, right.type, left.classname,
+                          right.classname))
+    {
+      snprintf(an_problem, sizeof(an_problem), "'%s' and '%s' are incompatible",
+               an_typetostr(left.type, left.classname),
+               an_typetostr(right.type, right.classname));
+      an_push_error(analyzer, cond_node->binary_op.right->token, an_problem);
+      return (fzl_an_res_t){.error = true};
+    }
+  }
+  else if (left.type == FZL_TYPE_STRING)
+  {
+    if (right.type != FZL_TYPE_STRING)
+    {
+      an_push_error(analyzer, cond_node->binary_op.right->token,
+                    "right operand must be a string");
+      return (fzl_an_res_t){.error = true};
+    }
+  }
+  else if (!an_is_compatible(left.type, right.type, left.classname,
+                             right.classname))
+  {
+    snprintf(an_problem, sizeof(an_problem),
+             "equality not supported between %s and %s",
+             an_typetostr(left.type, left.classname),
+             an_typetostr(right.type, right.classname));
+    return (fzl_an_res_t){.error = true};
+  }
+
+  return (fzl_an_res_t){
+      .error = false, .type = FZL_TYPE_BOOL, .classname = NULL};
+}

src/compiler/analyzer/an_conditional.c

@@ -0,0 +1,44 @@
+#include <common/fzl_types.h>
+#include <compiler/fzl_analyzer.h>
+#include <compiler/fzl_parser.h>
+#include <compiler/fzl_token.h>
+#include <stdio.h>
+
+// Analyze conditional statement
+fzl_an_res_t analyze_conditional(fzl_analyzer_t *analyzer, fzl_node_t *cond)
+{
+  if (!analyzer)
+    return (fzl_an_res_t){.error = true};
+
+  if (!cond || cond->type != FZL_NODETYPE_CONDITIONAL)
+  {
+    an_push_error(analyzer, NULL, "provided node is a condition");
+    return (fzl_an_res_t){.error = true};
+  }
+
+  fzl_an_res_t cond_res = analyze_common(analyzer, cond->cond.condition);
+  fzl_an_res_t true_res = analyze_common(analyzer, cond->cond.true_block);
+
+  if (cond->cond.else_block)
+  {
+    fzl_an_res_t else_res = analyze_common(analyzer, cond->cond.else_block);
+    if (else_res.error)
+      return (fzl_an_res_t){.error = true};
+  }
+
+  if (cond_res.error || true_res.error)
+    return (fzl_an_res_t){.error = true};
+
+  if (cond_res.type != FZL_TYPE_BOOL)
+    an_push_warning(analyzer, cond->cond.condition->token,
+                    "resulting type is not bool");
+
+  if (cond->cond.condition->token->type == FZL_TOKTYPE_BOOL_LITERAL)
+  {
+    snprintf(an_problem, sizeof(an_problem), "condition is always %s",
+             (char *)cond->cond.condition->token->value);
+    an_push_warning(analyzer, cond->cond.condition->token, an_problem);
+  }
+
+  return (fzl_an_res_t){.error = false, .type = FZL_TYPE_NULL};
+}

src/compiler/analyzer/an_construct.c

@@ -0,0 +1,38 @@
+#include <common/fzl_types.h>
+#include <compiler/fzl_analyzer.h>
+#include <compiler/fzl_parser.h>
+#include <compiler/utils/fzl_symtable.h>
+#include <stdbool.h>
+#include <stdio.h>
+
+// Analyze class construct
+fzl_an_res_t analyze_construct(fzl_analyzer_t *analyzer, fzl_node_t *construct)
+{
+  if (!analyzer)
+    return (fzl_an_res_t){.error = true};
+
+  if (!construct || construct->type != FZL_NODETYPE_CONSTRUCT)
+  {
+    an_push_error(analyzer, NULL, "node is not a construct");
+    return (fzl_an_res_t){.error = true};
+  }
+
+  char *classname = (char *)construct->construct.name->token->value;
+  fzl_sym_t sym;
+  bool sym_found = false;
+  for (ssize_t i = analyzer->symbols_top - 1; i >= 0; i--)
+  {
+    if ((sym_found = fzl_symt_get(analyzer->symbols[i], classname, &sym)))
+      break;
+  }
+
+  if (!sym_found)
+  {
+    snprintf(an_problem, sizeof(an_problem), "class '%s' not found", classname);
+    an_push_error(analyzer, construct->token, an_problem);
+    return (fzl_an_res_t){.error = true};
+  }
+
+  return (fzl_an_res_t){
+      .error = false, .type = FZL_TYPE_OBJECT, .classname = classname};
+}

src/compiler/analyzer/an_declaration.c

@@ -0,0 +1,66 @@
+#include <common/fzl_types.h>
+#include <compiler/fzl_analyzer.h>
+#include <compiler/fzl_parser.h>
+#include <compiler/fzl_token.h>
+#include <compiler/utils/fzl_symtable.h>
+#include <stdbool.h>
+#include <stdio.h>
+
+// Analyze variable/field/argument declaration
+fzl_an_res_t analyze_declaration(fzl_analyzer_t *analyzer, fzl_node_t *decl)
+{
+  if (!analyzer)
+    return (fzl_an_res_t){.error = true};
+
+  if (!decl || decl->type != FZL_NODETYPE_DECLARATION)
+  {
+    an_push_error(analyzer, NULL, "node is not a declaration");
+    return (fzl_an_res_t){.error = true};
+  }
+
+  char *name      = (char *)decl->var.identifier->token->value;
+  fzl_type_t type = an_toktotype(decl->var.type);
+  char *classname = NULL;
+  if (type == FZL_TYPE_OBJECT)
+    classname = decl->var.type->value;
+
+  fzl_symtable_res_t res =
+      fzl_symt_put(analyzer->symbols[analyzer->symbols_top - 1], decl, name,
+                   an_toktotype(decl->var.type), 0);
+  if (res != FZL_SYMTABLE_RESULT_OK)
+  {
+    if (res == FZL_SYMTABLE_RESULT_EXISTS)
+      snprintf(an_problem, sizeof(an_problem), "'%s' already has been declared",
+               name);
+    else
+      snprintf(an_problem, sizeof(an_problem), "cannot store '%s'", name);
+
+    an_push_error(analyzer, decl->token, an_problem);
+    return (fzl_an_res_t){.error = true};
+  }
+
+  if (type == FZL_TYPE_OBJECT)
+  {
+    fzl_sym_t class;
+    bool class_found = false;
+    for (ssize_t i = analyzer->symbols_top - 1; i >= 0; i--)
+    {
+      if ((class_found = fzl_symt_get(analyzer->symbols[i],
+                                      decl->var.type->value, &class)))
+        break;
+    }
+
+    if (!class_found || class.node->type != FZL_NODETYPE_CLASS)
+    {
+      snprintf(an_problem, sizeof(an_problem), "class '%s' does not exists",
+               (char *)decl->var.type->value);
+      an_push_error(analyzer, decl->var.type, an_problem);
+      return (fzl_an_res_t){.error = true};
+    }
+
+    fzl_symt_setobjclass(analyzer->symbols[analyzer->symbols_top - 1], name,
+                         classname);
+  }
+
+  return (fzl_an_res_t){.error = false, .type = type, .classname = classname};
+}

src/compiler/analyzer/an_field.c

@@ -0,0 +1,78 @@
+#include <common/fzl_types.h>
+#include <compiler/fzl_analyzer.h>
+#include <compiler/fzl_parser.h>
+#include <compiler/utils/fzl_symtable.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <string.h>
+
+// Analyze field access
+fzl_an_res_t analyze_field(fzl_analyzer_t *analyzer, fzl_node_t *field)
+{
+  if (!analyzer)
+    return (fzl_an_res_t){.error = true};
+
+  if (!field || field->type != FZL_NODETYPE_FIELD)
+  {
+    an_push_error(analyzer, NULL, "node is not field access");
+    return (fzl_an_res_t){.error = true};
+  }
+
+  fzl_an_res_t parent = analyze_common(analyzer, field->memb.parent);
+  if (parent.error)
+    return (fzl_an_res_t){.error = true};
+
+  if (parent.type != FZL_TYPE_OBJECT || parent.classname == NULL)
+  {
+    snprintf(an_problem, sizeof(an_problem), "access to non-object value (%s)",
+             an_typetostr(parent.type, parent.classname));
+    an_push_error(analyzer, field->token, an_problem);
+    return (fzl_an_res_t){.error = true};
+  }
+
+  char *field_name = field->memb.field->token->value;
+  fzl_sym_t sym;
+  bool sym_found = false;
+  for (ssize_t i = analyzer->symbols_top - 1; i >= 0; i--)
+  {
+    if ((sym_found =
+             fzl_symt_get(analyzer->symbols[i], parent.classname, &sym)))
+      break;
+  }
+
+  if (!sym_found)
+  {
+    snprintf(an_problem, sizeof(an_problem), "class '%s' not found",
+             parent.classname);
+    an_push_error(analyzer, field->parent->token, an_problem);
+    return (fzl_an_res_t){.error = true};
+  }
+
+  fzl_node_t *field_node = NULL;
+  for (size_t i = 0; i < sym.node->class.fields_count; i++)
+  {
+    if (strcmp(sym.node->class.fields[i]->var.identifier->token->value,
+               field_name) == 0)
+    {
+      field_node = sym.node->class.fields[i];
+      break;
+    }
+  }
+
+  if (field_node == NULL)
+  {
+    snprintf(an_problem, sizeof(an_problem), "field '%s.%s' does not exists",
+             parent.classname, field_name);
+    an_push_error(analyzer, field->memb.field->token, an_problem);
+    return (fzl_an_res_t){.error = true};
+  }
+
+  fzl_type_t field_type = an_toktotype(field_node->var.type);
+  char *classname       = NULL;
+  if (field_type == FZL_TYPE_OBJECT)
+    classname = field_node->var.type->value;
+
+  return (fzl_an_res_t){
+      .error = false, .type = field_type, .classname = classname};
+}

src/compiler/analyzer/an_function.c

@@ -0,0 +1,128 @@
+#include <common/fzl_types.h>
+#include <compiler/fzl_analyzer.h>
+#include <compiler/fzl_parser.h>
+#include <compiler/utils/fzl_symtable.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+fzl_an_res_t analyze_function(fzl_analyzer_t *analyzer, fzl_node_t *fn_node)
+{
+  if (!analyzer)
+    return (fzl_an_res_t){.error = true};
+
+  if (!fn_node || fn_node->type != FZL_NODETYPE_FUNCTION)
+  {
+    an_push_error(analyzer, NULL, "node is not a function");
+    return (fzl_an_res_t){.error = true};
+  }
+
+  fzl_an_ctx_t *fnctx = an_nest_ctx(analyzer, FZL_AN_CTX_TYPE_FUNCTION);
+  fnctx->fn           = fn_node;
+
+  for (size_t i = 0; i < fn_node->fn.args_count; i++)
+  {
+    fzl_an_res_t res = analyze_common(analyzer, fn_node->fn.args[i]);
+    if (res.error)
+      return (fzl_an_res_t){.error = true};
+  }
+
+  fzl_an_ctx_t *ctx = analyzer->ctx;
+  while (ctx != NULL)
+  {
+    if (ctx->type == FZL_AN_CTX_TYPE_CLASS)
+      break;
+
+    ctx = ctx->parent;
+  }
+
+  fzl_type_t rettype = an_toktotype(fn_node->fn.type);
+  char *classname    = NULL;
+  if (rettype == FZL_TYPE_OBJECT)
+    classname = (char *)fn_node->fn.type->value;
+
+  if (ctx != NULL && ctx->type == FZL_AN_CTX_TYPE_CLASS)
+  {
+    for (size_t i = 0; i < fn_node->fn.args_count; i++)
+    {
+      fzl_node_t *decl = fn_node->fn.args[i];
+      if (decl->type != FZL_NODETYPE_DECLARATION)
+      {
+        an_push_error(analyzer, decl->token, "argument must be a declaration");
+        an_fin_ctx(analyzer);
+        return (fzl_an_res_t){.error = true};
+      }
+
+      char *argname = (char *)decl->var.identifier->token->value;
+      if (strcmp(argname, "this") == 0 && i > 0)
+      {
+        an_push_error(analyzer, decl->token,
+                      "manual declaration of 'this' is not allowed in methods");
+        an_fin_ctx(analyzer);
+        return (fzl_an_res_t){.error = true};
+      }
+    }
+
+    size_t classname_len  = strlen(ctx->classname);
+    size_t methodname_len = strlen((char *)fn_node->fn.name->value);
+    char *methodname      = malloc(classname_len + methodname_len + 2);
+
+    strcpy(methodname, ctx->classname);
+    methodname[classname_len] = '_';
+    strcpy(methodname + classname_len + 1, fn_node->fn.name->value);
+    methodname[classname_len + methodname_len + 1] = 0;
+
+    analyzer->alloc_names[analyzer->alloc_names_top++] = methodname;
+
+    fzl_symtable_res_t putres =
+        fzl_symt_put(analyzer->symbols[ctx->symbols_level - 1], fn_node,
+                     methodname, rettype, 0);
+    if (putres != FZL_SYMTABLE_RESULT_OK)
+    {
+      if (putres == FZL_SYMTABLE_RESULT_EXISTS)
+      {
+        snprintf(an_problem, sizeof(an_problem),
+                 "method '%s.%s' already has been declared", classname,
+                 (char *)fn_node->fn.name->value);
+        an_push_error(analyzer, fn_node->token, an_problem);
+      }
+      else
+        an_push_error(analyzer, fn_node->token, "failed to store method");
+
+      free(analyzer->alloc_names[--analyzer->alloc_names_top]);
+      an_fin_ctx(analyzer);
+      return (fzl_an_res_t){.error = true};
+    }
+    fzl_symt_setobjclass(analyzer->symbols[ctx->symbols_level - 1], methodname,
+                         classname);
+  }
+  else
+  {
+    fzl_symtable_res_t putres =
+        fzl_symt_put(analyzer->symbols[analyzer->symbols_top - 2], fn_node,
+                     (char *)fn_node->fn.name->value, rettype, 0);
+    if (putres != FZL_SYMTABLE_RESULT_OK)
+    {
+      if (putres == FZL_SYMTABLE_RESULT_EXISTS)
+      {
+        snprintf(an_problem, sizeof(an_problem),
+                 "function '%s' already has been declared",
+                 (char *)fn_node->fn.name->value);
+        an_push_error(analyzer, fn_node->token, an_problem);
+      }
+      else
+        an_push_error(analyzer, fn_node->token, "failed to store function");
+
+      free(analyzer->alloc_names[--analyzer->alloc_names_top]);
+      an_fin_ctx(analyzer);
+      return (fzl_an_res_t){.error = true};
+    }
+  }
+
+  fzl_an_res_t body_res = analyze_common(analyzer, fn_node->fn.body);
+  an_fin_ctx(analyzer);
+
+  return (fzl_an_res_t){
+      .error = body_res.error, .type = rettype, .classname = classname};
+}

