Support unstable moves via stable in unstable items

compiler/rustc_middle/src/middle/stability.rs

@@ -471,13 +471,15 @@ impl<'tcx> TyCtxt<'tcx> {
     ///
     /// This function will also check if the item is deprecated.
     /// If so, and `id` is not `None`, a deprecated lint attached to `id` will be emitted.
+    ///
+    /// Returns `true` if item is allowed aka, stable or unstable under an enabled feature.
     pub fn check_stability(
         self,
         def_id: DefId,
         id: Option<HirId>,
         span: Span,
         method_span: Option<Span>,
-    ) {
+    ) -> bool {
         self.check_stability_allow_unstable(def_id, id, span, method_span, AllowUnstable::No)
     }
 
@@ -497,7 +499,7 @@ impl<'tcx> TyCtxt<'tcx> {
         span: Span,
         method_span: Option<Span>,
         allow_unstable: AllowUnstable,
-    ) {
+    ) -> bool {
         self.check_optional_stability(
             def_id,
             id,
@@ -516,6 +518,8 @@ impl<'tcx> TyCtxt<'tcx> {
     /// missing stability attributes (not necessarily just emit a `bug!`). This is necessary
     /// for default generic parameters, which only have stability attributes if they were
     /// added after the type on which they're defined.
+    ///
+    /// Returns `true` if item is allowed aka, stable or unstable under an enabled feature.
     pub fn check_optional_stability(
         self,
         def_id: DefId,
@@ -524,13 +528,16 @@ impl<'tcx> TyCtxt<'tcx> {
         method_span: Option<Span>,
         allow_unstable: AllowUnstable,
         unmarked: impl FnOnce(Span, DefId),
-    ) {
+    ) -> bool {
         let soft_handler = |lint, span, msg: &_| {
             self.struct_span_lint_hir(lint, id.unwrap_or(hir::CRATE_HIR_ID), span, |lint| {
                 lint.build(msg).emit();
             })
         };
-        match self.eval_stability_allow_unstable(def_id, id, span, method_span, allow_unstable) {
+        let eval_result =
+            self.eval_stability_allow_unstable(def_id, id, span, method_span, allow_unstable);
+        let is_allowed = matches!(eval_result, EvalResult::Allow);
+        match eval_result {
             EvalResult::Allow => {}
             EvalResult::Deny { feature, reason, issue, suggestion, is_soft } => report_unstable(
                 self.sess,
@@ -544,6 +551,8 @@ impl<'tcx> TyCtxt<'tcx> {
             ),
             EvalResult::Unmarked => unmarked(span, def_id),
         }
+
+        is_allowed
     }
 
     pub fn lookup_deprecation(self, id: DefId) -> Option<Deprecation> {

compiler/rustc_passes/src/stability.rs

@@ -807,7 +807,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'tcx> {
     fn visit_path(&mut self, path: &'tcx hir::Path<'tcx>, id: hir::HirId) {
         if let Some(def_id) = path.res.opt_def_id() {
             let method_span = path.segments.last().map(|s| s.ident.span);
-            self.tcx.check_stability_allow_unstable(
+            let item_is_allowed = self.tcx.check_stability_allow_unstable(
                 def_id,
                 Some(id),
                 path.span,
@@ -817,8 +817,33 @@ impl<'tcx> Visitor<'tcx> for Checker<'tcx> {
                 } else {
                     AllowUnstable::No
                 },
-            )
+            );
+
+            if item_is_allowed {
+                // Check parent modules stability as well
+                //
+                // We check here rather than in `visit_path_segment` to prevent visiting the last
+                // path segment twice
+                let parents = path.segments.iter().rev().skip(1);
+                for path_segment in parents {
+                    if let Some(def_id) = path_segment.res.as_ref().and_then(Res::opt_def_id) {
+                        // use `None` for id to prevent deprecation check
+                        self.tcx.check_stability_allow_unstable(
+                            def_id,
+                            None,
+                            path.span,
+                            None,
+                            if is_unstable_reexport(self.tcx, id) {
+                                AllowUnstable::Yes
+                            } else {
+                                AllowUnstable::No
+                            },
+                        )
+                    }
+                }
+            }
         }
+
         intravisit::walk_path(self, path)
     }
 }

