go/scanner: emit implicit semicolon tokens in correct order

Prior to this change, the scanner, in ScanComments mode, would emit
the implicit SEMICOLON token generated by a newline ahead of any
immediately preceding comment "tokens". For example:

 foo /*a*/ /*b*/ /*c*/ \n   =>  [IDENT SEMICOLON COMMENT COMMENT COMMENT]

Now, tokens and comments are emitted by the scanner in lexical order
of their start position. SEMICOLON tokens corresponding to newlines
always have the position of the newline (even in the special case
in which the newline is in the middle of a general comment /*\n*/).

The scanner no longer needs to look ahead, possibly across multiple
comments, for a newline, when it encounters a comment.
The scanner semicolon tests have been rewritten to be less magical.

The parser must now expect line comments before an implicit semicolon.
Line comments for an explicit semicolon still appear after.
The new assertions in the parser TestLeadAndLineComments are
not changes to behavior.

Fixes golang/go#54941

Change-Id: Iffe97fd10e9e0b52882da8659307698ccb31c093
Reviewed-on: https://go-review.googlesource.com/c/go/+/429635
Auto-Submit: Alan Donovan <adonovan@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Alan Donovan <adonovan@google.com>

src/go/parser/error_test.go

@@ -62,8 +62,9 @@ func getPos(fset *token.FileSet, filename string, offset int) token.Pos {
 // a regular expression that matches the expected error message.
 // The special form /* ERROR HERE "rx" */ must be used for error
 // messages that appear immediately after a token, rather than at
-// a token's position.
+// a token's position, and ERROR AFTER means after the comment
-var errRx = regexp.MustCompile(`^/\* *ERROR *(HERE)? *"([^"]*)" *\*/$`)
+// (e.g. at end of line).
+var errRx = regexp.MustCompile(`^/\* *ERROR *(HERE|AFTER)? *"([^"]*)" *\*/$`)
 
 // expectedErrors collects the regular expressions of ERROR comments found
 // in files and returns them as a map of error positions to error messages.
@@ -86,9 +87,12 @@ func expectedErrors(fset *token.FileSet, filename string, src []byte) map[token.
 		case token.COMMENT:
 			s := errRx.FindStringSubmatch(lit)
 			if len(s) == 3 {
-				pos := prev
 				if s[1] == "HERE" {
-					pos = here
+					pos = here // start of comment
+				} else if s[1] == "AFTER" {
+					pos += token.Pos(len(lit)) // end of comment
+				} else {
+					pos = prev // token prior to comment
 				}
 				errors[pos] = s[2]
 			}

src/go/parser/parser.go

@@ -213,7 +213,7 @@ func (p *parser) next() {
 			// The comment is on same line as the previous token; it
 			// cannot be a lead comment but may be a line comment.
 			comment, endline = p.consumeCommentGroup(0)
-			if p.file.Line(p.pos) != endline || p.tok == token.EOF {
+			if p.file.Line(p.pos) != endline || p.tok == token.SEMICOLON || p.tok == token.EOF {
 				// The next token is on a different line, thus
 				// the last comment group is a line comment.
 				p.lineComment = comment
@@ -313,7 +313,8 @@ func (p *parser) expectClosing(tok token.Token, context string) token.Pos {
 	return p.expect(tok)
 }
 
-func (p *parser) expectSemi() {
+// expectSemi consumes a semicolon and returns the applicable line comment.
+func (p *parser) expectSemi() (comment *ast.CommentGroup) {
 	// semicolon is optional before a closing ')' or '}'
 	if p.tok != token.RPAREN && p.tok != token.RBRACE {
 		switch p.tok {
@@ -322,12 +323,22 @@ func (p *parser) expectSemi() {
 			p.errorExpected(p.pos, "';'")
 			fallthrough
 		case token.SEMICOLON:
-			p.next()
+			if p.lit == ";" {
+				// explicit semicolon
+				p.next()
+				comment = p.lineComment // use following comments
+			} else {
+				// artificial semicolon
+				comment = p.lineComment // use preceding comments
+				p.next()
+			}
+			return comment
 		default:
 			p.errorExpected(p.pos, "';'")
 			p.advance(stmtStart)
 		}
 	}
+	return nil
 }
 
 func (p *parser) atComma(context string, follow token.Token) bool {
@@ -695,9 +706,9 @@ func (p *parser) parseFieldDecl() *ast.Field {
 		p.next()
 	}
 
