go/parser: cleanups following CL 7307085

- use the new AllErrors flag where appropriate
- unless AllErrors is set, eliminate spurious
  errors before they are added to the errors list
  (it turns out that reporting spurious errors always
  leads to too many uninformative errors after all)

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/7323065

src/cmd/gofmt/gofmt.go

@@ -29,7 +29,7 @@ var (
 	rewriteRule = flag.String("r", "", "rewrite rule (e.g., 'a[b:len(a)] -> a[b:]')")
 	simplifyAST = flag.Bool("s", false, "simplify code")
 	doDiff      = flag.Bool("d", false, "display diffs instead of rewriting files")
-	allErrors   = flag.Bool("e", false, "print all (including spurious) errors")
+	allErrors   = flag.Bool("e", false, "report all errors (not just the first 10 on different lines)")
 
 	// layout control
 	comments  = flag.Bool("comments", true, "print comments")
@@ -65,7 +65,7 @@ func initParserMode() {
 		parserMode |= parser.ParseComments
 	}
 	if *allErrors {
-		parserMode |= parser.SpuriousErrors
+		parserMode |= parser.AllErrors
 	}
 }
 

src/pkg/exp/gotype/gotype.go

@@ -23,7 +23,7 @@ var (
 	pkgName   = flag.String("p", "", "process only those files in package pkgName")
 	recursive = flag.Bool("r", false, "recursively process subdirectories")
 	verbose   = flag.Bool("v", false, "verbose mode")
-	allErrors = flag.Bool("e", false, "print all (including spurious) errors")
+	allErrors = flag.Bool("e", false, "report all errors (not just the first 10 on different lines)")
 
 	// debugging support
 	parseComments = flag.Bool("comments", false, "parse comments (ignored if -ast not set)")
@@ -71,7 +71,7 @@ func parse(fset *token.FileSet, filename string, src []byte) *ast.File {
 	// parse entire file
 	mode := parser.DeclarationErrors
 	if *allErrors {
-		mode |= parser.SpuriousErrors
+		mode |= parser.AllErrors
 	}
 	if *parseComments && *printAST {
 		mode |= parser.ParseComments

src/pkg/go/parser/error_test.go

@@ -139,7 +139,7 @@ func checkErrors(t *testing.T, filename string, input interface{}) {
 		return
 	}
 
-	_, err = ParseFile(fsetErrs, filename, src, DeclarationErrors)
+	_, err = ParseFile(fsetErrs, filename, src, DeclarationErrors|AllErrors)
 	found, ok := err.(scanner.ErrorList)
 	if err != nil && !ok {
 		t.Error(err)

src/pkg/go/parser/interface.go

@@ -52,13 +52,13 @@ func readSource(filename string, src interface{}) ([]byte, error) {
 type Mode uint
 
 const (
-	PackageClauseOnly Mode             = 1 << iota // parsing stops after package clause
-	ImportsOnly                                    // parsing stops after import declarations
+	PackageClauseOnly Mode             = 1 << iota // stop parsing after package clause
+	ImportsOnly                                    // stop parsing after import declarations
 	ParseComments                                  // parse comments and add them to AST
 	Trace                                          // print a trace of parsed productions
 	DeclarationErrors                              // report declaration errors
 	SpuriousErrors                                 // same as AllErrors, for backward-compatibility
-	AllErrors         = SpuriousErrors             // report all (not just the first 10) errors per file
+	AllErrors         = SpuriousErrors             // report all errors (not just the first 10 on different lines)
 )
 
 // ParseFile parses the source code of a single Go source file and returns

src/pkg/go/parser/parser.go

@@ -344,10 +344,22 @@ func (p *parser) next() {
 type bailout struct{}
 
 func (p *parser) error(pos token.Pos, msg string) {
-	if p.mode&SpuriousErrors == 0 && p.errors.Len() >= 10 {
-		panic(bailout{})
+	epos := p.file.Position(pos)
+
+	// If AllErrors is not set, discard errors reported on the same line
+	// as the last recorded error and stop parsing if there are more than
+	// 10 errors.
+	if p.mode&AllErrors == 0 {
+		n := len(p.errors)
+		if n > 0 && p.errors[n-1].Pos.Line == epos.Line {
+			return // discard - likely a spurious error
+		}
+		if n > 10 {
+			panic(bailout{})
+		}
 	}
-	p.errors.Add(p.file.Position(pos), msg)
+
+	p.errors.Add(epos, msg)
 }
 
 func (p *parser) errorExpected(pos token.Pos, msg string) {

src/pkg/go/types/check_test.go

@@ -92,7 +92,7 @@ func parseFiles(t *testing.T, testname string, filenames []string) ([]*ast.File,
 	var files []*ast.File
 	var errlist []error
 	for _, filename := range filenames {
-		file, err := parser.ParseFile(fset, filename, nil, parser.DeclarationErrors)
+		file, err := parser.ParseFile(fset, filename, nil, parser.DeclarationErrors|parser.AllErrors)
 		if file == nil {
 			t.Fatalf("%s: could not parse file %s", testname, filename)
 		}