Auto merge of #46905 - pnkfelix:backport-46112-fix-to-beta, r=michaelwoerister

Backport 46112 fix to beta

Its probably easiest to focus on the diff rather than the commit series.

If you prefer I could squash them, but I figured preserving the cherry-picking will make it easier to relate what has happened here to what happens on the `master` branch.

Note: This is a backport of *just* #46838. It does not include #46708 (which we may end up wanting to revert).

Fix #46112

Author: bors

src/librustc_metadata/cstore_impl.rs

@@ -297,7 +297,17 @@ pub fn provide<'tcx>(providers: &mut Providers<'tcx>) {
             assert_eq!(cnum, LOCAL_CRATE);
             let mut visible_parent_map: DefIdMap<DefId> = DefIdMap();
 
-            for &cnum in tcx.crates().iter() {
+            // Preferring shortest paths alone does not guarantee a
+            // deterministic result; so sort by crate num to avoid
+            // hashtable iteration non-determinism. This only makes
+            // things as deterministic as crate-nums assignment is,
+            // which is to say, its not deterministic in general. But
+            // we believe that libstd is consistently assigned crate
+            // num 1, so it should be enough to resolve #46112.
+            let mut crates: Vec<CrateNum> = (*tcx.crates()).clone();
+            crates.sort();
+
+            for &cnum in crates.iter() {
                 // Ignore crates without a corresponding local `extern crate` item.
                 if tcx.missing_extern_crate_item(cnum) {
                     continue

src/test/compile-fail/auxiliary/issue_1920.rs

@@ -0,0 +1,14 @@
+// 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.
+
+// Just exporting some type to test for correct diagnostics when this
+// crate is pulled in at a non-root location in client crate.
+
+pub struct S;

src/test/compile-fail/issue-1920-1.rs

@@ -10,13 +10,15 @@
 
 //! Test that absolute path names are correct when a crate is not linked into the root namespace
 
+// aux-build:issue_1920.rs
+
 mod foo {
-    pub extern crate core;
+    pub extern crate issue_1920;
 }
 
 fn assert_clone<T>() where T : Clone { }
 
 fn main() {
-    assert_clone::<foo::core::sync::atomic::AtomicBool>();
-    //~^ ERROR `foo::core::sync::atomic::AtomicBool: foo::core::clone::Clone` is not satisfied
+    assert_clone::<foo::issue_1920::S>();
+    //~^ ERROR `foo::issue_1920::S: std::clone::Clone` is not satisfied
 }

src/test/compile-fail/issue-1920-2.rs

@@ -10,11 +10,13 @@
 
 //! Test that when a crate is linked under another name that name is used in global paths
 
-extern crate core as bar;
+// aux-build:issue_1920.rs
+
+extern crate issue_1920 as bar;
 
 fn assert_clone<T>() where T : Clone { }
 
 fn main() {
-    assert_clone::<bar::sync::atomic::AtomicBool>();
-    //~^ ERROR `bar::sync::atomic::AtomicBool: bar::clone::Clone` is not satisfied
+    assert_clone::<bar::S>();
+    //~^ ERROR `bar::S: std::clone::Clone` is not satisfied
 }

src/test/compile-fail/issue-1920-3.rs

@@ -10,15 +10,17 @@
 
 //! Test that when a crate is linked multiple times that the shortest absolute path name is used
 
+// aux-build:issue_1920.rs
+
 mod foo {
-    pub extern crate core;
+    pub extern crate issue_1920;
 }
 
-extern crate core;
+extern crate issue_1920;
 
 fn assert_clone<T>() where T : Clone { }
 
 fn main() {
-    assert_clone::<foo::core::sync::atomic::AtomicBool>();
-    //~^ ERROR `core::sync::atomic::AtomicBool: core::clone::Clone` is not satisfied
+    assert_clone::<foo::issue_1920::S>();
+    //~^ ERROR `issue_1920::S: std::clone::Clone` is not satisfied
 }

src/test/ui/auxiliary/xcrate_issue_46112_rexport_core.rs

@@ -0,0 +1,13 @@
+// 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.
+
+#![crate_type="lib"]
+
+pub extern crate core;

src/test/ui/issue-46112.rs

@@ -0,0 +1,20 @@
+// 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.
+
+// Issue 46112: An extern crate pub reexporting libcore was causing
+// paths rooted from `std` to be misrendered in the diagnostic output.
+
+// ignore-windows
+// aux-build:xcrate_issue_46112_rexport_core.rs
+
+extern crate xcrate_issue_46112_rexport_core;
+fn test(r: Result<Option<()>, &'static str>) { }
+fn main() { test(Ok(())); }
+//~^ mismatched types

src/test/ui/issue-46112.stderr

@@ -0,0 +1,14 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-46112.rs:19:21
+   |
+19 | fn main() { test(Ok(())); }
+   |                     ^^
+   |                     |
+   |                     expected enum `std::option::Option`, found ()
+   |                     help: try using a variant of the expected type: `Some(())`
+   |
+   = note: expected type `std::option::Option<()>`
+              found type `()`
+
+error: aborting due to previous error
+