gc: fix imported and not used message - show path

R=ken2
CC=golang-dev
https://golang.org/cl/229046

src/cmd/gc/lex.c

@@ -1610,7 +1610,7 @@ mkpackage(char* pkgname)
 					// errors if a conflicting top-level name is
 					// introduced by a different file.
 					if(!s->def->used && !nsyntaxerrors)
-						yyerrorl(s->def->lineno, "imported and not used: %s", s->def->sym->name);
+						yyerrorl(s->def->lineno, "imported and not used: %Z", s->def->pkg->path);
 					s->def = N;
 					continue;
 				}
@@ -1618,7 +1618,7 @@ mkpackage(char* pkgname)
 					// throw away top-level name left over
 					// from previous import . "x"
 					if(s->def->pack != N && !s->def->pack->used && !nsyntaxerrors) {
-						yyerrorl(s->def->pack->lineno, "imported and not used: %s", s->def->pack->sym->name);
+						yyerrorl(s->def->pack->lineno, "imported and not used: %Z", s->def->pack->pkg->path);
 						s->def->pack->used = 1;
 					}
 					s->def = N;

src/cmd/gc/subr.c

@@ -360,7 +360,7 @@ importdot(Pkg *opkg, Node *pack)
 	}
 	if(n == 0) {
 		// can't possibly be used - there were no symbols
-		yyerrorl(pack->lineno, "imported and not used: %s", pack->sym->name);
+		yyerrorl(pack->lineno, "imported and not used: %Z", opkg->path);
 	}
 }
 

src/cmd/gc/walk.c

@@ -1128,7 +1128,6 @@ walkexpr(Node **np, NodeList **init)
 	case OARRAYLIT:
 	case OMAPLIT:
 	case OSTRUCTLIT:
-	arraylit:
 		nvar = nod(OXXX, N, N);
 		tempname(nvar, n->type);
 		anylit(n, nvar, init);

test/import4.go

+// $G $D/empty.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
+
+// various kinds of imported and not used
+
+// standard
+import "fmt"	// ERROR "imported and not used.*fmt"
+
+// renamed
+import X "math"	// ERROR "imported and not used.*math"
+
+// import dot
+import . "bufio"	// ERROR "imported and not used.*bufio"
+
+// again, package without anything in it
+import "./empty"	// ERROR "imported and not used.*empty"
+import Z "./empty"	// ERROR "imported and not used.*empty"
+import . "./empty"	// ERROR "imported and not used.*empty"
+