Auto merge of #53400 - GuillaumeGomez:rollup, r=GuillaumeGomez

Rollup of 8 pull requests

Successful merges:

 - #52453 (improve diagnostics for tests with custom return values)
 - #53271 (use ? to simplify `TransitiveRelation.maybe_map`)
 - #53279 (Extend documentation of `rustc_on_unimplemented`)
 - #53342 (fix error for unsized packed struct field)
 - #53344 (Add doc examples for std::alloc::{alloc,alloc_zeroed}.)
 - #53368 (Ignore test that fails on stage1)
 - #53388 (Fix links' color)
 - #53396 (Fix since of Iterator::flatten to be a proper semver)

Failed merges:

r? @ghost

Author: bors

src/Cargo.lock

@@ -1226,6 +1226,11 @@ name = "mac"
 version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "macro-utils"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "maplit"
 version = "1.0.1"
@@ -1303,10 +1308,10 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "minifier"
-version = "0.0.14"
+version = "0.0.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "regex 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "macro-utils 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -2451,7 +2456,7 @@ dependencies = [
 name = "rustdoc"
 version = "0.0.0"
 dependencies = [
- "minifier 0.0.14 (registry+https://github.com/rust-lang/crates.io-index)",
+ "minifier 0.0.19 (registry+https://github.com/rust-lang/crates.io-index)",
  "pulldown-cmark 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "tempfile 3.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -3218,14 +3223,15 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum log_settings 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "19af41f0565d7c19b2058153ad0b42d4d5ce89ec4dbf06ed6741114a8b63e7cd"
 "checksum lzma-sys 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)" = "d1eaa027402541975218bb0eec67d6b0412f6233af96e0d096d31dbdfd22e614"
 "checksum mac 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "c41e0c4fef86961ac6d6f8a82609f55f31b05e4fce149ac5710e439df7619ba4"
+"checksum macro-utils 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "f2c4deaccc2ead6a28c16c0ba82f07d52b6475397415ce40876e559b0b0ea510"
 "checksum maplit 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "08cbb6b4fef96b6d77bfc40ec491b1690c779e77b05cd9f07f787ed376fd4c43"
 "checksum markup5ever 0.7.2 (registry+https://github.com/rust-lang/crates.io-index)" = "bfedc97d5a503e96816d10fedcd5b42f760b2e525ce2f7ec71f6a41780548475"
 "checksum matches 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)" = "835511bab37c34c47da5cb44844bea2cfde0236db0b506f90ea4224482c9774a"
 "checksum mdbook 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)" = "90b5a8d7e341ceee5db3882a06078d42661ddcfa2b3687319cc5da76ec4e782f"
 "checksum memchr 2.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "796fba70e76612589ed2ce7f45282f5af869e0fdd7cc6199fa1aa1f1d591ba9d"
 "checksum memmap 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)" = "e2ffa2c986de11a9df78620c01eeaaf27d94d3ff02bf81bfcca953102dd0c6ff"
 "checksum memoffset 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "0f9dc261e2b62d7a622bf416ea3c5245cdd5d9a7fcc428c0d06804dfce1775b3"
-"checksum minifier 0.0.14 (registry+https://github.com/rust-lang/crates.io-index)" = "78cb57f9a385530d60f2d67f6e108050b478b7a0ffd0bb9c350803e1356535dd"
+"checksum minifier 0.0.19 (registry+https://github.com/rust-lang/crates.io-index)" = "9908ed7c62f990c21ab41fdca53a864a3ada0da69d8729c4de727b397e27bc11"
 "checksum miniz-sys 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)" = "609ce024854aeb19a0ef7567d348aaa5a746b32fb72e336df7fcc16869d7e2b4"
 "checksum miow 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "9224c91f82b3c47cf53dcf78dfaa20d6888fbcc5d272d5f2fcdf8a697f3c987d"
 "checksum new_debug_unreachable 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "0cdc457076c78ab54d5e0d6fa7c47981757f1e34dc39ff92787f217dede586c4"

src/doc/unstable-book/src/language-features/on-unimplemented.md

@@ -8,7 +8,9 @@ The tracking issue for this feature is: [#29628]
 
 The `on_unimplemented` feature provides the `#[rustc_on_unimplemented]`
 attribute, which allows trait definitions to add specialized notes to error
-messages when an implementation was expected but not found.
+messages when an implementation was expected but not found. You can refer
+to the trait's generic arguments by name and to the resolved type using
+`Self`.
 
