function type generic cannot have a different generic letter when used as a parameter

[Trakis196]

Describe the bug

A generic function type with type T errors if used as a parameter for another function that has a different generic letter to T. A version of this with a struct does work.

struct Foo[T] {
	a T
}

fn f[X](foo Foo[X]) X {
	return foo.a
}

fn main() {
	foo := Foo[int]{10}
	println(f[int](foo))

}

however the function type version does not. This leads me to believe even though it is a V error instead of a builder or c error that this is a bug, as I don't see any reason why function types should be excluded from this behavior that structs have.

Reproduction Steps

type Fn[T] = fn () T

fn problem[X](f Fn[X]) X {
	return f[X]()
}

fn foo() int {
	return 1
}

fn main() {
	t := problem[int](foo)
	println(t)
}

Expected Behavior

To print 1

Current Behavior

error: generic type name T is not mentioned in fn problem[X]

Possible Solution

No response

Additional Information/Context

No response

V version

V 0.4.7 9088970.4248fc5

Environment details (OS name and version, etc.)

OS: linux, "Arch Linux"
Processor: 8 cpus, 64bit, little endian, 11th Gen Intel(R) Core(TM) i5-1135G7 @ 2.40GHz

vroot: OK
VMODULES: OK
VTMP: OK
Git version: git version 2.46.0
Git vroot status: weekly.2024.37-64-g4248fc55
.git/config present: true

CC version: cc (GCC) 14.2.1 20240805
thirdparty/tcc status: thirdparty-linux-amd64 a0799a5b

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