Emit a better error for attempted unsafe-pointer-self. Close rust-lang#8306.

Author: bblum

src/libsyntax/parse/parser.rs

@@ -3571,6 +3571,19 @@ impl Parser {
             self.bump();
             sty_value
           }
+          token::BINOP(token::STAR) => {
+            // Possibly "*self" or "*mut self" -- not supported. Try to avoid
+            // emitting cryptic "unexpected token" errors.
+            self.bump();
+            if self.token_is_mutability(self.token) {
+                self.bump();
+            }
+            if self.is_self_ident() {
+                self.span_err(*self.span, "cannot pass self by unsafe pointer");
+                self.bump();
+            }
+            sty_value
+          }
           _ => {
             sty_static
           }

src/test/compile-fail/no-unsafe-self.rs

@@ -0,0 +1,22 @@
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+trait A {
+    fn foo(*mut self); //~ ERROR cannot pass self by unsafe pointer
+    fn bar(*self); //~ ERROR cannot pass self by unsafe pointer
+}
+
+struct X;
+impl A for X {
+    fn foo(*mut self) { } //~ ERROR cannot pass self by unsafe pointer
+    fn bar(*self) { } //~ ERROR cannot pass self by unsafe pointer
+}
+
+fn main() { }