compiler/rustc_typeck/src/astconv/mod.rs

@@ -439,7 +439,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                                 // as the rest of the type. As such, we ignore missing
                                 // stability attributes.
                             },
-                        )
+                        );
                     }
                     if let (hir::TyKind::Infer, false) = (&ty.kind, self.astconv.allow_ty_infer()) {
                         self.inferred_params.push(ty.span);

library/core/src/intrinsics.rs

@@ -2649,6 +2649,7 @@ pub const unsafe fn write_bytes<T>(dst: *mut T, val: u8, count: usize) {
 /// Here is an example of how this could cause a problem:
 /// ```no_run
 /// #![feature(const_eval_select)]
+/// #![feature(core_intrinsics)]
 /// use std::hint::unreachable_unchecked;
 /// use std::intrinsics::const_eval_select;
 ///

library/core/src/unicode/mod.rs

@@ -1,7 +1,9 @@
-#![unstable(feature = "unicode_internals", issue = "none")]
+#![stable(feature = "unicode_version", since = "1.45.0")]
 #![allow(missing_docs)]
 
+#[unstable(feature = "unicode_internals", issue = "none")]
 pub(crate) mod printable;
+#[unstable(feature = "unicode_internals", issue = "none")]
 mod unicode_data;
 
 /// The version of [Unicode](https://www.unicode.org/) that the Unicode parts of
@@ -18,6 +20,7 @@ mod unicode_data;
 pub const UNICODE_VERSION: (u8, u8, u8) = unicode_data::UNICODE_VERSION;
 
 // For use in liballoc, not re-exported in libstd.
+#[unstable(feature = "unicode_internals", issue = "none")]
 pub use unicode_data::{
     case_ignorable::lookup as Case_Ignorable, cased::lookup as Cased, conversions,
 };

library/std/src/lib.rs

@@ -214,7 +214,7 @@
 #![cfg_attr(not(bootstrap), deny(ffi_unwind_calls))]
 // std may use features in a platform-specific way
 #![allow(unused_features)]
-#![cfg_attr(test, feature(internal_output_capture, print_internals, update_panic_count))]
+#![cfg_attr(test, feature(internal_output_capture, print_internals, update_panic_count, rt))]
 #![cfg_attr(
     all(target_vendor = "fortanix", target_env = "sgx"),
     feature(slice_index_methods, coerce_unsized, sgx_platform)
@@ -297,6 +297,7 @@
 // Library features (alloc):
 #![feature(alloc_layout_extra)]
 #![feature(alloc_c_string)]
+#![feature(alloc_ffi)]
 #![feature(allocator_api)]
 #![feature(get_mut_unchecked)]
 #![feature(map_try_insert)]

library/std/src/panic.rs

@@ -11,7 +11,7 @@ use crate::thread::Result;
 
 #[doc(hidden)]
 #[unstable(feature = "edition_panic", issue = "none", reason = "use panic!() instead")]
-#[allow_internal_unstable(libstd_sys_internals, const_format_args, core_panic)]
+#[allow_internal_unstable(libstd_sys_internals, const_format_args, core_panic, rt)]
 #[cfg_attr(not(test), rustc_diagnostic_item = "std_panic_2015_macro")]
 #[rustc_macro_transparency = "semitransparent"]
 pub macro panic_2015 {

src/test/codegen/intrinsics/const_eval_select.rs

@@ -2,6 +2,7 @@
 
 #![crate_type = "lib"]
 #![feature(const_eval_select)]
+#![feature(core_intrinsics)]
 
 use std::intrinsics::const_eval_select;
 

