Resolve absolute paths as extern under a feature flag

src/test/compile-fail/rfc-2126-extern-absolute-paths/auxiliary/xcrate.rs

@@ -0,0 +1,15 @@
+// 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.
+
+#[derive(Debug)]
+pub struct S;
+
+#[derive(Debug)]
+pub struct Z;

src/test/compile-fail/rfc-2126-extern-absolute-paths/non-existent-1.rs

@@ -0,0 +1,15 @@
+// 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.
+
+#![feature(extern_absolute_paths)]
+
+use xcrate::S; //~ ERROR can't find crate for `xcrate`
+
+fn main() {}

src/test/compile-fail/rfc-2126-extern-absolute-paths/non-existent-2.rs

@@ -0,0 +1,15 @@
+// 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.
+
+#![feature(extern_absolute_paths)]
+
+fn main() {
+    let s = ::xcrate::S; //~ ERROR can't find crate for `xcrate`
+}

src/test/compile-fail/rfc-2126-extern-absolute-paths/non-existent-3.rs

@@ -0,0 +1,15 @@
+// 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.
+
+#![feature(extern_absolute_paths)]
+
+use ycrate; //~ ERROR can't find crate for `ycrate`
+
+fn main() {}

src/test/compile-fail/rfc-2126-extern-absolute-paths/single-segment.rs

@@ -0,0 +1,24 @@
+// 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.
+
+// aux-build:xcrate.rs
+
+#![feature(crate_in_paths)]
+#![feature(extern_absolute_paths)]
+
+use crate; //~ ERROR unresolved import `crate`
+           //~^ NOTE crate root imports need to be explicitly named: `use crate as name;`
+use *; //~ ERROR unresolved import `*`
+       //~^ NOTE cannot glob-import all possible crates
+
+fn main() {
+    let s = ::xcrate; //~ ERROR expected value, found module `xcrate`
+                      //~^ NOTE not a value
+}

src/test/run-pass/rfc-2126-crate-paths/crate-path-absolute.rs

@@ -11,10 +11,12 @@
 #![feature(crate_in_paths)]
 
 use crate::m::f;
+use crate as root;
 
 mod m {
     pub fn f() -> u8 { 1 }
     pub fn g() -> u8 { 2 }
+    pub fn h() -> u8 { 3 }
 
     // OK, visibilities are implicitly absolute like imports
     pub(in crate::m) struct S;
@@ -23,14 +25,17 @@ mod m {
 mod n
 {
     use crate::m::f;
+    use crate as root;
     pub fn check() {
         assert_eq!(f(), 1);
         assert_eq!(::crate::m::g(), 2);
+        assert_eq!(root::m::h(), 3);
     }
 }
 
 fn main() {
     assert_eq!(f(), 1);
     assert_eq!(::crate::m::g(), 2);
+    assert_eq!(root::m::h(), 3);
     n::check();
 }

src/test/run-pass/rfc-2126-extern-absolute-paths/auxiliary/xcrate.rs

@@ -0,0 +1,15 @@
+// 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.
+
+#[derive(Debug)]
+pub struct S;
+
+#[derive(Debug)]
+pub struct Z;

src/test/run-pass/rfc-2126-extern-absolute-paths/basic.rs

@@ -0,0 +1,31 @@
+// 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.
+
+// aux-build:xcrate.rs
+
+#![feature(extern_absolute_paths)]
+
+use xcrate::Z;
+
+fn f() {
+    use xcrate;
+    use xcrate as ycrate;
+    let s = xcrate::S;
+    assert_eq!(format!("{:?}", s), "S");
+    let z = ycrate::Z;
+    assert_eq!(format!("{:?}", z), "Z");
+}
+
+fn main() {
+    let s = ::xcrate::S;
+    assert_eq!(format!("{:?}", s), "S");
+    let z = Z;
+    assert_eq!(format!("{:?}", z), "Z");
+}

src/test/ui/feature-gate-extern_absolute_paths.rs

@@ -0,0 +1,15 @@
+// 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.
+
+use core::default; //~ ERROR unresolved import `core`
+
+fn main() {
+    let _: u8 = ::core::default::Default(); //~ ERROR failed to resolve
+}

src/test/ui/feature-gate-extern_absolute_paths.stderr

@@ -0,0 +1,14 @@
+error[E0432]: unresolved import `core`
+  --> $DIR/feature-gate-extern_absolute_paths.rs:11:5
+   |
+11 | use core::default; //~ ERROR unresolved import `core`
+   |     ^^^^ Maybe a missing `extern crate core;`?
+
+error[E0433]: failed to resolve. Maybe a missing `extern crate core;`?
+  --> $DIR/feature-gate-extern_absolute_paths.rs:14:19
+   |
+14 |     let _: u8 = ::core::default::Default(); //~ ERROR failed to resolve
+   |                   ^^^^ Maybe a missing `extern crate core;`?
+
+error: aborting due to 2 previous errors
+