-	p.expectSemi() // call before accessing p.linecomment
+	comment := p.expectSemi()
 
-	field := &ast.Field{Doc: doc, Names: names, Type: typ, Tag: tag, Comment: p.lineComment}
+	field := &ast.Field{Doc: doc, Names: names, Type: typ, Tag: tag, Comment: comment}
 	return field
 }
 
@@ -1176,19 +1187,16 @@ parseElements:
 			if f.Names == nil {
 				f.Type = p.embeddedElem(f.Type)
 			}
-			p.expectSemi()
+			f.Comment = p.expectSemi()
-			f.Comment = p.lineComment
 			list = append(list, f)
 		case p.tok == token.TILDE:
 			typ := p.embeddedElem(nil)
-			p.expectSemi()
+			comment := p.expectSemi()
-			comment := p.lineComment
 			list = append(list, &ast.Field{Type: typ, Comment: comment})
 		default:
 			if t := p.tryIdentOrType(); t != nil {
 				typ := p.embeddedElem(t)
-				p.expectSemi()
+				comment := p.expectSemi()
-				comment := p.lineComment
 				list = append(list, &ast.Field{Type: typ, Comment: comment})
 			} else {
 				break parseElements
@@ -2446,14 +2454,14 @@ func (p *parser) parseImportSpec(doc *ast.CommentGroup, _ token.Token, _ int) as
 		p.error(pos, "missing import path")
 		p.advance(exprEnd)
 	}
-	p.expectSemi() // call before accessing p.linecomment
+	comment := p.expectSemi()
 
 	// collect imports
 	spec := &ast.ImportSpec{
 		Doc:     doc,
 		Name:    ident,
 		Path:    &ast.BasicLit{ValuePos: pos, Kind: token.STRING, Value: path},
-		Comment: p.lineComment,
+		Comment: comment,
 	}
 	p.imports = append(p.imports, spec)
 
@@ -2489,14 +2497,14 @@ func (p *parser) parseValueSpec(doc *ast.CommentGroup, keyword token.Token, iota
 	default:
 		panic("unreachable")
 	}
-	p.expectSemi() // call before accessing p.linecomment
+	comment := p.expectSemi()
 
 	spec := &ast.ValueSpec{
 		Doc:     doc,
 		Names:   idents,
 		Type:    typ,
 		Values:  values,
-		Comment: p.lineComment,
+		Comment: comment,
 	}
 	return spec
 }
@@ -2589,8 +2597,7 @@ func (p *parser) parseTypeSpec(doc *ast.CommentGroup, _ token.Token, _ int) ast.
 		spec.Type = p.parseType()
 	}
 
-	p.expectSemi() // call before accessing p.linecomment
+	spec.Comment = p.expectSemi()
-	spec.Comment = p.lineComment
 
 	return spec
 }

src/go/parser/parser_test.go

@@ -415,6 +415,11 @@ type T struct {
 	F2 int  // F2 line comment
 	// f3 lead comment
 	f3 int  // f3 line comment
+
+	f4 int   /* not a line comment */ ;
+        f5 int ; // f5 line comment
+	f6 int ; /* f6 line comment */
+	f7 int ; /*f7a*/ /*f7b*/ //f7c
 }
 `, ParseComments)
 	if err != nil {
@@ -423,6 +428,11 @@ type T struct {
 	checkFieldComments(t, f, "T.F1", "/* F1 lead comment *///", "/* F1 */// line comment")
 	checkFieldComments(t, f, "T.F2", "// F2 lead// comment", "// F2 line comment")
 	checkFieldComments(t, f, "T.f3", "// f3 lead comment", "// f3 line comment")
+	checkFieldComments(t, f, "T.f4", "", "")
+	checkFieldComments(t, f, "T.f5", "", "// f5 line comment")
+	checkFieldComments(t, f, "T.f6", "", "/* f6 line comment */")
+	checkFieldComments(t, f, "T.f7", "", "/*f7a*//*f7b*///f7c")
+
 	ast.FileExports(f)
 	checkFieldComments(t, f, "T.F1", "/* F1 lead comment *///", "/* F1 */// line comment")
 	checkFieldComments(t, f, "T.F2", "// F2 lead// comment", "// F2 line comment")

src/go/parser/testdata/commas.src

@@ -8,12 +8,12 @@
 package p
 
 var _ = []int{
-	0/* ERROR HERE "missing ','" */
+	0/* ERROR AFTER "missing ','" */
 }
 
