code review 3225042: go/printer: preserve newlines in func parameter lists

src/pkg/go/printer/testdata/declarations.golden

 // Copyright 2009 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.
 
 package imports
 
 import "io"
 
 import (
         _       "io"
@@ skipping 638 matching lines @@
 
 func _(b bool, x ...int)
 func _(b bool, x ...*int)
 func _(b bool, x ...[]int)
 func _(b bool, x ...struct{})
 func _(x ...interface{})
 func _(x ...func())
 func _(x ...func(...int))
 func _(x ...map[string]int)
 func _(x ...chan int)
+
+
+// these parameter lists must remain multi-line since they are multi-line in the source
+func _(bool,
+int) {
+}
+func _(x bool,
+y int) {
+}
+func _(x,
+y bool) {
+}
+func _(bool,    // comment
+int) {
+}
+func _(x bool,  // comment
+y int) {
+}
+func _(x,       // comment
+y bool) {
+}
+func _(bool,    // comment
+// comment
+int) {
+}
+func _(x bool,  // comment
+// comment
+y int) {
+}
+func _(x,       // comment
+// comment
+y bool) {
+}
+func _(bool,
+// comment
+int) {
+}
+func _(x bool,
+// comment
+y int) {
+}
+func _(x,
+// comment
+y bool) {
+}
+func _(x,       // comment
+y,      // comment
+z bool) {
+}
+func _(x,       // comment
+y,      // comment
+z bool) {
+}
+func _(x int,   // comment
+y float,        // comment
+z bool) {
+}