src/test/ui/intrinsics/const-eval-select-bad.rs

@@ -1,4 +1,5 @@
 #![feature(const_eval_select)]
+#![feature(core_intrinsics)]
 
 use std::intrinsics::const_eval_select;
 

src/test/ui/intrinsics/const-eval-select-bad.stderr

@@ -1,3 +1,4 @@
+<<<<<<< HEAD
 error[E0277]: the trait bound `[closure@$DIR/const-eval-select-bad.rs:6:27: 6:29]: ~const FnOnce<()>` is not satisfied
   --> $DIR/const-eval-select-bad.rs:6:27
    |
@@ -13,6 +14,23 @@ note: the trait `FnOnce<()>` is implemented for `[closure@$DIR/const-eval-select
 LL |     const_eval_select((), || {}, || {});
    |                           ^^^^^
    = note: wrap the `[closure@$DIR/const-eval-select-bad.rs:6:27: 6:29]` in a closure with no arguments: `|| { /* code */ }`
+=======
+error[E0277]: the trait bound `[closure@$DIR/const-eval-select-bad.rs:7:27: 7:32]: ~const FnOnce<()>` is not satisfied
+  --> $DIR/const-eval-select-bad.rs:7:27
+   |
+LL |     const_eval_select((), || {}, || {});
+   |     -----------------     ^^^^^ expected an `FnOnce<()>` closure, found `[closure@$DIR/const-eval-select-bad.rs:7:27: 7:32]`
+   |     |
+   |     required by a bound introduced by this call
+   |
+   = help: the trait `~const FnOnce<()>` is not implemented for `[closure@$DIR/const-eval-select-bad.rs:7:27: 7:32]`
+note: the trait `FnOnce<()>` is implemented for `[closure@$DIR/const-eval-select-bad.rs:7:27: 7:32]`, but that implementation is not `const`
+  --> $DIR/const-eval-select-bad.rs:7:27
+   |
+LL |     const_eval_select((), || {}, || {});
+   |                           ^^^^^
+   = note: wrap the `[closure@$DIR/const-eval-select-bad.rs:7:27: 7:32]` in a closure with no arguments: `|| { /* code */ }`
+>>>>>>> c1798b7c60e... Support unstable moves via stable in unstable items
 note: required by a bound in `const_eval_select`
   --> $SRC_DIR/core/src/intrinsics.rs:LL:COL
    |
@@ -20,7 +38,7 @@ LL |     F: ~const FnOnce<ARG, Output = RET>,
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `const_eval_select`
 
 error[E0277]: the trait bound `{integer}: ~const FnOnce<()>` is not satisfied
-  --> $DIR/const-eval-select-bad.rs:8:27
+  --> $DIR/const-eval-select-bad.rs:9:27
    |
 LL |     const_eval_select((), 42, 0xDEADBEEF);
    |     -----------------     ^^ expected an `FnOnce<()>` closure, found `{integer}`
@@ -36,7 +54,7 @@ LL |     F: ~const FnOnce<ARG, Output = RET>,
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `const_eval_select`
 
 error[E0277]: expected a `FnOnce<()>` closure, found `{integer}`
-  --> $DIR/const-eval-select-bad.rs:8:31
+  --> $DIR/const-eval-select-bad.rs:9:31
    |
 LL |     const_eval_select((), 42, 0xDEADBEEF);
    |     -----------------         ^^^^^^^^^^ expected an `FnOnce<()>` closure, found `{integer}`
@@ -52,7 +70,7 @@ LL |     G: FnOnce<ARG, Output = RET> + ~const Destruct,
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `const_eval_select`
 
 error[E0271]: type mismatch resolving `<fn(i32) -> bool {bar} as FnOnce<(i32,)>>::Output == i32`
-  --> $DIR/const-eval-select-bad.rs:28:5
+  --> $DIR/const-eval-select-bad.rs:29:5
    |
 LL |     const_eval_select((1,), foo, bar);
    |     ^^^^^^^^^^^^^^^^^ expected `i32`, found `bool`
@@ -64,7 +82,7 @@ LL |     G: FnOnce<ARG, Output = RET> + ~const Destruct,
    |                    ^^^^^^^^^^^^ required by this bound in `const_eval_select`
 
