go/types, types2: report better error messages for slice expressions
Explicitly compute the common underlying type and while doing
so report better slice-expression relevant error messages.
Streamline message format for index and slice errors.
This removes the last uses of the coreString and match functions.
Delete them.
Change-Id: I4b50dda1ef7e2ab5e296021458f7f0b6f6e229cd
Reviewed-on: https://go-review.googlesource.com/c/go/+/655935 Reviewed-by: Robert Griesemer <gri@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Robert Findley <rfindley@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>