Auto merge of #53944 - oli-obk:beta, r=nikomatsakis

[beta] Properly prevent the promotion of unstable const fns

backport of #53699

r? @nikomatsakis (the other PR was merged and beta nominated but not beta approved)

Author: bors

src/librustc_mir/transform/qualify_consts.rs

@@ -127,6 +127,7 @@ impl<'a, 'tcx> Qualifier<'a, 'tcx, 'tcx> {
            mir: &'a Mir<'tcx>,
            mode: Mode)
            -> Qualifier<'a, 'tcx, 'tcx> {
+        assert!(def_id.is_local());
         let mut rpo = traversal::reverse_postorder(mir);
         let temps = promote_consts::collect_temps(mir, &mut rpo);
         rpo.reset();
@@ -915,9 +916,6 @@ This does not pose a problem by itself because they can't be accessed directly."
                             .iter()
                             .any(|&(ref sym, _)| sym == feature_name) &&
 
-                        // this doesn't come from a crate with the feature-gate enabled,
-                        self.def_id.is_local() &&
-
                         // this doesn't come from a macro that has #[allow_internal_unstable]
                         !self.span.allows_unstable()
                     {

src/librustc_passes/rvalue_promotion.rs

@@ -189,9 +189,6 @@ impl<'a, 'gcx> CheckCrateVisitor<'a, 'gcx> {
                     .iter()
                     .any(|&(ref sym, _)| sym == feature_name) ||
 
-                    // this comes from a crate with the feature-gate enabled,
-                    !def_id.is_local() ||
-
                     // this comes from a macro that has #[allow_internal_unstable]
                     span.allows_unstable();
             if !stable_check {

src/test/ui/const-eval/dont_promote_unstable_const_fn.nll.stderr

@@ -11,6 +11,7 @@ error[E0597]: borrowed value does not live long enough
    |
 LL |     let x: &'static _ = &std::time::Duration::from_millis(42).subsec_millis();
    |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ temporary value does not live long enough
+LL |     //~^ does not live long enough
 LL | }
    | - temporary value only lives until here
    |

src/test/ui/const-eval/dont_promote_unstable_const_fn.rs

@@ -31,4 +31,5 @@ fn a() {
 fn main() {
     let _: &'static u32 = &meh(); //~ ERROR does not live long enough
     let x: &'static _ = &std::time::Duration::from_millis(42).subsec_millis();
+    //~^ does not live long enough
 }

src/test/ui/const-eval/dont_promote_unstable_const_fn.stderr

@@ -21,12 +21,23 @@ error[E0597]: borrowed value does not live long enough
    |
 LL |     let _: &'static u32 = &meh(); //~ ERROR does not live long enough
    |                            ^^^^^ temporary value does not live long enough
+...
+LL | }
+   | - temporary value only lives until here
+   |
+   = note: borrowed value must be valid for the static lifetime...
+
+error[E0597]: borrowed value does not live long enough
+  --> $DIR/dont_promote_unstable_const_fn.rs:33:26
+   |
 LL |     let x: &'static _ = &std::time::Duration::from_millis(42).subsec_millis();
+   |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ temporary value does not live long enough
+LL |     //~^ does not live long enough
 LL | }
    | - temporary value only lives until here
    |
    = note: borrowed value must be valid for the static lifetime...
 
-error: aborting due to 3 previous errors
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0597`.

src/test/ui/consts/const-eval/auxiliary/stability.rs

@@ -0,0 +1,21 @@
+// Copyright 2015 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 that exports a const fn. Used for testing cross-crate.
+
+#![crate_type="rlib"]
+#![stable(feature = "rust1", since = "1.0.0")]
+
+#![feature(rustc_const_unstable, const_fn)]
+#![feature(staged_api)]
+
+#[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_const_unstable(feature="foo")]
+pub const fn foo() -> u32 { 42 }

src/test/ui/consts/const-eval/dont_promote_unstable_const_fn_cross_crate.nll.stderr

@@ -0,0 +1,13 @@
+error[E0597]: borrowed value does not live long enough
+  --> $DIR/dont_promote_unstable_const_fn_cross_crate.rs:19:29
+   |
+LL |     let _x: &'static u32 = &foo(); //~ ERROR does not live long enough
+   |                             ^^^^^ temporary value does not live long enough
+LL | }
+   | - temporary value only lives until here
+   |
+   = note: borrowed value must be valid for the static lifetime...
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0597`.

src/test/ui/consts/const-eval/dont_promote_unstable_const_fn_cross_crate.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.
+
+// aux-build:stability.rs
+
+extern crate stability;
+
+use stability::foo;
+
+fn main() {
+    let _: &'static u32 = &foo(); //~ ERROR does not live long enough
+    let _x: &'static u32 = &foo(); //~ ERROR does not live long enough
+}

src/test/ui/consts/const-eval/dont_promote_unstable_const_fn_cross_crate.stderr

@@ -0,0 +1,24 @@
+error[E0597]: borrowed value does not live long enough
+  --> $DIR/dont_promote_unstable_const_fn_cross_crate.rs:18:28
+   |
+LL |     let _: &'static u32 = &foo(); //~ ERROR does not live long enough
+   |                            ^^^^^ temporary value does not live long enough
+LL |     let _x: &'static u32 = &foo(); //~ ERROR does not live long enough
+LL | }
+   | - temporary value only lives until here
+   |
+   = note: borrowed value must be valid for the static lifetime...
+
+error[E0597]: borrowed value does not live long enough
+  --> $DIR/dont_promote_unstable_const_fn_cross_crate.rs:19:29
+   |
+LL |     let _x: &'static u32 = &foo(); //~ ERROR does not live long enough
+   |                             ^^^^^ temporary value does not live long enough
+LL | }
+   | - temporary value only lives until here
+   |
+   = note: borrowed value must be valid for the static lifetime...
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0597`.