Add tests

Author: petrochenkov

src/test/parse-fail/closure-return-syntax.rs

@@ -13,5 +13,5 @@
 
 fn main() {
     let x = || -> i32 22;
-    //~^ ERROR expected one of `!`, `(`, `::`, `<`, or `{`, found `22`
+    //~^ ERROR expected one of `!`, `(`, `+`, `::`, `<`, or `{`, found `22`
 }

src/test/parse-fail/impl-trait-plus-priority.rs

@@ -0,0 +1,47 @@
+// Copyright 2017 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.
+
+// compile-flags: -Z parse-only -Z continue-parse-after-error
+
+fn f() -> impl A + B {} // OK
+fn f() -> dyn A + B {} // OK
+fn f() -> A + B {} // OK
+
+impl S {
+    fn f(self) -> impl A + B { // OK
+        let _ = |a, b| -> impl A + B {}; // OK
+    }
+    fn f(self) -> dyn A + B { // OK
+        let _ = |a, b| -> dyn A + B {}; // OK
+    }
+    fn f(self) -> A + B { // OK
+        let _ = |a, b| -> A + B {}; // OK
+    }
+}
+
+type A = fn() -> impl A + B;
+//~^ ERROR expected a path on the left-hand side of `+`, not `fn() -> impl A`
+type A = fn() -> dyn A + B;
+//~^ ERROR expected a path on the left-hand side of `+`, not `fn() -> dyn A`
+type A = fn() -> A + B;
+//~^ ERROR expected a path on the left-hand side of `+`, not `fn() -> A`
+
+type A = Fn() -> impl A + B; // OK, interpreted as `(Fn() -> impl A) + B`
+type A = Fn() -> dyn A + B; // OK, interpreted as `(Fn() -> dyn A) + B`
+type A = Fn() -> A + B; // OK, interpreted as `(Fn() -> A) + B`
+
+type A = &impl A + B;
+//~^ ERROR expected a path on the left-hand side of `+`, not `&impl A`
+type A = &dyn A + B;
+//~^ ERROR expected a path on the left-hand side of `+`, not `&dyn A`
+type A = &A + B;
+//~^ ERROR expected a path on the left-hand side of `+`, not `&A`
+
+fn main() {}

src/test/parse-fail/issue-24780.rs

@@ -15,6 +15,6 @@
 // compile-flags: -Z parse-only
 
 fn foo() -> Vec<usize>> {
-    //~^ ERROR expected one of `!`, `::`, `where`, or `{`, found `>`
+    //~^ ERROR expected one of `!`, `+`, `::`, `where`, or `{`, found `>`
     Vec::new()
 }