rustc_resolve: inject uniform_paths canaries regardless of the feature-gate, on Rust 2018.

src/test/ui/rust-2018/uniform-paths-forward-compat/ambiguity-macros-nested.rs

@@ -0,0 +1,29 @@
+// Copyright 2018 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.
+
+// edition:2018
+
+// This test is similar to `ambiguity-macros.rs`, but nested in a module.
+
+mod foo {
+    pub use std::io;
+    //~^ ERROR `std` import is ambiguous
+
+    macro_rules! m {
+        () => {
+            mod std {
+                pub struct io;
+            }
+        }
+    }
+    m!();
+}
+
+fn main() {}

src/test/ui/rust-2018/uniform-paths-forward-compat/ambiguity-macros-nested.stderr

@@ -0,0 +1,16 @@
+error: `std` import is ambiguous
+  --> $DIR/ambiguity-macros-nested.rs:16:13
+   |
+LL |       pub use std::io;
+   |               ^^^ can refer to external crate `::std`
+...
+LL | /             mod std {
+LL | |                 pub struct io;
+LL | |             }
+   | |_____________- may refer to `self::std` in the future
+   |
+   = help: write `::std` or `self::std` explicitly instead
+   = note: in the future, `#![feature(uniform_paths)]` may become the default
+
+error: aborting due to previous error
+

src/test/ui/rust-2018/uniform-paths-forward-compat/ambiguity-macros.rs

@@ -0,0 +1,27 @@
+// Copyright 2018 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.
+
+// edition:2018
+
+// This test is similar to `ambiguity.rs`, but with macros defining local items.
+
+use std::io;
+//~^ ERROR `std` import is ambiguous
+
+macro_rules! m {
+    () => {
+        mod std {
+            pub struct io;
+        }
+    }
+}
+m!();
+
+fn main() {}

src/test/ui/rust-2018/uniform-paths-forward-compat/ambiguity-macros.stderr

@@ -0,0 +1,16 @@
+error: `std` import is ambiguous
+  --> $DIR/ambiguity-macros.rs:15:5
+   |
+LL |   use std::io;
+   |       ^^^ can refer to external crate `::std`
+...
+LL | /         mod std {
+LL | |             pub struct io;
+LL | |         }
+   | |_________- may refer to `self::std` in the future
+   |
+   = help: write `::std` or `self::std` explicitly instead
+   = note: in the future, `#![feature(uniform_paths)]` may become the default
+
+error: aborting due to previous error
+

src/test/ui/rust-2018/uniform-paths-forward-compat/ambiguity-nested.rs

@@ -0,0 +1,24 @@
+// Copyright 2018 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.
+
+// edition:2018
+
+// This test is similar to `ambiguity.rs`, but nested in a module.
+
+mod foo {
+    pub use std::io;
+    //~^ ERROR `std` import is ambiguous
+
+    mod std {
+        pub struct io;
+    }
+}
+
+fn main() {}

src/test/ui/rust-2018/uniform-paths-forward-compat/ambiguity-nested.stderr

@@ -0,0 +1,16 @@
+error: `std` import is ambiguous
+  --> $DIR/ambiguity-nested.rs:16:13
+   |
+LL |       pub use std::io;
+   |               ^^^ can refer to external crate `::std`
+...
+LL | /     mod std {
+LL | |         pub struct io;
+LL | |     }
+   | |_____- may refer to `self::std` in the future
+   |
+   = help: write `::std` or `self::std` explicitly instead
+   = note: in the future, `#![feature(uniform_paths)]` may become the default
+
+error: aborting due to previous error
+

src/test/ui/rust-2018/uniform-paths-forward-compat/ambiguity.rs

@@ -0,0 +1,20 @@
+// Copyright 2018 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.
+
+// edition:2018
+
+use std::io;
+//~^ ERROR `std` import is ambiguous
+
+mod std {
+    pub struct io;
+}
+
+fn main() {}

src/test/ui/rust-2018/uniform-paths-forward-compat/ambiguity.stderr

@@ -0,0 +1,16 @@
+error: `std` import is ambiguous
+  --> $DIR/ambiguity.rs:13:5
+   |
+LL |   use std::io;
+   |       ^^^ can refer to external crate `::std`
+...
+LL | / mod std {
+LL | |     pub struct io;
+LL | | }
+   | |_- may refer to `self::std` in the future
+   |
+   = help: write `::std` or `self::std` explicitly instead
+   = note: in the future, `#![feature(uniform_paths)]` may become the default
+
+error: aborting due to previous error
+

src/test/ui/rust-2018/uniform-paths-forward-compat/block-scoped-shadow.rs

@@ -0,0 +1,21 @@
+// Copyright 2018 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.
+
+// edition:2018
+
+struct std;
+
+fn main() {
+    fn std() {}
+    enum std {}
+    use std as foo;
+    //~^ ERROR `std` import is ambiguous
+    //~| ERROR `std` import is ambiguous
+}

src/test/ui/rust-2018/uniform-paths-forward-compat/block-scoped-shadow.stderr

@@ -0,0 +1,31 @@
+error: `std` import is ambiguous
+  --> $DIR/block-scoped-shadow.rs:18:9
+   |
+LL | struct std;
+   | ----------- may refer to `self::std` in the future
+...
+LL |     enum std {}
+   |     ----------- shadowed by block-scoped `std`
+LL |     use std as foo;
+   |         ^^^ can refer to external crate `::std`
+   |
+   = help: write `::std` or `self::std` explicitly instead
+   = note: in the future, `#![feature(uniform_paths)]` may become the default
+
+error: `std` import is ambiguous
+  --> $DIR/block-scoped-shadow.rs:18:9
+   |
+LL | struct std;
+   | ----------- may refer to `self::std` in the future
+...
+LL |     fn std() {}
+   |     ----------- shadowed by block-scoped `std`
+LL |     enum std {}
+LL |     use std as foo;
+   |         ^^^
+   |
+   = help: write `self::std` explicitly instead
+   = note: in the future, `#![feature(uniform_paths)]` may become the default
+
+error: aborting due to 2 previous errors
+