Undefined ident: b when using mut b := '' after cond := node in [aa.S1, aa.S2]

[yuyi98]

Describe the bug

Undefined ident: b when using mut b := '' after cond := node in [aa.S1, aa.S2]

This is a reproducible example, what actually went wrong was assign_stmt() in gen/c/assign.v.

	mut af := g.is_autofree && !g.is_builtin_mod && node.op == .assign && node.left_types.len == 1
		&& (node.left[0] is ast.Ident || node.left[0] is ast.SelectorExpr)
	// node.left_types[0] in [ast.string_type, ast.array_type] &&
	mut sref_name := ''
	mut type_to_free := ''

If using node.left[0] in [ast.Ident, ast.SelectorExpr] instead of (node.left[0] is ast.Ident || node.left[0] is ast.SelectorExpr)

	mut af := g.is_autofree && !g.is_builtin_mod && node.op == .assign && node.left_types.len == 1
		&& node.left[0] in [ast.Ident, ast.SelectorExpr]
	// node.left_types[0] in [ast.string_type, ast.array_type] &&
	mut sref_name := ''
	mut type_to_free := ''

This will result in a compilation error.

Reproduction Steps

aa/aa.v

module aa

pub type MySumType = S1 | S2

pub struct S1 {}

pub struct S2 {}

tt1.v

import aa

fn main() {
	node := aa.MySumType(aa.S1{})

	cond := node in [aa.S1, aa.S2]
	mut b := 'b'
	mut c := 'c'

	if cond {
		println('${cond} --- ${b} ---- ${c}')
	}
}

Expected Behavior

output:

true --- b ---- c

Current Behavior

PS D:\Test\v\tt1> v run .
tt1.v:7:6: warning: unused variable: `aa.b`
    5 |
    6 |     cond := node in [aa.S1, aa.S2]
    7 |     mut b := 'b'
      |         ^
    8 |     mut c := 'c'
    9 |
tt1.v:8:6: warning: unused variable: `aa.c`
    6 |     cond := node in [aa.S1, aa.S2]
    7 |     mut b := 'b'
    8 |     mut c := 'c'
      |         ^
    9 |
   10 |     if cond {
tt1.v:11:26: error: undefined ident: `b`
    9 |
   10 |     if cond {
   11 |         println('${cond} --- ${b} ---- ${c}')
      |                                ^
   12 |     }
   13 | }

Possible Solution

No response

Additional Information/Context

No response

V version

V 0.4.1 ed42341

Environment details (OS name and version, etc.)

V full version: V 0.4.1 ed42341
OS: windows, Microsoft Windows 11 Home China v22621 64-bit
Processor: 16 cpus, 64bit, little endian,

getwd: D:\Vlang\v
vexe: D:\Vlang\v\v.exe
vexe mtime: 2023-09-22 13:09:55

vroot: OK, value: D:\Vlang\v
VMODULES: OK, value: C:\Users\yuyi9.vmodules
VTMP: OK, value: C:\Users\yuyi9\AppData\Local\Temp\v_0

Git version: git version 2.37.3.windows.1
Git vroot status: weekly.2023.38-22-ged423416
.git/config present: true

CC version: Error: 'cc' is not recognized as an internal or external command,
operable program or batch file.

thirdparty/tcc status: thirdparty-windows-amd64 e90c2620

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