Add Error member to yyLexer type (yyError

has no access to yylex)

R=ken2, ken3
CC=golang-dev
https://golang.org/cl/813047

src/cmd/goyacc/doc.go

@@ -24,10 +24,12 @@ argument that conforms to the following interface:
 
 	type yyLexer interface {
 		Lex(lval *yySymType) int
+		Error(e string)
 	}
 
 Lex should return the token identifier, and place other token
 information in lval (which replaces the usual yylval).
+Error is equivalent to yyerror in the original yacc.
 
 Code inside the parser may refer to the variable yylex
 which holds the yyLexer passed to Parse.

src/cmd/goyacc/goyacc.go

@@ -3080,6 +3080,7 @@ var yyDebug = 0
 
 type yyLexer interface {
 	Lex(lval *yySymType) int
+	Error(s string)
 }
 
 const yyFlag = -1000
@@ -3162,7 +3163,7 @@ ret1:
 yystack:
 	/* put a state and value onto the stack */
 	if yyDebug >= 4 {
-		fmt.Printf("char %v in %v", yyTokname(yychar), yyStatname(yystate))
+		fmt.Printf("char %v in %v\n", yyTokname(yychar), yyStatname(yystate))
 	}
 
 	yyp++
@@ -3228,7 +3229,7 @@ yydefault:
 		/* error ... attempt to resume parsing */
 		switch Errflag {
 		case 0: /* brand new error */
-			yyError("syntax error")
+			yylex.Error("syntax error")
 			Nerrs++
 			if yyDebug >= 1 {
 				fmt.Printf("%s", yyStatname(yystate))
@@ -3273,7 +3274,7 @@ yydefault:
 
 	/* reduction by production yyn */
 	if yyDebug >= 2 {
-		fmt.Printf("reduce %v in:\n\t%v", yyn, yyStatname(yystate))
+		fmt.Printf("reduce %v in:\n\t%v\n", yyn, yyStatname(yystate))
 	}
 
 	yynt := yyn

src/cmd/goyacc/units.y

@@ -215,7 +215,7 @@ expr0:
 
 type UnitsLex int
 
-func (l UnitsLex) Lex(yylval *yySymType) int {
+func (_ UnitsLex) Lex(yylval *yySymType) int {
 	var c, i int
 
 	c = peekrune
@@ -280,6 +280,10 @@ numb:
 	return VAL
 }
 
+func (_ UnitsLex) Error(s string) {
+	Error("syntax error, last name: %v", sym)
+}
+
 func main() {
 	var file string
 
@@ -384,10 +388,6 @@ func rdigit(c int) bool {
 	return false
 }
 
-func yyError(s string) {
-	Error("syntax error, last name: %v", sym)
-}
-
 func Error(s string, v ...interface{}) {
 	fmt.Printf("%v: %v\n\t", lineno, line)
 	fmt.Printf(s, v)