Type inference with generic structs and generic interfaces

[tom65536]

Describe the bug

Type inference does not bind generic structs as expected.
(Unless my expectation is wrong)

Reproduction Steps

module main

interface MyInterface[T] {
        is_good(a T) bool
}

struct MyStruct[T] {}

struct Opt[T] {
        x ?T
}

fn (_ MyStruct[T]) is_good(a Opt[T]) bool {
        if _ := a.x {
                return true
        }
        return false
}

fn check[T](a MyInterface[T], b T) {
        println('${a.is_good(b)}')
}

fn main() {
        a := MyStruct[int]{}
        b := Opt[int]{6}
        check(a, b)
}

Expected Behavior

In call to fn check, T should be bound as Opt[int] and MyStruct[int] should be accepted as implementation of MyInterface[Opt[int]].

Current Behavior

Looks like the compiler can only infer struct X[T] as implementation of interface Y[S] if S can be bound to T (as a type variable)

src/main.v:27:8: error: could not infer generic type `T` in interface `MyInterface`
   25 |     a := MyStruct[int]{}
   26 |     b := Opt[int]{6}
   27 |     check(a, b)
      |           ^
   28 | }
src/main.v:27:8: error: cannot use `MyStruct[int]` as `MyInterface[int]` in argument 1 to `check`
   25 |     a := MyStruct[int]{}
   26 |     b := Opt[int]{6}
   27 |     check(a, b)
      |           ^
   28 | }
src/main.v:27:11: error: cannot use `Opt[int]` as `int` in argument 2 to `check`
   25 |     a := MyStruct[int]{}
   26 |     b := Opt[int]{6}
   27 |     check(a, b)
      |              ^
   28 | }
src/main.v:21:23: error: cannot use `int` as `Opt[int]` in argument 1 to `MyInterface[int].is_good`
   19 |
   20 | fn check[T](a MyInterface[T], b T) {
   21 |     println('${a.is_good(b)}')
      |                          ^
   22 | }
   23 |

Possible Solution

No response

Additional Information/Context

No response

V version

V 0.4.2 20a1af3

Environment details (OS name and version, etc.)

Android, Termux

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[yuyi98]

fn (_ MyStruct[T]) is_good(a Opt[T]) bool {
        if _ := a.x {
                return true
        }
        return false
}

a Opt[T] ???
a T will only correspond to the interface method.