bug197

R=ken
OCL=33765
CL=33765

src/cmd/gc/const.c

@@ -77,6 +77,8 @@ convlit1(Node **np, Type *t, int explicit)
 		return;
 	if(eqtype(t, n->type))
 		return;
+	if(!explicit && n->type->etype != TIDEAL && n->type != idealstring && n->type->etype != TNIL)
+		return;
 
 //dump("convlit1", n);
 	if(n->op == OLITERAL) {

src/cmd/gc/go.h

@@ -330,7 +330,7 @@ enum
 	OCMPIFACE, OCMPSTR,
 	OCOMPLIT, OMAPLIT, OSTRUCTLIT, OARRAYLIT,
 	OCOMPSLICE, OCOMPMAP,
-	OCONV, OCONVNOP, OCONVA2S, OCONVIFACE, OCONVSLICE,
+	OCONV, OCONVNOP, OCONVIFACE, OCONVSLICE,
 	ODCL, ODCLFUNC, ODCLFIELD, ODCLCONST, ODCLTYPE,
 	ODOT, ODOTPTR, ODOTMETH, ODOTINTER, OXDOT,
 	ODOTTYPE,

src/cmd/gc/print.c

@@ -258,6 +258,9 @@ exprfmt(Fmt *f, Node *n, int prec)
 		break;
 
 	case OCONV:
+	case OCONVNOP:
+	case OCONVSLICE:
+	case OCONVIFACE:
 		fmtprint(f, "%T(", n->type);
 		exprfmt(f, n->left, 0);
 		fmtprint(f, ")");

src/cmd/gc/typecheck.c

@@ -87,6 +87,8 @@ reswitch:
 		ok |= Erv;
 		if(n->iota && !(top & Eiota))
 			yyerror("use of iota not in constant initializer");
+		if(n->val.ctype == CTSTR)
+			n->type = idealstring;
 		goto ret;
 
 	case ONONAME:
@@ -1268,7 +1270,9 @@ typecheckconv(Node *nconv, Node *n, Type *t, int explicit)
 	if(n->type == T)
 		return n;
 
-	if(cvttype(t, n->type) && n->op == OLITERAL) {
+	if(n->op == OLITERAL)
+	if(explicit || n->type->etype == TIDEAL || n->type == idealstring || n->type->etype == TNIL)
+	if(cvttype(t, n->type)) {
 		// can convert literal in place
 		// TODO(rsc) is this needed?
 		n1 = nod(OXXX, N, N);
@@ -1286,6 +1290,10 @@ typecheckconv(Node *nconv, Node *n, Type *t, int explicit)
 		return n;
 
 	case 0:
+		if(nconv) {
+			nconv->op = OCONVNOP;
+			return nconv;
+		}
 		return n;
 	}
 

test/fixedbugs/bug197.go

+// errchk $G $D/$F.go
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+type T int
+type U int
+
+var x int
+
+var t T = int(0)	// ERROR "cannot use"
+var t1 T = int(x)	// ERROR "cannot use"
+var u U = int(0)	// ERROR "cannot use"
+var u1 U = int(x)	// ERROR "cannot use"
+
+type S string
+var s S
+
+var s1 = s + "hello"
+var s2 = "hello" + s
+var s3 = s + string("hello")	// ERROR "invalid operation"
+var s4 = string("hello") + s	// ERROR "invalid operation"
+
+var r string
+
+var r1 = r + "hello"
+var r2 = "hello" + r
+var r3 = r + string("hello")
+var r4 = string("hello") + r
+