cmd/compile: fix compilation of inferred type arguments
Previously, type arguments could only be inferred for generic
functions in call expressions, whereas with the reverse type inference
proposal they can now be inferred in assignment contexts too. As a
consequence, we now need to check Info.Instances to find the inferred
type for more cases now.
Updates #59338.
Fixes #59955.
Change-Id: I9b6465395869459c2387d0424febe7337b28b90e
Reviewed-on: https://go-review.googlesource.com/c/go/+/492455
Auto-Submit: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>