cmd/compile/internal/types: change NewNamed to use TypeObject

Semantically, TypeObject is the interface that go/types.TypeName would
implement, so we might as well use that instead of the more generic
Object (analog to go/types.Object) for NewNamed. In practice, this
doesn't really matter though, because we use *ir.Name for almost all
Objects anyway.

Also, remove VarObject: its last use was removed in CL 302071 (March
2021).

Change-Id: I6e987ecd419105e09f74fc8d60cadb61bcbc751f
Reviewed-on: https://go-review.googlesource.com/c/go/+/345810
Trust: Matthew Dempsky <[email protected]>
Run-TryBot: Matthew Dempsky <[email protected]>
Reviewed-by: Robert Griesemer <[email protected]>
TryBot-Result: Go Bot <[email protected]>

Author: mdempsky

src/cmd/compile/internal/types/type.go

@@ -27,12 +27,6 @@ type TypeObject interface {
 	TypeDefn() *Type // for "type T Defn", returns Defn
 }
 
-// A VarObject is an Object representing a function argument, variable, or struct field.
-type VarObject interface {
-	Object
-	RecordFrameOffset(int64) // save frame offset
-}
-
 //go:generate stringer -type Kind -trimprefix T type.go
 
 // Kind describes a kind of type.
@@ -1726,7 +1720,7 @@ var (
 // 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 {
+func NewNamed(obj TypeObject) *Type {
 	t := newType(TFORW)
 	t.sym = obj.Sym()
 	t.nod = obj