cgen: invalid C cast to array type when or-block returns fixed array constant

[demizer]

Describe the bug

When an or-block returns a fixed array constant or variable, the C code generator produces invalid C code that attempts to cast to an array type. This causes compilation failure when using GCC 15.2 as the C backend.

Reproduction Steps

const default_arr = [f32(1.0), 2.0, 3.0, 4.0]!

fn get_arr(key string) ?[4]f32 {
	if key == 'valid' {
		return [f32(0.1), 0.2, 0.3, 0.4]!
	}
	return none
}

fn main() {
	result := get_arr('invalid') or { default_arr }
	println(result)
}

Compile with GCC:

v -cc gcc test.v

Expected Behavior

The code should compile successfully with all supported C compilers.

Current Behavior

GCC compilation fails with:

error: cast specifies array type
 8489 |                 memcpy(_t1.data, (Array_fixed_f32_4)_const_main__default_arr, sizeof(Array_fixed_f32_4));
      |                                  ^

The generated C code incorrectly casts a constant/variable to an array type, which is invalid C. The cast (Array_fixed_f32_4) is only valid for compound literals (brace-enclosed initializers), not for existing variables or constants.

Note: TCC accepts this cast, so the bug only manifests when using GCC. Per C99 6.5.4, cast operators shall not specify array types.

Possible Solution

In gen_or_block_stmts(), only apply the compound literal cast for expressions that generate brace-enclosed initializers (ArrayInit, StructInit, or CastExpr wrapping ArrayInit). For constants and variables, omit the cast and pass them directly to memcpy.

Additional Information/Context

The fix needs to distinguish between:

• or { [1, 2, 3]! }
  • generates {1, 2, 3} which needs cast to become compound literal
• or { some_const }
  • generates _const_some_const which should not be cast

Environment details (OS name and version, etc.)

V full version	V 0.5.0 c3b924c.0b0bc20
OS	linux, "Arch Linux" (VM)
Processor	12 cpus, 64bit, little endian, AMD Ryzen Threadripper 7960X 24-Cores
Memory	5.1GB/47GB
V executable	/home/jesusa/code/v/v/v
V last modified time	2026-01-25 19:00:59
V home dir	OK, value: /home/jesusa/code/v/v
VMODULES	OK, value: /home/jesusa/.vmodules
VTMP	OK, value: /tmp/v_1000
Current working dir	OK, value: /home/jesusa/code/v/vrasta
Git version	git version 2.52.0
V git status	weekly.2026.03-49-g0b0bc205 (26 commit(s) behind V master)
.git/config present	true
cc version	cc (GCC) 15.2.1 20260103
gcc version	gcc (GCC) 15.2.1 20260103
clang version	clang version 21.1.6
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 (GNU libc) 2.42

Note

You can use the 👍 reaction to increase the issue's priority for developers.

Please note that only the 👍 reaction to the issue itself counts as a vote.
Other reactions and those to comments will not be taken into account.