[WIP] Add support for custom allocator for String

RELEASES.md

@@ -1735,7 +1735,7 @@ Stabilized APIs
 
 - [`impl<T: Send> Sync for mpsc::Sender<T>`](https://doc.rust-lang.org/stable/std/sync/mpsc/struct.Sender.html#impl-Sync-for-Sender%3CT%3E)
 - [`impl TryFrom<&OsStr> for &str`](https://doc.rust-lang.org/stable/std/primitive.str.html#impl-TryFrom%3C%26'a+OsStr%3E-for-%26'a+str)
-- [`String::leak`](https://doc.rust-lang.org/stable/alloc/string/struct.String.html#method.leak)
+- [`String::leak`](https://doc.rust-lang.org/stable/alloc/string/type.String.html#method.leak)
 
 These APIs are now stable in const contexts:
 
@@ -3794,8 +3794,8 @@ and related tools.
 [`collections::TryReserveError`]: https://doc.rust-lang.org/std/collections/struct.TryReserveError.html
 [`HashMap::try_reserve`]: https://doc.rust-lang.org/std/collections/hash_map/struct.HashMap.html#method.try_reserve
 [`HashSet::try_reserve`]: https://doc.rust-lang.org/std/collections/hash_set/struct.HashSet.html#method.try_reserve
-[`String::try_reserve`]: https://doc.rust-lang.org/alloc/string/struct.String.html#method.try_reserve
-[`String::try_reserve_exact`]: https://doc.rust-lang.org/alloc/string/struct.String.html#method.try_reserve_exact
+[`String::try_reserve`]: https://doc.rust-lang.org/alloc/string/type.String.html#method.try_reserve
+[`String::try_reserve_exact`]: https://doc.rust-lang.org/alloc/string/type.String.html#method.try_reserve_exact
 [`Vec::try_reserve`]: https://doc.rust-lang.org/std/vec/struct.Vec.html#method.try_reserve
 [`Vec::try_reserve_exact`]: https://doc.rust-lang.org/std/vec/struct.Vec.html#method.try_reserve_exact
 [`VecDeque::try_reserve`]: https://doc.rust-lang.org/std/collections/struct.VecDeque.html#method.try_reserve
@@ -3936,7 +3936,7 @@ and related tools.
 [`BufWriter::into_parts`]: https://doc.rust-lang.org/stable/std/io/struct.BufWriter.html#method.into_parts
 [`core::panic::{UnwindSafe, RefUnwindSafe, AssertUnwindSafe}`]: https://github.com/rust-lang/rust/pull/84662
 [`Vec::shrink_to`]: https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.shrink_to
-[`String::shrink_to`]: https://doc.rust-lang.org/stable/std/string/struct.String.html#method.shrink_to
+[`String::shrink_to`]: https://doc.rust-lang.org/stable/std/string/type.String.html#method.shrink_to
 [`OsString::shrink_to`]: https://doc.rust-lang.org/stable/std/ffi/struct.OsString.html#method.shrink_to
 [`PathBuf::shrink_to`]: https://doc.rust-lang.org/stable/std/path/struct.PathBuf.html#method.shrink_to
 [`BinaryHeap::shrink_to`]: https://doc.rust-lang.org/stable/std/collections/struct.BinaryHeap.html#method.shrink_to
@@ -8131,7 +8131,7 @@ Compatibility Notes
 [`Iterator::try_for_each`]: https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.try_for_each
 [`NonNull::cast`]: https://doc.rust-lang.org/std/ptr/struct.NonNull.html#method.cast
 [`Option::filter`]: https://doc.rust-lang.org/std/option/enum.Option.html#method.filter
-[`String::replace_range`]: https://doc.rust-lang.org/std/string/struct.String.html#method.replace_range
+[`String::replace_range`]: https://doc.rust-lang.org/std/string/type.String.html#method.replace_range
 [`Take::set_limit`]: https://doc.rust-lang.org/std/io/struct.Take.html#method.set_limit
 [`hint::unreachable_unchecked`]: https://doc.rust-lang.org/std/hint/fn.unreachable_unchecked.html
 [`os::unix::process::parent_id`]: https://doc.rust-lang.org/std/os/unix/process/fn.parent_id.html
@@ -8376,7 +8376,7 @@ Compatibility Notes
 [`process::id`]: https://doc.rust-lang.org/std/process/fn.id.html
 [`slice::rotate_left`]: https://doc.rust-lang.org/std/primitive.slice.html#method.rotate_left
 [`slice::rotate_right`]: https://doc.rust-lang.org/std/primitive.slice.html#method.rotate_right
-[`String::retain`]: https://doc.rust-lang.org/std/string/struct.String.html#method.retain
+[`String::retain`]: https://doc.rust-lang.org/std/string/type.String.html#method.retain
 [cargo/5041]: https://github.com/rust-lang/cargo/pull/5041
 [cargo/5083]: https://github.com/rust-lang/cargo/pull/5083
 
