TOML encoding C compilation error

[stilvoid]

V version: V 0.4.10, press to see full `v doctor` output

V full version	V 0.4.10 9b1937a.
OS	macos, macOS, 15.4.1, 24E263
Processor	8 cpus, 64bit, little endian, Apple M1 Pro
Memory	0.24GB/16GB
V executable	/opt/homebrew/Cellar/vlang/0.4.10/libexec/v
V last modified time	2025-03-20 11:42:00
V home dir	OK, value: /opt/homebrew/Cellar/vlang/0.4.10/libexec
VMODULES	OK, value: /Users/steve/.vmodules
VTMP	OK, value: /tmp/v_501
Current working dir	OK, value: /Users/steve/code/github.com/stilvoid/bleng
Git version	git version 2.39.5 (Apple Git-154)
V git status	4.5.1 (64816 commit(s) behind V master)
.git/config present	false
cc version	Apple clang version 17.0.0 (clang-1700.0.13.3)
gcc version	Apple clang version 17.0.0 (clang-1700.0.13.3)
clang version	Apple clang version 17.0.0 (clang-1700.0.13.3)
tcc version	N/A
tcc git status	N/A
emcc version	N/A
glibc version	N/A

What did you do?
./v -g -o vdbg cmd/v && ./vdbg toml_bug.v && toml_bug

module main

import toml

fn main() {
    // Create a TOML document
    mut doc := map[string]toml.Any{}
    doc['key'] = toml.Any('value')
    
    // Try to encode it - this is where the bug occurs
    toml_content := toml.encode(doc)
    
    println(toml_content)
}

What did you see?

================== C compilation error (from cc): ==============
cc: /tmp/v_501/toml_bug.01JTRA3CD8YK3RM5YZNS5PM84Q.tmp.c:12313:12: error: unexpected type name 'map': expected expression
cc:  12313 |                                 return map[string]toml__Any_to_toml(typ);
cc:        |                                        ^
cc: /tmp/v_501/toml_bug.01JTRA3CD8YK3RM5YZNS5PM84Q.tmp.c:12313:16: error: unexpected type name 'string': expected expression
cc:  12313 |                                 return map[string]toml__Any_to_toml(typ);
cc:        |                                            ^
cc: /tmp/v_501/toml_bug.01JTRA3CD8YK3RM5YZNS5PM84Q.tmp.c:12313:23: error: expected ';' after return statement
cc:  12313 |                                 return map[string]toml__Any_to_toml(typ);
cc:        |                                                   ^
cc:        |                                                   ;
cc: 3 errors generated.
================================================================
(You can pass `-cg`, or `-show-c-output` as well, to print all the C error messages).
builder error: 
==================
C error found. It should never happen, when compiling pure V code.
This is a V compiler bug, please report it using `v bug file.v`,
or goto https://github.com/vlang/v/issues/new/choose .
You can also use #help on Discord: https://discord.gg/vlang .

What did you expect to see?

Correctly encoded toml or a V error, not a C compilation error.

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[huly-for-github]

Connected to Huly®: V_0.6-22806

[larpon]

I've opened #24443 to fix it in the toml module, but I think the C error should still be fixed some how.

The following MRE (not importing toml) have the same compile error on my machine:

module main

type Any = string | int

fn (a Any) to_toml() string {
	return match a {
		string {
			'TOML string'
		}
		int {
			'TOML int'
		}
	}
}

fn (m map[string]Any) to_toml() string {
	mut t := ''
	for _, v in m {
		t += v.to_toml() + ','
	}
	return t
}

fn main() {
	mut doc := map[string]Any{}
	doc['key'] = Any('value')

	// Try to encode it - this is where the bug occurs
	toml_content := encode(doc)

	println(toml_content)
}

fn encode[T](typ T) string {
	$for method in T.methods {
		$if method.name == 'to_toml' {
			return typ.$method()
		}
	}
	mp := encode_struct[T](typ)
	return mp.to_toml()
}

fn encode_struct[T](typ T) map[string]Any {
	mut mp := map[string]Any{}
	$for field in T.fields {
		mut skip := false
		mut field_name := field.name
		for attr in field.attrs {
			if attr == 'skip' {
				skip = true
				break
			}
			if attr.starts_with('toml:') {
				field_name = attr.all_after(':').trim_space()
			}
		}
		if !skip {
			mp[field_name] = to_any(typ.$(field.name))
		}
	}
	return mp
}