`$match` assignment will crash compiler

[kbkpbot]

Describe the bug

Assignment with $match will cause compiler panic.

Reproduction Steps

match.v

module main

import strconv

fn ret[T](str string) !T {
        val := $match T.unaliased_typ {
                i8 { strconv.atoi8(str)! }
                i16 { strconv.atoi16(str)! }
                i32 { strconv.atoi32(str)! }
                i64 { strconv.atoi64(str)! }
                u8 { strconv.atou8(str)! }
                u16 { strconv.atou16(str)! }
                u32 { strconv.atou32(str)! }
                u64 { strconv.atou64(str)! }
                int { strconv.atoi(str)! }
                $float { T(strconv.atof_quick(str)) }
                $else { return error('`decode_number` can not decode ${T.name} type') }
        }
        return val
}

fn main() {
        x := ret[f32]('1.0')!
        dump(x)
}

v match.v

Expected Behavior

compile ok or report error/warnings

Current Behavior

$ v match.v
V panic: table.sym: invalid type (typ=ast.Type(0x0 = 0) idx=0). Compiler bug. This should never happen. Please report the bug using `v bug file.v`.

 v hash: fd31771
    pid: 0x3ce22
    tid: 0x3ce22
/tmp/v_1000/v2.tmp.c:21745: at builtin___v_panic: Backtrace
/tmp/v_1000/v2.tmp.c:37908: by v__ast__default_table_panic_handler
/tmp/v_1000/v2.tmp.c:37914: by v__ast__Table_panic
/tmp/v_1000/v2.tmp.c:38616: by v__ast__Table_sym
/tmp/v_1000/v2.tmp.c:5954: by v__checker__Checker_match_expr
/tmp/v_1000/v2.tmp.c:56723: by v__checker__Checker_expr
/tmp/v_1000/v2.tmp.c:50308: by v__checker__Checker_assign_stmt
/tmp/v_1000/v2.tmp.c:55442: by v__checker__Checker_stmt
/tmp/v_1000/v2.tmp.c:56078: by v__checker__Checker_stmts_ending_with_expression
/tmp/v_1000/v2.tmp.c:56055: by v__checker__Checker_stmts
/tmp/v_1000/v2.tmp.c:64893: by v__checker__Checker_fn_decl
/tmp/v_1000/v2.tmp.c:1761: by v__checker__Checker_post_process_generic_fns
/tmp/v_1000/v2.tmp.c:53491: by v__checker__Checker_check_files
/tmp/v_1000/v2.tmp.c:56777: by v__builder__Builder_middle_stages
/tmp/v_1000/v2.tmp.c:56818: by v__builder__Builder_front_and_middle_stages
/tmp/v_1000/v2.tmp.c:59342: by v__builder__cbuilder__gen_c
/tmp/v_1000/v2.tmp.c:59314: by v__builder__cbuilder__build_c
/tmp/v_1000/v2.tmp.c:59305: by v__builder__cbuilder__compile_c
/tmp/v_1000/v2.tmp.c:59222: by v__builder__Builder_rebuild
/tmp/v_1000/v2.tmp.c:58368: by v__builder__compile
/tmp/v_1000/v2.tmp.c:59734: by main__rebuild
/tmp/v_1000/v2.tmp.c:59686: by main__main
/tmp/v_1000/v2.tmp.c:60702: by main

Possible Solution

fix checker

Additional Information/Context

No response

V version

V 0.4.12 1cdb0f5.fd31771

Environment details (OS name and version, etc.)

V full version	V 0.4.12 1cdb0f5.fd31771
OS	linux, Ubuntu 24.04.3 LTS
Processor	8 cpus, 64bit, little endian, Intel(R) Core(TM) i7-9700 CPU @ 3.00GHz
Memory	9.9GB/15.51GB
V executable	/media/HD/github/kbkpbot/v/v
V last modified time	2025-12-20 13:56:50
V home dir	OK, value: /media/HD/github/kbkpbot/v
VMODULES	OK, value: /home/mars/.vmodules
VTMP	OK, value: /tmp/v_1000
Current working dir	OK, value: /home/mars/v/bug/json
Git version	git version 2.43.0
V git status	weekly.2025.46-243-gfd317711-dirty
.git/config present	true
cc version	cc (Ubuntu 13.3.0-6ubuntu2~24.04) 13.3.0
gcc version	gcc (Ubuntu 13.3.0-6ubuntu2~24.04) 13.3.0
clang version	Ubuntu clang version 18.1.3 (1ubuntu1)
tcc version	tcc version 0.9.28rc 2025-02-13 HEAD@f8bd136d (x86_64 Linux)
tcc git status	thirdparty-linux-amd64 696c1d84
emcc version	N/A
glibc version	ldd (Ubuntu GLIBC 2.39-0ubuntu8.6) 2.39

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[kbkpbot]

match assignment need type in every branches are same type. But this is not true for $match assignment.

[Delta456]

I will take this up. Thanks @kbkpbot for pointing!

[Delta456]

match assignment need type in every branches are same type. But this is not true for $match assignment.

Does this need to work or it needs to a checker error?

[Delta456]

I don't have the time to work on this issue. I hope someone else can pick this up :)

[JalonSolov]

To be consistent, match and $match should have the same constraints (as much as possible), so yes, it should be a checker error unless all branches are the same type.

[Delta456]

As per my investigation, node.is_expr is false when it should be true

Same as @dy-tea reported in #26061 (comment)

[dy-tea]

I was trying to trace where node.is_expr was supposed to be set to true but couldn't figure it out :/
Maybe someone other than me has an idea.

[dy-tea]

I have a partial fix for this and full fix for the $if issue on the way, looking if I can fully fix this one too.