src/compiler/analyzer/an_identifier.c

@@ -0,0 +1,37 @@
+#include <compiler/fzl_analyzer.h>
+#include <compiler/fzl_parser.h>
+#include <compiler/utils/fzl_symtable.h>
+#include <stdio.h>
+
+// Analyze identifier
+fzl_an_res_t analyze_identifier(fzl_analyzer_t *analyzer, fzl_node_t *id)
+{
+  if (!analyzer)
+    return (fzl_an_res_t){.error = true};
+
+  if (!id || id->type != FZL_NODETYPE_IDENTIFIER)
+  {
+    an_push_error(analyzer, NULL, "node is not an identifier");
+    return (fzl_an_res_t){.error = true};
+  }
+
+  char *symname = id->token->value;
+  fzl_sym_t sym;
+  bool sym_found = false;
+  for (ssize_t i = analyzer->symbols_top - 1; i >= 0; i--)
+  {
+    if ((sym_found = fzl_symt_get(analyzer->symbols[i], symname, &sym)))
+      break;
+  }
+
+  if (!sym_found)
+  {
+    snprintf(an_problem, sizeof(an_problem), "cannot find symbol '%s'",
+             symname);
+    an_push_error(analyzer, id->token, an_problem);
+    return (fzl_an_res_t){.error = true};
+  }
+
+  return (fzl_an_res_t){
+      .error = false, .type = sym.type, .classname = sym.classname};
+}

src/compiler/analyzer/an_loop.c

@@ -0,0 +1,455 @@
+#include <common/fzl_types.h>
+#include <compiler/fzl_analyzer.h>
+#include <compiler/fzl_parser.h>
+#include <compiler/fzl_token.h>
+#include <compiler/utils/fzl_symtable.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+
+// Init block analysis result
+typedef struct
+{
+  bool has_var;
+  char *name;
+  fzl_type_t type;
+  char *classname;
+} init_analysis;
+
+// Check init block
+init_analysis check_init(fzl_analyzer_t *analyzer, fzl_node_t *init)
+{
+  if (!analyzer || !init)
+    return (init_analysis){.has_var = false};
+
+  if (init->type == FZL_NODETYPE_IDENTIFIER)
+  {
+    char *name = init->token->value;
+
+    fzl_sym_t sym;
+    bool sym_found = false;
+    for (ssize_t i = analyzer->symbols_top - 1; i >= 0; i--)
+    {
+      if ((sym_found = fzl_symt_get(analyzer->symbols[i], name, &sym)))
+        break;
+    }
+
+    if (!sym_found)
+      return (init_analysis){.has_var = false};
+
+    char *classname = NULL;
+    if (sym.type == FZL_TYPE_OBJECT)
+      classname = sym.classname;
+
+    return (init_analysis){.has_var   = true,
+                           .name      = name,
+                           .type      = sym.type,
+                           .classname = classname};
+  }
+  else if (init->type == FZL_NODETYPE_DECLARATION)
+  {
+    char *name      = init->var.identifier->token->value;
+    fzl_type_t type = an_toktotype(init->var.type);
+    char *classname = NULL;
+    if (type == FZL_TYPE_OBJECT)
+      classname = init->var.type->value;
+
+    return (init_analysis){
+        .has_var = true, .name = name, .type = type, .classname = classname};
+  }
+  else if (init->type == FZL_NODETYPE_ASSIGN)
+  {
+    return (init_analysis)check_init(analyzer, init->binary_op.left);
+  }
+
+  return (init_analysis){.has_var = false};
+}
+
+// Condition block analysis result type
+typedef enum
+{
+  COND_TYPE_CONST_TRUE,  // `true` is used as condition
+  COND_TYPE_CONST_FALSE, // `false` is used as condition
+  COND_TYPE_VAR_LESS,    // until variable value is less
+  COND_TYPE_VAR_GREATER, // until variable value is greater
+  COND_TYPE_UNKNOWN,     // cannot determine in compilation time
+} cond_type;
+
+// Condition block analysis result
+typedef struct
+{
+  cond_type type;
+  bool result_bool;
+  char *varname;
+  fzl_type_t vartype;
+  char *classname;
+} cond_analysis;
+
+// Check condition block
+cond_analysis check_condition(fzl_analyzer_t *analyzer, fzl_node_t *cond,
+                              bool report)
+{
+  if (!cond)
+    return (cond_analysis){.type = COND_TYPE_UNKNOWN, .result_bool = false};
+
+  switch (cond->type)
+  {
+    case FZL_NODETYPE_LITERAL:
+      if (cond->token->type == FZL_TOKTYPE_STR_LITERAL)
+      {
+        if (report)
+          an_push_warning(analyzer, cond->token,
+                          "string literal is used as condition");
+        return (cond_analysis){.type = COND_TYPE_UNKNOWN, .result_bool = false};
+      }
+      else if (cond->token->type == FZL_TOKTYPE_NULL_LITERAL)
+      {
+        if (report)
+          an_push_warning(analyzer, cond->token,
+                          "null literal is used as condition");
+        return (cond_analysis){.type = COND_TYPE_UNKNOWN, .result_bool = false};
+      }
+      else if (cond->token->type == FZL_TOKTYPE_BOOL_LITERAL)
+      {
+        if (strcmp(cond->token->value, "true") == 0)
+          return (cond_analysis){.type        = COND_TYPE_CONST_TRUE,
+                                 .result_bool = true};
+        else
+          return (cond_analysis){.type        = COND_TYPE_CONST_FALSE,
+                                 .result_bool = true};
+      }
+      else if (cond->token->type == FZL_TOKTYPE_NUM_LITERAL)
+      {
+        if (strcmp(cond->token->value, "0") == 0)
+          return (cond_analysis){.type        = COND_TYPE_CONST_FALSE,
+                                 .result_bool = false};
+        else
+          return (cond_analysis){.type        = COND_TYPE_CONST_TRUE,
+                                 .result_bool = false};
+      }
+      break;
+
+    case FZL_NODETYPE_LESS:
+    case FZL_NODETYPE_LESS_EQUAL:
+    {
+      fzl_node_t *comp_left    = cond->binary_op.left;
+      cond_analysis left_check = check_condition(analyzer, comp_left, false);
+      if (left_check.varname != NULL)
+        return (cond_analysis){.type        = COND_TYPE_VAR_LESS,
+                               .result_bool = true,
+                               .varname     = left_check.varname,
+                               .vartype     = left_check.vartype,
+                               .classname   = left_check.classname};
+
+      fzl_node_t *comp_right    = cond->binary_op.right;
+      cond_analysis right_check = check_condition(analyzer, comp_right, false);
+      if (right_check.varname != NULL)
+        return (cond_analysis){.type        = COND_TYPE_VAR_GREATER,
+                               .result_bool = true,
+                               .varname     = right_check.varname,
+                               .vartype     = right_check.vartype,
+                               .classname   = right_check.classname};
+
+      return (cond_analysis){.type = COND_TYPE_UNKNOWN};
+    }
+
+    case FZL_NODETYPE_GREATER:
+    case FZL_NODETYPE_GREATER_EQUAL:
+    {
+      fzl_node_t *comp_left    = cond->binary_op.left;
+      cond_analysis left_check = check_condition(analyzer, comp_left, false);
+      if (left_check.varname != NULL)
+        return (cond_analysis){.type        = COND_TYPE_VAR_GREATER,
+                               .result_bool = true,
+                               .varname     = left_check.varname,
+                               .vartype     = left_check.vartype,
+                               .classname   = left_check.classname};
+
+      fzl_node_t *comp_right    = cond->binary_op.right;
+      cond_analysis right_check = check_condition(analyzer, comp_right, false);
+      if (right_check.varname != NULL)
+        return (cond_analysis){.type        = COND_TYPE_VAR_LESS,
+                               .result_bool = true,
+                               .varname     = right_check.varname,
+                               .vartype     = right_check.vartype,
+                               .classname   = right_check.classname};
+
+      return (cond_analysis){.type = COND_TYPE_UNKNOWN};
+    }
+
+    case FZL_NODETYPE_IDENTIFIER:
+    {
+      char *name = cond->token->value;
+      fzl_sym_t sym;
+      bool sym_found = false;
+      for (ssize_t i = analyzer->symbols_top - 1; i >= 0; i--)
+      {
+        if ((sym_found = fzl_symt_get(analyzer->symbols[i], name, &sym)))
+          break;
+      }
+
+      if (!sym_found)
+        return (cond_analysis){.type = COND_TYPE_UNKNOWN, .varname = NULL};
+
+      return (cond_analysis){.type      = COND_TYPE_UNKNOWN,
+                             .varname   = name,
+                             .vartype   = sym.type,
+                             .classname = sym.classname};
+    }
+
+    default:
+      break;
+  }
+
+  fzl_an_res_t custom_res = analyze_common(analyzer, cond);
+  if (custom_res.type == FZL_TYPE_BOOL)
+    return (cond_analysis){.type = COND_TYPE_UNKNOWN, .result_bool = true};
+
+  return (cond_analysis){.type = COND_TYPE_UNKNOWN, .result_bool = false};
+}
+
+// Step block change direction
+typedef enum
+{
+  STEP_DIR_TYPE_INCREASE,
+  STEP_DIR_TYPE_DECREASE,
+  STEP_DIR_TYPE_STALL,
+  STEP_DIR_UNKNOWN,
+} step_dir_type;
+
+// Step block analysis
+typedef struct
+{
+  bool changing;
+  char *changing_var;
+  step_dir_type dir;
+} step_analysis;
+
+// Check step block
+step_analysis check_step(fzl_node_t *step)
+{
+  if (!step)
+    return (step_analysis){.changing = false};
+
+  if (step->type == FZL_NODETYPE_ASSIGN)
+  {
+    if (step->binary_op.left->type != FZL_NODETYPE_IDENTIFIER)
+      return (step_analysis){
+          .changing = true, .changing_var = "-", .dir = STEP_DIR_UNKNOWN};
+
+    int dir           = 0;
+    fzl_node_t *right = step->binary_op.right;
+    fzl_node_t *num   = NULL;
+    char *varname     = NULL;
+    if (right->binary_op.left->type != FZL_NODETYPE_IDENTIFIER)
+    {
+      num = right->binary_op.left;
+      if (right->binary_op.right->type == FZL_NODETYPE_IDENTIFIER)
+        varname = right->binary_op.right->token->value;
+    }
+    else
+    {
+      num = right->binary_op.right;
+      if (right->binary_op.left->type == FZL_NODETYPE_IDENTIFIER)
+        varname = right->binary_op.left->token->value;
+    }
+
+    if (right->type == FZL_NODETYPE_ADD || right->type == FZL_NODETYPE_MUL ||
+        right->type == FZL_NODETYPE_POW)
+      dir = 1;
+    else if (right->type == FZL_NODETYPE_SUB ||
+             right->type == FZL_NODETYPE_DIV || right->type == FZL_NODETYPE_MOD)
+      dir = -1;
+
+    if (num && num->type == FZL_NODETYPE_UNARY_MINUS)
+      dir *= -1;
+
+    step_dir_type dirtype = varname == NULL ? STEP_DIR_UNKNOWN
+                            : dir > 0       ? STEP_DIR_TYPE_INCREASE
+                            : dir < 0       ? STEP_DIR_TYPE_DECREASE
+                                            : STEP_DIR_TYPE_STALL;
+
+    return (step_analysis){.changing     = varname != NULL && dir != 0,
+                           .changing_var = varname,
+                           .dir          = dirtype};
+  }
+
+  return (step_analysis){.changing = false, .dir = STEP_DIR_UNKNOWN};
+}
+
+// Body analysis result
+typedef struct
+{
+  bool has_exit;
+} body_analysis;
+
+body_analysis check_body(fzl_node_t *body, bool nested_loop)
+{
+  body_analysis result = {.has_exit = false};
+  switch (body->type)
+  {
+    case FZL_NODETYPE_RETURN:
+      result.has_exit = true;
+      break;
+
+    case FZL_NODETYPE_BREAK:
+      if (!nested_loop)
+        result.has_exit = true;
+      break;
+
+    case FZL_NODETYPE_LOOP:
+      if (body->loop.body)
+      {
+        body_analysis res = check_body(body->loop.body, true);
+        if (res.has_exit)
+          result.has_exit = true;
+      }
+      break;
+
+    case FZL_NODETYPE_CONDITIONAL:
+      if (check_body(body->cond.true_block, nested_loop).has_exit)
+      {
+        result.has_exit = true;
+        break;
+      }
+      break;
+
+    case FZL_NODETYPE_BLOCK:
+      for (size_t i = 0; i < body->list.entry_count; i++)
+      {
+        body_analysis res = check_body(body->list.entries[i], nested_loop);
+        if (res.has_exit)
+        {
+          result.has_exit = true;
+          break;
+        }
+      }
+      break;
+
+    default:
+      break;
+  }
+
+  return result;
+}
+
+// Analyze loop
+fzl_an_res_t analyze_loop(fzl_analyzer_t *analyzer, fzl_node_t *loop_node)
+{
+  if (!analyzer)
+    return (fzl_an_res_t){.error = true};
+
+  if (!loop_node || loop_node->type != FZL_NODETYPE_LOOP)
+  {
+    an_push_error(analyzer, NULL, "node is not typeof LOOP");
+    return (fzl_an_res_t){.error = true};
+  }
+
+  an_nest_ctx(analyzer, FZL_AN_CTX_TYPE_LOOP);
+
+  init_analysis init_data = {
+      .has_var = false, .type = FZL_TYPE_NULL, .name = NULL, .classname = NULL};
+  if (loop_node->loop.init)
+  {
+    fzl_an_res_t init_res = analyze_common(analyzer, loop_node->loop.init);
+    if (init_res.error)
+      return (fzl_an_res_t){.error = true};
+
+    init_data = check_init(analyzer, loop_node->loop.init);
+  }
+
+  cond_analysis cond_data = {.type      = COND_TYPE_CONST_TRUE,
+                             .varname   = NULL,
+                             .vartype   = FZL_TYPE_NULL,
+                             .classname = NULL};
+  if (loop_node->loop.cond)
+  {
+    fzl_an_res_t cond_res = analyze_common(analyzer, loop_node->loop.cond);
+    if (cond_res.error)
+      return (fzl_an_res_t){.error = true};
+
+    cond_data = check_condition(analyzer, loop_node->loop.cond, true);
+
+    if (!cond_data.result_bool && cond_data.type != COND_TYPE_UNKNOWN)
+      an_push_warning(analyzer, loop_node->loop.cond->token,
+                      "resulting type is not boolean");
+
+    if (cond_data.type == COND_TYPE_CONST_FALSE)
+      an_push_warning(analyzer, loop_node->loop.cond->token,
+                      "loop will never execute");
+
+    if (init_data.name && cond_data.varname &&
+        strcmp(init_data.name, cond_data.varname) != 0)
+    {
+      snprintf(an_problem, sizeof(an_problem),
+               "'%s' is used in condition but '%s' is declared. Maybe there is "
+               "mistake?",
+               cond_data.varname, init_data.name);
+      an_push_warning(analyzer, loop_node->loop.cond->token, an_problem);
+    }
+  }
+
+  step_analysis step_data = {
+      .changing = false, .changing_var = NULL, .dir = STEP_DIR_UNKNOWN};
+  if (loop_node->loop.step)
+  {
+    fzl_an_res_t step_res = analyze_common(analyzer, loop_node->loop.step);
+    if (step_res.error)
+      return (fzl_an_res_t){.error = true};
+
+    step_data = check_step(loop_node->loop.step);
+
+    if (step_data.dir != STEP_DIR_UNKNOWN)
+    {
+      if (step_data.changing_var && cond_data.varname &&
+          strcmp(step_data.changing_var, cond_data.varname) != 0)
+      {
+        snprintf(an_problem, sizeof(an_problem),
+                 "changing '%s' but condition checking '%s'",
+                 step_data.changing_var, cond_data.varname);
+        an_push_warning(analyzer, loop_node->loop.step->token, an_problem);
+      }
+
+      if (cond_data.type == COND_TYPE_VAR_GREATER &&
+          step_data.dir == STEP_DIR_TYPE_INCREASE)
+      {
+        snprintf(an_problem, sizeof(an_problem),
+                 "'%s' is increasing while condition is 'greater than'",
+                 step_data.changing_var);
+        an_push_warning(analyzer, loop_node->loop.step->token, an_problem);
+      }
+      else if (cond_data.type == COND_TYPE_VAR_LESS &&
+               step_data.dir == STEP_DIR_TYPE_DECREASE)
+      {
+        snprintf(an_problem, sizeof(an_problem),
+                 "'%s' is decreasing while condition is 'less than'",
+                 step_data.changing_var);
+        an_push_warning(analyzer, loop_node->loop.step->token, an_problem);
+      }
+      else if ((cond_data.type == COND_TYPE_VAR_LESS ||
+                cond_data.type == COND_TYPE_VAR_GREATER) &&
+               step_data.dir == STEP_DIR_TYPE_STALL)
+      {
+        snprintf(an_problem, sizeof(an_problem), "'%s' is stalled",
+                 cond_data.varname);
+        an_push_warning(analyzer, loop_node->loop.step->token, an_problem);
+      }
+    }
+  }
+
+  body_analysis body_data = {.has_exit = false};
+  if (cond_data.type != COND_TYPE_CONST_FALSE)
+  {
+    fzl_an_res_t body_res = analyze_common(analyzer, loop_node->loop.body);
+    if (body_res.error)
+      return (fzl_an_res_t){.error = true};
+
+    body_data = check_body(loop_node->loop.body, false);
+    if (cond_data.type == COND_TYPE_CONST_TRUE && !body_data.has_exit)
+      an_push_warning(analyzer, loop_node->token, "possibly infinite loop");
+  }
+
+  an_fin_ctx(analyzer);
+
+  return (fzl_an_res_t){.error = false, .type = FZL_TYPE_NULL};
+}

