Sum Type Field Access Fails Inside closure

[bbodi]

Describe the bug

When using a sum type (Type = Aa | Bb) inside a function literal (fn[t]), the compiler fails to recognize the specific type variant of t and treats it as the general Type, rather than the matched variant (Aa).

Reproduction Steps

struct Aa {a int}
struct Bb {b int}
type Type = Aa | Bb

fn main() {
	t := Type(Aa{})
	match t {
		Aa {
			println(t.a)            // works
			func := fn[t] () {
				println(typeof(t))  // works, prints "Aa"
				// println(t.a) // error: field `a` does not exist or have the same type in these sumtype `Type` variants: Bb
			}
			func()
		}
		Bb {}
	}
}

Expected Behavior

The expected behavior is that inside the function literal (fn[t]), the compiler should preserve the type information from the surrounding match branch. Since t is already matched as Aa, it should be treated as an Aa inside the function, allowing direct access to t.a without requiring additional casting.

Current Behavior

t's type inside the closure is the sumtyp (Type), and not Aa

Possible Solution

No response

Additional Information/Context

No response

V version

V 0.4.9 5be2fca

Environment details (OS name and version, etc.)

V full version	V 0.4.9 5be2fca
OS	linux, Ubuntu 24.10
Processor	16 cpus, 64bit, little endian, AMD Ryzen 7 8840U w/ Radeon 780M Graphics
Memory	9.51GB/22.78GB
V executable	/home/sharp/dev/v/v
V last modified time	2025-02-13 12:21:16
V home dir	OK, value: /home/sharp/dev/v
VMODULES	OK, value: /home/sharp/.vmodules
VTMP	OK, value: /tmp/v_1000
Git version	git version 2.45.2
V git status	weekly.2025.03-35-g5be2fcab-dirty (99 commit(s) behind V master)
.git/config present	true
cc version	cc (Ubuntu 14.2.0-4ubuntu2) 14.2.0
gcc version	gcc (Ubuntu 14.2.0-4ubuntu2) 14.2.0
clang version	Ubuntu clang version 19.1.1 (1ubuntu1)
tcc version	tcc version 0.9.28rc 2024-07-31 HEAD@1cee0908 (x86_64 Linux)
tcc git status	thirdparty-linux-amd64 0134e9b9
emcc version	emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.6 ()
glibc version	ldd (Ubuntu GLIBC 2.40-1ubuntu3.1) 2.40

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.

[huly-for-github]

Connected to Huly®: V_0.6-22134