 error[E0631]: type mismatch in function arguments
-  --> $DIR/const-eval-select-bad.rs:33:32
+  --> $DIR/const-eval-select-bad.rs:34:32
    |
 LL | const fn foo(n: i32) -> i32 {
    | --------------------------- found signature of `fn(i32) -> _`

src/test/ui/intrinsics/const-eval-select-stability.rs

@@ -1,5 +1,6 @@
 #![feature(staged_api)]
 #![feature(const_eval_select)]
+#![feature(core_intrinsics)]
 #![stable(since = "1.0", feature = "ui_test")]
 
 use std::intrinsics::const_eval_select;

src/test/ui/intrinsics/const-eval-select-stability.stderr

@@ -1,5 +1,5 @@
 error: `const_eval_select` is not yet stable as a const fn
-  --> $DIR/const-eval-select-stability.rs:16:5
+  --> $DIR/const-eval-select-stability.rs:17:5
    |
 LL |     const_eval_select((), nothing, log);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/intrinsics/const-eval-select-x86_64.rs

@@ -2,6 +2,7 @@
 // only-x86_64
 
 #![feature(const_eval_select)]
+#![feature(core_intrinsics)]
 use std::intrinsics::const_eval_select;
 use std::arch::x86_64::*;
 use std::mem::transmute;

src/test/ui/intrinsics/const-eval-select.rs

@@ -1,6 +1,7 @@
 // run-pass
 
 #![feature(const_eval_select)]
+#![feature(core_intrinsics)]
 
 use std::intrinsics::const_eval_select;
 

src/test/ui/lint/lint-stability.rs

@@ -191,11 +191,11 @@ mod inheritance {
         stable_mod::unstable(); //~ ERROR use of unstable library feature
         stable_mod::stable();
 
-        unstable_mod::deprecated();
+        unstable_mod::deprecated(); //~ ERROR use of unstable library feature
         unstable_mod::unstable(); //~ ERROR use of unstable library feature
 
         let _ = Unstable::UnstableVariant; //~ ERROR use of unstable library feature
-        let _ = Unstable::StableVariant;
+        let _ = Unstable::StableVariant; //~ ERROR use of unstable library feature
 
         let x: usize = 0;
         x.stable();

src/test/ui/lint/lint-stability.stderr

@@ -294,6 +294,14 @@ LL |         stable_mod::unstable();
    |
    = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
 
+error[E0658]: use of unstable library feature 'unstable_test_feature'
+  --> $DIR/lint-stability.rs:194:9
+   |
+LL |         unstable_mod::deprecated();
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
+
 error[E0658]: use of unstable library feature 'unstable_test_feature'
   --> $DIR/lint-stability.rs:195:9
    |
@@ -310,6 +318,14 @@ LL |         let _ = Unstable::UnstableVariant;
    |
    = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
 
+error[E0658]: use of unstable library feature 'unstable_test_feature'
+  --> $DIR/lint-stability.rs:198:17
+   |
+LL |         let _ = Unstable::StableVariant;
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
+
 error[E0658]: use of unstable library feature 'unstable_test_feature'
   --> $DIR/lint-stability.rs:88:48
    |
@@ -326,6 +342,6 @@ LL |             TypeUnstable = u8,
    |
    = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
 
-error: aborting due to 41 previous errors
+error: aborting due to 43 previous errors
 
 For more information about this error, try `rustc --explain E0658`.