 For example:
 
@@ -41,7 +43,98 @@ error[E0277]: the trait bound `&[{integer}]: MyIterator<char>` is not satisfied
    |
    = help: the trait `MyIterator<char>` is not implemented for `&[{integer}]`
    = note: required by `iterate_chars`
+```
+
+`on_unimplemented` also supports advanced filtering for better targeting
+of messages, as well as modifying specific parts of the error message. You
+target the text of:
+
+ - the main error message (`message`)
+ - the label (`label`)
+ - an extra note (`note`)
+
+For example, the following attribute
+
+```rust,compile_fail
+#[rustc_on_unimplemented(
+    message="message",
+    label="label",
+    note="note"
+)]
+trait MyIterator<A> {
+    fn next(&mut self) -> A;
+}
+```
+
+Would generate the following output:
+
+```text
+error[E0277]: message
+  --> <anon>:14:5
+   |
+14 |     iterate_chars(&[1, 2, 3][..]);
+   |     ^^^^^^^^^^^^^ label
+   |
+   = note: note
+   = help: the trait `MyIterator<char>` is not implemented for `&[{integer}]`
+   = note: required by `iterate_chars`
+```
+
+To allow more targeted error messages, it is possible to filter the
+application of these fields based on a variety of attributes when using
+`on`:
 
