go/types: better errors for invalid short var decls
This is a port of CL 312170 to go/types, adjusted to use go/ast and to
add error codes. go/parser already emits errors for non-identifiers on
the LHS of a short var decl, so a TODO is added to reconsider this
redundancy.
A new error code is added for repeated identifiers in short var decls.
This is a bit specific, but I considered it to be a unique kind of
error.
The x/tools tests for this port turned up a bug: the new logic failed to
call recordDef for blank identifiers. Patchset #2 contains the fix for
this bug, both in go/types and cmd/compile/internal/types2.
Change-Id: Ibdc40b8b4ad0e0696111d431682e1f1056fd5eeb
Reviewed-on: https://go-review.googlesource.com/c/go/+/314629
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>