cmd/compile/internal/gc: remove unneeded Type.Pos field

Change-Id: I9ab650d9d2d0a99186009362454e1eabc9f6bad6
Reviewed-on: https://go-review.googlesource.com/38393
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/compile/internal/gc/sizeof_test.go

@@ -27,7 +27,7 @@ func TestSizeof(t *testing.T) {
 		{Param{}, 28, 56},
 		{Node{}, 84, 136},
 		{Sym{}, 64, 112},
-		{Type{}, 60, 96},
+		{Type{}, 52, 88},
 		{MapType{}, 20, 40},
 		{ForwardType{}, 20, 32},
 		{FuncType{}, 28, 48},

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

@@ -150,9 +150,8 @@ type Type struct {
 	sliceOf *Type
 	ptrTo   *Type
 
-	Sym    *Sym     // symbol containing name, for named types
-	Vargen int32    // unique name for OTYPE/ONAME
-	Pos    src.XPos // position at which this type was declared, implicitly or explicitly
+	Sym    *Sym  // symbol containing name, for named types
+	Vargen int32 // unique name for OTYPE/ONAME
 
 	Etype  EType // kind of type
 	Trecur uint8 // to detect loops
@@ -408,7 +407,6 @@ func typ(et EType) *Type {
 	t := &Type{
 		Etype: et,
 		Width: BADWIDTH,
-		Pos:   lineno,
 	}
 	t.Orig = t
 	// TODO(josharian): lazily initialize some of these?