cmd/compile, types2: avoid confusing follow-on error in invalid type assertion
This CL avoids a useless follow-on error (that gets reported before the
actual error due to source position). This addresses the first part of
the issue below.
Thanks to @cuonglm for the suggestion for the fix.
For #49005.
Change-Id: Ifdd83072a05c32e115dc58a0233868a64f336f3f
Reviewed-on: https://go-review.googlesource.com/c/go/+/356449
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>