src/compiler/analyzer/an_return.c

@@ -0,0 +1,101 @@
+#include <common/fzl_types.h>
+#include <compiler/fzl_analyzer.h>
+#include <compiler/fzl_parser.h>
+#include <compiler/fzl_token.h>
+#include <stdio.h>
+
+// Analyze return statement
+fzl_an_res_t analyze_return(fzl_analyzer_t *analyzer, fzl_node_t *ret_node)
+{
+  if (!analyzer)
+    return (fzl_an_res_t){.error = true};
+
+  if (!ret_node || ret_node->type != FZL_NODETYPE_RETURN)
+  {
+    an_push_error(analyzer, NULL, "node is not a return statement");
+    return (fzl_an_res_t){.error = false};
+  }
+
+  fzl_an_ctx_t *fnctx = analyzer->ctx;
+  while (fnctx != NULL)
+  {
+    if (fnctx->type == FZL_AN_CTX_TYPE_FUNCTION)
+      break;
+
+    fnctx = fnctx->parent;
+  }
+
+  fzl_an_ctx_t *classctx = analyzer->ctx;
+  while (classctx != NULL)
+  {
+    if (classctx && classctx->type == FZL_AN_CTX_TYPE_CLASS)
+      break;
+
+    classctx = classctx->parent;
+  }
+
+  bool is_in_method =
+      classctx != NULL && classctx->type == FZL_AN_CTX_TYPE_CLASS;
+
+  if (!fnctx || fnctx->type != FZL_AN_CTX_TYPE_FUNCTION)
+  {
+    an_push_error(analyzer, ret_node->token,
+                  "cannot use 'return' outside the function");
+    return (fzl_an_res_t){.error = true};
+  }
+
+  fzl_type_t rettype = an_toktotype(fnctx->fn->fn.type);
+  char *classname    = NULL;
+  if (rettype == FZL_TYPE_OBJECT)
+    classname = (char *)fnctx->fn->fn.type->value;
+
+  char *rettype_str = an_typetostr(rettype, classname);
+  if (rettype != FZL_TYPE_NULL)
+  {
+    if (ret_node->ret.value == NULL)
+    {
+      if (is_in_method)
+      {
+        snprintf(an_problem, sizeof(an_problem),
+                 "cannot return null as method '%s.%s' have return type '%s'",
+                 classctx->classname, (char *)fnctx->fn->fn.name->value,
+                 rettype_str);
+      }
+      else
+      {
+        snprintf(an_problem, sizeof(an_problem),
+                 "cannot return null as function '%s' have return type '%s'",
+                 (char *)fnctx->fn->fn.name->value, rettype_str);
+      }
+      an_push_error(analyzer, ret_node->token, an_problem);
+      return (fzl_an_res_t){.error = true};
+    }
+
+    fzl_an_res_t ret_res = analyze_common(analyzer, ret_node->ret.value);
+    if (ret_res.error)
+      return (fzl_an_res_t){.error = true};
+
+    if (!an_is_compatible(ret_res.type, rettype, ret_res.classname, classname))
+    {
+      if (is_in_method)
+      {
+        snprintf(an_problem, sizeof(an_problem),
+                 "method '%s.%s' is expecting return type '%s', got '%s'",
+                 classctx->classname, (char *)fnctx->fn->fn.name->value,
+                 rettype_str, an_typetostr(ret_res.type, ret_res.classname));
+      }
+      else
+      {
+        snprintf(an_problem, sizeof(an_problem),
+                 "function '%s' is expecting return type '%s', got '%s'",
+                 (char *)fnctx->fn->fn.name->value, rettype_str,
+                 an_typetostr(ret_res.type, ret_res.classname));
+      }
+      an_push_error(analyzer, ret_node->token, an_problem);
+      return (fzl_an_res_t){.error = true};
+    }
+  }
+
+  return (fzl_an_res_t){
+      .error = false, .type = rettype, .classname = classname};
+}

src/compiler/analyzer/an_unarycond.c

@@ -0,0 +1,30 @@
+#include <common/fzl_types.h>
+#include <compiler/fzl_analyzer.h>
+#include <compiler/fzl_parser.h>
+
+// Analyze unary condition
+fzl_an_res_t analyze_unarycond(fzl_analyzer_t *analyzer, fzl_node_t *unary)
+{
+  if (!analyzer)
+    return (fzl_an_res_t){.error = true};
+
+  if (!unary || unary->type != FZL_NODETYPE_NOT)
+  {
+    an_push_error(analyzer, NULL, "node is not an unary condition operator");
+    return (fzl_an_res_t){.error = true};
+  }
+
+  fzl_an_res_t operand_res = analyze_common(analyzer, unary->unary_op.operand);
+  if (operand_res.error)
+    return (fzl_an_res_t){.error = true};
+
+  if (operand_res.type != FZL_TYPE_BOOL && operand_res.type < FZL_TYPE_INT8)
+  {
+    an_push_error(analyzer, unary->unary_op.operand->token,
+                  "unary condition only support bool and integer types");
+    return (fzl_an_res_t){.error = true};
+  }
+
+  return (fzl_an_res_t){
+      .error = false, .type = FZL_TYPE_BOOL, .classname = NULL};
+}

src/compiler/analyzer/an_unarymath.c

@@ -0,0 +1,32 @@
+#include <common/fzl_types.h>
+#include <compiler/fzl_analyzer.h>
+#include <compiler/fzl_parser.h>
+#include <stdbool.h>
+
+// Analyze unary arithmetic
+fzl_an_res_t analyze_unarymath(fzl_analyzer_t *analyzer, fzl_node_t *unary)
+{
+  if (!analyzer)
+    return (fzl_an_res_t){.error = true};
+
+  if (!unary || (unary->type != FZL_NODETYPE_UNARY_MINUS &&
+                 unary->type != FZL_NODETYPE_UNARY_PLUS))
+  {
+    an_push_error(analyzer, NULL, "node is not an unary math operator");
+    return (fzl_an_res_t){.error = true};
+  }
+
+  fzl_an_res_t operand_res = analyze_common(analyzer, unary->unary_op.operand);
+  if (operand_res.error)
+    return (fzl_an_res_t){.error = true};
+
+  if (operand_res.type < FZL_TYPE_INT8)
+  {
+    an_push_error(analyzer, unary->unary_op.operand->token,
+                  "unary operator only support integer types");
+    return (fzl_an_res_t){.error = true};
+  }
+
+  return (fzl_an_res_t){
+      .error = false, .type = operand_res.type, .classname = NULL};
+}

src/compiler/analyzer/context.c

@@ -0,0 +1,46 @@
+#include <compiler/fzl_analyzer.h>
+#include <compiler/utils/fzl_symtable.h>
+#include <stdlib.h>
+#include <string.h>
+
+// Nest context
+fzl_an_ctx_t *an_nest_ctx(fzl_analyzer_t *analyzer, fzl_an_ctx_type_t type)
+{
+  if (!analyzer)
+    return NULL;
+
+  fzl_an_ctx_t *ctx = malloc(sizeof(fzl_an_ctx_t));
+  if (!ctx)
+    return NULL;
+
+  memset(ctx, 0, sizeof(fzl_an_ctx_t));
+
+  ctx->type = type;
+  if (analyzer->ctx != NULL)
+    ctx->parent = analyzer->ctx;
+  else
+    ctx->parent = NULL;
+
+  ctx->symbols                               = fzl_mksymt();
+  ctx->symbols_level                         = analyzer->symbols_top;
+  analyzer->ctx                              = ctx;
+  analyzer->symbols[analyzer->symbols_top++] = ctx->symbols;
+
+  return ctx;
+}
+
+// Close context and return parent
+fzl_an_ctx_t *an_fin_ctx(fzl_analyzer_t *analyzer)
+{
+  if (!analyzer || analyzer->ctx == NULL)
+    return NULL;
+
+  fzl_an_ctx_t *current = analyzer->ctx;
+  fzl_an_ctx_t *parent  = current->parent;
+  analyzer->ctx         = parent;
+
+  free(current);
+  fzl_freesymt(analyzer->symbols[--analyzer->symbols_top]);
+
+  return parent;
+}

src/compiler/analyzer/utility.c

@@ -0,0 +1,124 @@
+#include <common/fzl_types.h>
+#include <compiler/fzl_token.h>
+#include <stdbool.h>
+#include <string.h>
+
+// Check compatibility between A and B types (and classnames)
+bool an_is_compatible(fzl_type_t a, fzl_type_t b, char *ac, char *bc)
+{
+  if (a == b)
+    return true;
+
+  if (a == FZL_TYPE_OBJECT && b == FZL_TYPE_OBJECT)
+  {
+    if (strcmp(ac, "null") == 0 || strcmp(bc, "null") == 0)
+      return true;
+
+    return strcmp(ac, bc) == 0;
+  }
+
+  if (a >= FZL_TYPE_INT8 && b >= FZL_TYPE_INT8)
+    return true;
+
+  return false;
+}
+
+// Convert type to string
+char *an_typetostr(fzl_type_t type, char *classname)
+{
+  if (classname)
+    return classname;
+
+  switch (type)
+  {
+    case FZL_TYPE_NULL:
+      return "null";
+
+    case FZL_TYPE_BOOL:
+      return "boolean";
+
+    case FZL_TYPE_STRING:
+      return "string";
+
+    case FZL_TYPE_CHAR:
+      return "char";
+
+    case FZL_TYPE_INT8:
+      return "i8";
+
+    case FZL_TYPE_INT16:
+      return "i16";
+
+    case FZL_TYPE_INT32:
+      return "i32";
+
+    case FZL_TYPE_INT64:
+      return "i64";
+
+    case FZL_TYPE_UINT8:
+      return "u8";
+
+    case FZL_TYPE_UINT16:
+      return "u16";
+
+    case FZL_TYPE_UINT32:
+      return "u32";
+
+    case FZL_TYPE_UINT64:
+      return "u64";
+
+    case FZL_TYPE_INT:
+      return "int";
+
+    case FZL_TYPE_UINT:
+      return "uint";
+
+    default:
+      return "<unknown>";
+  }
+}
+
+// Convert type token to type
+fzl_type_t an_toktotype(fzl_token_t *tok)
+{
+  if (!tok)
+    return FZL_TYPE_NULL;
+
+  if (tok->type == FZL_TOKTYPE_NAME)
+    return FZL_TYPE_OBJECT;
+
+  if (strcmp(tok->value, "null") == 0)
+    return FZL_TYPE_NULL;
+
+  if (strcmp((char *)tok->value, "i8") == 0)
+    return FZL_TYPE_INT8;
+  if (strcmp((char *)tok->value, "i16") == 0)
+    return FZL_TYPE_INT16;
+  if (strcmp((char *)tok->value, "i32") == 0)
+    return FZL_TYPE_INT32;
+  if (strcmp((char *)tok->value, "i64") == 0)
+    return FZL_TYPE_INT64;
+
+  if (strcmp((char *)tok->value, "u8") == 0)
+    return FZL_TYPE_UINT8;
+  if (strcmp((char *)tok->value, "u16") == 0)
+    return FZL_TYPE_UINT16;
+  if (strcmp((char *)tok->value, "u32") == 0)
+    return FZL_TYPE_UINT32;
+  if (strcmp((char *)tok->value, "u64") == 0)
+    return FZL_TYPE_UINT64;
+
+  if (strcmp((char *)tok->value, "int") == 0)
+    return FZL_TYPE_INT;
+  if (strcmp((char *)tok->value, "uint") == 0)
+    return FZL_TYPE_UINT;
+
+  if (strcmp((char *)tok->value, "bool") == 0)
+    return FZL_TYPE_BOOL;
+  if (strcmp((char *)tok->value, "str") == 0)
+    return FZL_TYPE_STRING;
+  if (strcmp((char *)tok->value, "char") == 0)
+    return FZL_TYPE_CHAR;
+
+  return FZL_TYPE_NULL;
+}