-error: aborting due to previous error
+ - `crate_local`: whether the code causing the trait bound to not be
+   fulfilled is part of the user's crate. This is used to avoid suggesting
+   code changes that would require modifying a dependency.
+ - Any of the generic arguments that can be substituted in the text can be
+   referred by name as well for filtering, like `Rhs="i32"`, except for
+   `Self`.
+ - `_Self`: to filter only on a particular calculated trait resolution, like
+   `Self="std::iter::Iterator<char>"`. This is needed because `Self` is a
+   keyword which cannot appear in attributes.
+ - `direct`: user-specified rather than derived obligation.
+ - `from_method`: usable both as boolean (whether the flag is present, like
+   `crate_local`) or matching against a particular method. Currently used
+   for `try`.
+ - `from_desugaring`: usable both as boolean (whether the flag is present)
+   or matching against a particular desugaring.
+
+For example, the `Iterator` trait can be annotated in the following way:
+
+```rust,compile_fail
+#[rustc_on_unimplemented(
+    on(
+        _Self="&str",
+        note="call `.chars()` or `.as_bytes()` on `{Self}"
+    ),
+    message="`{Self}` is not an iterator",
+    label="`{Self}` is not an iterator",
+    note="maybe try calling `.iter()` or a similar method"
+)]
+pub trait Iterator {}
 ```
 
+Which would produce the following outputs:
+
+```text
+error[E0277]: `Foo` is not an iterator
+ --> src/main.rs:4:16
+  |
+4 |     for foo in Foo {}
+  |                ^^^ `Foo` is not an iterator
+  |
+  = note: maybe try calling `.iter()` or a similar method
+  = help: the trait `std::iter::Iterator` is not implemented for `Foo`
+  = note: required by `std::iter::IntoIterator::into_iter`
+
+error[E0277]: `&str` is not an iterator
+ --> src/main.rs:5:16
+  |
+5 |     for foo in "" {}
+  |                ^^ `&str` is not an iterator
+  |
+  = note: call `.chars()` or `.bytes() on `&str`
+  = help: the trait `std::iter::Iterator` is not implemented for `&str`
+  = note: required by `std::iter::IntoIterator::into_iter`
+```

src/liballoc/alloc.rs

@@ -56,6 +56,22 @@ pub struct Global;
 /// # Safety
 ///
 /// See [`GlobalAlloc::alloc`].
+///
+/// # Examples
+///
+/// ```
+/// use std::alloc::{alloc, dealloc, Layout};
+///
+/// unsafe {
+///     let layout = Layout::new::<u16>();
+///     let ptr = alloc(layout);
+///
+///     *(ptr as *mut u16) = 42;
+///     assert_eq!(*(ptr as *mut u16), 42);
+///
+///     dealloc(ptr, layout);
+/// }
+/// ```
 #[stable(feature = "global_alloc", since = "1.28.0")]
 #[inline]
 pub unsafe fn alloc(layout: Layout) -> *mut u8 {
@@ -110,6 +126,21 @@ pub unsafe fn realloc(ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8
 /// # Safety
 ///
 /// See [`GlobalAlloc::alloc_zeroed`].
+///
+/// # Examples
+///
+/// ```
+/// use std::alloc::{alloc_zeroed, dealloc, Layout};
+///
+/// unsafe {
+///     let layout = Layout::new::<u16>();
+///     let ptr = alloc_zeroed(layout);
+///
+///     assert_eq!(*(ptr as *mut u16), 0);
+///
+///     dealloc(ptr, layout);
+/// }
+/// ```
 #[stable(feature = "global_alloc", since = "1.28.0")]
 #[inline]
 pub unsafe fn alloc_zeroed(layout: Layout) -> *mut u8 {

src/libcore/iter/iterator.rs

@@ -1110,7 +1110,7 @@ pub trait Iterator {
     ///
     /// [`flat_map()`]: #method.flat_map
     #[inline]
-    #[stable(feature = "iterator_flatten", since = "1.29")]
+    #[stable(feature = "iterator_flatten", since = "1.29.0")]
     fn flatten(self) -> Flatten<Self>
     where Self: Sized, Self::Item: IntoIterator {
         Flatten { inner: flatten_compat(self) }

src/libcore/iter/mod.rs

@@ -2577,13 +2577,13 @@ impl<I, U, F> FusedIterator for FlatMap<I, U, F>
 /// [`flatten`]: trait.Iterator.html#method.flatten
 /// [`Iterator`]: trait.Iterator.html
 #[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
-#[stable(feature = "iterator_flatten", since = "1.29")]
+#[stable(feature = "iterator_flatten", since = "1.29.0")]
 pub struct Flatten<I: Iterator>
 where I::Item: IntoIterator {
     inner: FlattenCompat<I, <I::Item as IntoIterator>::IntoIter>,
 }
 
-#[stable(feature = "iterator_flatten", since = "1.29")]
+#[stable(feature = "iterator_flatten", since = "1.29.0")]
 impl<I, U> fmt::Debug for Flatten<I>
     where I: Iterator + fmt::Debug, U: Iterator + fmt::Debug,
           I::Item: IntoIterator<IntoIter = U, Item = U::Item>,
@@ -2593,15 +2593,15 @@ impl<I, U> fmt::Debug for Flatten<I>
     }
 }
 
-#[stable(feature = "iterator_flatten", since = "1.29")]
+#[stable(feature = "iterator_flatten", since = "1.29.0")]
 impl<I, U> Clone for Flatten<I>
     where I: Iterator + Clone, U: Iterator + Clone,
           I::Item: IntoIterator<IntoIter = U, Item = U::Item>,
 {
     fn clone(&self) -> Self { Flatten { inner: self.inner.clone() } }
 }
 
-#[stable(feature = "iterator_flatten", since = "1.29")]
+#[stable(feature = "iterator_flatten", since = "1.29.0")]
 impl<I, U> Iterator for Flatten<I>
     where I: Iterator, U: Iterator,
           I::Item: IntoIterator<IntoIter = U, Item = U::Item>
@@ -2629,7 +2629,7 @@ impl<I, U> Iterator for Flatten<I>
     }
 }
 
-#[stable(feature = "iterator_flatten", since = "1.29")]
+#[stable(feature = "iterator_flatten", since = "1.29.0")]
 impl<I, U> DoubleEndedIterator for Flatten<I>
     where I: DoubleEndedIterator, U: DoubleEndedIterator,
           I::Item: IntoIterator<IntoIter = U, Item = U::Item>
@@ -2652,7 +2652,7 @@ impl<I, U> DoubleEndedIterator for Flatten<I>
     }
 }
 
-#[stable(feature = "iterator_flatten", since = "1.29")]
+#[stable(feature = "iterator_flatten", since = "1.29.0")]
 impl<I, U> FusedIterator for Flatten<I>
     where I: FusedIterator, U: Iterator,
           I::Item: IntoIterator<IntoIter = U, Item = U::Item> {}

src/librustc/traits/error_reporting.rs

