parser: Refactor return statement to return an ast_node

During the refactoring process, I identified a memory leak where the
return argument was allocated but not freed in case of an error.

It also introduces the concept of keyword tokens. Where return is now a
keyword simplifying the parser.

Signed-off-by: Carlos Maniero <carlos@maniero.me>

1 files changed, 14 insertions, 2 deletions

diff --git a/src/lexer.c b/src/lexer.c
index b60fbb5..9f2a57b 100644
--- a/src/lexer.c
+++ b/src/lexer.c
@@ -85,6 +85,7 @@ lexer_tokenize_name(lexer_t *lexer, token_t *token)
   while (lexer_is_not_eof(lexer) && isalnum(lexer_current_char(lexer))) {
     lexer_drop_char(lexer);
   }
+
   token->kind = TOKEN_NAME;
   token->value = string_view_new(lexer->src + begin, lexer->cur - begin);
   token->filepath = lexer->filepath;
@@ -93,6 +94,15 @@ lexer_tokenize_name(lexer_t *lexer, token_t *token)
   token->bol = lexer->bol;
 }
 
+static void
+lexer_token_process_keyword(token_t *token)
+{
+  if (string_view_eq(string_view_from_str("return"), token->value)) {
+    token->kind = TOKEN_KEYWORD_RETURN;
+    return;
+  }
+}
+
 void
 lexer_next_token(lexer_t *lexer, token_t *token)
 {
@@ -111,6 +121,7 @@ lexer_next_token(lexer_t *lexer, token_t *token)
 
   if (isalpha(lexer_current_char(lexer))) {
     lexer_tokenize_name(lexer, token);
+    lexer_token_process_keyword(token);
     return;
   }
 
@@ -292,11 +303,12 @@ token_kind_to_str(token_kind_t kind)
       return "/";
     case TOKEN_EQUAL:
       return "=";
+    case TOKEN_KEYWORD_RETURN:
+      return "return";
     case TOKEN_EOF:
       return "TOKEN_EOF";
     case TOKEN_UNKNOWN:
       return "TOKEN_UNKNOWN";
-    default:
-      assert(false && "unreachable");
   }
+  assert(false && "unreachable");
 }