src/compiler/checkers/fzl_loop_check.c

@@ -0,0 +1,229 @@
+#include <common/fzl_opcodes.h>
+#include <common/fzl_types.h>
+#include <compiler/fzl_parser.h>
+#include <compiler/fzl_walker.h>
+#include <compiler/utils/fzl_const_pool.h>
+#include <compiler/utils/fzl_symtable.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <string.h>
+
+ssize_t check_top;
+fzl_nodetype_t check_tree[256];
+
+// Ghost walk AST tree (w/o adding opcodes) to check if
+// variable used in condition is changed
+void ghost_walk_changed(fzl_node_t *node, bool *changed, fzl_sym_t *sym)
+{
+  if (!node || !changed || *changed)
+    return;
+
+  check_tree[check_top++] = node->type;
+
+  switch (node->type)
+  {
+    case FZL_NODETYPE_BREAK:
+    case FZL_NODETYPE_DECLARATION:
+    case FZL_NODETYPE_CONSTRUCT:
+    case FZL_NODETYPE_CLASS:
+    case FZL_NODETYPE_FUNCTION:
+    case FZL_NODETYPE_LITERAL:
+      break;
+
+    case FZL_NODETYPE_UNARY_PLUS:
+    case FZL_NODETYPE_UNARY_MINUS:
+    case FZL_NODETYPE_NOT:
+      ghost_walk_changed(node->unary_op.operand, changed, sym);
+      break;
+
+    case FZL_NODETYPE_ADD:
+    case FZL_NODETYPE_SUB:
+    case FZL_NODETYPE_MUL:
+    case FZL_NODETYPE_DIV:
+    case FZL_NODETYPE_POW:
+    case FZL_NODETYPE_MOD:
+    case FZL_NODETYPE_OR:
+    case FZL_NODETYPE_AND:
+    case FZL_NODETYPE_EQUAL:
+    case FZL_NODETYPE_NEQUAL:
+    case FZL_NODETYPE_LESS:
+    case FZL_NODETYPE_LESS_EQUAL:
+    case FZL_NODETYPE_GREATER:
+    case FZL_NODETYPE_GREATER_EQUAL:
+    case FZL_NODETYPE_ASSIGN:
+      ghost_walk_changed(node->binary_op.left, changed, sym);
+      ghost_walk_changed(node->binary_op.right, changed, sym);
+      break;
+
+    case FZL_NODETYPE_FIELD:
+      ghost_walk_changed(node->memb.parent, changed, sym);
+      ghost_walk_changed(node->memb.field, changed, sym);
+      break;
+
+    case FZL_NODETYPE_RETURN:
+      ghost_walk_changed(node->ret.value, changed, sym);
+      break;
+
+    case FZL_NODETYPE_CONDITIONAL:
+      ghost_walk_changed(node->cond.condition, changed, sym);
+      ghost_walk_changed(node->cond.true_block, changed, sym);
+      ghost_walk_changed(node->cond.else_block, changed, sym);
+      break;
+
+    case FZL_NODETYPE_LOOP:
+      ghost_walk_changed(node->loop.cond, changed, sym);
+      ghost_walk_changed(node->loop.step, changed, sym);
+      ghost_walk_changed(node->loop.body, changed, sym);
+      break;
+
+    case FZL_NODETYPE_BLOCK:
+      for (size_t i = 0; i < node->list.entry_count; i++)
+        ghost_walk_changed(node->list.entries[i], changed, sym);
+      break;
+
+    case FZL_NODETYPE_CALL:
+      ghost_walk_changed(node->call.callee, changed, sym);
+      for (size_t i = 0; i < node->call.args_count; i++)
+        ghost_walk_changed(node->call.args[i], changed, sym);
+      break;
+
+    case FZL_NODETYPE_IDENTIFIER:
+      if (strcmp(node->token->value, sym->name) == 0)
+      {
+        *changed = true;
+      }
+
+      if (*changed)
+      {
+        *changed = false;
+        for (ssize_t i = check_top - 1; i >= 0; i--)
+        {
+          fzl_nodetype_t cur_t = check_tree[i];
+          if (cur_t == FZL_NODETYPE_ADD || cur_t == FZL_NODETYPE_SUB ||
+              cur_t == FZL_NODETYPE_MUL || cur_t == FZL_NODETYPE_DIV ||
+              cur_t == FZL_NODETYPE_POW || cur_t == FZL_NODETYPE_MOD ||
+              cur_t == FZL_NODETYPE_UNARY_MINUS)
+          {
+            *changed = true;
+            break;
+          }
+        }
+      }
+      break;
+  }
+
+  check_tree[--check_top] = 0;
+}
+
+// Whether value changed in loop body
+bool value_is_changed(fzl_node_t *node, fzl_sym_t *sym)
+{
+  if (!node || !sym)
+    return false;
+
+  bool changed = false;
+  check_top    = 0;
+  memset(check_tree, 0, sizeof(check_tree));
+  ghost_walk_changed(node, &changed, sym);
+
+  return changed;
+}
+
+// Try to find symbol in loop condition node
+bool retrieve_cond_sym(fzl_walker_t *walker, fzl_node_t *node, fzl_sym_t *sym)
+{
+  if (!walker || !node)
+    return false;
+
+  switch (node->type)
+  {
+    case FZL_NODETYPE_BREAK:
+    case FZL_NODETYPE_BLOCK:
+    case FZL_NODETYPE_CALL:
+    case FZL_NODETYPE_LITERAL:
+    case FZL_NODETYPE_CONDITIONAL:
+    case FZL_NODETYPE_FUNCTION:
+    case FZL_NODETYPE_RETURN:
+    case FZL_NODETYPE_CLASS:
+    case FZL_NODETYPE_FIELD:
+    case FZL_NODETYPE_CONSTRUCT:
+    case FZL_NODETYPE_LOOP:
+    case FZL_NODETYPE_ASSIGN:
+    case FZL_NODETYPE_DECLARATION:
+      return false;
+
+    case FZL_NODETYPE_UNARY_MINUS:
+    case FZL_NODETYPE_UNARY_PLUS:
+    case FZL_NODETYPE_NOT:
+      return retrieve_cond_sym(walker, node->unary_op.operand, sym);
+
+    case FZL_NODETYPE_ADD:
+    case FZL_NODETYPE_SUB:
+    case FZL_NODETYPE_MUL:
+    case FZL_NODETYPE_DIV:
+    case FZL_NODETYPE_POW:
+    case FZL_NODETYPE_MOD:
+    case FZL_NODETYPE_AND:
+    case FZL_NODETYPE_OR:
+    case FZL_NODETYPE_LESS:
+    case FZL_NODETYPE_LESS_EQUAL:
+    case FZL_NODETYPE_GREATER:
+    case FZL_NODETYPE_GREATER_EQUAL:
+    case FZL_NODETYPE_EQUAL:
+    case FZL_NODETYPE_NEQUAL:
+      if (retrieve_cond_sym(walker, node->binary_op.left, sym))
+        return true;
+      if (retrieve_cond_sym(walker, node->binary_op.right, sym))
+        return true;
+      return false;
+
+    case FZL_NODETYPE_IDENTIFIER:
+    {
+      bool exists;
+      for (ssize_t i = walker->sym_top - 1; i >= 0; i--)
+      {
+        if ((exists = fzl_symt_get(walker->syms[i], (char *)node->token->value,
+                                   sym)))
+          break;
+      }
+      return exists;
+    }
+  }
+
+  return false;
+}
+
+// Check for infinite loop
+bool is_infinite_loop(fzl_walker_t *walker, fzl_node_t *node, size_t start_ip,
+                      size_t end_ip)
+{
+  if (!walker)
+    return false;
+
+  end_ip = (end_ip >= walker->op_count) ? (walker->op_count - 1) : end_ip;
+
+  fzl_sym_t sym;
+  bool sym_exists = retrieve_cond_sym(walker, node->loop.cond, &sym);
+  if (sym_exists)
+  {
+    if (sym.type >= FZL_TYPE_INT8)
+    {
+      bool value_changed = value_is_changed(node, &sym);
+      if (value_changed)
+        return false;
+    }
+  }
+
+  // At least has jump outside
+  for (size_t i = start_ip; i <= end_ip; i++)
+  {
+    if (walker->ops[i] != FZL_OPCODE_JMP)
+      continue;
+
+    size_t jump_ip = walker->ops[++i];
+    if (jump_ip >= end_ip)
+      return false;
+  }
+
+  return true;
+}

src/compiler/fzl_analyzer.c

@@ -0,0 +1,118 @@
+#include <compiler/fzl_analyzer.h>
+#include <compiler/fzl_parser.h>
+#include <compiler/fzl_token.h>
+#include <compiler/utils/fzl_symtable.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+char aerrors[256][256];
+size_t aerrors_top;
+
+char awarnings[256][256];
+size_t awarnings_top;
+
+char an_problem[256];
+
+fzl_analyzer_t *fzl_mkanalyzer(fzl_node_t *node)
+{
+  if (!node)
+    return NULL;
+
+  fzl_analyzer_t *analyzer = malloc(sizeof(fzl_analyzer_t));
+  if (!analyzer)
+    return NULL;
+
+  analyzer->root            = node;
+  analyzer->warnings_top    = 0;
+  analyzer->errors_top      = 0;
+  analyzer->symbols_top     = 0;
+  analyzer->alloc_names_top = 0;
+
+  memset(analyzer->errors, 0, sizeof(analyzer->errors));
+  memset(analyzer->warnings, 0, sizeof(analyzer->warnings));
+  memset(analyzer->symbols, 0, sizeof(analyzer->symbols));
+  memset(analyzer->alloc_names, 0, sizeof(analyzer->alloc_names));
+
+  memset(aerrors, 0, sizeof(aerrors));
+  memset(awarnings, 0, sizeof(awarnings));
+
+  return analyzer;
+}
+
+bool an_push_error(fzl_analyzer_t *analyzer, fzl_token_t *tok, char *error)
+{
+  if (analyzer->errors_top >= 256 || !analyzer || !error)
+    return false;
+
+  size_t ei = aerrors_top++;
+  if (tok != NULL)
+    snprintf(aerrors[ei], sizeof(aerrors[ei]), "'%s':%zu:%zu => %s",
+             tok->filename, tok->ln, tok->cn, error);
+  else
+    snprintf(aerrors[ei], sizeof(aerrors[ei]), "<unknown location> => %s",
+             error);
+
+  analyzer->errors[analyzer->errors_top++] = aerrors[ei];
+  return true;
+}
+
+bool an_push_warning(fzl_analyzer_t *analyzer, fzl_token_t *tok, char *warning)
+{
+  if (analyzer->warnings_top >= 256 || !analyzer || !warning)
+    return false;
+
+  size_t wi = awarnings_top++;
+  if (tok != NULL)
+    snprintf(awarnings[wi], sizeof(awarnings[wi]), "'%s':%zu:%zu => %s",
+             tok->filename, tok->ln, tok->cn, warning);
+  else
+    snprintf(awarnings[wi], sizeof(awarnings[wi]), "<unknown location> => %s",
+             warning);
+
+  analyzer->warnings[analyzer->warnings_top++] = awarnings[wi];
+  return true;
+}
+
+void fzl_analyze(fzl_analyzer_t *analyzer)
+{
+  if (!analyzer)
+    return;
+
+  if (an_nest_ctx(analyzer, FZL_AN_CTX_TYPE_UNNECESSARY) == NULL)
+  {
+    an_push_error(analyzer, NULL, "failed to make global context");
+    return;
+  }
+
+  fzl_node_t *current = analyzer->root;
+  while (current != NULL)
+  {
+    fzl_an_res_t res = analyze_common(analyzer, current);
+    if (res.error)
+      break;
+
+    current = current->next;
+  }
+
+  for (ssize_t i = analyzer->symbols_top; i > 0; i--)
+    an_fin_ctx(analyzer);
+}
+
+void fzl_freeanalyzer(fzl_analyzer_t *analyzer)
+{
+  if (!analyzer)
+    return;
+
+  if (analyzer->alloc_names_top > 0)
+    for (ssize_t i = analyzer->alloc_names_top - 1; i >= 0; i--)
+      free(analyzer->alloc_names[i]);
+
+  memset(analyzer->errors, 0, sizeof(analyzer->errors));
+  memset(analyzer->warnings, 0, sizeof(analyzer->warnings));
+  memset(analyzer->symbols, 0, sizeof(analyzer->symbols));
+  memset(analyzer->alloc_names, 0, sizeof(analyzer->alloc_names));
+  free(analyzer);
+}

src/compiler/fzl_debug.c

@@ -31,6 +31,22 @@ void print_node(fzl_node_t *node, int level)
 
   switch (node->type)
   {
+    case FZL_NODETYPE_LOOP:
+      printf("%s Loop:\n", levelbuf);
+      printf("-%s Init:\n", levelbuf);
+      if (node->loop.init)
+        print_node(node->loop.init, level + 2);
+      printf("-%s Condition:\n", levelbuf);
+      if (node->loop.cond)
+        print_node(node->loop.cond, level + 2);
+      printf("-%s Step:\n", levelbuf);
+      if (node->loop.step)
+        print_node(node->loop.step, level + 2);
+      printf("-%s Body:\n", levelbuf);
+      if (node->loop.body)
+        print_node(node->loop.body, level + 2);
+      break;
+
     case FZL_NODETYPE_CONSTRUCT:
       printf("%s Construct class '%s':\n", levelbuf,
              (char *)node->construct.name->token->value);
@@ -169,7 +185,7 @@ void fzl_debug_print_ast(fzl_node_t *root)
   fzl_node_t *curr = root;
   while (curr != NULL)
   {
-    print_node(curr, 2);
+    print_node(curr, 3);
     curr = curr->next;
   }
 

