Fix some of the tests

- removed the inherent impls compile-fail test, because we’ll be
supporting them
- remove E0308-2 because it’s gonna be supported now (behind a feature
gate)
- replaced the mismatched method receiver error message with something
better, so fixed the tests that that broke

Author: mikeyhew

src/test/compile-fail/E0308-2.rs

@@ -1,17 +1,17 @@
 use std::rc::Rc;
 
 trait Foo {
-    fn foo(self: Rc<Box<Self>>); //~ ERROR arbitrary self types are unstable
+    fn foo(self: Rc<Box<Self>>); //~ ERROR arbitrary `self` types are unstable
 }
 
 struct Bar;
 
 impl Foo for Bar {
-    fn foo(self: Rc<Box<Self>>) {} //~ ERROR arbitrary self types are unstable
+    fn foo(self: Rc<Box<Self>>) {} //~ ERROR arbitrary `self` types are unstable
 }
 
 impl Bar {
-    fn bar(self: Box<Rc<Self>>) {} //~ ERROR arbitrary self types are unstable
+    fn bar(self: Box<Rc<Self>>) {} //~ ERROR arbitrary `self` types are unstable
 }
 
 fn main() {}

src/test/compile-fail/arbitrary-self-types-inherent-impl.rs

@@ -12,7 +12,7 @@ struct S(String);
 
 impl S {
     fn f(self: *mut S) -> String { self.0 }
-    //~^ ERROR mismatched method receiver
+    //~^ ERROR invalid `self` type
 }
 
 fn main() { S("".to_owned()).f(); }

src/test/compile-fail/feature-gate-arbitrary-self-types.rs

@@ -15,7 +15,7 @@ struct Foo {
 }
 
 impl Foo {
-    fn foo(self: isize, x: isize) -> isize {  //~ ERROR mismatched method receiver
+    fn foo(self: isize, x: isize) -> isize {  //~ ERROR invalid `self` type
         self.f + x
     }
 }
@@ -25,10 +25,10 @@ struct Bar<T> {
 }
 
 impl<T> Bar<T> {
-    fn foo(self: Bar<isize>, x: isize) -> isize { //~ ERROR mismatched method receiver
+    fn foo(self: Bar<isize>, x: isize) -> isize { //~ ERROR invalid `self` type
         x
     }
-    fn bar(self: &Bar<usize>, x: isize) -> isize {   //~ ERROR mismatched method receiver
+    fn bar(self: &Bar<usize>, x: isize) -> isize {   //~ ERROR invalid `self` type
         x
     }
 }