Rollup of 7 pull requests

compiler/rustc_data_structures/src/functor.rs

@@ -34,38 +34,43 @@ impl<T> IdFunctor for Vec<T> {
     type Inner = T;
 
     #[inline]
-    fn try_map_id<F, E>(mut self, mut f: F) -> Result<Self, E>
+    fn try_map_id<F, E>(self, mut f: F) -> Result<Self, E>
     where
         F: FnMut(Self::Inner) -> Result<Self::Inner, E>,
     {
-        // FIXME: We don't really care about panics here and leak
-        // far more than we should, but that should be fine for now.
-        let len = self.len();
-        unsafe {
-            self.set_len(0);
-            let start = self.as_mut_ptr();
-            for i in 0..len {
-                let p = start.add(i);
-                match f(p.read()) {
-                    Ok(val) => p.write(val),
-                    Err(err) => {
-                        // drop all other elements in self
-                        // (current element was "moved" into the call to f)
-                        for j in (0..i).chain(i + 1..len) {
-                            start.add(j).drop_in_place();
-                        }
+        struct HoleVec<T> {
+            vec: Vec<mem::ManuallyDrop<T>>,
+            hole: Option<usize>,
+        }
 
-                        // returning will drop self, releasing the allocation
-                        // (len is 0 so elements will not be re-dropped)
-                        return Err(err);
+        impl<T> Drop for HoleVec<T> {
+            fn drop(&mut self) {
+                unsafe {
+                    for (index, slot) in self.vec.iter_mut().enumerate() {
+                        if self.hole != Some(index) {
+                            mem::ManuallyDrop::drop(slot);
+                        }
                     }
                 }
             }
-            // Even if we encountered an error, set the len back
-            // so we don't leak memory.
-            self.set_len(len);
         }
-        Ok(self)
+
+        unsafe {
+            let (ptr, length, capacity) = self.into_raw_parts();
+            let vec = Vec::from_raw_parts(ptr.cast(), length, capacity);
+            let mut hole_vec = HoleVec { vec, hole: None };
+
+            for (index, slot) in hole_vec.vec.iter_mut().enumerate() {
+                hole_vec.hole = Some(index);
+                let original = mem::ManuallyDrop::take(slot);
+                let mapped = f(original)?;
+                *slot = mem::ManuallyDrop::new(mapped);
+                hole_vec.hole = None;
+            }
+
+            mem::forget(hole_vec);
+            Ok(Vec::from_raw_parts(ptr, length, capacity))
+        }
     }
 }
 

compiler/rustc_data_structures/src/lib.rs

@@ -23,6 +23,7 @@
 #![feature(once_cell)]
 #![feature(test)]
 #![feature(thread_id_value)]
+#![feature(vec_into_raw_parts)]
 #![allow(rustc::default_hash_types)]
 #![deny(unaligned_references)]
 

compiler/rustc_middle/src/ty/list.rs

@@ -1,7 +1,5 @@
 use crate::arena::Arena;
-
 use rustc_serialize::{Encodable, Encoder};
-
 use std::alloc::Layout;
 use std::cmp::Ordering;
 use std::fmt;
@@ -12,49 +10,69 @@ use std::ops::Deref;
 use std::ptr;
 use std::slice;
 
