go/printer, gofmt: simplify struct formatting and respect line breaks

Also: gofmt src misc

Fixes #1627.

R=rsc
CC=golang-dev
https://golang.org/cl/4303042

misc/cgo/test/callback.go

@@ -29,7 +29,7 @@ func goCallback(p unsafe.Pointer) {
 
 func TestCallback(t *testing.T) {
 	var x = false
-	nestedCall(func(){x = true})
+	nestedCall(func() { x = true })
 	if !x {
 		t.Fatal("nestedCall did not call func")
 	}
@@ -39,7 +39,7 @@ func TestCallbackGC(t *testing.T) {
 	nestedCall(runtime.GC)
 }
 
-func lockedOSThread() bool  // in runtime.c
+func lockedOSThread() bool // in runtime.c
 
 func TestCallbackPanic(t *testing.T) {
 	// Make sure panic during callback unwinds properly.
@@ -58,7 +58,7 @@ func TestCallbackPanic(t *testing.T) {
 			t.Fatal("locked OS thread on exit from TestCallbackPanic")
 		}
 	}()
-	nestedCall(func(){panic("callback panic")})
+	nestedCall(func() { panic("callback panic") })
 	panic("nestedCall returned")
 }
 
@@ -88,7 +88,7 @@ func TestCallbackPanicLocked(t *testing.T) {
 			t.Fatal("lost lock on OS thread after panic")
 		}
 	}()
-	nestedCall(func(){panic("callback panic")})
+	nestedCall(func() { panic("callback panic") })
 	panic("nestedCall returned")
 }
 
@@ -125,7 +125,7 @@ func TestBlocking(t *testing.T) {
 			c <- <-c
 		}
 	}()
-	nestedCall(func(){
+	nestedCall(func() {
 		for i := 0; i < 10; i++ {
 			c <- i
 			if j := <-c; j != i {

misc/cgo/test/cgo_test.go

@@ -3,4 +3,3 @@ package cgotest
 // dummy file so gotest thinks there are tests.
 // the actual tests are in the main go files, next
 // to the code they test.
-

misc/cgo/test/issue1560.go

@@ -28,8 +28,8 @@ func parallelSleep(n int) {
 }
 
 //export BackgroundSleep
-func BackgroundSleep(n int){
-	go func(){
+func BackgroundSleep(n int) {
+	go func() {
 		C.sleep(C.uint(n))
 		sleepDone <- true
 	}()

src/pkg/go/printer/nodes.go

@@ -367,7 +367,7 @@ func (p *printer) setLineComment(text string) {
 }
 
 
-func (p *printer) fieldList(fields *ast.FieldList, isIncomplete bool, ctxt exprContext) {
+func (p *printer) fieldList(fields *ast.FieldList, isStruct, isIncomplete bool) {
 	p.nesting++
 	defer func() {
 		p.nesting--
@@ -376,15 +376,15 @@ func (p *printer) fieldList(fields *ast.FieldList, isIncomplete bool, ctxt exprC
 	lbrace := fields.Opening
 	list := fields.List
 	rbrace := fields.Closing
+	srcIsOneLine := lbrace.IsValid() && rbrace.IsValid() && p.fset.Position(lbrace).Line == p.fset.Position(rbrace).Line
 
-	if !isIncomplete && !p.commentBefore(p.fset.Position(rbrace)) {
+	if !isIncomplete && !p.commentBefore(p.fset.Position(rbrace)) && srcIsOneLine {
 		// possibly a one-line struct/interface
 		if len(list) == 0 {
 			// no blank between keyword and {} in this case
 			p.print(lbrace, token.LBRACE, rbrace, token.RBRACE)
 			return
-		} else if ctxt&(compositeLit|structType) == compositeLit|structType &&
-			p.isOneLineFieldList(list) { // for now ignore interfaces
+		} else if isStruct && p.isOneLineFieldList(list) { // for now ignore interfaces
 			// small enough - print on one line
 			// (don't use identList and ignore source line breaks)
 			p.print(lbrace, token.LBRACE, blank)
@@ -406,7 +406,7 @@ func (p *printer) fieldList(fields *ast.FieldList, isIncomplete bool, ctxt exprC
 
