Now that we use square brackets for instantiations, we
can tell type arguments from ordinary arguments without
"guessing" which permits a simpler implementation.
Specifically, replace use of Checker.exprOrTypeList with
Checker.exprList, and delete Checker.exprOrTypeList and
Checker.multiExprOrType.
Disable a test for an (esoteric) failure due to an
unrelated problem with error matching when running
the test.
Change-Id: I17f18fffc32f03fa90d93a68ebf56e5f2fcc9dab
Reviewed-on: https://go-review.googlesource.com/c/go/+/306171
Trust: Robert Griesemer <gri@golang.org> Reviewed-by: Robert Findley <rfindley@google.com>