src/compiler/fzl_parser.c

@@ -30,10 +30,7 @@ fzl_token_t this_tok = {.type        = FZL_TOKTYPE_NAME,
 fzl_parser_t *fzl_mkparser(fzl_reader_ll_t *first)
 {
   if (!first)
-  {
-    snprintf(plast_err, sizeof(plast_err), "token is null");
     return NULL;
-  }
 
   fzl_parser_t *parser = malloc(sizeof(fzl_parser_t));
   if (!parser)
@@ -161,7 +158,9 @@ fzl_node_t *parse_primary(fzl_parser_t *parser)
     if (!is(parser, FZL_TOKTYPE_RPAREN))
     {
       snprintf(plast_err, sizeof(plast_err), "'%s': expected ')' at %ld:%ld",
-               peek(parser)->filename, peek(parser)->ln, peek(parser)->cn);
+               last_known_tok->filename, last_known_tok->ln,
+               last_known_tok->cn);
+      fzl_freeast(node);
       return NULL;
     }
     consume(parser);
@@ -183,11 +182,12 @@ fzl_node_t *parse_primary(fzl_parser_t *parser)
   {
     fzl_token_t *type = consume(parser);
     fzl_token_t *name = consume(parser);
-    if (name->type != FZL_TOKTYPE_NAME)
+    if (!name || name->type != FZL_TOKTYPE_NAME)
     {
       snprintf(plast_err, sizeof(plast_err),
-               "'%s': expected name after type at %ld:%ld", type->filename,
+               "'%s': expected name after type at %ld:%ld",
-               type->ln, type->cn);
+               last_known_tok->filename, last_known_tok->ln,
+               last_known_tok->cn);
       return NULL;
     }
 
@@ -199,8 +199,8 @@ fzl_node_t *parse_primary(fzl_parser_t *parser)
 
   if (!plast_err[0])
     snprintf(plast_err, sizeof(plast_err),
-             "'%s': failed to parse primary at %ld:%ld", peek(parser)->filename,
+             "'%s': expected expression at %ld:%ld", last_known_tok->filename,
-             peek(parser)->ln, peek(parser)->cn);
+             last_known_tok->ln, last_known_tok->cn);
   return NULL;
 }
 
@@ -213,13 +213,7 @@ fzl_node_t *parse_postfix(fzl_parser_t *parser)
   fzl_node_t *left = parse_primary(parser);
 
   if (!left)
-  {
-    if (!plast_err[0])
-      snprintf(plast_err, sizeof(plast_err),
-               "'%s': failed to parse postfix at %ld:%ld",
-               peek(parser)->filename, peek(parser)->ln, peek(parser)->cn);
     return NULL;
-  }
 
   if (is(parser, FZL_TOKTYPE_LPAREN) || is(parser, FZL_TOKTYPE_DOT))
   {
@@ -238,7 +232,10 @@ fzl_node_t *parse_postfix(fzl_parser_t *parser)
           fzl_node_t *arg = parse_expression(parser);
           if (!arg)
           {
+            for (size_t i = 0; i < args_count; i++)
+              fzl_freeast(args[i]);
             free(args);
+            fzl_freeast(left);
             return NULL;
           }
 
@@ -258,10 +255,14 @@ fzl_node_t *parse_postfix(fzl_parser_t *parser)
         fzl_token_t *rparen = consume(parser);
         if (!rparen || rparen->type != FZL_TOKTYPE_RPAREN)
         {
+          for (size_t i = 0; i < args_count; i++)
+            fzl_freeast(args[i]);
           free(args);
+          fzl_freeast(left);
           snprintf(plast_err, sizeof(plast_err),
                    "'%s': expected ')' after argument list at %ld:%ld",
-                   peek(parser)->filename, peek(parser)->ln, peek(parser)->cn);
+                   last_known_tok->filename, last_known_tok->ln,
+                   last_known_tok->cn);
           return NULL;
         }
 
@@ -276,6 +277,7 @@ fzl_node_t *parse_postfix(fzl_parser_t *parser)
       {
         if (!is(parser, FZL_TOKTYPE_NAME))
         {
+          fzl_freeast(left);
           snprintf(plast_err, sizeof(plast_err),
                    "'%s': expected name after '.' at %ld:%ld",
                    last_known_tok->filename, last_known_tok->ln,
@@ -327,13 +329,7 @@ fzl_node_t *parse_power(fzl_parser_t *parser)
   fzl_node_t *right = NULL;
 
   if (!left)
-  {
-    if (!plast_err[0])
-      snprintf(plast_err, sizeof(plast_err),
-               "'%s': failed to parse power at %ld:%ld", peek(parser)->filename,
-               peek(parser)->ln, peek(parser)->cn);
     return NULL;
-  }
 
   if (is(parser, FZL_TOKTYPE_CARET))
   {
@@ -342,10 +338,12 @@ fzl_node_t *parse_power(fzl_parser_t *parser)
     right = parse_unary(parser);
     if (!right)
     {
+      fzl_freeast(left);
       if (!plast_err[0])
         snprintf(plast_err, sizeof(plast_err),
-                 "'%s': failed to parse right side of power at %ld:%ld",
+                 "'%s': expected expression at %ld:%ld",
-                 peek(parser)->filename, peek(parser)->ln, peek(parser)->cn);
+                 last_known_tok->filename, last_known_tok->ln,
+                 last_known_tok->cn);
       return NULL;
     }
 
@@ -369,13 +367,7 @@ fzl_node_t *parse_factor(fzl_parser_t *parser)
   fzl_node_t *right = NULL;
 
   if (!left)
-  {
-    if (!plast_err[0])
-      snprintf(plast_err, sizeof(plast_err),
-               "'%s': invalid expression at %ld:%ld", peek(parser)->filename,
-               peek(parser)->ln, peek(parser)->cn);
     return NULL;
-  }
 
   while (is(parser, FZL_TOKTYPE_STAR) || is(parser, FZL_TOKTYPE_SLASH) ||
          is(parser, FZL_TOKTYPE_PERCENT))
@@ -385,10 +377,12 @@ fzl_node_t *parse_factor(fzl_parser_t *parser)
     right = parse_factor(parser);
     if (!right)
     {
+      fzl_freeast(left);
       if (!plast_err[0])
         snprintf(plast_err, sizeof(plast_err),
-                 "'%s': unfinished factor (mul/div) expression at %ld:%ld",
+                 "'%s': expected expression at %ld:%ld",
-                 left->token->filename, left->token->ln, left->token->cn);
+                 last_known_tok->filename, last_known_tok->ln,
+                 last_known_tok->cn);
       return NULL;
     }
 
@@ -411,13 +405,7 @@ fzl_node_t *parse_term(fzl_parser_t *parser)
   fzl_node_t *right = NULL;
 
   if (!left)
-  {
-    if (!plast_err[0])
-      snprintf(plast_err, sizeof(plast_err),
-               "'%s': invalid expression at %ld:%ld", peek(parser)->filename,
-               peek(parser)->ln, peek(parser)->cn);
     return NULL;
-  }
 
   while (is(parser, FZL_TOKTYPE_PLUS) || is(parser, FZL_TOKTYPE_MINUS))
   {
@@ -426,10 +414,12 @@ fzl_node_t *parse_term(fzl_parser_t *parser)
     right = parse_factor(parser);
     if (!right)
     {
+      fzl_freeast(left);
       if (!plast_err[0])
         snprintf(plast_err, sizeof(plast_err),
-                 "'%s': unfinished term (add/sub) expression at %ld:%ld",
+                 "'%s': expected expression at %ld:%ld",
-                 left->token->filename, left->token->ln, left->token->cn);
+                 last_known_tok->filename, last_known_tok->ln,
+                 last_known_tok->cn);
       return NULL;
     }
 
@@ -462,10 +452,7 @@ fzl_node_t *parse_cond(fzl_parser_t *parser)
     right           = parse_term(parser);
     if (!right)
     {
-      if (!plast_err[0])
+      fzl_freeast(left);
-        snprintf(plast_err, sizeof(plast_err),
-                 "'%s': unfinished expression at %ld:%ld", op->filename, op->ln,
-                 op->cn);
       return NULL;
     }
 
@@ -520,10 +507,7 @@ fzl_node_t *parse_and(fzl_parser_t *parser)
     right            = parse_cond(parser);
     if (!right)
     {
-      if (!plast_err[0])
+      fzl_freeast(left);
-        snprintf(plast_err, sizeof(plast_err),
-                 "'%s': unfinished expression at %ld:%ld", or->filename, or->ln,
-                 or->cn);
       return NULL;
     }
 
@@ -554,10 +538,7 @@ fzl_node_t *parse_or(fzl_parser_t *parser)
     right            = parse_and(parser);
     if (!right)
     {
-      if (!plast_err[0])
+      fzl_freeast(left);
-        snprintf(plast_err, sizeof(plast_err),
-                 "'%s': unfinished expression at %ld:%ld", or->filename, or->ln,
-                 or->cn);
       return NULL;
     }
 
@@ -581,8 +562,9 @@ fzl_node_t *parse_new(fzl_parser_t *parser)
   if (objname->type != FZL_NODETYPE_IDENTIFIER &&
       objname->type != FZL_NODETYPE_FIELD)
   {
+    fzl_freeast(objname);
     snprintf(plast_err, sizeof(plast_err),
-             "'%s': expect class name after 'new' keyword at %ld:%ld",
+             "'%s': expected class name after 'new' keyword at %ld:%ld",
              last_known_tok->filename, last_known_tok->ln, last_known_tok->cn);
     return NULL;
   }
@@ -603,19 +585,24 @@ fzl_node_t *parse_assignment(fzl_parser_t *parser)
   if (is(parser, FZL_TOKTYPE_EQ))
   {
     fzl_token_t *asn = consume(parser);
-    if (left->type != FZL_NODETYPE_IDENTIFIER &&
+    if (!left || (left->type != FZL_NODETYPE_IDENTIFIER &&
-        left->type != FZL_NODETYPE_DECLARATION &&
+                  left->type != FZL_NODETYPE_DECLARATION &&
-        left->type != FZL_NODETYPE_FIELD)
+                  left->type != FZL_NODETYPE_FIELD))
     {
+      fzl_freeast(left);
       snprintf(plast_err, sizeof(plast_err),
-               "'%s': cannot assign to '%s' at %ld:%ld", left->token->filename,
+               "'%s': cannot assign to '%s' at %ld:%ld",
-               (char *)left->token->value, asn->ln, asn->cn);
+               last_known_tok->filename, (char *)left->token->value,
+               last_known_tok->ln, last_known_tok->cn);
       return NULL;
     }
 
     fzl_node_t *right = parse_assignment(parser);
     if (!right)
+    {
+      fzl_freeast(left);
       return NULL;
+    }
 
     fzl_node_t *node      = fzl_mknode(FZL_NODETYPE_ASSIGN, asn);
     node->binary_op.left  = left;
@@ -643,20 +630,20 @@ fzl_node_t *parse_class(fzl_parser_t *parser)
 
   fzl_token_t *class = consume(parser);
   fzl_token_t *name  = consume(parser);
-  if (name->type != FZL_TOKTYPE_NAME)
+  if (!name || name->type != FZL_TOKTYPE_NAME)
   {
     snprintf(plast_err, sizeof(plast_err),
-             "'%s': expected class name at %ld:%ld", name->filename, name->ln,
+             "'%s': expected class name at %ld:%ld", last_known_tok->filename,
-             name->cn);
+             last_known_tok->ln, last_known_tok->cn);
     return NULL;
   }
 
   fzl_token_t *lbrace = consume(parser);
-  if (lbrace->type != FZL_TOKTYPE_LBRACE)
+  if (!lbrace || lbrace->type != FZL_TOKTYPE_LBRACE)
   {
     snprintf(plast_err, sizeof(plast_err),
-             "'%s': expected '{' after class name at %ld:%ld", lbrace->filename,
+             "'%s': expected '{' after class name at %ld:%ld",
-             lbrace->ln, lbrace->cn);
+             last_known_tok->filename, last_known_tok->ln, last_known_tok->cn);
     return NULL;
   }
 
@@ -697,6 +684,7 @@ fzl_node_t *parse_class(fzl_parser_t *parser)
         {
           snprintf(plast_err, sizeof(plast_err),
                    "failed to resize fields array");
+          fzl_freeast(node);
           free(methods);
           return NULL;
         }
@@ -714,6 +702,7 @@ fzl_node_t *parse_class(fzl_parser_t *parser)
         {
           snprintf(plast_err, sizeof(plast_err),
                    "failed to resize methods array");
+          fzl_freeast(node);
           free(fields);
           return NULL;
         }
@@ -726,6 +715,7 @@ fzl_node_t *parse_class(fzl_parser_t *parser)
         snprintf(plast_err, sizeof(plast_err),
                  "failed to reallocate method args list");
         free(fields);
+        fzl_freeast(node);
         return NULL;
       }
 
