From a265f2e90eb928ab773ecabf48aefb11b188296d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Mart=C3=AD?= <mvdan@mvdan.cc>
Date: Sun, 29 Oct 2017 21:04:01 +0000
Subject: [PATCH] go/printer: indent lone comments in composite lits
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If a composite literal contains any comments on their own lines without
any elements, the printer would unindent the comments.

The comments in this edge case are written when the closing '}' is
written. Indent and outdent first so that the indentation is
interspersed before the comment is written.

Also note that the go/printer golden tests don't show the exact same
behaviour that gofmt does. Added a TODO to figure this out in a separate
CL.

While at it, ensure that the tree conforms to gofmt. The changes are
unrelated to this indentation fix, however.

Fixes #22355.

Change-Id: I5ac25ac6de95a236f1e123479127cc4dd71e93fe
Reviewed-on: https://go-review.googlesource.com/74232
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Robert Griesemer <gri@golang.org>
---
 src/go/printer/nodes.go                 |  4 +++-
 src/go/printer/testdata/comments.golden | 28 +++++++++++++++++++++++++
 src/go/printer/testdata/comments.input  | 28 +++++++++++++++++++++++++
 src/math/big/int.go                     |  2 --
 4 files changed, 59 insertions(+), 3 deletions(-)

diff --git a/src/go/printer/nodes.go b/src/go/printer/nodes.go
index 83c17fef5e..5b5b6063fb 100644
--- a/src/go/printer/nodes.go
+++ b/src/go/printer/nodes.go
@@ -865,7 +865,9 @@ func (p *printer) expr1(expr ast.Expr, prec1, depth int) {
 		if len(x.Elts) > 0 {
 			mode |= noExtraBlank
 		}
-		p.print(mode, x.Rbrace, token.RBRACE, mode)
+		// need the initial indent to print lone comments with
+		// the proper level of indentation
+		p.print(indent, unindent, mode, x.Rbrace, token.RBRACE, mode)
 		p.level--
 
 	case *ast.Ellipsis:
diff --git a/src/go/printer/testdata/comments.golden b/src/go/printer/testdata/comments.golden
index d14d8d6cbb..3fc29ccf91 100644
--- a/src/go/printer/testdata/comments.golden
+++ b/src/go/printer/testdata/comments.golden
@@ -831,4 +831,32 @@ func _() {
 	*/
 }
 
+var _ = []T{ /* lone comment */ }
+
+var _ = []T{
+	/* lone comment */
+}
+
+var _ = []T{
+	// lone comments
+	// in composite lit
+}
+
+var _ = [][]T{
+	{
+		// lone comments
+		// in composite lit
+	},
+}
+
+// TODO: gofmt doesn't add these tabs; make it so that these golden
+// tests run the printer in a way that it's exactly like gofmt.
+
+var _ = []T{	// lone comment
+}
+
+var _ = []T{	// lone comments
+	// in composite lit
+}
+
 /* This comment is the last entry in this file. It must be printed and should be followed by a newline */
diff --git a/src/go/printer/testdata/comments.input b/src/go/printer/testdata/comments.input
index df98056a65..985e334795 100644
--- a/src/go/printer/testdata/comments.input
+++ b/src/go/printer/testdata/comments.input
@@ -832,4 +832,32 @@ func _() {
 */
 }
 
+var _ = []T{/* lone comment */}
+
+var _ = []T{
+/* lone comment */
+}
+
+var _ = []T{
+// lone comments
+// in composite lit
+}
+
+var _ = [][]T{
+	{
+		// lone comments
+		// in composite lit
+	},
+}
+
+// TODO: gofmt doesn't add these tabs; make it so that these golden
+// tests run the printer in a way that it's exactly like gofmt.
+
+var _ = []T{// lone comment
+}
+
+var _ = []T{// lone comments
+// in composite lit
+}
+
 /* This comment is the last entry in this file. It must be printed and should be followed by a newline */
diff --git a/src/math/big/int.go b/src/math/big/int.go
index 135ebd083f..0eda9cd4e1 100644
--- a/src/math/big/int.go
+++ b/src/math/big/int.go
@@ -533,7 +533,6 @@ func (z *Int) GCD(x, y, a, b *Int) *Int {
 // See Jebelean, "Improving the multiprecision Euclidean algorithm",
 // Design and Implementation of Symbolic Computation Systems, pp 45-58.
 func (z *Int) lehmerGCD(a, b *Int) *Int {
-
 	// ensure a >= b
 	if a.abs.cmp(b.abs) < 0 {
 		a, b = b, a
@@ -551,7 +550,6 @@ func (z *Int) lehmerGCD(a, b *Int) *Int {
 
 	// loop invariant A >= B
 	for len(B.abs) > 1 {
-
 		// initialize the digits
 		var a1, a2, u0, u1, u2, v0, v1, v2 Word