Auto merge of rust-lang#116621 - aliemjay:rollup-0e2of3c, r=aliemjay

Rollup of 4 pull requests

Successful merges:

 - rust-lang#95967 (Add explicit-endian String::from_utf16 variants)
 - rust-lang#116530 (delay a bug when encountering an ambiguity in MIR typeck)
 - rust-lang#116611 (Document `diagnostic_namespace` feature)
 - rust-lang#116612 (Remove unused dominator iterator)

r? `@ghost`
`@rustbot` modify labels: rollup

compiler/rustc_data_structures/src/graph/dominators/mod.rs

@@ -349,7 +349,7 @@ struct Inner<N: Idx> {
     post_order_rank: IndexVec<N, usize>,
     // Even though we track only the immediate dominator of each node, it's
     // possible to get its full list of dominators by looking up the dominator
-    // of each dominator. (See the `impl Iterator for Iter` definition).
+    // of each dominator.
     immediate_dominators: IndexVec<N, Option<N>>,
     time: IndexVec<N, Time>,
 }
@@ -377,13 +377,6 @@ impl<Node: Idx> Dominators<Node> {
         }
     }
 
-    /// Provides an iterator over each dominator up the CFG, for the given Node.
-    /// See the `impl Iterator for Iter` definition to understand how this works.
-    pub fn dominators(&self, node: Node) -> Iter<'_, Node> {
-        assert!(self.is_reachable(node), "node {node:?} is not reachable");
-        Iter { dom_tree: self, node: Some(node) }
-    }
-
     /// Provide deterministic ordering of nodes such that, if any two nodes have a dominator
     /// relationship, the dominator will always precede the dominated. (The relative ordering
     /// of two unrelated nodes will also be consistent, but otherwise the order has no
@@ -413,24 +406,6 @@ impl<Node: Idx> Dominators<Node> {
     }
 }
 
-pub struct Iter<'dom, Node: Idx> {
-    dom_tree: &'dom Dominators<Node>,
-    node: Option<Node>,
-}
-
-impl<'dom, Node: Idx> Iterator for Iter<'dom, Node> {
-    type Item = Node;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        if let Some(node) = self.node {
-            self.node = self.dom_tree.immediate_dominator(node);
-            Some(node)
-        } else {
-            None
-        }
-    }
-}
-
 /// Describes the number of vertices discovered at the time when processing of a particular vertex
 /// started and when it finished. Both values are zero for unreachable vertices.
 #[derive(Copy, Clone, Default, Debug)]

compiler/rustc_trait_selection/src/traits/query/type_op/mod.rs

@@ -157,10 +157,18 @@ where
         }
 
         let mut region_constraints = QueryRegionConstraints::default();
-        let (output, error_info, mut obligations, _) =
-            Q::fully_perform_into(self, infcx, &mut region_constraints).map_err(|_| {
-                infcx.tcx.sess.delay_span_bug(span, format!("error performing {self:?}"))
-            })?;
+        let (output, error_info, mut obligations) =
+            Q::fully_perform_into(self, infcx, &mut region_constraints)
+                .map_err(|_| {
+                    infcx.tcx.sess.delay_span_bug(span, format!("error performing {self:?}"))
+                })
+                .and_then(|(output, error_info, obligations, certainty)| match certainty {
+                    Certainty::Proven => Ok((output, error_info, obligations)),
+                    Certainty::Ambiguous => Err(infcx
+                        .tcx
+                        .sess
+                        .delay_span_bug(span, format!("ambiguity performing {self:?}"))),
+                })?;
 
