gofmt: indent multi-line signatures

There may be more fine-tuning down the line,
but this CL fixes the most pressing issue at
hand.

Also: gofmt -w src misc

Fixes #1524.

R=rsc, bradfitz
CC=golang-dev
https://golang.org/cl/4975053

4 files changed, 178 insertions, 27 deletions

diff --git a/misc/cgo/test/helpers.go b/misc/cgo/test/helpers.go
index 3a4f014225..de14d19abf 100644
--- a/misc/cgo/test/helpers.go
+++ b/misc/cgo/test/helpers.go
@@ -16,7 +16,7 @@ import (
 const greeting = "hello, world"
 
 type testPair struct {
-	Name string
+	Name      string
 	Got, Want interface{}
 }
 
diff --git a/src/pkg/go/printer/nodes.go b/src/pkg/go/printer/nodes.go
index 9cd975ec1b..364530634a 100644
--- a/src/pkg/go/printer/nodes.go
+++ b/src/pkg/go/printer/nodes.go
@@ -269,6 +269,7 @@ func (p *printer) exprList(prev0 token.Pos, list []ast.Expr, depth int, mode exp
 func (p *printer) parameters(fields *ast.FieldList, multiLine *bool) {
 	p.print(fields.Opening, token.LPAREN)
 	if len(fields.List) > 0 {
+		ws := indent
 		var prevLine, line int
 		for i, par := range fields.List {
 			if i > 0 {
@@ -278,19 +279,30 @@ func (p *printer) parameters(fields *ast.FieldList, multiLine *bool) {
 				} else {
 					line = p.fset.Position(par.Type.Pos()).Line
 				}
-				if 0 < prevLine && prevLine < line && p.linebreak(line, 0, ignore, true) {
+				if 0 < prevLine && prevLine < line && p.linebreak(line, 0, ws, true) {
+					ws = ignore
 					*multiLine = true
 				} else {
 					p.print(blank)
 				}
 			}
 			if len(par.Names) > 0 {
-				p.identList(par.Names, false, multiLine)
+				// Very subtle: If we indented before (ws == ignore), identList
+				// won't indent again. If we didn't (ws == indent), identList will
+				// indent if the identList spans multiple lines, and it will outdent
+				// again at the end (and still ws == indent). Thus, a subsequent indent
+				// by a linebreak call after a type, or in the next multi-line identList
+				// will do the right thing.
+				p.identList(par.Names, ws == indent, multiLine)
 				p.print(blank)
 			}
 			p.expr(par.Type, multiLine)
 			prevLine = p.fset.Position(par.Type.Pos()).Line
 		}
+		if ws == ignore {
+			// unindent if we indented
+			p.print(unindent)
+		}
 	}
 	p.print(fields.Closing, token.RPAREN)
 }
diff --git a/src/pkg/go/printer/testdata/declarations.golden b/src/pkg/go/printer/testdata/declarations.golden
index 970533e8cf..bfa2568c21 100644
--- a/src/pkg/go/printer/testdata/declarations.golden
+++ b/src/pkg/go/printer/testdata/declarations.golden
@@ -692,56 +692,119 @@ func _(x ...chan int)
 