 var _ = []int{
 	0,
 	1,
 	2,
-	3/* ERROR HERE "missing ','" */
+	3/* ERROR AFTER "missing ','" */
 }

src/go/scanner/example_test.go

@@ -41,6 +41,6 @@ func ExampleScanner_Scan() {
 	// 1:16	(	""
 	// 1:17	IDENT	"x"
 	// 1:18	)	""
-	// 1:20	;	"\n"
 	// 1:20	COMMENT	"// Euler"
+	// 1:28	;	"\n"
 }

src/go/scanner/scanner.go

@@ -35,11 +35,12 @@ type Scanner struct {
 	mode Mode         // scanning mode
 
 	// scanning state
-	ch         rune // current character
+	ch         rune      // current character
-	offset     int  // character offset
+	offset     int       // character offset
-	rdOffset   int  // reading offset (position after current character)
+	rdOffset   int       // reading offset (position after current character)
-	lineOffset int  // current line offset
+	lineOffset int       // current line offset
-	insertSemi bool // insert a semicolon before next newline
+	insertSemi bool      // insert a semicolon before next newline
+	nlPos      token.Pos // position of newline in preceding comment
 
 	// public state - ok to modify
 	ErrorCount int // number of errors encountered
@@ -154,11 +155,15 @@ func (s *Scanner) errorf(offs int, format string, args ...any) {
 	s.error(offs, fmt.Sprintf(format, args...))
 }
 
-func (s *Scanner) scanComment() string {
+// scanComment returns the text of the comment and (if nonzero)
+// the offset of the first newline within it, which implies a
+// /*...*/ comment.
+func (s *Scanner) scanComment() (string, int) {
 	// initial '/' already consumed; s.ch == '/' || s.ch == '*'
 	offs := s.offset - 1 // position of initial '/'
 	next := -1           // position immediately following the comment; < 0 means invalid comment
 	numCR := 0
+	nlOffset := 0 // offset of first newline within /*...*/ comment
 
 	if s.ch == '/' {
 		//-style comment
@@ -184,6 +189,8 @@ func (s *Scanner) scanComment() string {
 		ch := s.ch
 		if ch == '\r' {
 			numCR++
+		} else if ch == '\n' && nlOffset == 0 {
+			nlOffset = s.offset
 		}
 		s.next()
 		if ch == '*' && s.ch == '/' {
@@ -218,7 +225,7 @@ exit:
 		lit = stripCR(lit, lit[1] == '*')
 	}
 
-	return string(lit)
+	return string(lit), nlOffset
 }
 
 var prefix = []byte("line ")
@@ -295,50 +302,6 @@ func trailingDigits(text []byte) (int, int, bool) {
 	return i + 1, int(n), err == nil
 }
 
-func (s *Scanner) findLineEnd() bool {
-	// initial '/' already consumed
-
-	defer func(offs int) {
-		// reset scanner state to where it was upon calling findLineEnd
-		s.ch = '/'
-		s.offset = offs
-		s.rdOffset = offs + 1
-		s.next() // consume initial '/' again
-	}(s.offset - 1)
-
-	// read ahead until a newline, EOF, or non-comment token is found
-	for s.ch == '/' || s.ch == '*' {
-		if s.ch == '/' {
-			//-style comment always contains a newline
-			return true
-		}
-		/*-style comment: look for newline */
-		s.next()
-		for s.ch >= 0 {
-			ch := s.ch
-			if ch == '\n' {
-				return true
-			}
-			s.next()
-			if ch == '*' && s.ch == '/' {
-				s.next()
-				break
-			}
-		}
-		s.skipWhitespace() // s.insertSemi is set
-		if s.ch < 0 || s.ch == '\n' {
-			return true
-		}
-		if s.ch != '/' {
-			// non-comment token
-			return false
-		}
-		s.next() // consume '/'
-	}
-
-	return false
-}
-
 func isLetter(ch rune) bool {
 	return 'a' <= lower(ch) && lower(ch) <= 'z' || ch == '_' || ch >= utf8.RuneSelf && unicode.IsLetter(ch)
 }
@@ -822,6 +785,14 @@ func (s *Scanner) switch4(tok0, tok1 token.Token, ch2 rune, tok2, tok3 token.Tok
 // and thus relative to the file set.
 func (s *Scanner) Scan() (pos token.Pos, tok token.Token, lit string) {
 scanAgain:
+	if s.nlPos.IsValid() {
+		// Return artificial ';' token after /*...*/ comment
+		// containing newline, at position of first newline.
+		pos, tok, lit = s.nlPos, token.SEMICOLON, "\n"
+		s.nlPos = token.NoPos
+		return
+	}
+
 	s.skipWhitespace()
 
