go/types: Remove ancient Go 1.1 compatibility indirections.

Change-Id: Ie16cc01ea2bd4806eaa7bd77cfbd2fa90f11ea36
Reviewed-on: https://go-review.googlesource.com/17792
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

go/types/expr.go

@@ -1246,7 +1246,7 @@ func (check *Checker) exprInternal(x *operand, e ast.Expr, hint Type) exprKind {
 		switch typ := x.typ.Underlying().(type) {
 		case *Basic:
 			if isString(typ) {
-				if slice3(e) {
+				if e.Slice3 {
 					check.invalidOp(x.pos(), "3-index slice of string")
 					goto Error
 				}
@@ -1290,7 +1290,7 @@ func (check *Checker) exprInternal(x *operand, e ast.Expr, hint Type) exprKind {
 		x.mode = value
 
 		// spec: "Only the first index may be omitted; it defaults to 0."
-		if slice3(e) && (e.High == nil || sliceMax(e) == nil) {
+		if e.Slice3 && (e.High == nil || e.Max == nil) {
 			check.error(e.Rbrack, "2nd and 3rd index required in 3-index slice")
 			goto Error
 		}

go/types/go11.go

@@ -1,17 +0,0 @@
-// Copyright 2013 The Go Authors.  All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// +build !go1.2
-
-package types
-
-import "go/ast"
-
-func slice3(x *ast.SliceExpr) bool {
-	return false
-}
-
-func sliceMax(x *ast.SliceExpr) ast.Expr {
-	return nil
-}

go/types/go12.go

@@ -1,17 +0,0 @@
-// Copyright 2013 The Go Authors.  All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// +build go1.2
-
-package types
-
-import "go/ast"
-
-func slice3(x *ast.SliceExpr) bool {
-	return x.Slice3
-}
-
-func sliceMax(x *ast.SliceExpr) ast.Expr {
-	return x.Max
-}