From 96e593145dcdb53ca02f2a365abc68415c4302b6 Mon Sep 17 00:00:00 2001 From: lars Date: Thu, 6 May 2021 08:33:45 +0200 Subject: [PATCH] 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. --- src/stage1/parser.cpp | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/src/stage1/parser.cpp b/src/stage1/parser.cpp index d57277cd5136a8f3e2c5472ff90d5ce286996913..f152f245b75659c4599b70887db64d1655199e87 100644 --- a/src/stage1/parser.cpp +++ b/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); -- 2.54.0