cmd/compile: rename newNamedTypeWithSym, add some commemnts

Renamed newNamedTypeWithSym to newIncompleteNamedType. Added some extra
comments to types.NewNamed and types.SetUnderlying.

Change-Id: Idc5a6379991c26b429d91bae9fe1adef8457a75c
Reviewed-on: https://go-review.googlesource.com/c/go/+/307029
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Dan Scales <danscales@google.com>
Reviewed-by: Ingo Oeser <nightlyone@googlemail.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>

3 files changed, 10 insertions, 6 deletions

diff --git a/src/cmd/compile/internal/noder/stencil.go b/src/cmd/compile/internal/noder/stencil.go
index 350f8f8c2a..4db688571e 100644
--- a/src/cmd/compile/internal/noder/stencil.go
+++ b/src/cmd/compile/internal/noder/stencil.go
@@ -716,7 +716,7 @@ func (subst *subster) typ(t *types.Type) *types.Type {
 		// In order to deal with recursive generic types, create a TFORW
 		// type initially and set the Def field of its sym, so it can be
 		// found if this type appears recursively within the type.
-		forw = newNamedTypeWithSym(t.Pos(), newsym)
+		forw = newIncompleteNamedType(t.Pos(), newsym)
 		//println("Creating new type by sub", newsym.Name, forw.HasTParam())
 		forw.SetRParams(neededTargs)
 	}
@@ -896,9 +896,9 @@ func deref(t *types.Type) *types.Type {
 	return t
 }
 
-// newNamedTypeWithSym returns a TFORW type t with name specified by sym, such
+// newIncompleteNamedType returns a TFORW type t with name specified by sym, such
 // that t.nod and sym.Def are set correctly.
-func newNamedTypeWithSym(pos src.XPos, sym *types.Sym) *types.Type {
+func newIncompleteNamedType(pos src.XPos, sym *types.Sym) *types.Type {
 	name := ir.NewDeclNameAt(pos, ir.OTYPE, sym)
 	forw := types.NewNamed(name)
 	name.SetType(forw)
diff --git a/src/cmd/compile/internal/noder/types.go b/src/cmd/compile/internal/noder/types.go
index 06c584714e..8680559a41 100644
--- a/src/cmd/compile/internal/noder/types.go
+++ b/src/cmd/compile/internal/noder/types.go
@@ -120,7 +120,7 @@ func (g *irgen) typ0(typ types2.Type) *types.Type {
 			// which may set HasTParam) before translating the
 			// underlying type itself, so we handle recursion
 			// correctly, including via method signatures.
-			ntyp := newNamedTypeWithSym(g.pos(typ.Obj().Pos()), s)
+			ntyp := newIncompleteNamedType(g.pos(typ.Obj().Pos()), s)
 			g.typs[typ] = ntyp
 
 			// If ntyp still has type params, then we must be
diff --git a/src/cmd/compile/internal/types/type.go b/src/cmd/compile/internal/types/type.go
index 31a99781d1..762cdd3258 100644
--- a/src/cmd/compile/internal/types/type.go
+++ b/src/cmd/compile/internal/types/type.go
@@ -1643,7 +1643,10 @@ var (
 	TypeResultMem = newResults([]*Type{TypeMem})
 )
 
-// NewNamed returns a new named type for the given type name. obj should be an ir.Name.
+// NewNamed returns a new named type for the given type name. obj should be an
+// ir.Name. The new type is incomplete, and the underlying type should be set
+// later via SetUnderlying(). References to the type are maintained until the type
+// is filled in, so those references can be updated when the type is complete.
 func NewNamed(obj Object) *Type {
 	t := New(TFORW)
 	t.sym = obj.Sym()
@@ -1659,7 +1662,8 @@ func (t *Type) Obj() Object {
 	return nil
 }
 
-// SetUnderlying sets the underlying type.
+// SetUnderlying sets the underlying type. SetUnderlying automatically updates any
+// types that were waiting for this type to be completed.
 func (t *Type) SetUnderlying(underlying *Type) {
 	if underlying.kind == TFORW {
 		// This type isn't computed yet; when it is, update n.