gofmt: if a semicolon is found unexpectedly, report detailed cause

go/scanner: return information on semicolon (real or inserted) when
	    found in source
go/parser:  better error message when a semicolon is found unexpectedly

For instance, if an unexpected semicolon is found that was automatically
inserted, the parser error message is now:

    "expected '}', found newline"

Fixes #1006.

R=rsc
CC=golang-dev
https://golang.org/cl/1936044

diff --git a/src/cmd/gofmt/test.sh b/src/cmd/gofmt/test.sh
index a8309421a7dbd84f360cba7f5273bab17d745400..133cc8a64fd45e3c46dbb73baf09e69f2d14d596 100755 (executable)
--- a/src/cmd/gofmt/test.sh
+++ b/src/cmd/gofmt/test.sh
@@ -41,7 +41,8 @@ apply1() {
        bug106.go | bug121.go | bug125.go | bug133.go | bug160.go | \
        bug163.go | bug166.go | bug169.go | bug217.go | bug222.go | \
        bug226.go | bug228.go | bug248.go | bug274.go | bug280.go | \
-       bug282.go | bug287.go | bug298.go | bug299.go | bug300.go ) return ;;
+       bug282.go | bug287.go | bug298.go | bug299.go | bug300.go | \
+       bug302.go ) return ;;
        esac
        # the following directories are skipped because they contain test
        # cases for syntax errors and thus won't parse in the first place:

diff --git a/src/pkg/go/parser/parser.go b/src/pkg/go/parser/parser.go
index a492e738f710bf71498d57102258e91e338c9466..51ed2f2eb11fb6fa69859d652d33197a6541b06a 100644 (file)
--- a/src/pkg/go/parser/parser.go
+++ b/src/pkg/go/parser/parser.go
@@ -245,9 +245,13 @@ func (p *parser) errorExpected(pos token.Position, msg string) {
        if pos.Offset == p.pos.Offset {
                // the error happened at the current position;
                // make the error message more specific
-               msg += ", found '" + p.tok.String() + "'"
-               if p.tok.IsLiteral() {
-                       msg += " " + string(p.lit)
+               if p.tok == token.SEMICOLON && p.lit[0] == '\n' {
+                       msg += ", found newline"
+               } else {
+                       msg += ", found '" + p.tok.String() + "'"
+                       if p.tok.IsLiteral() {
+                               msg += " " + string(p.lit)
+                       }
                }
        }
        p.Error(pos, msg)

diff --git a/src/pkg/go/scanner/scanner.go b/src/pkg/go/scanner/scanner.go
index e5ac9d7729c15ffc4cd1cbce68c20ba6ba65fd99..a623e7331e57db219565bf5ede99903291d1499b 100644 (file)
--- a/src/pkg/go/scanner/scanner.go
+++ b/src/pkg/go/scanner/scanner.go
@@ -499,12 +499,16 @@ func (S *Scanner) switch4(tok0, tok1 token.Token, ch2 int, tok2, tok3 token.Toke
 }
 
 
-var semicolon = []byte{';'}
+var newline = []byte{'\n'}
 
 // Scan scans the next token and returns the token position pos,
 // the token tok, and the literal text lit corresponding to the
 // token. The source end is indicated by token.EOF.
 //
+// If the returned token is token.SEMICOLON, the corresponding
+// literal value is ";" if the semicolon was present in the source,
+// and "\n" if the semicolon was inserted because of a newline.
+//
 // For more tolerant parsing, Scan will return a valid token if
 // possible even if a syntax error was encountered. Thus, even
 // if the resulting token sequence contains no illegal tokens,
@@ -541,7 +545,7 @@ scanAgain:
                        // set in the first place and exited early
                        // from S.skipWhitespace()
                        S.insertSemi = false // newline consumed
-                       return pos, token.SEMICOLON, semicolon
+                       return pos, token.SEMICOLON, newline
                case '"':
                        insertSemi = true
                        tok = token.STRING
@@ -609,7 +613,7 @@ scanAgain:
                                        S.offset = pos.Offset + 1
                                        S.ch = '/'
                                        S.insertSemi = false // newline consumed
-                                       return pos, token.SEMICOLON, semicolon
+                                       return pos, token.SEMICOLON, newline
                                }
                                S.scanComment(pos)
                                if S.mode&ScanComments == 0 {

diff --git a/src/pkg/go/scanner/scanner_test.go b/src/pkg/go/scanner/scanner_test.go
index 002a81dd9efc2cbb90068688814a9bddb7ec7313..c3bb9d023b2fb6c4ebe713ea1b433bdf71665050 100644 (file)
--- a/src/pkg/go/scanner/scanner_test.go
+++ b/src/pkg/go/scanner/scanner_test.go
@@ -269,6 +269,12 @@ func checkSemi(t *testing.T, line string, mode uint) {
        pos, tok, lit := S.Scan()
        for tok != token.EOF {
                if tok == token.ILLEGAL {
+                       // the illegal token literal indicates what
+                       // kind of semicolon literal to expect
+                       semiLit := "\n"
+                       if lit[0] == '#' {
+                               semiLit = ";"
+                       }
                        // next token must be a semicolon
                        offs := pos.Offset + 1
                        pos, tok, lit = S.Scan()
@@ -276,8 +282,8 @@ func checkSemi(t *testing.T, line string, mode uint) {
                                if pos.Offset != offs {
                                        t.Errorf("bad offset for %q: got %d, expected %d", line, pos.Offset, offs)
                                }
-                               if string(lit) != ";" {
-                                       t.Errorf(`bad literal for %q: got %q, expected ";"`, line, lit)
+                               if string(lit) != semiLit {
+                                       t.Errorf(`bad literal for %q: got %q, expected %q`, line, lit, semiLit)
                                }
                        } else {
                                t.Errorf("bad token for %q: got %s, expected ;", line, tok.String())
@@ -291,9 +297,10 @@ func checkSemi(t *testing.T, line string, mode uint) {
 
 
 var lines = []string{
-       // the $ character indicates where a semicolon is expected
+       // # indicates a semicolon present in the source
+       // $ indicates an automatically inserted semicolon
        "",
-       "$;",
+       "#;",
        "foo$\n",
        "123$\n",
        "1.2$\n",
@@ -354,7 +361,7 @@ var lines = []string{
        ")$\n",
        "]$\n",
        "}$\n",
-       "$;\n",
+       "#;\n",
        ":\n",
 
        "break$\n",