Auto merge of rust-lang#59590 - Centril:rollup, r=Centril

Rollup of 7 pull requests

Successful merges:

 - rust-lang#58805 (Lint for redundant imports)
 - rust-lang#59506 (Use platform dependent mcount function)
 - rust-lang#59519 (rustc_target: factor out common fields of non-Single Variants.)
 - rust-lang#59580 (Allow closure to unsafe fn coercion)
 - rust-lang#59581 (Stabilize refcell_replace_swap feature)
 - rust-lang#59583 (match match match match match)
 - rust-lang#59587 (Remove #[doc(hidden)] from Error::type_id)

Failed merges:

r? @ghost

Author: bors

src/liballoc/borrow.rs

@@ -135,7 +135,7 @@ impl<T> ToOwned for T
 /// Another example showing how to keep `Cow` in a struct:
 ///
 /// ```
-/// use std::borrow::{Cow, ToOwned};
+/// use std::borrow::Cow;
 ///
 /// struct Items<'a, X: 'a> where [X]: ToOwned<Owned = Vec<X>> {
 ///     values: Cow<'a, [X]>,

src/libcore/cell.rs

@@ -702,24 +702,21 @@ impl<T> RefCell<T> {
     /// Replaces the wrapped value with a new one computed from `f`, returning
     /// the old value, without deinitializing either one.
     ///
-    /// This function corresponds to [`std::mem::replace`](../mem/fn.replace.html).
-    ///
     /// # Panics
     ///
     /// Panics if the value is currently borrowed.
     ///
     /// # Examples
     ///
     /// ```
-    /// #![feature(refcell_replace_swap)]
     /// use std::cell::RefCell;
     /// let cell = RefCell::new(5);
     /// let old_value = cell.replace_with(|&mut old| old + 1);
     /// assert_eq!(old_value, 5);
     /// assert_eq!(cell, RefCell::new(6));
     /// ```
     #[inline]
-    #[unstable(feature = "refcell_replace_swap", issue="43570")]
+    #[stable(feature = "refcell_replace_swap", since="1.35.0")]
     pub fn replace_with<F: FnOnce(&mut T) -> T>(&self, f: F) -> T {
         let mut_borrow = &mut *self.borrow_mut();
         let replacement = f(mut_borrow);
@@ -1421,7 +1418,6 @@ impl<T: ?Sized + fmt::Display> fmt::Display for RefMut<'_, T> {
 ///
 /// ```
 /// use std::cell::UnsafeCell;
-/// use std::marker::Sync;
 ///
 /// # #[allow(dead_code)]
 /// struct NotThreadSafe<T> {

src/libcore/tests/lib.rs

@@ -16,7 +16,6 @@
 #![feature(pattern)]
 #![feature(range_is_empty)]
 #![feature(raw)]
-#![feature(refcell_replace_swap)]
 #![feature(slice_patterns)]
 #![feature(sort_internals)]
 #![feature(specialization)]

src/librustc/lib.rs

@@ -45,7 +45,6 @@
 #![feature(proc_macro_internals)]
 #![feature(optin_builtin_traits)]
 #![feature(range_is_empty)]
-#![feature(refcell_replace_swap)]
 #![feature(rustc_diagnostic_macros)]
 #![feature(rustc_attrs)]
 #![feature(slice_patterns)]

src/librustc/lint/builtin.rs

@@ -483,6 +483,7 @@ pub enum BuiltinLintDiagnostics {
     UnknownCrateTypes(Span, String, String),
     UnusedImports(String, Vec<(Span, String)>),
     NestedImplTrait { outer_impl_trait_span: Span, inner_impl_trait_span: Span },
+    RedundantImport(Vec<(Span, bool)>, ast::Ident),
 }
 