src/test/ui/stability-attribute/auxiliary/stable-in-unstable-core.rs

@@ -0,0 +1,8 @@
+#![feature(staged_api)]
+#![stable(feature = "stable_test_feature", since = "1.2.0")]
+
+#[unstable(feature = "unstable_test_feature", issue = "1")]
+pub mod new_unstable_module {
+    #[stable(feature = "stable_test_feature", since = "1.2.0")]
+    pub trait OldTrait {}
+}

src/test/ui/stability-attribute/auxiliary/stable-in-unstable-std.rs

@@ -0,0 +1,11 @@
+#![feature(staged_api)]
+#![feature(unstable_test_feature)]
+#![stable(feature = "stable_test_feature", since = "1.2.0")]
+
+extern crate stable_in_unstable_core;
+
+#[stable(feature = "stable_test_feature", since = "1.2.0")]
+pub mod old_stable_module {
+    #[stable(feature = "stable_test_feature", since = "1.2.0")]
+    pub use stable_in_unstable_core::new_unstable_module::OldTrait;
+}

src/test/ui/stability-attribute/stable-in-unstable.rs

@@ -0,0 +1,46 @@
+// This test is meant to test that we can have a stable item in an unstable module, and that
+// calling that item through the unstable module is unstable, but that re-exporting it from another
+// crate in a stable module is fine.
+//
+// This is necessary to support moving items from `std` into `core` or `alloc` unstably while still
+// exporting the original stable interface in `std`, such as moving `Error` into `core`.
+//
+// aux-build:stable-in-unstable-core.rs
+// aux-build:stable-in-unstable-std.rs
+#![crate_type = "lib"]
+
+extern crate stable_in_unstable_core;
+extern crate stable_in_unstable_std;
+
+mod isolated1 {
+    use stable_in_unstable_core::new_unstable_module; //~ ERROR use of unstable library feature 'unstable_test_feature'
+    use stable_in_unstable_core::new_unstable_module::OldTrait; //~ ERROR use of unstable library feature 'unstable_test_feature'
+}
+
+mod isolated2 {
+    use stable_in_unstable_std::old_stable_module::OldTrait;
+
+    struct LocalType;
+
+    impl OldTrait for LocalType {}
+}
+
+mod isolated3 {
+    use stable_in_unstable_core::new_unstable_module::OldTrait; //~ ERROR use of unstable library feature 'unstable_test_feature'
+
+    struct LocalType;
+
+    impl OldTrait for LocalType {}
+}
+
+mod isolated4 {
+    struct LocalType;
+
+    impl stable_in_unstable_core::new_unstable_module::OldTrait for LocalType {} //~ ERROR use of unstable library feature 'unstable_test_feature'
+}
+
+mod isolated5 {
+    struct LocalType;
+
+    impl stable_in_unstable_std::old_stable_module::OldTrait for LocalType {}
+}

src/test/ui/stability-attribute/stable-in-unstable.stderr

@@ -0,0 +1,39 @@
+error[E0658]: use of unstable library feature 'unstable_test_feature'
+  --> $DIR/stable-in-unstable.rs:16:9
+   |
+LL |     use stable_in_unstable_core::new_unstable_module;
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
+   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
+
+error[E0658]: use of unstable library feature 'unstable_test_feature'
+  --> $DIR/stable-in-unstable.rs:17:9
+   |
+LL |     use stable_in_unstable_core::new_unstable_module::OldTrait;
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
+   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
+
+error[E0658]: use of unstable library feature 'unstable_test_feature'
+  --> $DIR/stable-in-unstable.rs:29:9
+   |
+LL |     use stable_in_unstable_core::new_unstable_module::OldTrait;
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
+   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
+
+error[E0658]: use of unstable library feature 'unstable_test_feature'
+  --> $DIR/stable-in-unstable.rs:39:10
+   |
+LL |     impl stable_in_unstable_core::new_unstable_module::OldTrait for LocalType {}
+   |          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #1 <https://github.com/rust-lang/rust/issues/1> for more information
+   = help: add `#![feature(unstable_test_feature)]` to the crate attributes to enable
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0658`.