 	// at least one entry or incomplete
 	p.print(blank, lbrace, token.LBRACE, indent, formfeed)
-	if ctxt&structType != 0 {
+	if isStruct {
 
 		sep := vtab
 		if len(list) == 1 {
@@ -489,15 +489,6 @@ func (p *printer) fieldList(fields *ast.FieldList, isIncomplete bool, ctxt exprC
 // ----------------------------------------------------------------------------
 // Expressions
 
-// exprContext describes the syntactic environment in which an expression node is printed.
-type exprContext uint
-
-const (
-	compositeLit exprContext = 1 << iota
-	structType
-)
-
-
 func walkBinary(e *ast.BinaryExpr) (has4, has5 bool, maxProblem int) {
 	switch e.Op.Precedence() {
 	case 4:
@@ -642,7 +633,7 @@ func (p *printer) binaryExpr(x *ast.BinaryExpr, prec1, cutoff, depth int, multiL
 	printBlank := prec < cutoff
 
 	ws := indent
-	p.expr1(x.X, prec, depth+diffPrec(x.X, prec), 0, multiLine)
+	p.expr1(x.X, prec, depth+diffPrec(x.X, prec), multiLine)
 	if printBlank {
 		p.print(blank)
 	}
@@ -661,7 +652,7 @@ func (p *printer) binaryExpr(x *ast.BinaryExpr, prec1, cutoff, depth int, multiL
 	if printBlank {
 		p.print(blank)
 	}
-	p.expr1(x.Y, prec+1, depth+1, 0, multiLine)
+	p.expr1(x.Y, prec+1, depth+1, multiLine)
 	if ws == ignore {
 		p.print(unindent)
 	}
@@ -734,7 +725,7 @@ func selectorExprList(expr ast.Expr) (list []ast.Expr) {
 
 
 // Sets multiLine to true if the expression spans multiple lines.
-func (p *printer) expr1(expr ast.Expr, prec1, depth int, ctxt exprContext, multiLine *bool) {
+func (p *printer) expr1(expr ast.Expr, prec1, depth int, multiLine *bool) {
 	p.print(expr.Pos())
 
 	switch x := expr.(type) {
@@ -784,7 +775,7 @@ func (p *printer) expr1(expr ast.Expr, prec1, depth int, ctxt exprContext, multi
 				// TODO(gri) Remove this code if it cannot be reached.
 				p.print(blank)
 			}
-			p.expr1(x.X, prec, depth, 0, multiLine)
+			p.expr1(x.X, prec, depth, multiLine)
 		}
 
 	case *ast.BasicLit:
@@ -810,7 +801,7 @@ func (p *printer) expr1(expr ast.Expr, prec1, depth int, ctxt exprContext, multi
 		p.exprList(token.NoPos, parts, depth, periodSep, multiLine, token.NoPos)
 
 	case *ast.TypeAssertExpr:
-		p.expr1(x.X, token.HighestPrec, depth, 0, multiLine)
+		p.expr1(x.X, token.HighestPrec, depth, multiLine)
 		p.print(token.PERIOD, token.LPAREN)
 		if x.Type != nil {
 			p.expr(x.Type, multiLine)
@@ -821,14 +812,14 @@ func (p *printer) expr1(expr ast.Expr, prec1, depth int, ctxt exprContext, multi
 
 	case *ast.IndexExpr:
 		// TODO(gri): should treat[] like parentheses and undo one level of depth
-		p.expr1(x.X, token.HighestPrec, 1, 0, multiLine)
+		p.expr1(x.X, token.HighestPrec, 1, multiLine)
 		p.print(x.Lbrack, token.LBRACK)
 		p.expr0(x.Index, depth+1, multiLine)
 		p.print(x.Rbrack, token.RBRACK)
 