 // these parameter lists must remain multi-line since they are multi-line in the source
 func _(bool,
-int) {
+	int) {
 }
 func _(x bool,
-y int) {
+	y int) {
 }
 func _(x,
-y bool) {
+	y bool) {
 }
 func _(bool,	// comment
-int) {
+	int) {
 }
 func _(x bool,	// comment
-y int) {
+	y int) {
 }
 func _(x,	// comment
-y bool) {
+	y bool) {
 }
 func _(bool,	// comment
-// comment
-int) {
+	// comment
+	int) {
 }
 func _(x bool,	// comment
-// comment
-y int) {
+	// comment
+	y int) {
 }
 func _(x,	// comment
-// comment
-y bool) {
+	// comment
+	y bool) {
 }
 func _(bool,
-// comment
-int) {
+	// comment
+	int) {
 }
 func _(x bool,
-// comment
-y int) {
+	// comment
+	y int) {
 }
 func _(x,
-// comment
-y bool) {
+	// comment
+	y bool) {
 }
 func _(x,	// comment
-y,	// comment
-z bool) {
+	y,	// comment
+	z bool) {
 }
 func _(x,	// comment
-y,	// comment
-z bool) {
+	y,	// comment
+	z bool) {
 }
 func _(x int,	// comment
-y float,	// comment
-z bool) {
+	y float,	// comment
+	z bool) {
+}
+
+// properly indent multi-line signatures
+func ManageStatus(in <-chan *Status, req <-chan Request,
+	stat chan<- *TargetInfo,
+	TargetHistorySize int) {
+}
+
+func MultiLineSignature0(a, b, c int) {
+}
+
+func MultiLineSignature1(a, b, c int,
+	u, v, w float) {
+}
+
+func MultiLineSignature2(a, b,
+	c int) {
+}
+
+func MultiLineSignature3(a, b,
+	c int, u, v,
+	w float,
+	x ...int) {
+}
+
+func MultiLineSignature4(a, b, c int,
+	u, v,
+	w float,
+	x ...int) {
+}
+
+func MultiLineSignature5(a, b, c int,
+	u, v, w float,
+	p, q,
+	r string,
+	x ...int) {
+}
+
+// make sure it also works for methods in interfaces
+type _ interface {
+	MultiLineSignature0(a, b, c int)
+
+	MultiLineSignature1(a, b, c int,
+		u, v, w float)
+
+	MultiLineSignature2(a, b,
+		c int)
+
+	MultiLineSignature3(a, b,
+		c int, u, v,
+		w float,
+		x ...int)
+
+	MultiLineSignature4(a, b, c int,
+		u, v,
+		w float,
+		x ...int)
+
+	MultiLineSignature5(a, b, c int,
+		u, v, w float,
+		p, q,
+		r string,
+		x ...int)
 }
diff --git a/src/pkg/go/printer/testdata/declarations.input b/src/pkg/go/printer/testdata/declarations.input
index c6134096bf..1d69c57b51 100644
--- a/src/pkg/go/printer/testdata/declarations.input
+++ b/src/pkg/go/printer/testdata/declarations.input
@@ -755,3 +755,79 @@ func _(x int,	// comment
 	y float,	// comment
 	z bool) {
 }
+
+
+// properly indent multi-line signatures
+func ManageStatus(in <-chan *Status, req <-chan Request,
+stat chan<- *TargetInfo,
+TargetHistorySize int) {
+}
+
+func MultiLineSignature0(
+a, b, c int,
+) {}
+
+func MultiLineSignature1(
+a, b, c int,
+u, v, w float,
+) {}
+
+func MultiLineSignature2(
+a, b,
+c int,
+) {}
+
+func MultiLineSignature3(
+a, b,
+c int, u, v,
+w float,
+		x ...int) {}
+
+func MultiLineSignature4(
+a, b, c int,
+u, v,
+w float,
+		x ...int) {}
+
+func MultiLineSignature5(
+a, b, c int,
+u, v, w float,
+p, q,
+r string,
+		x ...int) {}
+
+// make sure it also works for methods in interfaces
+type _ interface {
+MultiLineSignature0(
+a, b, c int,
+)
+
+MultiLineSignature1(
+a, b, c int,
+u, v, w float,
+)
+
+MultiLineSignature2(
+a, b,
+c int,
+)
+
+MultiLineSignature3(
+a, b,
+c int, u, v,
+w float,
+		x ...int)
+
+MultiLineSignature4(
+a, b, c int,
+u, v,
+w float,
+		x ...int)
+
+MultiLineSignature5(
+a, b, c int,
+u, v, w float,
+p, q,
+r string,
+		x ...int)
+}