-extern "C" {
-    /// A dummy type used to force `List` to be unsized while not requiring references to it be wide
-    /// pointers.
-    type OpaqueListContents;
-}
-
-/// A wrapper for slices with the additional invariant
-/// that the slice is interned and no other slice with
-/// the same contents can exist in the same context.
-/// This means we can use pointer for both
-/// equality comparisons and hashing.
-///
-/// Unlike slices, the types contained in `List` are expected to be `Copy`
-/// and iterating over a `List` returns `T` instead of a reference.
-///
-/// Note: `Slice` was already taken by the `Ty`.
+/// `List<T>` is a bit like `&[T]`, but with some critical differences.
+/// - IMPORTANT: Every `List<T>` is *required* to have unique contents. The
+///   type's correctness relies on this, *but it does not enforce it*.
+///   Therefore, any code that creates a `List<T>` must ensure uniqueness
+///   itself. In practice this is achieved by interning.
+/// - The length is stored within the `List<T>`, so `&List<Ty>` is a thin
+///   pointer.
+/// - Because of this, you cannot get a `List<T>` that is a sub-list of another
+///   `List<T>`. You can get a sub-slice `&[T]`, however.
+/// - `List<T>` can be used with `CopyTaggedPtr`, which is useful within
+///   structs whose size must be minimized.
+/// - Because of the uniqueness assumption, we can use the address of a
+///   `List<T>` for faster equality comparisons and hashing.
+/// - `T` must be `Copy`. This lets `List<T>` be stored in a dropless arena and
+///   iterators return a `T` rather than a `&T`.
+/// - `T` must not be zero-sized.
 #[repr(C)]
 pub struct List<T> {
     len: usize,
+
+    /// Although this claims to be a zero-length array, in practice `len`
+    /// elements are actually present.
     data: [T; 0],
+
     opaque: OpaqueListContents,
 }
 
-unsafe impl<'a, T: 'a> rustc_data_structures::tagged_ptr::Pointer for &'a List<T> {
-    const BITS: usize = std::mem::align_of::<usize>().trailing_zeros() as usize;
-    #[inline]
-    fn into_usize(self) -> usize {
-        self as *const List<T> as usize
-    }
-    #[inline]
-    unsafe fn from_usize(ptr: usize) -> Self {
-        &*(ptr as *const List<T>)
-    }
-    unsafe fn with_ref<R, F: FnOnce(&Self) -> R>(ptr: usize, f: F) -> R {
-        // Self: Copy so this is fine
-        let ptr = Self::from_usize(ptr);
-        f(&ptr)
-    }
+extern "C" {
+    /// A dummy type used to force `List` to be unsized while not requiring
+    /// references to it be wide pointers.
+    type OpaqueListContents;
 }
 
-unsafe impl<T: Sync> Sync for List<T> {}
+impl<T> List<T> {
+    /// Returns a reference to the (unique, static) empty list.
+    #[inline(always)]
+    pub fn empty<'a>() -> &'a List<T> {
+        #[repr(align(64))]
+        struct MaxAlign;
+
+        assert!(mem::align_of::<T>() <= mem::align_of::<MaxAlign>());
+
+        #[repr(C)]
+        struct InOrder<T, U>(T, U);
+
+        // The empty slice is static and contains a single `0` usize (for the
+        // length) that is 64-byte aligned, thus featuring the necessary
+        // trailing padding for elements with up to 64-byte alignment.
+        static EMPTY_SLICE: InOrder<usize, MaxAlign> = InOrder(0, MaxAlign);
+        unsafe { &*(&EMPTY_SLICE as *const _ as *const List<T>) }
+    }
+}
 
 impl<T: Copy> List<T> {
+    /// Allocates a list from `arena` and copies the contents of `slice` into it.
+    ///
+    /// WARNING: the contents *must be unique*, such that no list with these
+    /// contents has been previously created. If not, operations such as `eq`
+    /// and `hash` might give incorrect results.
+    ///
+    /// Panics if `T` is `Drop`, or `T` is zero-sized, or the slice is empty
+    /// (because the empty list exists statically, and is available via
+    /// `empty()`).
     #[inline]
     pub(super) fn from_arena<'tcx>(arena: &'tcx Arena<'tcx>, slice: &[T]) -> &'tcx List<T> {
         assert!(!mem::needs_drop::<T>());
@@ -73,7 +91,7 @@ impl<T: Copy> List<T> {
                 .cast::<T>()
                 .copy_from_nonoverlapping(slice.as_ptr(), slice.len());
 