@@ -1472,11 +1472,16 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
             ObligationCauseCode::StructInitializerSized => {
                 err.note("structs must have a statically known size to be initialized");
             }
-            ObligationCauseCode::FieldSized(ref item) => {
+            ObligationCauseCode::FieldSized { adt_kind: ref item, last } => {
                 match *item {
                     AdtKind::Struct => {
-                        err.note("only the last field of a struct may have a dynamically \
-                                  sized type");
+                        if last {
+                            err.note("the last field of a packed struct may only have a \
+                                      dynamically sized type if it does not need drop to be run");
+                        } else {
+                            err.note("only the last field of a struct may have a dynamically \
+                                      sized type");
+                        }
                     }
                     AdtKind::Union => {
                         err.note("no field of a union may have a dynamically sized type");

src/librustc/traits/mod.rs

@@ -192,8 +192,8 @@ pub enum ObligationCauseCode<'tcx> {
     /// [T,..n] --> T must be Copy
     RepeatVec,
 
-    /// Types of fields (other than the last) in a struct must be sized.
-    FieldSized(AdtKind),
+    /// Types of fields (other than the last, except for packed structs) in a struct must be sized.
+    FieldSized { adt_kind: AdtKind, last: bool },
 
     /// Constant expressions must be sized.
     ConstSized,

src/librustc/traits/structural_impls.rs

@@ -206,7 +206,7 @@ impl<'a, 'tcx> Lift<'tcx> for traits::ObligationCauseCode<'a> {
             super::SizedReturnType => Some(super::SizedReturnType),
             super::SizedYieldType => Some(super::SizedYieldType),
             super::RepeatVec => Some(super::RepeatVec),
-            super::FieldSized(item) => Some(super::FieldSized(item)),
+            super::FieldSized { adt_kind, last } => Some(super::FieldSized { adt_kind, last }),
             super::ConstSized => Some(super::ConstSized),
             super::SharedStatic => Some(super::SharedStatic),
             super::BuiltinDerivedObligation(ref cause) => {

src/librustc_data_structures/transitive_relation.rs

@@ -97,12 +97,7 @@ impl<T: Clone + Debug + Eq + Hash> TransitiveRelation<T> {
     {
         let mut result = TransitiveRelation::new();
         for edge in &self.edges {
-            f(&self.elements[edge.source.0]).and_then(|source| {
-                f(&self.elements[edge.target.0]).and_then(|target| {
-                    result.add(source, target);
-                    Some(())
-                })
-            })?;
+            result.add(f(&self.elements[edge.source.0])?, f(&self.elements[edge.target.0])?);
         }
         Some(result)
     }

src/librustc_typeck/check/wfcheck.rs

@@ -258,25 +258,35 @@ fn check_type_defn<'a, 'tcx, F>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                     ty.needs_drop(fcx_tcx, fcx_tcx.param_env(def_id))
                 }
             };
-            let unsized_len = if
+            let all_sized =
                 all_sized ||
                 variant.fields.is_empty() ||
-                needs_drop_copy()
-            {
+                needs_drop_copy();
+            let unsized_len = if all_sized {
                 0
             } else {
                 1
             };
-            for field in &variant.fields[..variant.fields.len() - unsized_len] {
+            for (idx, field) in variant.fields[..variant.fields.len() - unsized_len]
+                .iter()
+                .enumerate()
+            {
+                let last = idx == variant.fields.len() - 1;
                 fcx.register_bound(
                     field.ty,
                     fcx.tcx.require_lang_item(lang_items::SizedTraitLangItem),
-                    traits::ObligationCause::new(field.span,
-                                                    fcx.body_id,
-                                                    traits::FieldSized(match item.node.adt_kind() {
-                                                    Some(i) => i,
-                                                    None => bug!(),
-                                                    })));
+                    traits::ObligationCause::new(
+                        field.span,
+                        fcx.body_id,
+                        traits::FieldSized {
+                            adt_kind: match item.node.adt_kind() {
+                                Some(i) => i,
+                                None => bug!(),
+                            },
+                            last
+                        }
+                    )
+                );
             }
 
             // All field types must be well-formed.

src/librustdoc/Cargo.toml

@@ -9,5 +9,5 @@ path = "lib.rs"
 
 [dependencies]
 pulldown-cmark = { version = "0.1.2", default-features = false }
-minifier = "0.0.14"
+minifier = "0.0.19"
 tempfile = "3"

src/librustdoc/html/static/themes/dark.css

@@ -165,8 +165,8 @@ a {
 	color: #ddd;
 }
 
-.docblock:not(.type-decl) a:not(.srclink):not(.test-arrow), .docblock-short
-a:not(.srclink):not(.test-arrow), .stability a {
+.docblock:not(.type-decl) a:not(.srclink):not(.test-arrow),
+.docblock-short a:not(.srclink):not(.test-arrow), .stability a {
 	color: #D2991D;
 }
 

src/librustdoc/html/static/themes/light.css

@@ -165,8 +165,8 @@ a {
 	color: #000;
 }
 
-.docblock:not(.type-decl) a:not(.srclink):not(.test-arrow), .docblock-short
-a:not(.srclink):not(.test-arrow), .stability a {
+.docblock:not(.type-decl) a:not(.srclink):not(.test-arrow),
+.docblock-short a:not(.srclink):not(.test-arrow), .stability a {
 	color: #3873AD;
 }