[dev.typeparams] cmd/compile: change types2.Union API to accept a list of Terms

Instead of providing a list of tildes and types, use a list of
Terms to create a Union, with suitable accessors.

Define the (exported) notion of a Term representing a union term.

This simplified various uses and also will be easier to extend
should we want to add more information to a Term in the future.

Change-Id: I52fd73938bfa11bac60adbf10580b6d0680df4f1
Reviewed-on: https://go-review.googlesource.com/c/go/+/340250
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/src/cmd/compile/internal/types2/subst.go b/src/cmd/compile/internal/types2/subst.go
index 6c5f756491..26796fc604 100644
--- a/src/cmd/compile/internal/types2/subst.go
+++ b/src/cmd/compile/internal/types2/subst.go
@@ -387,19 +387,19 @@ func (subst *subster) typeList(in []Type) (out []Type, copied bool) {
 	return
 }
 
-func (subst *subster) termlist(in []*term) (out []*term, copied bool) {
+func (subst *subster) termlist(in []*Term) (out []*Term, copied bool) {
 	out = in
 	for i, t := range in {
 		if u := subst.typ(t.typ); u != t.typ {
 			if !copied {
 				// first function that got substituted => allocate new out slice
 				// and copy all functions
-				new := make([]*term, len(in))
+				new := make([]*Term, len(in))
 				copy(new, out)
 				out = new
 				copied = true
 			}
-			out[i] = &term{t.tilde, u}
+			out[i] = NewTerm(t.tilde, u)
 		}
 	}
 	return