 	// current token start
@@ -918,23 +889,23 @@ scanAgain:
 		case '/':
 			if s.ch == '/' || s.ch == '*' {
 				// comment
-				if s.insertSemi && s.findLineEnd() {
+				comment, nlOffset := s.scanComment()
-					// reset position to the beginning of the comment
+				if s.insertSemi && nlOffset != 0 {
-					s.ch = '/'
+					// For /*...*/ containing \n, return
-					s.offset = s.file.Offset(pos)
+					// COMMENT then artificial SEMICOLON.
-					s.rdOffset = s.offset + 1
+					s.nlPos = s.file.Pos(nlOffset)
-					s.insertSemi = false // newline consumed
+					s.insertSemi = false
-					return pos, token.SEMICOLON, "\n"
+				} else {
+					insertSemi = s.insertSemi // preserve insertSemi info
 				}
-				comment := s.scanComment()
 				if s.mode&ScanComments == 0 {
 					// skip comment
-					s.insertSemi = false // newline consumed
 					goto scanAgain
 				}
 				tok = token.COMMENT
 				lit = comment
 			} else {
+				// division
 				tok = s.switch2(token.QUO, token.QUO_ASSIGN)
 			}
 		case '%':

src/go/scanner/scanner_test.go

@@ -334,173 +334,171 @@ func TestStripCR(t *testing.T) {
 	}
 }
 
-func checkSemi(t *testing.T, line string, mode Mode) {
+func checkSemi(t *testing.T, input, want string, mode Mode) {
-	var S Scanner
+	if mode&ScanComments == 0 {
-	file := fset.AddFile("TestSemis", fset.Base(), len(line))
+		want = strings.ReplaceAll(want, "COMMENT ", "")
-	S.Init(file, []byte(line), nil, mode)
+		want = strings.ReplaceAll(want, " COMMENT", "") // if at end
-	pos, tok, lit := S.Scan()
+		want = strings.ReplaceAll(want, "COMMENT", "")  // if sole token
-	for tok != token.EOF {
+	}
-		if tok == token.ILLEGAL {
+
-			// the illegal token literal indicates what
+	file := fset.AddFile("TestSemis", fset.Base(), len(input))
-			// kind of semicolon literal to expect
+	var scan Scanner
-			semiLit := "\n"
+	scan.Init(file, []byte(input), nil, mode)
-			if lit[0] == '#' {
+	var tokens []string
-				semiLit = ";"
+	for {
-			}
+		pos, tok, lit := scan.Scan()
-			// next token must be a semicolon
+		if tok == token.EOF {
-			semiPos := file.Position(pos)
+			break
-			semiPos.Offset++
-			semiPos.Column++
-			pos, tok, lit = S.Scan()
-			if tok == token.SEMICOLON {
-				if lit != semiLit {
-					t.Errorf(`bad literal for %q: got %q, expected %q`, line, lit, semiLit)
-				}
-				checkPos(t, line, pos, semiPos)
-			} else {
-				t.Errorf("bad token for %q: got %s, expected ;", line, tok)
-			}
-		} else if tok == token.SEMICOLON {
-			t.Errorf("bad token for %q: got ;, expected no ;", line)
 		}
-		pos, tok, lit = S.Scan()
+		if tok == token.SEMICOLON && lit != ";" {
+			// Artifical semicolon:
+			// assert that position is EOF or that of a newline.
+			off := file.Offset(pos)
+			if off != len(input) && input[off] != '\n' {
+				t.Errorf("scanning <<%s>>, got SEMICOLON at offset %d, want newline or EOF", input, off)
+			}
+		}
+		lit = tok.String() // "\n" => ";"
+		tokens = append(tokens, lit)
+	}
+	if got := strings.Join(tokens, " "); got != want {
+		t.Errorf("scanning <<%s>>, got [%s], want [%s]", input, got, want)
 	}
 }
 