 impl BuiltinLintDiagnostics {
@@ -579,6 +580,15 @@ impl BuiltinLintDiagnostics {
                 db.span_label(outer_impl_trait_span, "outer `impl Trait`");
                 db.span_label(inner_impl_trait_span, "nested `impl Trait` here");
             }
+            BuiltinLintDiagnostics::RedundantImport(spans, ident) => {
+                for (span, is_imported) in spans {
+                    let introduced = if is_imported { "imported" } else { "defined" };
+                    db.span_label(
+                        span,
+                        format!("the item `{}` is already {} here", ident, introduced)
+                    );
+                }
+            }
         }
     }
 }

src/librustc/middle/expr_use_visitor.rs

@@ -707,7 +707,7 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
                 adjustment::Adjust::NeverToAny |
                 adjustment::Adjust::ReifyFnPointer |
                 adjustment::Adjust::UnsafeFnPointer |
-                adjustment::Adjust::ClosureFnPointer |
+                adjustment::Adjust::ClosureFnPointer(_) |
                 adjustment::Adjust::MutToConstPointer |
                 adjustment::Adjust::Unsize => {
                     // Creating a closure/fn-pointer or unsizing consumes

src/librustc/middle/mem_categorization.rs

@@ -621,7 +621,7 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
             adjustment::Adjust::NeverToAny |
             adjustment::Adjust::ReifyFnPointer |
             adjustment::Adjust::UnsafeFnPointer |
-            adjustment::Adjust::ClosureFnPointer |
+            adjustment::Adjust::ClosureFnPointer(_) |
             adjustment::Adjust::MutToConstPointer |
             adjustment::Adjust::Borrow(_) |
             adjustment::Adjust::Unsize => {

src/librustc/mir/mod.rs

@@ -2247,8 +2247,9 @@ pub enum CastKind {
     /// Converts unique, zero-sized type for a fn to fn()
     ReifyFnPointer,
 
-    /// Converts non capturing closure to fn()
-    ClosureFnPointer,
+    /// Converts non capturing closure to fn() or unsafe fn().
+    /// It cannot convert a closure that requires unsafe.
+    ClosureFnPointer(hir::Unsafety),
 
     /// Converts safe fn() to unsafe fn()
     UnsafeFnPointer,

src/librustc/ty/adjustment.rs

@@ -62,8 +62,9 @@ pub enum Adjust<'tcx> {
     /// Go from a safe fn pointer to an unsafe fn pointer.
     UnsafeFnPointer,
 
-    /// Go from a non-capturing closure to an fn pointer.
-    ClosureFnPointer,
+    /// Go from a non-capturing closure to an fn pointer or an unsafe fn pointer.
+    /// It cannot convert a closure that requires unsafe.
+    ClosureFnPointer(hir::Unsafety),
 
     /// Go from a mut raw pointer to a const raw pointer.
     MutToConstPointer,

src/librustc/ty/context.rs

@@ -2441,7 +2441,11 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     /// type with the same signature. Detuples and so forth -- so
     /// e.g., if we have a sig with `Fn<(u32, i32)>` then you would get
     /// a `fn(u32, i32)`.
-    pub fn coerce_closure_fn_ty(self, sig: PolyFnSig<'tcx>) -> Ty<'tcx> {
+    /// `unsafety` determines the unsafety of the `fn` type. If you pass
+    /// `hir::Unsafety::Unsafe` in the previous example, then you would get
+    /// an `unsafe fn (u32, i32)`.
+    /// It cannot convert a closure that requires unsafe.
+    pub fn coerce_closure_fn_ty(self, sig: PolyFnSig<'tcx>, unsafety: hir::Unsafety) -> Ty<'tcx> {
         let converted_sig = sig.map_bound(|s| {
             let params_iter = match s.inputs()[0].sty {
                 ty::Tuple(params) => {
@@ -2453,7 +2457,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                 params_iter,
                 s.output(),
                 s.c_variadic,
-                hir::Unsafety::Normal,
+                unsafety,
                 abi::Abi::Rust,
             )
         });