Fix for #29

5 files changed, 77 insertions, 14 deletions

diff --git a/src/ast/ast.h b/src/ast/ast.h
index 8c5bff4..1e14369 100644
--- a/src/ast/ast.h
+++ b/src/ast/ast.h
@@ -416,6 +416,8 @@ struct ASTNode
         struct
         {
             char *content;
+            char **used_symbols;
+            int used_symbol_count;
         } raw_stmt;
 
         struct
diff --git a/src/parser/parser.h b/src/parser/parser.h
index e3a5e6b..9cdd0d2 100644
--- a/src/parser/parser.h
+++ b/src/parser/parser.h
@@ -377,7 +377,7 @@ void init_builtins();
 
 // Expression rewriting
 char *rewrite_expr_methods(ParserContext *ctx, char *raw);
-char *process_fstring(ParserContext *ctx, const char *content);
+char *process_fstring(ParserContext *ctx, const char *content, char ***used_syms, int *count);
 char *instantiate_function_template(ParserContext *ctx, const char *name,
                                     const char *concrete_type);
 FuncSig *find_func(ParserContext *ctx, const char *name);
@@ -409,8 +409,8 @@ ASTNode *parse_guard(ParserContext *ctx, Lexer *l);
 ASTNode *parse_match(ParserContext *ctx, Lexer *l);
 ASTNode *parse_return(ParserContext *ctx, Lexer *l);
 
-char *process_printf_sugar(ParserContext *ctx, const char *content, int newline,
-                           const char *target);
+char *process_printf_sugar(ParserContext *ctx, const char *content, int newline, const char *target,
+                           char ***used_syms, int *count);
 ASTNode *parse_assert(ParserContext *ctx, Lexer *l);
 ASTNode *parse_defer(ParserContext *ctx, Lexer *l);
 ASTNode *parse_asm(ParserContext *ctx, Lexer *l);
diff --git a/src/parser/parser_expr.c b/src/parser/parser_expr.c
index f7af80f..9861de6 100644
--- a/src/parser/parser_expr.c
+++ b/src/parser/parser_expr.c
@@ -2240,7 +2240,7 @@ ASTNode *parse_expr_prec(ParserContext *ctx, Lexer *l, Precedence min_prec)
             }
 
             // Reuse printf sugar to generate the prompt print
-            char *print_code = process_printf_sugar(ctx, inner, 0, "stdout");
+            char *print_code = process_printf_sugar(ctx, inner, 0, "stdout", NULL, NULL);
             free(inner);
 
             // Checks for (args...) suffix for SCAN mode
@@ -2405,7 +2405,7 @@ ASTNode *parse_expr_prec(ParserContext *ctx, Lexer *l, Precedence min_prec)
                 newline = 0;
             }
 
-            char *code = process_printf_sugar(ctx, inner, newline, "stderr");
+            char *code = process_printf_sugar(ctx, inner, newline, "stderr", NULL, NULL);
             free(inner);
 
             ASTNode *n = ast_create(NODE_RAW_STMT);
diff --git a/src/parser/parser_stmt.c b/src/parser/parser_stmt.c
index 4478d22..484d742 100644
--- a/src/parser/parser_stmt.c
+++ b/src/parser/parser_stmt.c
@@ -1673,7 +1673,8 @@ ASTNode *parse_for(ParserContext *ctx, Lexer *l)
     return n;
 }
 
-char *process_printf_sugar(ParserContext *ctx, const char *content, int newline, const char *target)
+char *process_printf_sugar(ParserContext *ctx, const char *content, int newline, const char *target,
+                           char ***used_syms, int *count)
 {
     char *gen = xmalloc(8192);
     strcpy(gen, "({ ");
@@ -1765,12 +1766,34 @@ char *process_printf_sugar(ParserContext *ctx, const char *content, int newline,
             clean_expr++; // Skip leading spaces
         }
 