-var lines = []string{
+var semicolonTests = [...]struct{ input, want string }{
-	// # indicates a semicolon present in the source
+	{"", ""},
-	// $ indicates an automatically inserted semicolon
+	{"\ufeff;", ";"}, // first BOM is ignored
-	"",
+	{";", ";"},
-	"\ufeff#;", // first BOM is ignored
+	{"foo\n", "IDENT ;"},
-	"#;",
+	{"123\n", "INT ;"},
-	"foo$\n",
+	{"1.2\n", "FLOAT ;"},
-	"123$\n",
+	{"'x'\n", "CHAR ;"},
-	"1.2$\n",
+	{`"x"` + "\n", "STRING ;"},
-	"'x'$\n",
+	{"`x`\n", "STRING ;"},
-	`"x"` + "$\n",
-	"`x`$\n",
 
-	"+\n",
+	{"+\n", "+"},
-	"-\n",
+	{"-\n", "-"},
-	"*\n",
+	{"*\n", "*"},
-	"/\n",
+	{"/\n", "/"},
-	"%\n",
+	{"%\n", "%"},
 
-	"&\n",
+	{"&\n", "&"},
-	"|\n",
+	{"|\n", "|"},
-	"^\n",
+	{"^\n", "^"},
-	"<<\n",
+	{"<<\n", "<<"},
-	">>\n",
+	{">>\n", ">>"},
-	"&^\n",
+	{"&^\n", "&^"},
 
-	"+=\n",
+	{"+=\n", "+="},
-	"-=\n",
+	{"-=\n", "-="},
-	"*=\n",
+	{"*=\n", "*="},
-	"/=\n",
+	{"/=\n", "/="},
-	"%=\n",
+	{"%=\n", "%="},
 
-	"&=\n",
+	{"&=\n", "&="},
-	"|=\n",
+	{"|=\n", "|="},
-	"^=\n",
+	{"^=\n", "^="},
-	"<<=\n",
+	{"<<=\n", "<<="},
-	">>=\n",
+	{">>=\n", ">>="},
-	"&^=\n",
+	{"&^=\n", "&^="},
 
-	"&&\n",
+	{"&&\n", "&&"},
-	"||\n",
+	{"||\n", "||"},
-	"<-\n",
+	{"<-\n", "<-"},
-	"++$\n",
+	{"++\n", "++ ;"},
-	"--$\n",
+	{"--\n", "-- ;"},
 
-	"==\n",
+	{"==\n", "=="},
-	"<\n",
+	{"<\n", "<"},
-	">\n",
+	{">\n", ">"},
-	"=\n",
+	{"=\n", "="},
-	"!\n",
+	{"!\n", "!"},
 
-	"!=\n",
+	{"!=\n", "!="},
-	"<=\n",
+	{"<=\n", "<="},
-	">=\n",
+	{">=\n", ">="},
-	":=\n",
+	{":=\n", ":="},
-	"...\n",
+	{"...\n", "..."},
 
-	"(\n",
+	{"(\n", "("},
-	"[\n",
+	{"[\n", "["},
-	"{\n",
+	{"{\n", "{"},
-	",\n",
+	{",\n", ","},
-	".\n",
+	{".\n", "."},
 
-	")$\n",
+	{")\n", ") ;"},
-	"]$\n",
+	{"]\n", "] ;"},
-	"}$\n",
+	{"}\n", "} ;"},
-	"#;\n",
+	{";\n", ";"},
-	":\n",
+	{":\n", ":"},
 
-	"break$\n",
+	{"break\n", "break ;"},
-	"case\n",
+	{"case\n", "case"},
-	"chan\n",
+	{"chan\n", "chan"},
-	"const\n",
+	{"const\n", "const"},
-	"continue$\n",
+	{"continue\n", "continue ;"},
 
-	"default\n",
+	{"default\n", "default"},
-	"defer\n",
+	{"defer\n", "defer"},
-	"else\n",
+	{"else\n", "else"},
-	"fallthrough$\n",
+	{"fallthrough\n", "fallthrough ;"},
-	"for\n",
+	{"for\n", "for"},
 
-	"func\n",
+	{"func\n", "func"},
-	"go\n",
+	{"go\n", "go"},
-	"goto\n",
+	{"goto\n", "goto"},
-	"if\n",
+	{"if\n", "if"},
-	"import\n",
+	{"import\n", "import"},
 