         // Typically, instantiating NLL query results does not
         // create obligations. However, in some cases there

library/alloc/src/string.rs

@@ -714,6 +714,156 @@ impl String {
             .collect()
     }
 
+    /// Decode a UTF-16LE–encoded vector `v` into a `String`, returning [`Err`]
+    /// if `v` contains any invalid data.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// #![feature(str_from_utf16_endian)]
+    /// // 𝄞music
+    /// let v = &[0x34, 0xD8, 0x1E, 0xDD, 0x6d, 0x00, 0x75, 0x00,
+    ///           0x73, 0x00, 0x69, 0x00, 0x63, 0x00];
+    /// assert_eq!(String::from("𝄞music"),
+    ///            String::from_utf16le(v).unwrap());
+    ///
+    /// // 𝄞mu<invalid>ic
+    /// let v = &[0x34, 0xD8, 0x1E, 0xDD, 0x6d, 0x00, 0x75, 0x00,
+    ///           0x00, 0xD8, 0x69, 0x00, 0x63, 0x00];
+    /// assert!(String::from_utf16le(v).is_err());
+    /// ```
+    #[cfg(not(no_global_oom_handling))]
+    #[unstable(feature = "str_from_utf16_endian", issue = "116258")]
+    pub fn from_utf16le(v: &[u8]) -> Result<String, FromUtf16Error> {
+        if v.len() % 2 != 0 {
+            return Err(FromUtf16Error(()));
+        }
+        match (cfg!(target_endian = "little"), unsafe { v.align_to::<u16>() }) {
+            (true, ([], v, [])) => Self::from_utf16(v),
+            _ => char::decode_utf16(v.array_chunks::<2>().copied().map(u16::from_le_bytes))
+                .collect::<Result<_, _>>()
+                .map_err(|_| FromUtf16Error(())),
+        }
+    }
+
+    /// Decode a UTF-16LE–encoded slice `v` into a `String`, replacing
+    /// invalid data with [the replacement character (`U+FFFD`)][U+FFFD].
+    ///
+    /// Unlike [`from_utf8_lossy`] which returns a [`Cow<'a, str>`],
+    /// `from_utf16le_lossy` returns a `String` since the UTF-16 to UTF-8
+    /// conversion requires a memory allocation.
+    ///
+    /// [`from_utf8_lossy`]: String::from_utf8_lossy
+    /// [`Cow<'a, str>`]: crate::borrow::Cow "borrow::Cow"
+    /// [U+FFFD]: core::char::REPLACEMENT_CHARACTER
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// #![feature(str_from_utf16_endian)]
+    /// // 𝄞mus<invalid>ic<invalid>
+    /// let v = &[0x34, 0xD8, 0x1E, 0xDD, 0x6d, 0x00, 0x75, 0x00,
+    ///           0x73, 0x00, 0x1E, 0xDD, 0x69, 0x00, 0x63, 0x00,
+    ///           0x34, 0xD8];
+    ///
+    /// assert_eq!(String::from("𝄞mus\u{FFFD}ic\u{FFFD}"),
+    ///            String::from_utf16le_lossy(v));
+    /// ```
+    #[cfg(not(no_global_oom_handling))]
+    #[unstable(feature = "str_from_utf16_endian", issue = "116258")]
+    pub fn from_utf16le_lossy(v: &[u8]) -> String {
+        match (cfg!(target_endian = "little"), unsafe { v.align_to::<u16>() }) {
+            (true, ([], v, [])) => Self::from_utf16_lossy(v),
+            (true, ([], v, [_remainder])) => Self::from_utf16_lossy(v) + "\u{FFFD}",
+            _ => {
+                let mut iter = v.array_chunks::<2>();
+                let string = char::decode_utf16(iter.by_ref().copied().map(u16::from_le_bytes))
+                    .map(|r| r.unwrap_or(char::REPLACEMENT_CHARACTER))
+                    .collect();
+                if iter.remainder().is_empty() { string } else { string + "\u{FFFD}" }