@@ -9827,8 +9827,8 @@ Compatibility Notes
 [`Result::unwrap_or_default`]: https://doc.rust-lang.org/std/result/enum.Result.html#method.unwrap_or_default
 [`SocketAddr::is_ipv4`]: https://doc.rust-lang.org/std/net/enum.SocketAddr.html#method.is_ipv4
 [`SocketAddr::is_ipv6`]: https://doc.rust-lang.org/std/net/enum.SocketAddr.html#method.is_ipv6
-[`String::insert_str`]: https://doc.rust-lang.org/std/string/struct.String.html#method.insert_str
-[`String::split_off`]: https://doc.rust-lang.org/std/string/struct.String.html#method.split_off
+[`String::insert_str`]: https://doc.rust-lang.org/std/string/type.String.html#method.insert_str
+[`String::split_off`]: https://doc.rust-lang.org/std/string/type.String.html#method.split_off
 [`Vec::dedup_by_key`]: https://doc.rust-lang.org/std/vec/struct.Vec.html#method.dedup_by_key
 [`Vec::dedup_by`]: https://doc.rust-lang.org/std/vec/struct.Vec.html#method.dedup_by
 [`VecDeque::resize`]:  https://doc.rust-lang.org/std/collections/vec_deque/struct.VecDeque.html#method.resize
@@ -11742,8 +11742,8 @@ Compatibility Notes
 [`Ipv6Addr::is_unspecified`]: http://doc.rust-lang.org/nightly/std/net/struct.Ipv6Addr.html#method.is_unspecified
 [`Path::strip_prefix`]: http://doc.rust-lang.org/nightly/std/path/struct.Path.html#method.strip_prefix
 [`RandomState::new`]: http://doc.rust-lang.org/nightly/std/collections/hash_map/struct.RandomState.html#method.new
-[`String::as_mut_str`]: http://doc.rust-lang.org/nightly/std/string/struct.String.html#method.as_mut_str
-[`String::as_str`]: http://doc.rust-lang.org/nightly/std/string/struct.String.html#method.as_str
+[`String::as_mut_str`]: http://doc.rust-lang.org/nightly/std/string/type.String.html#method.as_mut_str
+[`String::as_str`]: http://doc.rust-lang.org/nightly/std/string/type.String.html#method.as_str
 [`Vec::as_mut_slice`]: http://doc.rust-lang.org/nightly/std/vec/struct.Vec.html#method.as_mut_slice
 [`Vec::as_slice`]: http://doc.rust-lang.org/nightly/std/vec/struct.Vec.html#method.as_slice
 [`clone_from_slice`]: http://doc.rust-lang.org/nightly/std/primitive.slice.html#method.clone_from_slice
@@ -11929,7 +11929,7 @@ Compatibility Notes
 [`os::unix::fs::DirBuilderExt::mode`]: http://doc.rust-lang.org/nightly/std/os/unix/fs/trait.DirBuilderExt.html#tymethod.mode
 [`os::unix::fs::DirBuilderExt`]: http://doc.rust-lang.org/nightly/std/os/unix/fs/trait.DirBuilderExt.html
 [`string::Drain`]: http://doc.rust-lang.org/nightly/std/string/struct.Drain.html
-[`string::String::drain`]: http://doc.rust-lang.org/nightly/std/string/struct.String.html#method.drain
+[`string::String::drain`]: http://doc.rust-lang.org/nightly/std/string/type.String.html#method.drain
 [`vec::Drain`]: http://doc.rust-lang.org/nightly/std/vec/struct.Drain.html
 [`vec::Vec::drain`]: http://doc.rust-lang.org/nightly/std/vec/struct.Vec.html#method.drain
 [`vec_deque::Drain`]: http://doc.rust-lang.org/nightly/std/collections/vec_deque/struct.Drain.html

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -1563,7 +1563,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
             }
         };
 
-        let mut bad_struct_syntax_suggestion = |this: &mut Self, def_id: DefId| {
+        let bad_struct_syntax_suggestion = |this: &mut Self, err: &mut Diag<'_>, def_id: DefId| {
             let (followed_by_brace, closing_brace) = this.followed_by_brace(span);
 
             match source {
@@ -1737,12 +1737,10 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                 }
             }
             (
-                Res::Def(kind @ (DefKind::Mod | DefKind::Trait), _),
+                Res::Def(kind @ (DefKind::Mod | DefKind::Trait | DefKind::TyAlias), _),
                 PathSource::Expr(Some(parent)),
-            ) => {
-                if !path_sep(self, err, parent, kind) {
-                    return false;
-                }
+            ) if path_sep(self, err, parent, kind) => {
+                return true;
             }
             (
                 Res::Def(DefKind::Enum, def_id),
@@ -1774,13 +1772,13 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                 let (ctor_def, ctor_vis, fields) = if let Some(struct_ctor) = struct_ctor {
                     if let PathSource::Expr(Some(parent)) = source {
                         if let ExprKind::Field(..) | ExprKind::MethodCall(..) = parent.kind {
-                            bad_struct_syntax_suggestion(self, def_id);
+                            bad_struct_syntax_suggestion(self, err, def_id);
                             return true;
                         }
                     }
                     struct_ctor
                 } else {
-                    bad_struct_syntax_suggestion(self, def_id);
+                    bad_struct_syntax_suggestion(self, err, def_id);
                     return true;
                 };
 
