function pointer cast causes `token 'ARROW_RIGHT' != required ')' (`

[kevinw]

This line of code causes an error in my Jails logs:

fn := cast((*void, string) -> void) host_runtime_services.set_window_title;

The error:

token 'ARROW_RIGHT' != required ')' (some_file.jai:434:35)

[xThuby]

Looking at the code, this bug comes from the jai_parser module.
Can you provide repro steps?

[kevinw]

looking at the README for jai_parser I don't understand how to add a test there. I can open an issue there

[xThuby]

I meant, can you provide the minimal setup to reproduce this bug starting from an empty directory?

[kevinw]

In an empty directory:

1. Create main.jai:

main :: () {
    fn := cast((*void, string) -> void) main;
}

2. Create jails.json:

{
  "roots": [
    "main.jai"
  ]
}

3. Open in your IDE and see this in the Jails logs:

{
	"jsonrpc": "2.0",
	"method": "window/logMessage",
	"params": {
		"type": 1,
		"message": "token 'ARROW_RIGHT' != required ')' (/Users/kev/src/parser_bug/main.jai:1:31)"
	}
}

[xThuby]

Seems like the jai_parser is getting confused when parsing the cast, because of the extra parens in this case that usually would not be there.

Here's the stack trace when it hits the error, for future reference:

'eat_token' at Jails/modules/jai_parser/cmd/./src/../../../jai_parser/lexer.jai:292
'parse_cast' at Jails/modules/jai_parser/cmd/./src/../../../jai_parser/parser.jai:3593
'parse_node' at Jails/modules/jai_parser/cmd/./src/../../../jai_parser/parser.jai:1554
'parse' at Jails/modules/jai_parser/cmd/./src/../../../jai_parser/parser.jai:978
'parse_declaration_and_assign' at Jails/modules/jai_parser/cmd/./src/../../../jai_parser/parser.jai:1801
'parse_node' at Jails/modules/jai_parser/cmd/./src/../../../jai_parser/parser.jai:1423
'parse' at Jails/modules/jai_parser/cmd/./src/../../../jai_parser/parser.jai:978
'parse_file' at Jails/modules/jai_parser/cmd/./src/main.jai:119
'main' at Jails/modules/jai_parser/cmd/./src/main.jai:143
token 'ARROW_RIGHT' != required ')' (../tests/issue_jails_95.jai:0:27)

Temporary fix is to use the #type directive.

fn := cast(#type (*void, string) -> void) main;

Alternatively this might be a compiler bug, and you maybe shouldn't be allowed to cast without #type? I'm not sure, maybe go ask in the Discord too.