@@ -744,9 +734,11 @@ fzl_node_t *parse_class(fzl_parser_t *parser)
     }
     else
     {
+      fzl_freeast(node);
       snprintf(plast_err, sizeof(plast_err),
                "'%s': unknown type of class member at %ld:%ld",
-               node->token->filename, node->token->ln, node->token->cn);
+               last_known_tok->filename, last_known_tok->ln,
+               last_known_tok->cn);
       free(fields);
       free(methods);
       return NULL;
@@ -780,7 +772,7 @@ fzl_node_t *parse_function(fzl_parser_t *parser)
     return NULL;
 
   fzl_token_t *fn = consume(parser);
-  if (fn->type != FZL_TOKTYPE_FUNCTION)
+  if (!fn || fn->type != FZL_TOKTYPE_FUNCTION)
   {
     snprintf(plast_err, sizeof(plast_err),
              "'%s': expected keyword 'fn' at %ld:%ld", last_known_tok->filename,
@@ -830,6 +822,7 @@ fzl_node_t *parse_function(fzl_parser_t *parser)
   fzl_token_t *rpar = consume(parser);
   if (!rpar || rpar->type != FZL_TOKTYPE_RPAREN)
   {
+    free(args);
     snprintf(plast_err, sizeof(plast_err),
              "'%s': expected ')' after argument list at %ld:%ld",
              last_known_tok->filename, last_known_tok->ln, last_known_tok->cn);
@@ -845,6 +838,7 @@ fzl_node_t *parse_function(fzl_parser_t *parser)
 
   if (!is(parser, FZL_TOKTYPE_LBRACE))
   {
+    free(args);
     snprintf(plast_err, sizeof(plast_err),
              "'%s': expected '{' after function declaration at %ld:%ld",
              last_known_tok->filename, last_known_tok->ln, last_known_tok->cn);
@@ -853,7 +847,10 @@ fzl_node_t *parse_function(fzl_parser_t *parser)
 
   fzl_node_t *body = parse_statement(parser);
   if (!body)
+  {
+    free(args);
     return NULL;
+  }
 
   fzl_node_t *node    = fzl_mknode(FZL_NODETYPE_FUNCTION, name);
   node->fn.args       = args;
@@ -878,7 +875,10 @@ fzl_node_t *parse_return(fzl_parser_t *parser)
   {
     fzl_node_t *retval = parse_expression(parser);
     if (!retval)
+    {
+      fzl_freeast(node);
       return NULL;
+    }
 
     node->ret.value = retval;
   }
@@ -908,6 +908,7 @@ fzl_node_t *parse_if(fzl_parser_t *parser)
   fzl_token_t *rparen = consume(parser);
   if (rparen->type != FZL_TOKTYPE_RPAREN)
   {
+    fzl_freeast(condition);
     snprintf(plast_err, sizeof(plast_err),
              "'%s': expected ')' after condition at %ld:%ld", rparen->filename,
              rparen->ln, rparen->cn);
@@ -917,14 +918,21 @@ fzl_node_t *parse_if(fzl_parser_t *parser)
   fzl_node_t *else_block = NULL;
   fzl_node_t *true_block = parse_statement(parser);
   if (!true_block)
+  {
+    fzl_freeast(condition);
     return NULL;
+  }
 
   if (is(parser, FZL_TOKTYPE_ELSE))
   {
     consume(parser); // else
     else_block = parse_statement(parser);
     if (!else_block)
+    {
+      fzl_freeast(condition);
+      fzl_freeast(true_block);
       return NULL;
+    }
   }
 
   fzl_node_t *stmt_node      = fzl_mknode(FZL_NODETYPE_CONDITIONAL, if_tok);
@@ -951,7 +959,10 @@ fzl_node_t *parse_block(fzl_parser_t *parser)
   {
     fzl_node_t *node = parse_statement(parser);
     if (!node)
+    {
+      free(stmts);
       return NULL;
+    }
 
     if (remainder <= count)
     {
@@ -962,11 +973,15 @@ fzl_node_t *parse_block(fzl_parser_t *parser)
     stmts[count++] = node;
   }
   fzl_token_t *rbrace = consume(parser);
-  if (rbrace && rbrace->type != FZL_TOKTYPE_RBRACE)
+  if (!rbrace || rbrace->type != FZL_TOKTYPE_RBRACE)
   {
+    for (size_t i = 0; i < count; i++)
+      fzl_freeast(stmts[i]);
+    free(stmts);
+
     snprintf(plast_err, sizeof(plast_err),
-             "'%s': missing '}' after block at %ld:%ld", rbrace->filename,
+             "'%s': missing '}' after block at %ld:%ld",
-             rbrace->ln, rbrace->cn);
+             last_known_tok->filename, last_known_tok->ln, last_known_tok->cn);
     return NULL;
   }
 
@@ -976,6 +991,204 @@ fzl_node_t *parse_block(fzl_parser_t *parser)
   return node;
 }
 
+// For-loop parsing
+fzl_node_t *parse_for(fzl_parser_t *parser)
+{
+  fzl_token_t *tok  = consume(parser);
+  fzl_token_t *lpar = consume(parser);
+  if (!lpar || lpar->type != FZL_TOKTYPE_LPAREN)
+  {
+    snprintf(plast_err, sizeof(plast_err),
+             "'%s': expected '(' after for keyword at %ld:%ld",
+             last_known_tok->filename, last_known_tok->ln, last_known_tok->cn);
+    return NULL;
+  }
+
+  fzl_node_t *start = NULL;
+  if (!is(parser, FZL_TOKTYPE_SEMICOLON))
+  {
+    start = parse_expression(parser);
+    if (!start)
+    {
+      snprintf(plast_err, sizeof(plast_err),
+               "'%s': expected loop init or ';' at %ld:%ld",
+               last_known_tok->filename, last_known_tok->ln,
+               last_known_tok->cn);
+      return NULL;
+    }
+
+    fzl_token_t *sc = consume(parser);
+    if (!sc || sc->type != FZL_TOKTYPE_SEMICOLON)
+    {
+      fzl_freeast(start);
+      snprintf(plast_err, sizeof(plast_err),
+               "'%s': missing ';' after init section at %ld:%ld",
+               last_known_tok->filename, last_known_tok->ln,
+               last_known_tok->cn);
+      return NULL;
+    }
+  }
+  else
+    consume(parser);
+
+  fzl_node_t *condition = NULL;
+  if (!is(parser, FZL_TOKTYPE_SEMICOLON))
+  {
+    condition = parse_expression(parser);
+    if (!condition)
+    {
+      fzl_freeast(start);
+      snprintf(plast_err, sizeof(plast_err),
+               "'%s': expected loop condition or ';' at %ld:%ld",
+               last_known_tok->filename, last_known_tok->ln,
+               last_known_tok->cn);
+      return NULL;
+    }
+
+    fzl_token_t *sc = consume(parser);
+    if (!sc || sc->type != FZL_TOKTYPE_SEMICOLON)
+    {
+      fzl_freeast(start);
+      fzl_freeast(condition);
+      snprintf(plast_err, sizeof(plast_err),
+               "'%s': missing ';' after condition at %ld:%ld",
+               last_known_tok->filename, last_known_tok->ln,
+               last_known_tok->cn);
+      return NULL;
+    }
+  }
+  else
+    consume(parser);
+
+  fzl_node_t *step = NULL;
+  if (!is(parser, FZL_TOKTYPE_RPAREN))
+  {
+    step = parse_expression(parser);
+    if (!step)
+    {
+      fzl_freeast(start);
+      fzl_freeast(condition);
+      snprintf(plast_err, sizeof(plast_err),
+               "'%s': expected loop step end or ')' at %ld:%ld",
+               last_known_tok->filename, last_known_tok->ln,
+               last_known_tok->cn);
+      return NULL;
+    }
+  }
+
+  fzl_token_t *rpar = consume(parser);
+  if (!rpar || rpar->type != FZL_TOKTYPE_RPAREN)
+  {
+    fzl_freeast(start);
+    fzl_freeast(condition);
+    fzl_freeast(step);
+    snprintf(plast_err, sizeof(plast_err),
+             "'%s': missing ')' after loop setup at %ld:%ld",
+             last_known_tok->filename, last_known_tok->ln, last_known_tok->cn);
+    return NULL;
+  }
+
+  fzl_node_t *body = parse_statement(parser);
+  if (!body)
+  {
+    fzl_freeast(start);
+    fzl_freeast(condition);
+    fzl_freeast(step);
+    snprintf(plast_err, sizeof(plast_err),
+             "'%s': missing body of for loop at %ld:%ld",
+             last_known_tok->filename, last_known_tok->ln, last_known_tok->cn);
+    return NULL;
+  }
+
+  fzl_node_t *node = fzl_mknode(FZL_NODETYPE_LOOP, tok);
+  node->loop.init  = start;
+  node->loop.cond  = condition;
+  node->loop.step  = step;
+  node->loop.body  = body;
+
+  return node;
+}
+
+// While-loop parsing
+fzl_node_t *parse_while(fzl_parser_t *parser)
+{
+  fzl_token_t *tok  = consume(parser);
+  fzl_token_t *lpar = consume(parser);
+  if (!lpar || lpar->type != FZL_TOKTYPE_LPAREN)
+  {
+    snprintf(plast_err, sizeof(plast_err),
+             "'%s': missing '(' after while keyword at %ld:%ld",
+             last_known_tok->filename, last_known_tok->ln, last_known_tok->cn);
+    return NULL;
+  }
+
+  fzl_node_t *condition = parse_expression(parser);
+  if (!condition)
+  {
+    snprintf(plast_err, sizeof(plast_err),
+             "'%s': missing condition for 'while' at %ld:%ld",
+             last_known_tok->filename, last_known_tok->ln, last_known_tok->cn);
+    return NULL;
+  }
+
+  fzl_token_t *rpar = consume(parser);
+  if (!rpar || rpar->type != FZL_TOKTYPE_RPAREN)
+  {
+    fzl_freeast(condition);
+    snprintf(plast_err, sizeof(plast_err),
+             "'%s': missing ')' after while loop condition at %ld:%ld",
+             last_known_tok->filename, last_known_tok->ln, last_known_tok->cn);
+    return NULL;
+  }
+
+  fzl_node_t *body = parse_statement(parser);
+  if (!body)
+  {
+    fzl_freeast(condition);
+    snprintf(plast_err, sizeof(plast_err),
+             "'%s': missing while loop body at %ld:%ld",
+             last_known_tok->filename, last_known_tok->ln, last_known_tok->cn);
+    return NULL;
+  }
+
+  fzl_node_t *node = fzl_mknode(FZL_NODETYPE_LOOP, tok);
+  node->loop.cond  = condition;
+  node->loop.body  = body;
+
+  return node;
+}
+
+// `while` and `for` loops
+fzl_node_t *parse_loop(fzl_parser_t *parser)
+{
+  if (!peek(parser))
+    return NULL;
+
+  if (is(parser, FZL_TOKTYPE_FOR))
+    return parse_for(parser);
+  else if (is(parser, FZL_TOKTYPE_WHILE))
+    return parse_while(parser);
+
+  snprintf(plast_err, sizeof(plast_err),
+           "'%s': unknown type of loop at %ld:%ld", last_known_tok->filename,
+           last_known_tok->ln, last_known_tok->cn);
+  return NULL;
+}
+
+// `break` keyword parsing
+fzl_node_t *parse_break(fzl_parser_t *parser)
+{
+  fzl_token_t *tok = consume(parser);
+  if (!tok)
+  {
+    snprintf(plast_err, sizeof(plast_err), "'%s': EOF",
+             last_known_tok->filename);
+    return NULL;
+  }
+
+  return fzl_mknode(FZL_NODETYPE_BREAK, tok);
+}
+
 // Statement parsing
 fzl_node_t *parse_statement(fzl_parser_t *parser)
 {
@@ -994,12 +1207,23 @@ fzl_node_t *parse_statement(fzl_parser_t *parser)
     return parse_if(parser);
   else if (is(parser, FZL_TOKTYPE_LBRACE))
     return parse_block(parser);
+  else if (is(parser, FZL_TOKTYPE_FOR) || is(parser, FZL_TOKTYPE_WHILE))
+    return parse_loop(parser);
+  else if (is(parser, FZL_TOKTYPE_BREAK))
+    res = parse_break(parser);
 
   if (!res)
     res = parse_expression(parser);
 
+  if (!res)
+  {
+    fzl_freeast(res);
+    return NULL;
+  }
+
   if (!is(parser, FZL_TOKTYPE_SEMICOLON))
   {
+    fzl_freeast(res);
     snprintf(plast_err, sizeof(plast_err), "'%s': missing ';' at %ld:%ld",
              last_known_tok->filename, last_known_tok->ln, last_known_tok->cn);
     return NULL;
@@ -1079,6 +1303,7 @@ void fzl_freeast(fzl_node_t *root)
   {
     switch (root->type)
     {
+      case FZL_NODETYPE_BREAK:
       case FZL_NODETYPE_IDENTIFIER:
       case FZL_NODETYPE_LITERAL:
         break;
@@ -1119,6 +1344,20 @@ void fzl_freeast(fzl_node_t *root)
           fzl_freeast(root->cond.else_block);
         break;
 
+      case FZL_NODETYPE_LOOP:
+        if (root->loop.init)
+          fzl_freeast(root->loop.init);
+
+        if (root->loop.cond)
+          fzl_freeast(root->loop.cond);
+
+        if (root->loop.step)
+          fzl_freeast(root->loop.step);
+
+        if (root->loop.body)
+          fzl_freeast(root->loop.body);
+        break;
+
       case FZL_NODETYPE_ADD:
       case FZL_NODETYPE_SUB:
       case FZL_NODETYPE_MUL:

src/compiler/fzl_reader.c

@@ -73,6 +73,14 @@ fzl_token_t *parse_name(fzl_reader_t *reader)
   if (strcmp(value, "class") == 0)
     tok =
         fzl_mktoken(FZL_TOKTYPE_CLASS, l.line, l.col, value, size, l.filename);
+  else if (strcmp(value, "for") == 0)
+    tok = fzl_mktoken(FZL_TOKTYPE_FOR, l.line, l.col, value, size, l.filename);
+  else if (strcmp(value, "while") == 0)
+    tok =
+        fzl_mktoken(FZL_TOKTYPE_WHILE, l.line, l.col, value, size, l.filename);
+  else if (strcmp(value, "break") == 0)
+    tok =
+        fzl_mktoken(FZL_TOKTYPE_BREAK, l.line, l.col, value, size, l.filename);
   else if (strcmp(value, "new") == 0)
     tok = fzl_mktoken(FZL_TOKTYPE_NEW, l.line, l.col, value, size, l.filename);
   else if (strcmp(value, "fn") == 0)

src/compiler/fzl_walker.c

@@ -14,6 +14,9 @@
 #include <stdlib.h>
 #include <string.h>
 
+extern bool is_infinite_loop(fzl_walker_t *walker, fzl_node_t *node, size_t ls,
+                             size_t le);
+
 char *null_name = "<null>";
 char wlast_err[256];
 
