Repository navigation
spec: adjust scope of type parameters declared by method receivers #52038
Description
This proposal is about a small correction to the scope of function type parameters.
Per the current spec:
The scope of an identifier denoting a type parameter of a function or declared by a method receiver is the function body and all parameter lists of the function.
The proposal is to change this rule to:
The scope of an identifier denoting a type parameter of a function or declared by a method receiver starts after the function name and ends at the end of the function body.
There is only a difference for methods of generic types: type parameters declared by method receivers won't be visible in the receiver parameter list anymore. For example, currently we get an error for:
type T[T any] struct {}
func (T[T]) m() {} // error: T is not a generic typebecause the T inside the [T] is visible inside the receiver parameter list and shadows the outer T used in front of [T].
If this proposal is accepted, it will be possible to write this code without errors.
See #51503.
Activity
[-]proposal: spec: [/-][+]proposal: spec: adjust scope of type parameters declared by method receivers[/+]rsc commentedon Mar 30, 2022
Given that
type T[T any] struct {}works today, it does seem reasonable to try to makefunc (T[T]) m() {}work too.rsc commentedon Mar 30, 2022
This proposal has been added to the active column of the proposals project
and will now be reviewed at the weekly proposal review meetings.
— rsc for the proposal review group
rsc commentedon Apr 13, 2022
Based on the discussion above, this proposal seems like a likely accept.
— rsc for the proposal review group
rsc commentedon May 4, 2022
No change in consensus, so accepted. 🎉
This issue now tracks the work of implementing the proposal.
— rsc for the proposal review group
[-]proposal: spec: adjust scope of type parameters declared by method receivers[/-][+]spec: adjust scope of type parameters declared by method receivers[/+]gopherbot commentedon May 11, 2022
Change https://go.dev/cl/405754 mentions this issue:
spec: adjust scope of function/method type paramatersspec: adjust scope of function/method type parameters