 	case *ast.SliceExpr:
 		// TODO(gri): should treat[] like parentheses and undo one level of depth
-		p.expr1(x.X, token.HighestPrec, 1, 0, multiLine)
+		p.expr1(x.X, token.HighestPrec, 1, multiLine)
 		p.print(x.Lbrack, token.LBRACK)
 		if x.Low != nil {
 			p.expr0(x.Low, depth+1, multiLine)
@@ -848,7 +839,7 @@ func (p *printer) expr1(expr ast.Expr, prec1, depth int, ctxt exprContext, multi
 		if len(x.Args) > 1 {
 			depth++
 		}
-		p.expr1(x.Fun, token.HighestPrec, depth, 0, multiLine)
+		p.expr1(x.Fun, token.HighestPrec, depth, multiLine)
 		p.print(x.Lparen, token.LPAREN)
 		p.exprList(x.Lparen, x.Args, depth, commaSep|commaTerm, multiLine, x.Rparen)
 		if x.Ellipsis.IsValid() {
@@ -859,7 +850,7 @@ func (p *printer) expr1(expr ast.Expr, prec1, depth int, ctxt exprContext, multi
 	case *ast.CompositeLit:
 		// composite literal elements that are composite literals themselves may have the type omitted
 		if x.Type != nil {
-			p.expr1(x.Type, token.HighestPrec, depth, compositeLit, multiLine)
+			p.expr1(x.Type, token.HighestPrec, depth, multiLine)
 		}
 		p.print(x.Lbrace, token.LBRACE)
 		p.exprList(x.Lbrace, x.Elts, 1, commaSep|commaTerm, multiLine, x.Rbrace)
@@ -884,7 +875,7 @@ func (p *printer) expr1(expr ast.Expr, prec1, depth int, ctxt exprContext, multi
 
 	case *ast.StructType:
 		p.print(token.STRUCT)
-		p.fieldList(x.Fields, x.Incomplete, ctxt|structType)
+		p.fieldList(x.Fields, true, x.Incomplete)
 
 	case *ast.FuncType:
 		p.print(token.FUNC)
@@ -892,7 +883,7 @@ func (p *printer) expr1(expr ast.Expr, prec1, depth int, ctxt exprContext, multi
 
 	case *ast.InterfaceType:
 		p.print(token.INTERFACE)
-		p.fieldList(x.Methods, x.Incomplete, ctxt)
+		p.fieldList(x.Methods, false, x.Incomplete)
 
 	case *ast.MapType:
 		p.print(token.MAP, token.LBRACK)
@@ -921,14 +912,14 @@ func (p *printer) expr1(expr ast.Expr, prec1, depth int, ctxt exprContext, multi
 
 
 func (p *printer) expr0(x ast.Expr, depth int, multiLine *bool) {
-	p.expr1(x, token.LowestPrec, depth, 0, multiLine)
+	p.expr1(x, token.LowestPrec, depth, multiLine)
 }
 
 
 // Sets multiLine to true if the expression spans multiple lines.
 func (p *printer) expr(x ast.Expr, multiLine *bool) {
 	const depth = 1
-	p.expr1(x, token.LowestPrec, depth, 0, multiLine)
+	p.expr1(x, token.LowestPrec, depth, multiLine)
 }
 
 

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

@@ -224,11 +224,7 @@ func _() {
 	_ = struct{ x int }{0}
 	_ = struct{ x, y, z int }{0, 1, 2}
 	_ = struct{ int }{0}
-	_ = struct {
-		s struct {
-			int
-		}
-	}{struct{ int }{0}}	// compositeLit context not propagated => multiLine result
+	_ = struct{ s struct{ int } }{struct{ int }{0}}
 }
 
 

src/pkg/go/printer/testdata/expressions.input

@@ -224,7 +224,7 @@ func _() {
 	_ = struct{ x int }{0}
 	_ = struct{ x, y, z int }{0, 1, 2}
 	_ = struct{ int }{0}
-	_ = struct{ s struct { int } }{struct{ int}{0}}  // compositeLit context not propagated => multiLine result
+	_ = struct{ s struct { int } }{struct{ int}{0} }
 }
 
 

src/pkg/go/printer/testdata/expressions.raw

@@ -224,11 +224,7 @@ func _() {
 	_ = struct{ x int }{0}
 	_ = struct{ x, y, z int }{0, 1, 2}
 	_ = struct{ int }{0}
-	_ = struct {
-		s struct {
-			int
-		}
-	}{struct{ int }{0}}	// compositeLit context not propagated => multiLine result
+	_ = struct{ s struct{ int } }{struct{ int }{0}}
 }