cmd/gc: point "no new variables" error at right line number.

Fixes #3856.

R=dsymonds, rsc
CC=golang-dev
https://golang.org/cl/6455056

src/cmd/gc/dcl.c

@@ -464,7 +464,7 @@ colasdefn(NodeList *left, Node *defn)
 		if(isblank(n))
 			continue;
 		if(!colasname(n)) {
-			yyerror("non-name %N on left side of :=", n);
+			yyerrorl(defn->lineno, "non-name %N on left side of :=", n);
 			nerr++;
 			continue;
 		}
@@ -479,11 +479,11 @@ colasdefn(NodeList *left, Node *defn)
 		l->n = n;
 	}
 	if(nnew == 0 && nerr == 0)
-		yyerror("no new variables on left side of :=");
+		yyerrorl(defn->lineno, "no new variables on left side of :=");
 }
 
 Node*
-colas(NodeList *left, NodeList *right)
+colas(NodeList *left, NodeList *right, int32 lno)
 {
 	Node *as;
 
@@ -491,6 +491,7 @@ colas(NodeList *left, NodeList *right)
 	as->list = left;
 	as->rlist = right;
 	as->colas = 1;
+	as->lineno = lno;
 	colasdefn(left, as);
 
 	// make the tree prettier; not necessary

src/cmd/gc/go.h

@@ -928,7 +928,7 @@ void	nodfconst(Node *n, Type *t, Mpflt* fval);
 void	addmethod(Sym *sf, Type *t, int local);
 void	addvar(Node *n, Type *t, int ctxt);
 NodeList*	checkarglist(NodeList *all, int input);
-Node*	colas(NodeList *left, NodeList *right);
+Node*	colas(NodeList *left, NodeList *right, int32 lno);
 void	colasdefn(NodeList *left, Node *defn);
 NodeList*	constiter(NodeList *vl, Node *t, NodeList *cl);
 Node*	dclname(Sym *s);

src/cmd/gc/go.y

@@ -37,8 +37,8 @@ static void fixlbrace(int);
 // |sed 's/.*	//' |9 fmt -l1 |sort |9 fmt -l50 | sed 's/^/%xxx		/'
 
 %token	<val>	LLITERAL
-%token	<i>	LASOP
+%token	<i>	LASOP LCOLAS
-%token	<sym>	LBREAK LCASE LCHAN LCOLAS LCONST LCONTINUE LDDD
+%token	<sym>	LBREAK LCASE LCHAN LCONST LCONTINUE LDDD
 %token	<sym>	LDEFAULT LDEFER LELSE LFALL LFOR LFUNC LGO LGOTO
 %token	<sym>	LIF LIMPORT LINTERFACE LMAP LNAME
 %token	<sym>	LPACKAGE LRANGE LRETURN LSELECT LSTRUCT LSWITCH
@@ -437,7 +437,7 @@ simple_stmt:
 				$$->left = dclname($1->n->sym);  // it's a colas, so must not re-use an oldname.
 			break;
 		}
-		$$ = colas($1, $3);
+		$$ = colas($1, $3, $2);
 	}
 |	expr LINC
 	{
@@ -496,7 +496,7 @@ case:
 		// done in casebody()
 		markdcl();
 		$$ = nod(OXCASE, N, N);
-		$$->list = list1(colas($2, list1($4)));
+		$$->list = list1(colas($2, list1($4), $3));
 	}
 |	LDEFAULT ':'
 	{

src/cmd/gc/lex.c

@@ -973,6 +973,7 @@ l0:
 		c1 = getc();
 		if(c1 == '=') {
 			c = LCOLAS;
+			yylval.i = lexlineno;
 			goto lx;
 		}
 		break;

src/cmd/gc/y.tab.h

@@ -39,10 +39,10 @@
    enum yytokentype {
      LLITERAL = 258,
      LASOP = 259,
-     LBREAK = 260,
+     LCOLAS = 260,
-     LCASE = 261,
+     LBREAK = 261,
-     LCHAN = 262,
+     LCASE = 262,
-     LCOLAS = 263,
+     LCHAN = 263,
      LCONST = 264,
      LCONTINUE = 265,
      LDDD = 266,
@@ -91,10 +91,10 @@
 /* Tokens.  */
 #define LLITERAL 258
 #define LASOP 259
-#define LBREAK 260
+#define LCOLAS 260
-#define LCASE 261
+#define LBREAK 261
-#define LCHAN 262
+#define LCASE 262
-#define LCOLAS 263
+#define LCHAN 263
 #define LCONST 264
 #define LCONTINUE 265
 #define LDDD 266

test/declbad.go

@@ -38,6 +38,12 @@ func main() {
 		i, f := f2() // ERROR "redeclared|no new"
 		_, _, _ = i, f, s
 	}
+	{
+		// multiline no new variables
+		i := f1
+		i := func() int { // ERROR "redeclared|no new|incompatible"
+		}
+	}
 	{
 		// single redeclaration
 		i, f, s := f3()