+            }
+        }
+    }
+
+    /// Decode a UTF-16BE–encoded vector `v` into a `String`, returning [`Err`]
+    /// if `v` contains any invalid data.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// #![feature(str_from_utf16_endian)]
+    /// // 𝄞music
+    /// let v = &[0xD8, 0x34, 0xDD, 0x1E, 0x00, 0x6d, 0x00, 0x75,
+    ///           0x00, 0x73, 0x00, 0x69, 0x00, 0x63];
+    /// assert_eq!(String::from("𝄞music"),
+    ///            String::from_utf16be(v).unwrap());
+    ///
+    /// // 𝄞mu<invalid>ic
+    /// let v = &[0xD8, 0x34, 0xDD, 0x1E, 0x00, 0x6d, 0x00, 0x75,
+    ///           0xD8, 0x00, 0x00, 0x69, 0x00, 0x63];
+    /// assert!(String::from_utf16be(v).is_err());
+    /// ```
+    #[cfg(not(no_global_oom_handling))]
+    #[unstable(feature = "str_from_utf16_endian", issue = "116258")]
+    pub fn from_utf16be(v: &[u8]) -> Result<String, FromUtf16Error> {
+        if v.len() % 2 != 0 {
+            return Err(FromUtf16Error(()));
+        }
+        match (cfg!(target_endian = "big"), unsafe { v.align_to::<u16>() }) {
+            (true, ([], v, [])) => Self::from_utf16(v),
+            _ => char::decode_utf16(v.array_chunks::<2>().copied().map(u16::from_be_bytes))
+                .collect::<Result<_, _>>()
+                .map_err(|_| FromUtf16Error(())),
+        }
+    }
+
+    /// Decode a UTF-16BE–encoded slice `v` into a `String`, replacing
+    /// invalid data with [the replacement character (`U+FFFD`)][U+FFFD].
+    ///
+    /// Unlike [`from_utf8_lossy`] which returns a [`Cow<'a, str>`],
+    /// `from_utf16le_lossy` returns a `String` since the UTF-16 to UTF-8
+    /// conversion requires a memory allocation.
+    ///
+    /// [`from_utf8_lossy`]: String::from_utf8_lossy
+    /// [`Cow<'a, str>`]: crate::borrow::Cow "borrow::Cow"
+    /// [U+FFFD]: core::char::REPLACEMENT_CHARACTER
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// #![feature(str_from_utf16_endian)]
+    /// // 𝄞mus<invalid>ic<invalid>
+    /// let v = &[0xD8, 0x34, 0xDD, 0x1E, 0x00, 0x6d, 0x00, 0x75,
+    ///           0x00, 0x73, 0xDD, 0x1E, 0x00, 0x69, 0x00, 0x63,
+    ///           0xD8, 0x34];
+    ///
+    /// assert_eq!(String::from("𝄞mus\u{FFFD}ic\u{FFFD}"),
+    ///            String::from_utf16be_lossy(v));
+    /// ```
+    #[cfg(not(no_global_oom_handling))]
+    #[unstable(feature = "str_from_utf16_endian", issue = "116258")]
+    pub fn from_utf16be_lossy(v: &[u8]) -> String {
+        match (cfg!(target_endian = "big"), unsafe { v.align_to::<u16>() }) {
+            (true, ([], v, [])) => Self::from_utf16_lossy(v),
+            (true, ([], v, [_remainder])) => Self::from_utf16_lossy(v) + "\u{FFFD}",
+            _ => {
+                let mut iter = v.array_chunks::<2>();
+                let string = char::decode_utf16(iter.by_ref().copied().map(u16::from_be_bytes))
+                    .map(|r| r.unwrap_or(char::REPLACEMENT_CHARACTER))
+                    .collect();
+                if iter.remainder().is_empty() { string } else { string + "\u{FFFD}" }
+            }
+        }
+    }
+
     /// Decomposes a `String` into its raw components.
     ///
     /// Returns the raw pointer to the underlying data, the length of

