gofmt: don't remove syntactically relevant blank in f(42 ...)

R=rsc
CC=golang-dev
https://golang.org/cl/2246046

src/pkg/go/printer/nodes.go

@@ -848,6 +848,14 @@ func (p *printer) expr1(expr ast.Expr, prec1, depth int, ctxt exprContext, multi
 		p.print(x.Lparen, token.LPAREN)
 		p.exprList(x.Lparen, x.Args, depth, commaSep|commaTerm, multiLine, x.Rparen)
 		if x.Ellipsis.IsValid() {
+			if p.lastTok == token.INT {
+				// w/o a blank, the previous int will become a float
+				// (this could be solved more generally in the print
+				// function but it appears that this is the only
+				// place in the grammar where a token starting with
+				// a do may legally extend the previous token)
+				p.print(blank)
+			}
 			p.print(x.Ellipsis, token.ELLIPSIS)
 		}
 		p.print(x.Rparen, token.RPAREN)

src/pkg/go/printer/printer.go

@@ -69,6 +69,7 @@ type printer struct {
 	written int         // number of bytes written
 	indent  int         // current indentation
 	escape  bool        // true if in escape sequence
+	lastTok token.Token // the last token printed (token.ILLEGAL if it's whitespace)
 
 	// Buffered whitespace
 	buffer []whiteSpace
@@ -762,6 +763,7 @@ func (p *printer) print(args ...interface{}) {
 		var data []byte
 		var tag HTMLTag
 		var tok token.Token
+
 		switch x := f.(type) {
 		case whiteSpace:
 			if x == ignore {
@@ -798,7 +800,7 @@ func (p *printer) print(args ...interface{}) {
 			// bytes since they do not appear in legal UTF-8 sequences)
 			// TODO(gri): do this more efficiently.
 			data = []byte("\xff" + string(data) + "\xff")
-			tok = token.INT // representing all literal tokens
+			tok = x.Kind
 		case token.Token:
 			if p.Styler != nil {
 				data, tag = p.Styler.Token(x)
@@ -810,10 +812,12 @@ func (p *printer) print(args ...interface{}) {
 			if x.IsValid() {
 				next = x // accurate position of next item
 			}
+			tok = p.lastTok
 		default:
 			fmt.Fprintf(os.Stderr, "print: unsupported argument type %T\n", f)
 			panic("go/printer type")
 		}
+		p.lastTok = tok
 		p.pos = next
 
 		if data != nil {

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

@@ -173,6 +173,17 @@ func f(x int, args ...int) {
 	f(0, args...)
 	f(1, args)
 	f(2, args[0])
+
+	// make sure syntactically legal code remains syntactically legal
+	f(3, 42 ...)	// a blank must remain between 42 and ...
+	f(4, 42....)
+	f(5, 42....)
+	f(6, 42.0...)
+	f(7, 42.0...)
+	f(8, .42...)
+	f(9, .42...)
+	f(10, 42e0...)
+	f(11, 42e0...)
 }
 
 

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

@@ -173,6 +173,17 @@ func f(x int, args ...int) {
 	f(0, args...)
 	f(1, args)
 	f(2, args[0])
+
+	// make sure syntactically legal code remains syntactically legal
+	f(3, 42 ...) // a blank must remain between 42 and ...
+	f(4, 42. ...)
+	f(5, 42....)
+	f(6, 42.0 ...)
+	f(7, 42.0...)
+	f(8, .42 ...)
+	f(9, .42...)
+	f(10, 42e0 ...)
+	f(11, 42e0...)
 }
 
 

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

@@ -173,6 +173,17 @@ func f(x int, args ...int) {
 	f(0, args...)
 	f(1, args)
 	f(2, args[0])
+
+	// make sure syntactically legal code remains syntactically legal
+	f(3, 42 ...)	// a blank must remain between 42 and ...
+	f(4, 42....)
+	f(5, 42....)
+	f(6, 42.0...)
+	f(7, 42.0...)
+	f(8, .42...)
+	f(9, .42...)
+	f(10, 42e0...)
+	f(11, 42e0...)
 }