@@ -1858,7 +1856,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                 err.span_label(span, "constructor is not visible here due to private fields");
             }
             (Res::Def(DefKind::Union | DefKind::Variant, def_id), _) if ns == ValueNS => {
-                bad_struct_syntax_suggestion(self, def_id);
+                bad_struct_syntax_suggestion(self, err, def_id);
             }
             (Res::Def(DefKind::Ctor(_, CtorKind::Const), def_id), _) if ns == ValueNS => {
                 match source {

library/alloc/src/boxed.rs

@@ -1848,11 +1848,23 @@ impl<T: Clone, A: Allocator + Clone> Clone for Box<[T], A> {
 
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "box_slice_clone", since = "1.3.0")]
-impl Clone for Box<str> {
+impl<A: Allocator + Clone> Clone for Box<str, A> {
     fn clone(&self) -> Self {
-        // this makes a copy of the data
-        let buf: Box<[u8]> = self.as_bytes().into();
-        unsafe { from_boxed_utf8_unchecked(buf) }
+        let alloc = Box::allocator(self).clone();
+        let len = self.len();
+        let buf = RawVec::with_capacity_in(len, alloc);
+        unsafe {
+            ptr::copy_nonoverlapping(self.as_ptr(), buf.ptr(), len);
+            from_boxed_utf8_unchecked(buf.into_box(len).assume_init())
+        }
+    }
+
+    fn clone_from(&mut self, other: &Self) {
+        if self.len() == other.len() {
+            unsafe { self.as_bytes_mut().copy_from_slice(other.as_bytes()) }
+        } else {
+            *self = other.clone();
+        }
     }
 }
 

library/alloc/src/str.rs

@@ -49,10 +49,11 @@ pub use core::str::{from_raw_parts, from_raw_parts_mut};
 use core::unicode::conversions;
 use core::{mem, ptr};
 
+use crate::alloc::{Allocator, Global};
 use crate::borrow::ToOwned;
 use crate::boxed::Box;
 use crate::slice::{Concat, Join, SliceIndex};
-use crate::string::String;
+use crate::string::string::String;
 use crate::vec::Vec;
 
 /// Note: `str` in `Concat<str>` is not meaningful here.
@@ -186,15 +187,15 @@ where
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl Borrow<str> for String {
+impl<A: Allocator> Borrow<str> for String<A> {
     #[inline]
     fn borrow(&self) -> &str {
         &self[..]
     }
 }
 
 #[stable(feature = "string_borrow_mut", since = "1.36.0")]
-impl BorrowMut<str> for String {
+impl<A: Allocator> BorrowMut<str> for String<A> {
     #[inline]
     fn borrow_mut(&mut self) -> &mut str {
         &mut self[..]
@@ -235,7 +236,7 @@ impl str {
     #[stable(feature = "str_box_extras", since = "1.20.0")]
     #[must_use = "`self` will be dropped if the result is not used"]
     #[inline]
-    pub fn into_boxed_bytes(self: Box<str>) -> Box<[u8]> {
+    pub fn into_boxed_bytes<A: Allocator>(self: Box<str, A>) -> Box<[u8], A> {
         self.into()
     }
 
@@ -502,8 +503,8 @@ impl str {
     #[rustc_allow_incoherent_impl]
     #[must_use = "`self` will be dropped if the result is not used"]
     #[inline]
-    pub fn into_string(self: Box<str>) -> String {
-        let slice = Box::<[u8]>::from(self);
+    pub fn into_string<A: Allocator>(self: Box<str, A>) -> String<A> {
+        let slice = Box::<[u8], A>::from(self);
         unsafe { String::from_utf8_unchecked(slice.into_vec()) }
     }
 
@@ -615,8 +616,9 @@ impl str {
 #[stable(feature = "str_box_extras", since = "1.20.0")]
 #[must_use]
 #[inline]
-pub unsafe fn from_boxed_utf8_unchecked(v: Box<[u8]>) -> Box<str> {
-    unsafe { Box::from_raw(Box::into_raw(v) as *mut str) }
+pub unsafe fn from_boxed_utf8_unchecked<A: Allocator>(v: Box<[u8], A>) -> Box<str, A> {
+    let (raw, alloc) = Box::into_raw_with_allocator(v);
+    unsafe { Box::from_raw_in(raw as *mut str, alloc) }
 }
 
 /// Converts leading ascii bytes in `s` by calling the `convert` function.