cmd/compile: changed representation of typeparam bound in types1

Especially with typesets, we should be able to fully represent a
typeparam bound as just another type (actually an interface type).
Change the representation of a typeparam in types1 to include a bound,
which is just a type. Changed the signature for NewTypeParam() to take a
sym, and not a package, since we always set the sym (name) of the
typeparam when creating it. No need for an extra pkg field in Typeparam.

Also added index field in the types1 representation of typeparam. This
is especially needed to correctly export the typeparam, and re-import it
as a types2 type (which requires the index to be set correctly).

Change-Id: I50200e2489a97898c37d292b2bd025df790b0277
Reviewed-on: https://go-review.googlesource.com/c/go/+/319929
Reviewed-by: Robert Griesemer <gri@golang.org>
Trust: Robert Griesemer <gri@golang.org>
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/types2/type.go b/src/cmd/compile/internal/types2/type.go
index e6c260ff67..88dedbad45 100644
--- a/src/cmd/compile/internal/types2/type.go
+++ b/src/cmd/compile/internal/types2/type.go
@@ -760,6 +760,11 @@ func (check *Checker) NewTypeParam(obj *TypeName, index int, bound Type) *TypePa
 	return typ
 }
 
+// Index returns the index of the type param within its param list.
+func (t *TypeParam) Index() int {
+	return t.index
+}
+
 func (t *TypeParam) Bound() *Interface {
 	iface := asInterface(t.bound)
 	// use the type bound position if we have one