cmd/compile/internal/types2: use []*TypeParam rather than []*TypeName for type param lists

This is a port of CL 343932 from go/types, with the necessary adjustments
to the compiler.

This change improves type safety slightly, avoids many internal type
assertions, and simplifies some code paths.

Change-Id: Ie9c4734814f49cd248927152d7b3264d3578428c
Reviewed-on: https://go-review.googlesource.com/c/go/+/344614
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Dan Scales <danscales@google.com>

1 files changed, 5 insertions, 6 deletions

diff --git a/src/cmd/compile/internal/noder/reader2.go b/src/cmd/compile/internal/noder/reader2.go
index e72a6737ed..8f3f0a50e9 100644
--- a/src/cmd/compile/internal/noder/reader2.go
+++ b/src/cmd/compile/internal/noder/reader2.go
@@ -396,7 +396,7 @@ func (pr *pkgReader2) objIdx(idx int) (*types2.Package, string) {
 		case objType:
 			pos := r.pos()
 
-			return types2.NewTypeNameLazy(pos, objPkg, objName, func(named *types2.Named) (tparams []*types2.TypeName, underlying types2.Type, methods []*types2.Func) {
+			return types2.NewTypeNameLazy(pos, objPkg, objName, func(named *types2.Named) (tparams []*types2.TypeParam, underlying types2.Type, methods []*types2.Func) {
 				tparams = r.typeParamNames()
 
 				// TODO(mdempsky): Rewrite receiver types to underlying is an
@@ -453,7 +453,7 @@ func (pr *pkgReader2) objDictIdx(idx int) *reader2Dict {
 	return &dict
 }
 
-func (r *reader2) typeParamNames() []*types2.TypeName {
+func (r *reader2) typeParamNames() []*types2.TypeParam {
 	r.sync(syncTypeParamNames)
 
 	// Note: This code assumes it only processes objects without
@@ -470,21 +470,20 @@ func (r *reader2) typeParamNames() []*types2.TypeName {
 	// create all the TypeNames and TypeParams, then we construct and
 	// set the bound type.
 
-	names := make([]*types2.TypeName, len(r.dict.bounds))
 	r.dict.tparams = make([]*types2.TypeParam, len(r.dict.bounds))
 	for i := range r.dict.bounds {
 		pos := r.pos()
 		pkg, name := r.localIdent()
 
-		names[i] = types2.NewTypeName(pos, pkg, name, nil)
-		r.dict.tparams[i] = r.p.check.NewTypeParam(names[i], nil)
+		tname := types2.NewTypeName(pos, pkg, name, nil)
+		r.dict.tparams[i] = r.p.check.NewTypeParam(tname, nil)
 	}
 
 	for i, bound := range r.dict.bounds {
 		r.dict.tparams[i].SetConstraint(r.p.typIdx(bound, r.dict))
 	}
 
-	return names
+	return r.dict.tparams
 }
 
 func (r *reader2) method() *types2.Func {