generic methods passing lambda need type hint

[initdc]

Describe the bug

Hello, I have another problem related #26191 when passing lambda to the .map() method
Lambda need type hint

Reproduction Steps

check this commit

git clone -b lambda_need_type git@github.com:initdc/types.v.git

cd types.v
v run test.v

or playground: https://play.vlang.io/?query=d1bf7b2789

Expected Behavior

a.map(|x| x.len)) working

Current Behavior

need a type wrapper

fn typed[T, U](f fn (T) U) fn (T) U {
	return f
}

Possible Solution

No response

Additional Information/Context

https://docs.vlang.io/functions-2.html#lambda-expressions

V version

V 0.5.0 ef05fb1

Environment details (OS name and version, etc.)

|V full version      |V 0.5.0 ef05fb1210fcc8cd4c3814627e35b12dcc5b335d
|:-------------------|:-------------------
|OS                  |linux, Ubuntu 22.04.2 LTS (WSL 2)
|Processor           |4 cpus, 64bit, little endian, Intel(R) Core(TM) i3-8100 CPU @ 3.60GHz
|Memory              |4.56GB/7.73GB
|                    |
|V executable        |/home/ubuntu/vscode/v/v
|V last modified time|2026-01-04 07:12:29
|                    |
|V home dir          |OK, value: /home/ubuntu/vscode/v
|VMODULES            |OK, value: /home/ubuntu/.vmodules
|VTMP                |OK, value: /tmp/v_1000
|Current working dir |OK, value: /home/ubuntu/vscode/types.v
|                    |
|Git version         |git version 2.34.1
|V git status        |0.5-18-gef05fb12
|.git/config present |true
|                    |
|cc version          |cc (Ubuntu 11.4.0-1ubuntu1~22.04.2) 11.4.0
|gcc version         |gcc (Ubuntu 11.4.0-1ubuntu1~22.04.2) 11.4.0
|clang version       |N/A
|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 2.35-0ubuntu3.11) 2.35

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