include/compiler/fzl_analyzer.h

@@ -31,6 +31,11 @@ typedef struct fzl_an_ctx
   struct fzl_an_ctx *parent;
 
   fzl_an_ctx_type_t type;
+
+  union
+  {
+    fzl_node_t *fn;
+  };
 } fzl_an_ctx_t;
 
 // Analyzer descriptor
@@ -73,6 +78,7 @@ 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_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);

src/compiler/analyzer/an_block.c

@@ -1,11 +1,16 @@
 #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>
 
 char block_problem[256];
 
+// defined in `compiler/analyzer/utility.c`
+extern fzl_type_t an_toktotype(fzl_token_t *tok);
+extern char *an_typetostr(fzl_type_t type, char *classname);
+
 // Analyze block
 fzl_an_res_t analyze_block(fzl_analyzer_t *analyzer, fzl_node_t *block_node)
 {
@@ -38,6 +43,48 @@ fzl_an_res_t analyze_block(fzl_analyzer_t *analyzer, fzl_node_t *block_node)
       has_return = true;
   }
 
+  fzl_an_ctx_t *fnctx = analyzer->ctx;
+  while (fnctx != NULL)
+  {
+    if (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(block_problem, sizeof(block_problem),
+                 "expected 'return <%s>' in function because return type is %s",
+                 rettype_str, rettype_str);
+        an_push_error(analyzer, block_node->token, block_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)
+      {
+        snprintf(block_problem, sizeof(block_problem),
+                 "expected last statement in block to be 'return <%s>'",
+                 rettype_str);
+        an_push_error(analyzer, last_node->token, block_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_common.c

@@ -11,6 +11,10 @@ fzl_an_res_t analyze_common(fzl_analyzer_t *analyzer, fzl_node_t *node)
   fzl_an_res_t res = {.error = false, .type = FZL_TYPE_NULL, .classname = NULL};
   switch (node->type)
   {
+    case FZL_NODETYPE_RETURN:
+      res = analyze_return(analyzer, node);
+      break;
+
     case FZL_NODETYPE_FUNCTION:
       res = analyze_function(analyzer, node);
       break;

src/compiler/analyzer/an_return.c

@@ -0,0 +1,70 @@
+#include "common/fzl_types.h"
+#include <compiler/fzl_analyzer.h>
+#include <compiler/fzl_parser.h>
+#include <compiler/fzl_token.h>
+#include <stdio.h>
+
+char ret_problem[256];
+
+// defined in `compiler/analyzer/utility.c`
+extern bool an_is_compatible(fzl_type_t a, fzl_type_t b, char *ac, char *bc);
+extern fzl_type_t an_toktotype(fzl_token_t *tok);
+extern char *an_typetostr(fzl_type_t type, char *classname);
+
+// 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 typeof RETURN");
+    return (fzl_an_res_t){.error = false};
+  }
+
+  fzl_an_ctx_t *fnctx = analyzer->ctx;
+  while (!fnctx)
+  {
+    if (fnctx->type == FZL_AN_CTX_TYPE_FUNCTION)
+      break;
+
+    fnctx = fnctx->parent;
+  }
+
+  if (!fnctx)
+  {
+    an_push_error(analyzer, ret_node->token,
+                  "cannot use 'return' outside 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)
+    {
+      an_push_error(analyzer, ret_node->token,
+                    "return must be used with value in this function");
+      return (fzl_an_res_t){.error = true};
+    }
+
+    fzl_an_res_t ret_res = analyze_common(analyzer, ret_node->ret.value);
+    if (!an_is_compatible(ret_res.type, rettype, ret_res.classname, classname))
+    {
+      snprintf(ret_problem, sizeof(ret_problem),
+               "expected 'return <%s>' instead of 'return <%s>'", rettype_str,
+               an_typetostr(ret_res.type, ret_res.classname));
+      an_push_error(analyzer, ret_node->token, ret_problem);
+      return (fzl_an_res_t){.error = true};
+    }
+  }
+
+  return (fzl_an_res_t){
+      .error = false, .type = rettype, .classname = classname};
+}