Commit 96e593145d

lars <lars.scheme@gmail.com>
2021-05-06 08:33:45
stage1: improve message for missing fn return type
Coming from other languages it might be tempting for programmers to accidentally leave out the return type instead of returning 'void'. The error for this used to be error: invalid token: '{' pub fn main() { ^ which is misleading. The '{' is expected but only after a return type. The new message is error: expected return type (use 'void' to return nothing), found: '{' pub fn main() { ^ which not only points out the real error but also hints at a (probably) very common case where someone coming from e.g. Go is used to not specifying a return type if a function returns nothing and thus forgets to put 'void' there. It might seem overkill to hint at the 'void' option but then the compiler error messages are our user interface to the programmer. We can be better than other languages in our error messages and leaving out the return type seems to be a rather clear indication of the above mentioned issue. Adding this will help more than distract.
master
1 parent 88d40fc
Changed files (1)
src
stage1
parser.cpp
src/stage1/parser.cpp
@@ -825,7 +825,16 @@ static AstNode *ast_parse_fn_proto(ParseContext *pc) {
     AstNode *return_type = nullptr;
     if (anytype == nullptr) {
         exmark = eat_token_if(pc, TokenIdBang);
-        return_type = ast_expect(pc, ast_parse_type_expr);
+        return_type = ast_parse_type_expr(pc);
+        if (return_type == nullptr) {
+            Token *next = peek_token(pc);
+            ast_error(
+                pc,
+                next,
+                "expected return type (use 'void' to return nothing), found: '%s'",
+                token_name(next->id)
+            );
+        }
     }
 
     AstNode *res = ast_create_node(pc, NodeTypeFnProto, first);