-        // Mark the variable as used (fixes "Unused variable" warnings for f-string
-        // interpolation)
-        Symbol *sym = find_symbol_entry(ctx, clean_expr);
-        if (sym)
+        // Analyze usage
         {
-            sym->is_used = 1;
+            Lexer lex;
+            lexer_init(&lex, clean_expr);
+            Token t;
+            while ((t = lexer_next(&lex)).type != TOK_EOF)
+            {
+                if (t.type == TOK_IDENT)
+                {
+                    char *name = token_strdup(t);
+                    Symbol *sym = find_symbol_entry(ctx, name);
+                    if (sym)
+                    {
+                        sym->is_used = 1;
+                    }
+
+                    if (used_syms && count)
+                    {
+                        *used_syms = xrealloc(*used_syms, sizeof(char *) * (*count + 1));
+                        (*used_syms)[*count] = name;
+                        (*count)++;
+                    }
+                    else
+                    {
+                        free(name);
+                    }
+                }
+            }
         }
 
         char *type = find_symbol_type(ctx, clean_expr);
@@ -2097,7 +2120,9 @@ ASTNode *parse_statement(ParserContext *ctx, Lexer *l)
 
             // ; means println (end of line), .. means print (continuation)
             int is_ln = (next_type == TOK_SEMICOLON);
-            char *code = process_printf_sugar(ctx, inner, is_ln, "stdout");
+            char **used_syms = NULL;
+            int used_count = 0;
+            char *code = process_printf_sugar(ctx, inner, is_ln, "stdout", &used_syms, &used_count);
 
             if (next_type == TOK_SEMICOLON)
             {
@@ -2114,6 +2139,8 @@ ASTNode *parse_statement(ParserContext *ctx, Lexer *l)
 
             ASTNode *n = ast_create(NODE_RAW_STMT);
             n->raw_stmt.content = code;
+            n->raw_stmt.used_symbols = used_syms;
+            n->raw_stmt.used_symbol_count = used_count;
             free(inner);
             return n;
         }
@@ -2506,7 +2533,9 @@ ASTNode *parse_statement(ParserContext *ctx, Lexer *l)
                 inner[t.len - 2] = 0;
             }
 
-            char *code = process_printf_sugar(ctx, inner, is_ln, target);
+            char **used_syms = NULL;
+            int used_count = 0;
+            char *code = process_printf_sugar(ctx, inner, is_ln, target, &used_syms, &used_count);
             free(inner);
 
             if (lexer_peek(l).type == TOK_SEMICOLON)
@@ -2516,6 +2545,8 @@ ASTNode *parse_statement(ParserContext *ctx, Lexer *l)
 
             ASTNode *n = ast_create(NODE_RAW_STMT);
             n->raw_stmt.content = code;
+            n->raw_stmt.used_symbols = used_syms;
+            n->raw_stmt.used_symbol_count = used_count;
             return n;
         }
     }
diff --git a/src/parser/parser_utils.c b/src/parser/parser_utils.c
index 7733ef7..ba506a0 100644
--- a/src/parser/parser_utils.c
+++ b/src/parser/parser_utils.c
@@ -1554,7 +1554,7 @@ char *instantiate_function_template(ParserContext *ctx, const char *name, const
     return mangled;
 }
 
-char *process_fstring(ParserContext *ctx, const char *content)
+char *process_fstring(ParserContext *ctx, const char *content, char ***used_syms, int *count)
 {
     (void)ctx; // suppress unused parameter warning
     char *gen = xmalloc(4096);
@@ -1621,6 +1621,36 @@ char *process_fstring(ParserContext *ctx, const char *content)
             fmt = colon + 1;
         }
 
+        // Analyze usage in expression
+        {
+            Lexer lex;
+            lexer_init(&lex, expr);
+            Token t;
+            while ((t = lexer_next(&lex)).type != TOK_EOF)
+            {
+                if (t.type == TOK_IDENT)
+                {
+                    char *name = token_strdup(t);
+                    Symbol *sym = find_symbol_entry(ctx, name);
+                    if (sym)
+                    {
+                        sym->is_used = 1;
+                    }
+
+                    if (used_syms && count)
+                    {
+                        *used_syms = xrealloc(*used_syms, sizeof(char *) * (*count + 1));
+                        (*used_syms)[*count] = name;
+                        (*count)++;
+                    }
+                    else
+                    {
+                        free(name);
+                    }
+                }
+            }
+        }
+
         if (fmt)
         {
             strcat(gen, "sprintf(_t, \"%");