Fix handling of trait methods with bodies and improve efficiency

src/test/ui/E0642.rs

@@ -9,7 +9,11 @@
 // except according to those terms.
 
 trait Foo {
-    fn foo((x, y): (i32, i32)); //~ ERROR patterns aren't allowed in methods without bodies
+    fn foo((x, y): (i32, i32)); //~ ERROR patterns aren't allowed in trait methods
+}
+
+trait Bar {
+    fn bar((x, y): (i32, i32)) {} //~ ERROR patterns aren't allowed in trait methods
 }
 
 fn main() {}

src/test/ui/E0642.stderr

@@ -1,9 +1,23 @@
-error[E0642]: patterns aren't allowed in methods without bodies
+error[E0642]: patterns aren't allowed in trait methods
   --> $DIR/E0642.rs:12:12
    |
-LL |     fn foo((x, y): (i32, i32)); //~ ERROR patterns aren't allowed in methods without bodies
-   |            ^^^^^^ help: use an underscore to ignore the name: `_`
+LL |     fn foo((x, y): (i32, i32)); //~ ERROR patterns aren't allowed in trait methods
+   |            ^^^^^^
+help: give this argument a name or use an underscore to ignore it, instead of a tuple pattern
+   |
+LL |     fn foo(_: (i32, i32)); //~ ERROR patterns aren't allowed in trait methods
+   |            ^
 
-error: aborting due to previous error
+error[E0642]: patterns aren't allowed in trait methods
+  --> $DIR/E0642.rs:16:12
+   |
+LL |     fn bar((x, y): (i32, i32)) {} //~ ERROR patterns aren't allowed in trait methods
+   |            ^^^^^^
+help: give this argument a name or use an underscore to ignore it, instead of a tuple pattern
+   |
+LL |     fn bar(_: (i32, i32)) {} //~ ERROR patterns aren't allowed in trait methods
+   |            ^
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0642`.