Auto merge of #35015 - petrochenkov:forearg, r=nikomatsakis

Properly enforce the "patterns aren't allowed in foreign functions" rule

Cases like `arg @ PATTERN` or `mut arg` were missing.
Apply the same rule to function pointer types.

Closes https://github.com/rust-lang/rust/issues/35203
[breaking-change], no breakage in sane code is expected though
r? @nikomatsakis

This is somewhat related to https://github.com/rust-lang/rfcs/pull/1685 (cc @matklad).
The goal is to eventually support full pattern syntax where it makes sense (function body may present) and to support *only* the following forms - `TYPE`, `ident: TYPE`, `_: TYPE` - where patterns don't make sense (function body doesn't present), i.e. in foreign functions and function pointer types.

1 files changed, 30 insertions, 0 deletions

diff --git a/src/test/compile-fail/no-patterns-in-args.rs b/src/test/compile-fail/no-patterns-in-args.rs
new file mode 100644
index 00000000000..3edbdf4ebc9
--- /dev/null
+++ b/src/test/compile-fail/no-patterns-in-args.rs
@@ -0,0 +1,30 @@
+// Copyright 2016 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.
+
+extern {
+    fn f1(mut arg: u8); //~ ERROR patterns aren't allowed in foreign function declarations
+                        //~^ NOTE this is a recent error
+    fn f2(&arg: u8); //~ ERROR patterns aren't allowed in foreign function declarations
+    fn f3(arg @ _: u8); //~ ERROR patterns aren't allowed in foreign function declarations
+                        //~^ NOTE this is a recent error
+    fn g1(arg: u8); // OK
+    fn g2(_: u8); // OK
+    // fn g3(u8); // Not yet
+}
+
+type A1 = fn(mut arg: u8); //~ ERROR patterns aren't allowed in function pointer types
+                           //~^ NOTE this is a recent error
+type A2 = fn(&arg: u8); //~ ERROR patterns aren't allowed in function pointer types
+                        //~^ NOTE this is a recent error
+type B1 = fn(arg: u8); // OK
+type B2 = fn(_: u8); // OK
+type B3 = fn(u8); // OK
+
+fn main() {}