-            &mut *mem
+            &*mem
         }
     }
 
@@ -107,11 +125,24 @@ impl<S: Encoder, T: Encodable<S>> Encodable<S> for &List<T> {
     }
 }
 
+impl<T: PartialEq> PartialEq for List<T> {
+    #[inline]
+    fn eq(&self, other: &List<T>) -> bool {
+        // Pointer equality implies list equality (due to the unique contents
+        // assumption).
+        ptr::eq(self, other)
+    }
+}
+
+impl<T: Eq> Eq for List<T> {}
+
 impl<T> Ord for List<T>
 where
     T: Ord,
 {
     fn cmp(&self, other: &List<T>) -> Ordering {
+        // Pointer equality implies list equality (due to the unique contents
+        // assumption), but the contents must be compared otherwise.
         if self == other { Ordering::Equal } else { <[T] as Ord>::cmp(&**self, &**other) }
     }
 }
@@ -121,6 +152,8 @@ where
     T: PartialOrd,
 {
     fn partial_cmp(&self, other: &List<T>) -> Option<Ordering> {
+        // Pointer equality implies list equality (due to the unique contents
+        // assumption), but the contents must be compared otherwise.
         if self == other {
             Some(Ordering::Equal)
         } else {
@@ -129,17 +162,11 @@ where
     }
 }
 
-impl<T: PartialEq> PartialEq for List<T> {
-    #[inline]
-    fn eq(&self, other: &List<T>) -> bool {
-        ptr::eq(self, other)
-    }
-}
-impl<T: Eq> Eq for List<T> {}
-
 impl<T> Hash for List<T> {
     #[inline]
     fn hash<H: Hasher>(&self, s: &mut H) {
+        // Pointer hashing is sufficient (due to the unique contents
+        // assumption).
         (self as *const List<T>).hash(s)
     }
 }
@@ -168,13 +195,24 @@ impl<'a, T: Copy> IntoIterator for &'a List<T> {
     }
 }
 
-impl<T> List<T> {
-    #[inline(always)]
-    pub fn empty<'a>() -> &'a List<T> {
-        #[repr(align(64), C)]
-        struct EmptySlice([u8; 64]);
-        static EMPTY_SLICE: EmptySlice = EmptySlice([0; 64]);
-        assert!(mem::align_of::<T>() <= 64);
-        unsafe { &*(&EMPTY_SLICE as *const _ as *const List<T>) }
+unsafe impl<T: Sync> Sync for List<T> {}
+
+unsafe impl<'a, T: 'a> rustc_data_structures::tagged_ptr::Pointer for &'a List<T> {
+    const BITS: usize = std::mem::align_of::<usize>().trailing_zeros() as usize;
+
+    #[inline]
+    fn into_usize(self) -> usize {
+        self as *const List<T> as usize
+    }
+
+    #[inline]
+    unsafe fn from_usize(ptr: usize) -> &'a List<T> {
+        &*(ptr as *const List<T>)
+    }
+
+    unsafe fn with_ref<R, F: FnOnce(&Self) -> R>(ptr: usize, f: F) -> R {
+        // `Self` is `&'a List<T>` which impls `Copy`, so this is fine.
+        let ptr = Self::from_usize(ptr);
+        f(&ptr)
     }
 }

compiler/rustc_mir_transform/src/check_packed_ref.rs

@@ -105,6 +105,11 @@ impl<'tcx> Visitor<'tcx> for PackedRefChecker<'_, 'tcx> {
                                     a misaligned reference is undefined behavior (even if that \
                                     reference is never dereferenced)",
                                 )
+                                .help(
+                                    "copy the field contents to a local variable, or replace the \
+                                    reference with a raw pointer and use `read_unaligned`/`write_unaligned` \
+                                    (loads and stores via `*p` must be properly aligned even when using raw pointers)"
+                                )
                                 .emit()
                         },
                     );

