cmd/go: return and handle errors from loadImport for bad imports
And assign the error to the importing package. Before this change, for
some errors for bad imports, such as importing a vendored package with
the wrong path, we would make a dummy package for the imported package
with the error on it. Instead report the error on the importing
package where it belongs. Do so by returning an error from loadImport
and handling it on the importing package.
For #59157
Change-Id: I952e1a82af3857efc5da4fd3f8bc6be473a60cf5
Reviewed-on: https://go-review.googlesource.com/c/go/+/482877 Reviewed-by: Bryan Mills <bcmills@google.com>
Run-TryBot: Michael Matloob <matloob@golang.org> Reviewed-by: Michael Matloob <matloob@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>