fix a 6g crash after type errors.

do not bother warning about marks left
on stack after syntax errors.

leave OCONV nodes in tree to avoid type errors
arising from multiple walks.

R=ken
OCL=30639
CL=30662

src/cmd/5g/cgen.c

@@ -28,6 +28,9 @@ cgen(Node *n, Node *res)
 	if(res == N || res->type == T)
 		fatal("cgen: res nil");
 
+	while(n->op == OCONVNOP)
+		n = n->left;
+
 	// static initializations
 	if(initflag && gen_as_init(n, res))
 		goto ret;
@@ -197,10 +200,6 @@ cgen(Node *n, Node *res)
 		goto abop;
 
 	case OCONV:
-		if(eqtype(n->type, nl->type)) {
-			cgen(nl, res);
-			break;
-		}
 		regalloc(&n1, nl->type, res);
 		cgen(nl, &n1);
 		gmove(&n1, res);
@@ -373,7 +372,10 @@ agen(Node *n, Node *res)
 
 //	if(!isptr[res->type->etype])
 //		fatal("agen: not tptr: %T", res->type);
-
+//
+//	while(n->op == OCONVNOP)
+//		n = n->left;
+//
 //	if(n->addable) {
 //		regalloc(&n1, types[tptr], res);
 //		gins(ALEAQ, n, &n1);
@@ -390,12 +392,6 @@ agen(Node *n, Node *res)
 //		fatal("agen: unknown op %N", n);
 //		break;
 
-//	case OCONV:
-//		if(!cvttype(n->type, nl->type))
-//			fatal("agen: non-trivial OCONV");
-//		agen(nl, res);
-//		return;
-
 //	case OCALLMETH:
 //		cgen_callmeth(n, 0);
 //		cgen_aret(n, res);

src/cmd/6g/cgen.c

@@ -28,6 +28,9 @@ cgen(Node *n, Node *res)
 	if(res == N || res->type == T)
 		fatal("cgen: res nil");
 
+	while(n->op == OCONVNOP)
+		n = n->left;
+
 	// static initializations
 	if(initflag && gen_as_init(n, res))
 		goto ret;
@@ -196,10 +199,6 @@ cgen(Node *n, Node *res)
 		goto abop;
 
 	case OCONV:
-		if(eqtype(n->type, nl->type)) {
-			cgen(nl, res);
-			break;
-		}
 		regalloc(&n1, nl->type, res);
 		regalloc(&n2, n->type, &n1);
 		cgen(nl, &n1);
@@ -378,6 +377,9 @@ agen(Node *n, Node *res)
 	if(!isptr[res->type->etype])
 		fatal("agen: not tptr: %T", res->type);
 
+	while(n->op == OCONVNOP)
+		n = n->left;
+
 	if(n->addable) {
 		regalloc(&n1, types[tptr], res);
 		gins(ALEAQ, n, &n1);
@@ -394,12 +396,6 @@ agen(Node *n, Node *res)
 		fatal("agen: unknown op %N", n);
 		break;
 
-	case OCONV:
-		if(!cvttype(n->type, nl->type))
-			fatal("agen: non-trivial OCONV");
-		agen(nl, res);
-		return;
-
 	case OCALLMETH:
 		cgen_callmeth(n, 0);
 		cgen_aret(n, res);

src/cmd/8g/cgen.c

@@ -61,6 +61,9 @@ cgen(Node *n, Node *res)
 	if(res == N || res->type == T)
 		fatal("cgen: res nil");
 
+	while(n->op == OCONVNOP)
+		n = n->left;
+
 	// static initializations
 	if(initflag && gen_as_init(n, res))
 		return;
@@ -403,6 +406,9 @@ agen(Node *n, Node *res)
 	if(n == N || n->type == T || res == N || res->type == T)
 		fatal("agen");
 
+	while(n->op == OCONVNOP)
+		n = n->left;
+
 	// addressable var is easy
 	if(n->addable) {
 		if(n->op == OREGISTER)
@@ -422,12 +428,6 @@ agen(Node *n, Node *res)
 	default:
 		fatal("agen %O", n->op);
 
