types2, go/types: infinite loop typechecking (invalid) recursive generic struct

[mdempsky]

This package sends the type checker into an infinite loop:

package x
type A[T any] struct { x A[*T] }

/cc @griesemer @findleyr

[griesemer]

Thanks. Looks like it's trying to report an error but then writing out a type for the error message leads to infinite recursion. Seems related to instantiation somehow. If that's cut out, an error gets reported correctly (but perhaps too late).

[gopherbot]

Change https://golang.org/cl/355732 mentions this issue: cmd/compile/internal/types2: avoid infinite expansion for invalid recursive generic types

[gopherbot]

Change https://golang.org/cl/355733 mentions this issue: go/types: avoid infinite expansion for invalid recursive generic types

[jkmpariab]

I ran into similar problem.
Compiler runs indefinitely until the os crashes of lack of resources.

Here is the reproducer:

type Fooer interface {
	Foo()
}

type Fooable[F Fooer] struct {
	ptr F
}

func (f *Fooable[F]) Adapter() *Fooable[*FooerImpl[F]] {
	return &Fooable[*FooerImpl[F]]{&FooerImpl[F]{}}
}

//
// By removing the 'F Fooer' type param, program compiles sucessfully
//            |||||||||
//            vvvvvvvvv
type FooerImpl[F Fooer] struct {
}

func (fi *FooerImpl[F]) Foo() {}

[griesemer]

@jkmpariab Thanks for your report. Your issue is not fixed yet, and may or may not be related to this issue. I've opened #48974 to track it.