[dev.typeparams] go/types: import some support functions from dev.go2go
Import dev.go2go changes for exprstring.go, sizes.go, and scope.go.
These files have been reviewed, but are unmodified.
Change-Id: I9df9f8967bab73ce535a539b049346a872877572
Reviewed-on: https://go-review.googlesource.com/c/go/+/278593
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com> Reviewed-by: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>