-	case OCONV:
-		if(!cvttype(n->type, nl->type))
-			fatal("agen: non-trivial OCONV");
-		agen(nl, res);
-		break;
-
 	case OCALLMETH:
 		cgen_callmeth(n, 0);
 		cgen_aret(n, res);

src/cmd/gc/go.h

@@ -327,7 +327,7 @@ enum
 	OREGISTER, OINDREG,
 	OKEY, OPARAM,
 	OCOMPOS, OCOMPSLICE, OCOMPMAP,
-	OCONV,
+	OCONV, OCONVNOP,
 	ODOTTYPE, OTYPESW,
 	OBAD,
 
@@ -530,6 +530,7 @@ EXTERN	char*	outfile;
 EXTERN	char*	package;
 EXTERN	Biobuf*	bout;
 EXTERN	int	nerrors;
+EXTERN	int	nsyntaxerrors;
 EXTERN	char	namebuf[NSYMB];
 EXTERN	char	lexbuf[NSYMB];
 EXTERN	char	debug[256];

src/cmd/gc/go.y

@@ -129,7 +129,8 @@ file:
 		if(debug['f'])
 			frame(1);
 		fninit($4);
-		testdclstack();
+		if(nsyntaxerrors == 0)
+			testdclstack();
 	}
 
 package:

src/cmd/gc/sinit.c

@@ -144,6 +144,9 @@ slicerewrite(Node *n)
 	int b;
 	Node *a;
 
+	while(n->op == OCONVNOP)
+		n = n->left;
+
 	// call to newarray - find nel argument
 	nel = findarg(n, "nel", "newarray");
 	if(nel == N || !isslice(n->type))

src/cmd/gc/subr.c

@@ -22,8 +22,10 @@ yyerror(char *fmt, ...)
 	va_start(arg, fmt);
 	vfprint(1, fmt, arg);
 	va_end(arg);
-	if(strcmp(fmt, "syntax error") == 0)
+	if(strcmp(fmt, "syntax error") == 0) {
+		nsyntaxerrors++;
 		print(" near %s", lexbuf);
+	}
 	print("\n");
 	if(debug['h'])
 		*(int*)0 = 0;
@@ -670,6 +672,7 @@ opnames[] =
 	[OCOM]		= "COM",
 	[OCONTINUE]	= "CONTINUE",
 	[OCONV]		= "CONV",
+	[OCONVNOP]		= "CONVNOP",
 	[ODCLARG]	= "DCLARG",
 	[ODCLFIELD]	= "DCLFIELD",
 	[ODCLFUNC]	= "DCLFUNC",

src/cmd/gc/walk.c

@@ -618,6 +618,9 @@ loop:
 			goto nottop;
 		walkconv(n);
 		goto ret;
+	
+	case OCONVNOP:
+		goto ret;
 
 	case OCOMPMAP:
 	case OCOMPSLICE:
@@ -1284,10 +1287,8 @@ walkconv(Node *n)
 		if(!isinter(l->type))
 			yyerror("type assertion requires interface on left, have %T", l->type);
 		et = ifaceas1(t, l->type, 1);
-		if(et == I2Isame || et == E2Esame) {
-			n->op = OCONV;
+		if(et == I2Isame || et == E2Esame)
 			goto nop;
-		}
 		if(et != Inone) {
 			indir(n, ifacecvt(t, l, et));
 			return;
@@ -1303,10 +1304,15 @@ walkconv(Node *n)
 	// no-op conversion
 	if(cvttype(t, l->type) == 1) {
 	nop:
-		if(l->op != ONAME) {
+		if(l->op == OLITERAL) {
 			indir(n, l);
-			n->type = t;
+			l->type = t;
+			return;
 		}
+		// leave OCONV node in place
+		// in case tree gets walked again.
+		// back end will ignore.
+		n->op = OCONVNOP;
 		return;
 	}
 
@@ -3564,6 +3570,8 @@ colas(Node *nl, Node *nr)
 			// finish call - first half above
 			l = listfirst(&savel, &nl);
 			t = structfirst(&saver, getoutarg(t));
+			if(t == T)
+				return N;
 			while(l != N) {
 				a = mixedoldnew(l, t->type);
 				n = list(n, a);