@@ -200,6 +203,146 @@ fzl_walk_res_t walk(fzl_walker_t *walker, fzl_node_t *node)
   {
     switch (node->type)
     {
+      case FZL_NODETYPE_BREAK:
+      {
+        fzl_walk_ctx_t *ctx = walker->ctx;
+        while (ctx)
+        {
+          if (ctx->type == FZL_WALK_CTX_TYPE_LOOP)
+            break;
+
+          ctx = ctx->parent;
+        }
+
+        if (!ctx || ctx->type != FZL_WALK_CTX_TYPE_LOOP)
+        {
+          snprintf(wlast_err, sizeof(wlast_err),
+                   "'%s': usage of 'break' outsude the loop at %ld:%ld",
+                   node->token->filename, node->token->ln, node->token->cn);
+          return (fzl_walk_res_t){.error = true, .error_msg = wlast_err};
+        }
+
+        for (size_t i = walker->sym_top - 1; i > ctx->initial_env_lvl + 1; i--)
+          push_op(walker, FZL_OPCODE_RM_ENVTABLE);
+
+        if (ctx->breaks_remainder <= ctx->breaks_count)
+        {
+          ctx->breaks_remainder *= 2;
+          ctx->breaks =
+              realloc(ctx->breaks, ctx->breaks_remainder * sizeof(size_t));
+        }
+
+        push_op(walker, FZL_OPCODE_JMP);
+        ctx->breaks[ctx->breaks_count++] = walker->op_count;
+        push_word(walker, 0);
+
+        current_res = (fzl_walk_res_t){.type = FZL_TYPE_NULL, .error = false};
+        break;
+      }
+
+      // NOTE: add new levels for infinite loop check:
+      //  1. Step direction (f.e. `for (; i > 5; i = i - 1)`)
+      case FZL_NODETYPE_LOOP:
+      {
+        fzl_walk_ctx_t *newctx = nest_ctx(walker, FZL_WALK_CTX_TYPE_LOOP);
+        if (!newctx)
+        {
+          snprintf(wlast_err, sizeof(wlast_err), "failed to nest context");
+          return (fzl_walk_res_t){.error = true, .error_msg = wlast_err};
+        }
+
+        newctx->initial_env_lvl  = walker->sym_top - 1;
+        newctx->breaks_count     = 0;
+        newctx->breaks_remainder = 2;
+        newctx->breaks = malloc(newctx->breaks_remainder * sizeof(size_t));
+
+        push_op(walker, FZL_OPCODE_MK_ENVTABLE);
+        walker->syms[walker->sym_top++] = fzl_mksymt();
+        // size_t loop_begin_ip            = walker->op_count;
+
+        if (node->loop.init)
+        {
+          fzl_walk_res_t res = walk(walker, node->loop.init);
+          if (res.error)
+          {
+            free(newctx->breaks);
+            return res;
+          }
+        }
+
+        size_t start_ip = walker->op_count;
+        if (node->loop.cond)
+        {
+          fzl_walk_res_t res = walk(walker, node->loop.cond);
+          if (res.error)
+          {
+            free(newctx->breaks);
+            return res;
+          }
+        }
+        else
+        {
+          push_op(walker, FZL_OPCODE_PUSHNUM);
+          push_word(walker, 1);
+        }
+
+        push_op(walker, FZL_OPCODE_JZ);
+        newctx->breaks[newctx->breaks_count++] = walker->op_count;
+        push_word(walker, 0);
+
+        fzl_walk_res_t loop_body_res = walk(walker, node->loop.body);
+        if (loop_body_res.error)
+        {
+          free(newctx->breaks);
+          return loop_body_res;
+        }
+
+        if (node->loop.step)
+        {
+          fzl_walk_res_t res = walk(walker, node->loop.step);
+          if (res.error)
+          {
+            free(newctx->breaks);
+            return res;
+          }
+        }
+
+        push_op(walker, FZL_OPCODE_JMP);
+        push_word(walker, start_ip);
+
+        // backpatch `break`s
+        for (size_t i = 0; i < newctx->breaks_count; i++)
+          walker->ops[newctx->breaks[i]] = walker->op_count;
+
+        push_op(walker, FZL_OPCODE_RM_ENVTABLE);
+
+        // bool is_infinite =
+        //     is_infinite_loop(walker, node, loop_begin_ip, walker->op_count -
+        //     2);
+        // if (is_infinite)
+        // {
+        //   free(newctx->breaks);
+        //   snprintf(wlast_err, sizeof(wlast_err),
+        //            "'%s': infinite loop detected at %ld:%ld",
+        //            node->token->filename, node->token->ln, node->token->cn);
+        //   return (fzl_walk_res_t){.error = true, .error_msg = wlast_err};
+        // }
+
+        for (size_t i = walker->sym_top - 1; i > newctx->initial_env_lvl; i--)
+          fzl_freesymt(walker->syms[--walker->sym_top]);
+
+        free(newctx->breaks);
+        if (!fin_ctx(walker))
+        {
+          snprintf(wlast_err, sizeof(wlast_err),
+                   "failed to finish loop context");
+          return (fzl_walk_res_t){.error = true, .error_msg = wlast_err};
+        }
+
+        current_res = (fzl_walk_res_t){.type = FZL_TYPE_NULL, .error = false};
+        break;
+      }
+
       case FZL_NODETYPE_CLASS:
       {
         fzl_walk_ctx_t *newctx = nest_ctx(walker, FZL_WALK_CTX_TYPE_CLASS);
@@ -370,7 +513,7 @@ fzl_walk_res_t walk(fzl_walker_t *walker, fzl_node_t *node)
 
         fzl_type_t fntype = tok_to_type(node->fn.type);
         fzl_symtable_res_t putres =
-            fzl_symt_put(walker->syms[walker->sym_top - 1],
+            fzl_symt_put(walker->syms[walker->sym_top - 1], node,
                          node->fn.name->value, fntype, walker->op_count);
 
         if (putres != FZL_SYMTABLE_RESULT_OK)
@@ -461,7 +604,16 @@ fzl_walk_res_t walk(fzl_walker_t *walker, fzl_node_t *node)
 
       case FZL_NODETYPE_RETURN:
       {
-        if (!walker->ctx || walker->ctx->type != FZL_WALK_CTX_TYPE_FN)
+        fzl_walk_ctx_t *ctx = walker->ctx;
+        while (ctx)
+        {
+          if (ctx && ctx->type == FZL_WALK_CTX_TYPE_FN)
+            break;
+
+          ctx = ctx->parent;
+        }
+
+        if (!ctx || ctx->type != FZL_WALK_CTX_TYPE_FN)
         {
           snprintf(
               wlast_err, sizeof(wlast_err),
@@ -731,6 +883,7 @@ fzl_walk_res_t walk(fzl_walker_t *walker, fzl_node_t *node)
           }
         fzl_freesymt(walker->syms[--walker->sym_top]);
         push_op(walker, FZL_OPCODE_RM_ENVTABLE);
+        current_res = (fzl_walk_res_t){.type = FZL_TYPE_NULL, .error = false};
         break;
 
       case FZL_NODETYPE_CALL:
@@ -1045,7 +1198,7 @@ fzl_walk_res_t walk(fzl_walker_t *walker, fzl_node_t *node)
         }
 
         fzl_symtable_res_t res = fzl_symt_put(
-            walker->syms[walker->sym_top - 1],
+            walker->syms[walker->sym_top - 1], node,
             node->var.identifier->token->value,
             ct != NULL ? FZL_TYPE_OBJECT : tok_to_type(node->var.type), 0);
 
@@ -1056,9 +1209,19 @@ fzl_walk_res_t walk(fzl_walker_t *walker, fzl_node_t *node)
         if (res != FZL_SYMTABLE_RESULT_OK)
         {
           fzl_token_t *tok = node->var.identifier->token;
-          snprintf(wlast_err, sizeof(wlast_err),
+          if (res == FZL_SYMTABLE_RESULT_EXISTS)
-                   "'%s': cannot store '%s' at %ld:%ld", tok->filename,
+          {
-                   (char *)tok->value, tok->ln, tok->cn);
+            snprintf(wlast_err, sizeof(wlast_err),
+                     "'%s': cannot redefine '%s' at %ld:%ld", tok->filename,
+                     (char *)tok->value, tok->ln, tok->cn);
+          }
+          else
+          {
+            snprintf(wlast_err, sizeof(wlast_err),
+                     "'%s': cannot store '%s' at %ld:%ld", tok->filename,
+                     (char *)tok->value, tok->ln, tok->cn);
+          }
+
           return (fzl_walk_res_t){.error = true, .error_msg = wlast_err};
         }
 
@@ -1225,6 +1388,11 @@ int fzl_walk(fzl_walker_t *walker)
   push_op(walker, FZL_OPCODE_RM_ENVTABLE);
 
   fin_ctx(walker);
+  if (walker->ctx)
+  {
+    while (walker->ctx)
+      fin_ctx(walker);
+  }
 
   if (result.error && !wlast_err[0])
     snprintf(wlast_err, sizeof(wlast_err), "%s", result.error_msg);

src/compiler/main.c

@@ -1,4 +1,5 @@
 #include <common/fzl_colors.h>
+#include <compiler/fzl_analyzer.h>
 #include <compiler/fzl_debug.h>
 #include <compiler/fzl_parser.h>
 #include <compiler/fzl_reader.h>
@@ -96,11 +97,21 @@ int main(int argc, char **argv)
   }
 
   fzl_parser_t *parser = fzl_mkparser(rd->first);
-  result               = fzl_parse(parser);
+  if (!parser)
+  {
+    printf("%sError%s: failed to allocate writer\n", FZL_CERROR, FZL_CRST);
+    fzl_freeoptions(opts);
+    fzl_freereader(rd);
+    fzl_freelinked(linked);
+    return -1;
+  }
+
+  result = fzl_parse(parser);
   if (result != 0)
   {
     printf("%sError%s: %s\n", FZL_CERROR, FZL_CRST, fzl_parser_geterror());
     fzl_freeoptions(opts);
+    fzl_freeast(parser->root);
     fzl_freeparser(parser);
     fzl_freereader(rd);
     fzl_freelinked(linked);
@@ -112,16 +123,63 @@ int main(int argc, char **argv)
     printf("%sok%s!\n", FZL_COK, FZL_CRST);
     fzl_debug_print_ast(parser->root);
     printf("%s> building%s\n", FZL_CDEBUG, FZL_CRST);
-    printf("%s-> walking AST...%s\n", FZL_CDEBUG, FZL_CRST);
+    printf("%s-> analyzing AST...%s\n", FZL_CDEBUG, FZL_CRST);
+  }
+
+  fzl_analyzer_t *analyzer = fzl_mkanalyzer(parser->root);
+  if (!analyzer)
+  {
+    printf("%sError%s: failed to allocate analyzer\n", FZL_CERROR, FZL_CRST);
+    fzl_freeoptions(opts);
+    fzl_freeast(parser->root);
+    fzl_freeparser(parser);
+    fzl_freereader(rd);
+    fzl_freelinked(linked);
+  }
+
+  fzl_analyze(analyzer);
+  if (analyzer->errors_top > 0)
+  {
+    for (ssize_t i = analyzer->errors_top - 1; i >= 0; i--)
+      printf("%sError%s: %s\n", FZL_CERROR, FZL_CRST, analyzer->errors[i]);
+
+    fzl_freeoptions(opts);
+    fzl_freeanalyzer(analyzer);
+    fzl_freeast(parser->root);
+    fzl_freeparser(parser);
+    fzl_freereader(rd);
+    fzl_freelinked(linked);
+    return -1;
+  }
+
+  if (analyzer->warnings_top > 0)
+  {
+    for (ssize_t i = analyzer->warnings_top - 1; i >= 0; i--)
+      printf("%sWarning%s: %s\n", FZL_CWARNING, FZL_CRST,
+             analyzer->warnings[i]);
   }
 
   fzl_walker_t *walker = fzl_mkwalker(parser->root);
-  result               = fzl_walk(walker);
+  if (!walker)
+  {
+    printf("%sError%s: failed to allocate writer\n", FZL_CERROR, FZL_CRST);
+    fzl_freeoptions(opts);
+    fzl_freeast(parser->root);
+    fzl_freeanalyzer(analyzer);
+    fzl_freeparser(parser);
+    fzl_freereader(rd);
+    fzl_freelinked(linked);
+    return -1;
+  }
+
+  result = fzl_walk(walker);
   if (result != 0)
   {
     printf("%sError%s: %s\n", FZL_CERROR, FZL_CRST, fzl_walker_geterror());
     fzl_freeoptions(opts);
     fzl_freewalker(walker);
+    fzl_freeast(parser->root);
+    fzl_freeanalyzer(analyzer);
     fzl_freeparser(parser);
     fzl_freereader(rd);
     fzl_freelinked(linked);
@@ -162,13 +220,28 @@ int main(int argc, char **argv)
   }
 
   fzl_writer_t *writer = fzl_mkwriter(outpath);
-  result               = fzl_write(writer, walker);
+  if (!writer)
+  {
+    printf("%sError%s: failed to allocate writer\n", FZL_CERROR, FZL_CRST);
+    fzl_freeoptions(opts);
+    fzl_freewalker(walker);
+    fzl_freeast(parser->root);
+    fzl_freeanalyzer(analyzer);
+    fzl_freeparser(parser);
+    fzl_freereader(rd);
+    fzl_freelinked(linked);
+    return -1;
+  }
+
+  result = fzl_write(writer, walker);
   if (result != 0)
   {
     printf("%sError%s: %s\n", FZL_CERROR, FZL_CRST, fzl_writer_geterror());
     fzl_freeoptions(opts);
     fzl_freewriter(writer);
     fzl_freewalker(walker);
+    fzl_freeast(parser->root);
+    fzl_freeanalyzer(analyzer);
     fzl_freeparser(parser);
     fzl_freereader(rd);
     fzl_freelinked(linked);
@@ -182,6 +255,7 @@ int main(int argc, char **argv)
   fzl_freelinked(linked);
   fzl_freereader(rd);
   fzl_freeast(parser->root);
+  fzl_freeanalyzer(analyzer);
   fzl_freeparser(parser);
   fzl_freewalker(walker);
   fzl_freewriter(writer);

src/compiler/utils/fzl_linked.c

@@ -51,7 +51,7 @@ bool fzl_linked_add_files(fzl_linked_t *l, char **files, size_t files_count)
     rewind(fd);
 
     source = malloc(file_sz + 1);
-    fread(source, file_sz, 1, fd);
+    fread(source, file_sz, 1, fd); // NOTE: add red bytes check
     fclose(fd);
     source[file_sz] = 0;
 

src/compiler/utils/fzl_symtable.c

@@ -1,4 +1,5 @@
 #include <common/fzl_types.h>
+#include <compiler/fzl_parser.h>
 #include <compiler/utils/fzl_symtable.h>
 #include <stdbool.h>
 #include <stddef.h>
@@ -21,8 +22,8 @@ fzl_symtable_t *fzl_mksymt()
   return tbl;
 }
 
