…e version checking

Add the Config.Lang field which may be set to a Go version string,
such as "go1.12". This is a string rather than explicit semantic
version numbers (such as {1, 12}) for API robustness; a string
is more flexible should we need more or different information.

Add -lang flag to types2 package for use with (manual) testing
when running "go test -run Check$ -lang=... -files=...".

While changing flags, look for comma-separated (rather than space-
separated) files when providing the -file flag.

Check that numeric constant literals, signed shift counts are
accepted according to the selected language version.

Type alias declarations and overlapping embedded interfaces are
not yet checked.

Updates #31793.

Change-Id: I9ff238ed38a88f377eb2267dc3e8816b89a40635
Reviewed-on: https://go-review.googlesource.com/c/go/+/289509
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

…s go1.9

Add respective check to type checker.
Remove respective check from the compiler's new type2-based noder.

Updates #31793.

Change-Id: I907e3acab4c136027a8c3db1e9bac301d209c2e1
Reviewed-on: https://go-review.googlesource.com/c/go/+/289570
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

…terfaces requires go1.14

Add respective check to type checker.
Enables another excluded test in test/run.go.

This CL completes the currently required checks for
language compatibility in types2.

Updates #31793.

Change-Id: Icececff9e6023d38f600c93bcb54cdcafcf501b9
Reviewed-on: https://go-review.googlesource.com/c/go/+/290911
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

This is a port of CL 289509 to go/types. It differs from that CL in
codes added to errors, to fit the new factoring of check_test.go, and to
allow go/types to import regexp in deps_test.go

For #31793

Change-Id: Ia9e4c7f5aac1493001189184227c2ebc79a76e77
Reviewed-on: https://go-review.googlesource.com/c/go/+/291317
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>

This is a port of CL 289570 to go/types. It has some notable differences
with that CL:
 + A new _BadDecl error code is added, to indicate declarations with bad
   syntax.
 + declInfo is updated hold not an 'alias' bool, but an aliasPos
   token.Pos to identify the location of the type aliasing '=' token.
   This allows for error messages to be accurately placed on the '='

For #31793

Change-Id: Ib15969f9cd5be30228b7a4c6406f978d6fc58018
Reviewed-on: https://go-review.googlesource.com/c/go/+/291318
Trust: Robert Findley <rfindley@google.com>
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

This is an exact port of CL 290911 to go/types.

For #31793

Change-Id: I28c42727735f467a5984594b455ca58ab3375591
Reviewed-on: https://go-review.googlesource.com/c/go/+/291319
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>