go/printer: remove "written" result value - is never used

R=r
CC=golang-dev
https://golang.org/cl/5436052

src/cmd/gofix/main.go

@@ -109,7 +109,7 @@ func gofmtFile(f *ast.File) ([]byte, error) {
 	var buf bytes.Buffer
 
 	ast.SortImports(fset, f)
-	_, err := printConfig.Fprint(&buf, fset, f)
+	err := printConfig.Fprint(&buf, fset, f)
 	if err != nil {
 		return nil, err
 	}
@@ -203,7 +203,7 @@ var gofmtBuf bytes.Buffer
 
 func gofmt(n interface{}) string {
 	gofmtBuf.Reset()
-	_, err := printConfig.Fprint(&gofmtBuf, fset, n)
+	err := printConfig.Fprint(&gofmtBuf, fset, n)
 	if err != nil {
 		return "<" + err.Error() + ">"
 	}

src/cmd/gofmt/gofmt.go

@@ -121,7 +121,7 @@ func processFile(filename string, in io.Reader, out io.Writer, stdin bool) error
 	}
 
 	var buf bytes.Buffer
-	_, err = (&printer.Config{printerMode, *tabWidth}).Fprint(&buf, fset, file)
+	err = (&printer.Config{printerMode, *tabWidth}).Fprint(&buf, fset, file)
 	if err != nil {
 		return err
 	}

src/pkg/go/printer/performance_test.go

@@ -20,7 +20,7 @@ import (
 var testfile *ast.File
 
 func testprint(out io.Writer, file *ast.File) {
-	if _, err := (&Config{TabIndent | UseSpaces, 8}).Fprint(out, fset, file); err != nil {
+	if err := (&Config{TabIndent | UseSpaces, 8}).Fprint(out, fset, file); err != nil {
 		log.Fatalf("print error: %s", err)
 	}
 }

src/pkg/go/printer/printer.go

@@ -1000,21 +1000,18 @@ func (cfg *Config) fprint(output io.Writer, fset *token.FileSet, node interface{
 	return
 }
 
-// Fprint "pretty-prints" an AST node to output and returns the number
-// of bytes written and an error (if any) for a given configuration cfg.
+// Fprint "pretty-prints" an AST node to output for a given configuration cfg.
 // Position information is interpreted relative to the file set fset.
 // The node type must be *ast.File, or assignment-compatible to ast.Expr,
 // ast.Decl, ast.Spec, or ast.Stmt.
-// Note: The number of bytes written is always 0 and should be ignored.
 //
-func (cfg *Config) Fprint(output io.Writer, fset *token.FileSet, node interface{}) (int, error) {
-	return 0, cfg.fprint(output, fset, node, make(map[ast.Node]int))
+func (cfg *Config) Fprint(output io.Writer, fset *token.FileSet, node interface{}) error {
+	return cfg.fprint(output, fset, node, make(map[ast.Node]int))
 }
 
 // Fprint "pretty-prints" an AST node to output.
 // It calls Config.Fprint with default settings.
 //
 func Fprint(output io.Writer, fset *token.FileSet, node interface{}) error {
-	_, err := (&Config{Tabwidth: 8}).Fprint(output, fset, node)
-	return err
+	return (&Config{Tabwidth: 8}).Fprint(output, fset, node)
 }

src/pkg/go/printer/printer_test.go

@@ -62,7 +62,7 @@ func runcheck(t *testing.T, source, golden string, mode checkMode) {
 
 	// format source
 	var buf bytes.Buffer
-	if _, err := cfg.Fprint(&buf, fset, prog); err != nil {
+	if err := cfg.Fprint(&buf, fset, prog); err != nil {
 		t.Error(err)
 	}
 	res := buf.Bytes()