src/librustdoc/config.rs

@@ -327,6 +327,19 @@ impl Options {
             return Err(0);
         }
 
+        let color = config::parse_color(matches);
+        let config::JsonConfig { json_rendered, json_unused_externs, .. } =
+            config::parse_json(matches);
+        let error_format = config::parse_error_format(matches, color, json_rendered);
+
+        let codegen_options = CodegenOptions::build(matches, error_format);
+        let debugging_opts = DebuggingOptions::build(matches, error_format);
+
+        let diag = new_handler(error_format, None, &debugging_opts);
+
+        // check for deprecated options
+        check_deprecated_options(matches, &diag);
+
         if matches.opt_strs("passes") == ["list"] {
             println!("Available passes for running rustdoc:");
             for pass in passes::PASSES {
@@ -359,19 +372,6 @@ impl Options {
             return Err(0);
         }
 
-        let color = config::parse_color(matches);
-        let config::JsonConfig { json_rendered, json_unused_externs, .. } =
-            config::parse_json(matches);
-        let error_format = config::parse_error_format(matches, color, json_rendered);
-
-        let codegen_options = CodegenOptions::build(matches, error_format);
-        let debugging_opts = DebuggingOptions::build(matches, error_format);
-
-        let diag = new_handler(error_format, None, &debugging_opts);
-
-        // check for deprecated options
-        check_deprecated_options(matches, &diag);
-
         let mut emit = Vec::new();
         for list in matches.opt_strs("emit") {
             for kind in list.split(',') {

src/librustdoc/html/render/print_item.rs

@@ -976,6 +976,7 @@ fn item_typedef(
     // associated items from the aliased type (see discussion in #32077), but
     // we need #14072 to make sense of the generics.
     render_assoc_items(w, cx, it, def_id, AssocItemRender::All);
+    document_type_layout(w, cx, def_id);
 }
 
 fn item_union(w: &mut Buffer, cx: &Context<'_>, it: &clean::Item, s: &clean::Union) {

src/test/rustdoc-ui/issue-91713.rs

@@ -0,0 +1,3 @@
+// check-pass
+// compile-flags: --passes list
+// error-pattern: the `passes` flag is deprecated

src/test/rustdoc-ui/issue-91713.stderr

@@ -0,0 +1,4 @@
+warning: the `passes` flag is deprecated
+   |
+   = note: see issue #44136 <https://github.com/rust-lang/rust/issues/44136> for more information
+

src/test/rustdoc-ui/issue-91713.stdout

@@ -0,0 +1,31 @@
+Available passes for running rustdoc:
+check_doc_test_visibility - run various visibility-related lints on doctests
+        strip-hidden - strips all `#[doc(hidden)]` items from the output
+   unindent-comments - removes excess indentation on comments in order for markdown to like it
+       strip-private - strips all private items from a crate which cannot be seen externally, implies strip-priv-imports
+  strip-priv-imports - strips all private import statements (`use`, `extern crate`) from a crate
+   propagate-doc-cfg - propagates `#[doc(cfg(...))]` to child items
+collect-intra-doc-links - resolves intra-doc links
+check-code-block-syntax - validates syntax inside Rust code blocks
+ collect-trait-impls - retrieves trait impls for items in the crate
+calculate-doc-coverage - counts the number of items with and without documentation
+check-invalid-html-tags - detects invalid HTML tags in doc comments
+     check-bare-urls - detects URLs that are not hyperlinks
+
+Default passes for rustdoc:
+ collect-trait-impls
+   unindent-comments
+check_doc_test_visibility
+        strip-hidden  (when not --document-hidden-items)
+       strip-private  (when not --document-private-items)
+  strip-priv-imports  (when --document-private-items)
+collect-intra-doc-links
+check-code-block-syntax
+check-invalid-html-tags
+   propagate-doc-cfg
+     check-bare-urls
+
+Passes run with `--show-coverage`:
+        strip-hidden  (when not --document-hidden-items)
+       strip-private  (when not --document-private-items)
+calculate-doc-coverage