[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>

3 files changed, 14 insertions, 14 deletions

diff --git a/src/cmd/compile/internal/noder/reader2.go b/src/cmd/compile/internal/noder/reader2.go
index d183934900..0bea6675ea 100644
--- a/src/cmd/compile/internal/noder/reader2.go
+++ b/src/cmd/compile/internal/noder/reader2.go
@@ -281,13 +281,13 @@ func (r *reader2) structType() *types2.Struct {
 }
 
 func (r *reader2) unionType() *types2.Union {
-	terms := make([]types2.Type, r.len())
-	tildes := make([]bool, len(terms))
+	terms := make([]*types2.Term, r.len())
 	for i := range terms {
-		terms[i] = r.typ()
-		tildes[i] = r.bool()
+		typ := r.typ()
+		tilde := r.bool()
+		terms[i] = types2.NewTerm(tilde, typ)
 	}
-	return types2.NewUnion(terms, tildes)
+	return types2.NewUnion(terms)
 }
 
 func (r *reader2) interfaceType() *types2.Interface {
diff --git a/src/cmd/compile/internal/noder/types.go b/src/cmd/compile/internal/noder/types.go
index 3f7280a823..4e80b1a0ff 100644
--- a/src/cmd/compile/internal/noder/types.go
+++ b/src/cmd/compile/internal/noder/types.go
@@ -232,13 +232,13 @@ func (g *irgen) typ0(typ types2.Type) *types.Type {
 		return tp
 
 	case *types2.Union:
-		nt := typ.NumTerms()
+		nt := typ.Len()
 		tlist := make([]*types.Type, nt)
 		tildes := make([]bool, nt)
 		for i := range tlist {
-			term, tilde := typ.Term(i)
-			tlist[i] = g.typ1(term)
-			tildes[i] = tilde
+			t := typ.Term(i)
+			tlist[i] = g.typ1(t.Type())
+			tildes[i] = t.Tilde()
 		}
 		return types.NewUnion(tlist, tildes)
 
diff --git a/src/cmd/compile/internal/noder/writer.go b/src/cmd/compile/internal/noder/writer.go
index eb1db623b4..8b65559d1a 100644
--- a/src/cmd/compile/internal/noder/writer.go
+++ b/src/cmd/compile/internal/noder/writer.go
@@ -394,11 +394,11 @@ func (w *writer) structType(typ *types2.Struct) {
 }
 
 func (w *writer) unionType(typ *types2.Union) {
-	w.len(typ.NumTerms())
-	for i := 0; i < typ.NumTerms(); i++ {
-		term, tilde := typ.Term(i)
-		w.typ(term)
-		w.bool(tilde)
+	w.len(typ.Len())
+	for i := 0; i < typ.Len(); i++ {
+		t := typ.Term(i)
+		w.typ(t.Type())
+		w.bool(t.Tilde())
 	}
 }