-	"interface\n",
+	{"interface\n", "interface"},
-	"map\n",
+	{"map\n", "map"},
-	"package\n",
+	{"package\n", "package"},
-	"range\n",
+	{"range\n", "range"},
-	"return$\n",
+	{"return\n", "return ;"},
 
-	"select\n",
+	{"select\n", "select"},
-	"struct\n",
+	{"struct\n", "struct"},
-	"switch\n",
+	{"switch\n", "switch"},
-	"type\n",
+	{"type\n", "type"},
-	"var\n",
+	{"var\n", "var"},
 
-	"foo$//comment\n",
+	{"foo//comment\n", "IDENT COMMENT ;"},
-	"foo$//comment",
+	{"foo//comment", "IDENT COMMENT ;"},
-	"foo$/*comment*/\n",
+	{"foo/*comment*/\n", "IDENT COMMENT ;"},
-	"foo$/*\n*/",
+	{"foo/*\n*/", "IDENT COMMENT ;"},
-	"foo$/*comment*/    \n",
+	{"foo/*comment*/    \n", "IDENT COMMENT ;"},
-	"foo$/*\n*/    ",
+	{"foo/*\n*/    ", "IDENT COMMENT ;"},
 
-	"foo    $// comment\n",
+	{"foo    // comment\n", "IDENT COMMENT ;"},
-	"foo    $// comment",
+	{"foo    // comment", "IDENT COMMENT ;"},
-	"foo    $/*comment*/\n",
+	{"foo    /*comment*/\n", "IDENT COMMENT ;"},
-	"foo    $/*\n*/",
+	{"foo    /*\n*/", "IDENT COMMENT ;"},
-	"foo    $/*  */ /* \n */ bar$/**/\n",
+	{"foo    /*  */ /* \n */ bar/**/\n", "IDENT COMMENT COMMENT ; IDENT COMMENT ;"},
-	"foo    $/*0*/ /*1*/ /*2*/\n",
+	{"foo    /*0*/ /*1*/ /*2*/\n", "IDENT COMMENT COMMENT COMMENT ;"},
 
-	"foo    $/*comment*/    \n",
+	{"foo    /*comment*/    \n", "IDENT COMMENT ;"},
-	"foo    $/*0*/ /*1*/ /*2*/    \n",
+	{"foo    /*0*/ /*1*/ /*2*/    \n", "IDENT COMMENT COMMENT COMMENT ;"},
-	"foo	$/**/ /*-------------*/       /*----\n*/bar       $/*  \n*/baa$\n",
+	{"foo	/**/ /*-------------*/       /*----\n*/bar       /*  \n*/baa\n", "IDENT COMMENT COMMENT COMMENT ; IDENT COMMENT ; IDENT ;"},
-	"foo    $/* an EOF terminates a line */",
+	{"foo    /* an EOF terminates a line */", "IDENT COMMENT ;"},
-	"foo    $/* an EOF terminates a line */ /*",
+	{"foo    /* an EOF terminates a line */ /*", "IDENT COMMENT COMMENT ;"},
-	"foo    $/* an EOF terminates a line */ //",
+	{"foo    /* an EOF terminates a line */ //", "IDENT COMMENT COMMENT ;"},
 
-	"package main$\n\nfunc main() {\n\tif {\n\t\treturn /* */ }$\n}$\n",
+	{"package main\n\nfunc main() {\n\tif {\n\t\treturn /* */ }\n}\n", "package IDENT ; func IDENT ( ) { if { return COMMENT } ; } ;"},
-	"package main$",
+	{"package main", "package IDENT ;"},
 }
 
-func TestSemis(t *testing.T) {
+func TestSemicolons(t *testing.T) {
-	for _, line := range lines {
+	for _, test := range semicolonTests {
-		checkSemi(t, line, 0)
+		input, want := test.input, test.want
-		checkSemi(t, line, ScanComments)
+		checkSemi(t, input, want, 0)
+		checkSemi(t, input, want, ScanComments)
 
 		// if the input ended in newlines, the input must tokenize the
 		// same with or without those newlines
-		for i := len(line) - 1; i >= 0 && line[i] == '\n'; i-- {
+		for i := len(input) - 1; i >= 0 && input[i] == '\n'; i-- {
-			checkSemi(t, line[0:i], 0)
+			checkSemi(t, input[0:i], want, 0)
-			checkSemi(t, line[0:i], ScanComments)
+			checkSemi(t, input[0:i], want, ScanComments)
 		}
 	}
 }