From eeb15be84dce08ae731bbd2ec906ce99f8c246a8 Mon Sep 17 00:00:00 2001
From: Leonardo Araujo <leonardo.aa88@gmail.com>
Date: Sun, 5 Jan 2025 04:09:16 -0300
Subject: [PATCH] feat: enhanced error messages for undeclared identifiers

---
 ast.c  | 57 ++++++++++++++++++++++++++++++++++++++++++++++-----------
 ast.h  |  3 +++
 lang.y |  4 +++-
 3 files changed, 52 insertions(+), 12 deletions(-)

diff --git a/ast.c b/ast.c
index 061cb3f..510dc4c 100644
--- a/ast.c
+++ b/ast.c
@@ -108,6 +108,45 @@ TypeModifiers get_current_modifiers(void)
     return mods;
 }
 
+/* Include the symbol table functions */
+extern bool set_variable(char *name, int value, TypeModifiers mod);
+extern int get_variable(char *name);
+extern void yyerror(const char *s);
+extern void yapping(const char *format, ...);
+extern void yappin(const char *format, ...);
+extern void baka(const char *format, ...);
+extern TypeModifiers get_variable_modifiers(const char *name);
+extern int yylineno;
+
+/* Function implementations */
+
+bool check_and_mark_identifier(ASTNode *node, const char *contextErrorMessage)
+{
+    if (!node->alreadyChecked)
+    {
+        node->alreadyChecked = true;
+        node->isValidSymbol = false;
+
+        // Do the table lookup
+        for (int i = 0; i < var_count; i++)
+        {
+            if (strcmp(symbol_table[i].name, node->data.name) == 0)
+            {
+                node->isValidSymbol = true;
+                break;
+            }
+        }
+
+        if (!node->isValidSymbol)
+        {
+            yylineno = yylineno - 2;
+            yyerror(contextErrorMessage);
+        }
+    }
+
+    return node->isValidSymbol;
+}
+
 void execute_switch_statement(ASTNode *node)
 {
     int switch_value = evaluate_expression(node->data.switch_stmt.expression);
@@ -145,17 +184,6 @@ void execute_switch_statement(ASTNode *node)
     }
 }
 
-/* Include the symbol table functions */
-extern bool set_variable(char *name, int value, TypeModifiers mod);
-extern int get_variable(char *name);
-extern void yyerror(const char *s);
-extern void yapping(const char *format, ...);
-extern void yappin(const char *format, ...);
-extern void baka(const char *format, ...);
-extern TypeModifiers get_variable_modifiers(const char *name);
-
-/* Function implementations */
-
 ASTNode *create_int_node(int value)
 {
     ASTNode *node = malloc(sizeof(ASTNode));
@@ -436,6 +464,9 @@ int evaluate_expression_int(ASTNode *node)
     }
     case NODE_IDENTIFIER:
     {
+        if (!check_and_mark_identifier(node, "Undefined variable"))
+            exit(1);
+
         char *name = node->data.name;
         for (int i = 0; i < var_count; i++)
         {
@@ -728,6 +759,8 @@ bool is_float_expression(ASTNode *node)
         return false;
     case NODE_IDENTIFIER:
     {
+        if (!check_and_mark_identifier(node, "Undefined variable in type check"))
+            exit(1);
         for (int i = 0; i < var_count; i++)
         {
             if (strcmp(symbol_table[i].name, node->data.name) == 0)
@@ -764,6 +797,8 @@ bool is_double_expression(ASTNode *node)
         return false;
     case NODE_IDENTIFIER:
     {
+        if (!check_and_mark_identifier(node, "Undefined variable in type check"))
+            exit(1);
         for (int i = 0; i < var_count; i++)
         {
             if (strcmp(symbol_table[i].name, node->data.name) == 0)
diff --git a/ast.h b/ast.h
index b17c106..709a586 100644
--- a/ast.h
+++ b/ast.h
@@ -119,6 +119,8 @@ struct ASTNode
 {
     NodeType type;
     TypeModifiers modifiers;
+    bool alreadyChecked;
+    bool isValidSymbol;
     union
     {
         int ivalue;
@@ -220,6 +222,7 @@ void execute_yappin_call(ArgumentList *args);
 void execute_baka_call(ArgumentList *args);
 void free_ast(ASTNode *node);
 void reset_modifiers(void);
+bool check_and_mark_identifier(ASTNode *node, const char *contextErrorMessage);
 
 extern TypeModifiers current_modifiers;
 
diff --git a/lang.y b/lang.y
index ca59bf1..7c0035a 100644
--- a/lang.y
+++ b/lang.y
@@ -1,3 +1,4 @@
+%define parse.error verbose
 %{
 #include "ast.h"
 #include <stdio.h>
@@ -381,7 +382,8 @@ int main(void) {
 }
 
 void yyerror(const char *s) {
-    fprintf(stderr, "Error: %s at line %d\n", s, yylineno);
+    extern char *yytext;
+    fprintf(stderr, "Error: %s at line %d\n", s, yylineno - 1);
 }
 
 void yapping(const char* format, ...) {