-fzl_symtable_res_t fzl_symt_put(fzl_symtable_t *symt, char *name,
+fzl_symtable_res_t fzl_symt_put(fzl_symtable_t *symt, fzl_node_t *node,
-                                fzl_type_t type, uint64_t ip)
+                                char *name, fzl_type_t type, uint64_t ip)
 {
   if (!symt)
     return FZL_SYMTABLE_RESULT_ERR;
@@ -37,8 +38,8 @@ fzl_symtable_res_t fzl_symt_put(fzl_symtable_t *symt, char *name,
     symt->symbols = realloc(symt->symbols, symt->remainder * sizeof(fzl_sym_t));
   }
 
-  symt->symbols[symt->size++] =
+  symt->symbols[symt->size++] = (fzl_sym_t){
-      (fzl_sym_t){.name = name, .type = type, .ip = ip, .classname = NULL};
+      .name = name, .node = node, .type = type, .ip = ip, .classname = NULL};
   return FZL_SYMTABLE_RESULT_OK;
 }
 

src/vm/fzl_vm.c

@@ -4,6 +4,7 @@
 #include <common/fzl_value.h>
 #include <compiler/utils/fzl_const_pool.h>
 #include <stdbool.h>
+#include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -13,6 +14,8 @@
 #include <vm/fzl_vm_object.h>
 
 char last_err[256];
+size_t last_jmp_ip       = 0;
+size_t total_jmp_on_same = 0;
 
 static char *expect_hdr = "FZL\0\1";
 
@@ -47,7 +50,8 @@ fzl_vm_t *fzl_mkvm(const char *filepath)
   }
 
   char hdr[5];
-  fread(hdr, sizeof(char), 5, fd);
+  fread(hdr, sizeof(char), 5,
+        fd); // NOTE: add red bytes check (also for freads below)
   if (memcmp(hdr, expect_hdr, 5) != 0)
   {
     snprintf(last_err, sizeof(last_err), "magic check error");
@@ -202,7 +206,7 @@ void print_object(fzl_vm_object_t *obj)
       printf("<unknown>");
   }
 
-  printf(">\n");
+  printf(">");
 }
 
 void print_err_data(fzl_vm_t *vm)
@@ -273,7 +277,7 @@ void print_err_data(fzl_vm_t *vm)
     printf("\t> [%zd] %lu\n", i, vm->cstack[i]);
 }
 
-int fzl_vm_run(fzl_vm_t *vm)
+int fzl_vm_run(fzl_vm_t *vm, bool allow_infinite, uint64_t max_iter)
 {
   if (!vm)
   {
@@ -427,8 +431,11 @@ int fzl_vm_run(fzl_vm_t *vm)
       {
         uint64_t values_count = vm->ops[++vm->ip];
         fzl_vm_object_t *obj  = malloc(sizeof(fzl_vm_object_t));
-        obj->values           = malloc(values_count * sizeof(fzl_value_t));
+
-        obj->values_count     = values_count;
+        if (values_count > 0)
+          obj->values = malloc(values_count * sizeof(fzl_value_t));
+        obj->values_count = values_count;
+        memset(obj->values, 0, values_count * sizeof(fzl_value_t));
 
         fzl_vm_env_t *current_env = vm->estack[vm->etop - 1];
         if (current_env->owned_objects_remainder <=
@@ -666,8 +673,28 @@ int fzl_vm_run(fzl_vm_t *vm)
                    "runtime error - expected JMP addr");
           return -1;
         }
+
         uint64_t jmp_ip = vm->ops[++vm->ip];
-        vm->ip          = jmp_ip - 1;
+        if (!allow_infinite)
+        {
+          if (jmp_ip == last_jmp_ip)
+            total_jmp_on_same++;
+          else
+            total_jmp_on_same = 0;
+
+          if (total_jmp_on_same > max_iter)
+          {
+            snprintf(
+                last_err, sizeof(last_err),
+                "runtime error - exceeded max loop jumps (infinite loop?)\n"
+                "If you thinks there's mistake, change jumps limit with "
+                "--max-iter=N");
+            return -1;
+          }
+        }
+
+        vm->ip      = jmp_ip - 1;
+        last_jmp_ip = jmp_ip;
         break;
       }
 
@@ -837,7 +864,10 @@ int fzl_vm_run(fzl_vm_t *vm)
           else if (arg.type == FZL_TYPE_NULL)
             printf("<null>\n");
           else if (arg.type == FZL_TYPE_OBJECT)
+          {
             print_object(arg.as.obj);
+            printf("\n");
+          }
         }
         else if (fn_id == FZL_BUILTIN_EXIT)
         {

src/vm/main.c

@@ -1,5 +1,7 @@
+#include <common/fzl_colors.h>
 #include <stdbool.h>
 #include <stddef.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -10,14 +12,18 @@ typedef struct
   char *filepath;
   bool help;
   bool debug;
+  bool allow_infinite;
+  uint64_t max_iter;
 } run_args_t;
 
 void print_hint()
 {
   printf("Usage: fz [flags] <file path>\n");
   printf("Flags:\n");
-  printf("\t-h\t--help\tprint usage information\n");
+  printf("\t-h\t--help\t\t\tprint usage information\n");
-  printf("\t-d\t--debug\tdisplay program opcodes\n");
+  printf("\t-d\t--debug\t\t\tdisplay program opcodes\n");
+  printf("\t\t--allow-infinite\tallow infinite loops\n");
+  printf("\t\t--max-iter N\t\trestrict loops to maximum N iterations\n");
 }
 
 // Parse passed arguments and build args setup structure
@@ -29,10 +35,12 @@ run_args_t *parse_args(int argc, char **argv)
     return NULL;
   }
 
-  run_args_t *args = malloc(sizeof(run_args_t));
+  run_args_t *args     = malloc(sizeof(run_args_t));
-  args->filepath   = NULL;
+  args->filepath       = NULL;
-  args->help       = false;
+  args->help           = false;
-  args->debug      = false;
+  args->debug          = false;
+  args->allow_infinite = false;
+  args->max_iter       = 100000;
 
   for (int i = 0; i < argc; i++)
   {
@@ -46,9 +54,33 @@ run_args_t *parse_args(int argc, char **argv)
     }
     else if (strcmp(argv[i], "-d") == 0 || strcmp(argv[i], "--debug") == 0)
       args->debug = true;
+    else if (strcmp(argv[i], "--allow-infinite") == 0)
+      args->allow_infinite = true;
+    else if (strcmp(argv[i], "--max-iter") == 0)
+    {
+      char *n = argv[++i];
+      if (!n || argc <= i || !(n[0] >= '0' && n[0] <= '9'))
+      {
+        printf("%sError%s: --max-iter options requires number after it\n",
+               FZL_CERROR, FZL_CRST);
+        free(args);
+        return NULL;
+      }
+
+      uint64_t iters = strtol(n, NULL, 10);
+      if (iters < 1)
+      {
+        printf("%sError%s: '--max-iter 0' is not allowed\n", FZL_CERROR,
+               FZL_CRST);
+        free(args);
+        return NULL;
+      }
+
+      args->max_iter = iters;
+    }
     else
     {
-      printf("Error: unknown flag '%s'.\n", argv[i]);
+      printf("%sError%s: unknown flag '%s'.\n", FZL_CERROR, FZL_CRST, argv[i]);
       printf("Use 'fz --help' to read the usage\n");
       free(args);
       return NULL;
@@ -57,7 +89,8 @@ run_args_t *parse_args(int argc, char **argv)
 
   if (argv[argc - 1][0] == '-')
   {
-    printf("Error: last argument MUST be a file path\n");
+    printf("%sError%s: last argument MUST be a file path\n", FZL_CERROR,
+           FZL_CRST);
     printf("Use 'fz --help' for help\n");
     free(args);
     return NULL;
@@ -83,7 +116,7 @@ int main(int argc, char **argv)
   fzl_vm_t *vm = fzl_mkvm(args->filepath);
   if (!vm)
   {
-    printf("Error: %s\n", fzl_vm_geterror());
+    printf("%sError%s: %s\n", FZL_CERROR, FZL_CRST, fzl_vm_geterror());
     free(args);
     return -1;
   }
@@ -92,12 +125,12 @@ int main(int argc, char **argv)
     fzl_vm_print_ops(vm);
   else
   {
-    int result = fzl_vm_run(vm);
+    int result = fzl_vm_run(vm, args->allow_infinite, args->max_iter);
     if (result != 0)
     {
       char *err = fzl_vm_geterror();
       if (err && err[0])
-        printf("Error: %s\n", err);
+        printf("%sError%s: %s\n", FZL_CERROR, FZL_CRST, err);
 
       free(args);
       fzl_freevm(vm);

tests/programs/neg_analyzer_continues_after_if_without_else.fzs

@@ -0,0 +1,9 @@
+fn choose(bool flag) int
+{
+  if (flag)
+    return 1;
+  return 0;
+}
+
+int invalid = "not an integer";
+exit(1);

tests/programs/neg_missing_operand.fzs

@@ -0,0 +1,2 @@
+printline(1 + );
+

tests/programs/neg_missing_semicolon.fzs

@@ -0,0 +1,3 @@
+int value = 42
+printline(value);
+

tests/programs/neg_unclosed_block.fzs

@@ -0,0 +1,4 @@
+if (true)
+{
+  printline("missing closing brace");
+

tests/programs/neg_unterminated_string.fzs

@@ -0,0 +1,2 @@
+printline("unterminated string);
+

tests/programs/negr_infinite_for.fzs

@@ -0,0 +1,3 @@
+for (int i = 0; i < 5; i = i + 0)
+{}
+

tests/programs/negr_infinite_while.fzs

@@ -0,0 +1,3 @@
+while (true)
+{}
+

tests/programs/pos_arithmetic.fzs

@@ -1,7 +1,7 @@
+// Arithmetic precedence and operators.
 printline(2 + 2 * 2);
 printline(-1 + 1);
 printline(2 ^ 2);
-printline(1 + 1 * 1 / 1);
 printline(4 % 2);
 printline(10 / 2);
 

tests/programs/pos_class.fzs

@@ -0,0 +1,25 @@
+class Point
+{
+  int x;
+  int y;
+
+  fn move(int dx, int dy)
+  {
+    this.x = this.x + dx;
+    this.y = this.y + dy;
+  }
+}
+
+Point point = new Point;
+point.x = 1;
+point.y = 2;
+point.move(9, 8);
+
+if (point.x == 10 && point.y == 10)
+  printline("class method passed");
+else
+{
+  printline("class method failed");
+  exit(1);
+}
+

tests/programs/pos_comments_strings.fzs

@@ -0,0 +1,5 @@
+// Line comments are ignored by the parser.
+printline('single-quoted string');;;;;
+printline("");
+printline("double-quoted string");
+

tests/programs/pos_conditions.fzs

@@ -0,0 +1,21 @@
+bool flag = true;
+
+if (!flag)
+{
+  printline("unexpected false");
+  exit(1);
+}
+else if (2 + 2 >= 4)
+{
+  printline("condition passed");
+}
+else
+{
+  printline("unexpected branch");
+  exit(1);
+}
+
+{
+  printline("standalone block");
+}
+

tests/programs/pos_function_external_call.fzs

@@ -0,0 +1,12 @@
+fn doSomeWork()
+{
+  printline("Some work");
+}
+
+fn sum(int a, int b) int
+{
+  return a + b;
+}
+
+int result = sum(5, 6);
+printline(result);

tests/programs/pos_functions.fzs

@@ -0,0 +1,21 @@
+fn fib(int n) int
+{
+  if (n <= 1)
+    return n;
+
+  return fib(n - 1) + fib(n - 2);
+}
+
+fn sum(uint a, uint b) uint
+{
+  return a + b;
+}
+
+if (fib(7) == 13 && sum(2, 2) == 4)
+  printline("functions passed");
+else
+{
+  printline("functions failed");
+  exit(1);
+}
+

tests/programs/pos_loop_with_break.fzs

@@ -0,0 +1,7 @@
+int i = 0;
+
+for (;;)
+{
+  break;
+}
+

tests/programs/pos_loops.fzs

@@ -0,0 +1,27 @@
+for (int i = 0; i < 10; i = i + 1)
+  printline("check");
+
+int i = 0;
+for (i = 0; i <= 5; i = i + 1)
+{
+  printline("i is:");
+  printline(i);
+}
+
+if (i < 5)
+{
+  printline("external declared `i` != 5");
+  exit(1);
+}
+
+while (i > 0)
+{
+  i = i - 1;
+}
+
+if (i > 0)
+{
+  printline("decreased in while loop `i` > 0");
+  exit(1);
+}
+

tests/programs/pos_method_call_via_field.fzs

@@ -0,0 +1,19 @@
+class Node
+{
+  Node next;
+
+  fn ping()
+  {
+    printline("ping");
+  }
+
+  fn pingNext()
+  {
+    this.next.ping();
+  }
+}
+
+Node head = new Node;
+Node tail = new Node;
+head.next = tail;
+head.pingNext();

tests/programs/pos_null.fzs

@@ -0,0 +1,23 @@
+class Item
+{
+  int value;
+}
+
+fn maybe_item(bool create) Item
+{
+  if (create)
+    return new Item;
+
+  return null;
+}
+
+Item empty = maybe_item(false);
+Item present = maybe_item(true);
+if (empty == null && present != null)
+  printline("null handling passed");
+else
+{
+  printline("null handling failed");
+  exit(1);
+}
+

tests/programs/pos_variables.fzs

@@ -1,13 +1,13 @@
 uint work_it = 21 * 2 ^ 2;
-int  make_it = 10;
+int make_it = 10;
-
+u64 do_it;
-u64  do_it;
 do_it = 15;
+char make_us;
+str floyd = "hello, Pink Floyd!";
+bool flag = true;
 
 printline(work_it);
 printline(make_it + do_it);
-
-char make_us;
-str floyd = "hello, Pink Floyd!";
 printline(floyd);
+printline(flag);
 

tests/programs/pos_while_not_null.fzs

@@ -0,0 +1,28 @@
+class Some {
+  Some next;
+}
+
+Some l4 = new Some;
+
+Some l3 = new Some;
+l3.next = l4;
+
+Some l2 = new Some;
+l2.next = l3;
+
+Some l1 = new Some;
+l1.next = l2;
+
+Some root = new Some;
+root.next = l1;
+
+Some obj = root;
+while (obj != null)
+{
+  obj = obj.next;
+  printline("Now object is:");
+  printline(obj);
+}
+
+printline(obj);
+