catch package net import "net" for release

R=ken
OCL=34205
CL=34207

src/cmd/gc/go.y

@@ -230,6 +230,16 @@ import_package:
 		pkgimportname = $2;
 		if(strcmp($2->name, "main") == 0)
 			yyerror("cannot import package main");
+			
+		// TODO(rsc): This is not quite precise enough a check
+		// (it excludes google/util/hash from importing hash)
+		// but it is enough to reduce confusion during the 
+		// 2009/09/01 release when all the "import myself"
+		// statements have to go away in programs building
+		// against the release.  Once the programs have converted
+		// it should probably just go away.
+		if(strcmp($2->name, package) == 0)
+			yyerror("package cannot import itself (anymore)");
 	}
 
 import_there:

test/fixedbugs/bug133.dir/bug2.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package bug1
+package bug2
 
 import "./bug1"
 import "./bug0"