go/types: add a NewSignatureType constructor accepting type parameters
In #47916, consensus has emerged that adding a new constructor is
preferable to using setters for type parameters. This is more consistent
with the rest of the type API, which is immutable except in cases where
mutation is necessary to break cycles (such as Named.SetUnderlying).
This CL adds a new constructor NewSignatureType that accepts type
parameters and receiver type parameters, deprecating the existing
NewSignature constructor. SetTypeParams and SetRecvTypeParams are not
yet removed: this will be done in a follow-up CL once x/tools no longer
has a dependency on the old APIs.
Updates #47916
Change-Id: I9d04dcfd304344d2aa08e527b371c3faa9d738e8
Reviewed-on: https://go-review.googlesource.com/c/go/+/352615
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>