fix tyvar_behind_raw_pointer error code

Author: csmoe

src/librustc_typeck/check/method/probe.rs

@@ -337,7 +337,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                                 lint::builtin::TYVAR_BEHIND_RAW_POINTER,
                                 scope_expr_id,
                                 span,
-                                &format!("the type of this value must be known in this context"));
+                                &format!("type annotations needed"));
                         }
                     } else {
                         let t = self.structurally_resolved_type(span, final_ty);

src/test/ui/inference-variable-behind-raw-pointer.stderr

@@ -1,4 +1,4 @@
-warning: the type of this value must be known in this context
+warning: type annotations needed
   --> $DIR/inference-variable-behind-raw-pointer.rs:18:13
    |
 18 |     if data.is_null() {}