src/doc/unstable-book/src/language-features/diagnostic-namespace.md

@@ -0,0 +1,84 @@
+# `diagnostic_namespace`
+
+The tracking issue for this feature is: [#111996]
+
+[#111996]: https://github.com/rust-lang/rust/issues/111996
+
+------------------------
+
+The `diagnostic_namespace` feature permits customization of compilation errors.
+
+## diagnostic::on_unimplemented
+
+With [#114452] support for `diagnostic::on_unimplemented` was added.
+
+When used on a trait declaration, the following options are available:
+
+* `message` to customize the primary error message
+* `note` to add a customized note message to an error message
+* `label` to customize the label part of the error message
+
+The attribute will hint to the compiler to use these in error messages:
+```rust
+// some library
+#![feature(diagnostic_namespace)]
+
+#[diagnostic::on_unimplemented(
+    message = "cannot insert element",
+    label = "cannot be put into a table",
+    note = "see <link> for more information about the Table api"
+)]
+pub trait Element {
+    // ...
+}
+```
+
+```rust,compile_fail,E0277
+# #![feature(diagnostic_namespace)]
+#
+# #[diagnostic::on_unimplemented(
+#    message = "cannot insert element",
+#    label = "cannot be put into a table",
+#    note = "see <link> for more information about the Table api"
+# )]
+# pub trait Element {
+#    // ...
+# }
+# struct Table;
+# impl Table {
+#    fn insert<T: Element>(&self, element: T) {
+#        // ..
+#    }
+# }
+# fn main() {
+#    let table = Table;
+#    let element = ();
+// user code
+table.insert(element);
+# }
+```
+
+```text
+error[E0277]: cannot insert element
+  --> src/main.rs:24:18
+   |
+24 |     table.insert(element);
+   |           ------ ^^^^^^^ cannot be put into a table
+   |           |
+   |           required by a bound introduced by this call
+   |
+   = help: the trait `Element` is not implemented for `<type>`
+   = note: see <link> for more information about the Table api
+note: required by a bound in `Table::insert`
+  --> src/main.rs:15:18
+   |
+15 |     fn insert<T: Element>(&self, element: T) {
+   |                  ^^^^^^^ required by this bound in `Table::insert`
+
+For more information about this error, try `rustc --explain E0277`.
+```
+
+See [RFC 3368] for more information.
+
+[#114452]: https://github.com/rust-lang/rust/pull/114452
+[RFC 3368]: https://github.com/rust-lang/rfcs/blob/master/text/3368-diagnostic-attribute-namespace.md

tests/ui/type-alias-impl-trait/rpit_tait_equality_in_canonical_query.current.stderr

@@ -0,0 +1,20 @@
+error: internal compiler error: no errors encountered even though `delay_span_bug` issued
+
+error: internal compiler error: ambiguity performing ParamEnvAnd { param_env: ParamEnv { caller_bounds: [], reveal: UserFacing }, value: ProvePredicate { predicate: Binder { value: ProjectionPredicate(AliasTy { args: [FnDef(DefId(get_rpit), []), ()], def_id: DefId(ops::function::FnOnce::Output) }, Term::Ty(Alias(Opaque, AliasTy { args: [], def_id: DefId(Opaque::{opaque#0}) }))), bound_vars: [] } } }
+  --> $DIR/rpit_tait_equality_in_canonical_query.rs:28:5
+   |
+LL |     query(get_rpit);
+   |     ^^^^^^^^^^^^^^^
+   |
+  --> $DIR/rpit_tait_equality_in_canonical_query.rs:28:5
+   |
+LL |     query(get_rpit);
+   |     ^^^^^^^^^^^^^^^
+
+
+
+
+query stack during panic:
+end of query stack
+error: aborting due to 2 previous errors
+

tests/ui/type-alias-impl-trait/rpit_tait_equality_in_canonical_query.rs

@@ -7,7 +7,14 @@
 
 // revisions: current next
 //[next] compile-flags: -Ztrait-solver=next
-// check-pass
+//[next] check-pass
+
+//[current] known-bug: #108498
+//[current] failure-status: 101
+//[current] normalize-stderr-test: "DefId\(.*?\]::" -> "DefId("
+//[current] normalize-stderr-test: "(?m)^note: .*\n" -> ""
+//[current] normalize-stderr-test: "(?m)^ *\d+: .*\n" -> ""
+//[current] normalize-stderr-test: "(?m)^ *at .*\n" -> ""
 
 #![feature(type_alias_impl_trait)]