go/ssa: use NormalTerms

Use typeparams.NormalTerms in go/ssa.

Adjusts NormalTerms to preserve names and aliases. As a part of this, NormalTerms now no longer uses the Underlying() on *types.TypeParams.

Change-Id: Ic09c0fba46982b81066b396f11a5b0ea48739819
Reviewed-on: https://go-review.googlesource.com/c/tools/+/642155
Reviewed-by: Robert Findley <[email protected]>
Commit-Queue: Tim King <[email protected]>
Reviewed-by: Alan Donovan <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Tim King <[email protected]>

Author: Tim King

go/ssa/typeset.go

@@ -48,24 +48,7 @@ func typeset(typ types.Type, yield func(t, u types.Type) bool) {
 
 // termListOf returns the type set of typ as a normalized term set. Returns an empty set on an error.
 func termListOf(typ types.Type) []*types.Term {
-	// This is a adaptation of x/exp/typeparams.NormalTerms which x/tools cannot depend on.
-	var terms []*types.Term
-	var err error
-	// typeSetOf(t) == typeSetOf(Unalias(t))
-	switch typ := types.Unalias(typ).(type) {
-	case *types.TypeParam:
-		terms, err = typeparams.StructuralTerms(typ)
-	case *types.Union:
-		terms, err = typeparams.UnionTermSet(typ)
-	case *types.Interface:
-		terms, err = typeparams.InterfaceTermSet(typ)
-	default:
-		// Common case.
-		// Specializing the len=1 case to avoid a slice
-		// had no measurable space/time benefit.
-		terms = []*types.Term{types.NewTerm(false, typ)}
-	}
-
+	terms, err := typeparams.NormalTerms(typ)
 	if err != nil {
 		return nil
 	}

internal/typeparams/coretype.go

@@ -109,16 +109,21 @@ func CoreType(T types.Type) types.Type {
 //
 // NormalTerms makes no guarantees about the order of terms, except that it
 // is deterministic.
-func NormalTerms(typ types.Type) ([]*types.Term, error) {
-	switch typ := typ.Underlying().(type) {
+func NormalTerms(T types.Type) ([]*types.Term, error) {
+	// typeSetOf(T) == typeSetOf(Unalias(T))
+	typ := types.Unalias(T)
+	if named, ok := typ.(*types.Named); ok {
+		typ = named.Underlying()
+	}
+	switch typ := typ.(type) {
 	case *types.TypeParam:
 		return StructuralTerms(typ)
 	case *types.Union:
 		return UnionTermSet(typ)
 	case *types.Interface:
 		return InterfaceTermSet(typ)
 	default:
-		return []*types.Term{types.NewTerm(false, typ)}, nil
+		return []*types.Term{types.NewTerm(false, T)}, nil
 	}
 }