Auto merge of rust-lang#120663 - matthiaskrgr:rollup-fasba0u, r=matth…

…iaskrgr

Rollup of 7 pull requests

Successful merges:

 - rust-lang#113833 (`std::error::Error` -> Trait Implementations: lifetimes consistency improvement)
 - rust-lang#115386 (PartialEq, PartialOrd: update and synchronize handling of transitive chains)
 - rust-lang#116284 (make matching on NaN a hard error, and remove the rest of illegal_floating_point_literal_pattern)
 - rust-lang#118960 (Add LocalWaker and ContextBuilder types to core, and LocalWake trait to alloc.)
 - rust-lang#120060 (Use the same mir-opt bless targets on all platforms)
 - rust-lang#120214 (match lowering: consistently lower bindings deepest-first)
 - rust-lang#120384 (Use `<T, U>` for array/slice equality `impl`s)

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

compiler/rustc_lint/src/lib.rs

@@ -516,6 +516,10 @@ fn register_builtins(store: &mut LintStore) {
         "converted into hard error, see PR #118649 \
          <https://github.com/rust-lang/rust/pull/118649> for more information",
     );
+    store.register_removed(
+        "illegal_floating_point_literal_pattern",
+        "no longer a warning, float patterns behave the same as `==`",
+    );
 }
 
 fn register_internals(store: &mut LintStore) {

compiler/rustc_lint_defs/src/builtin.rs

@@ -45,7 +45,6 @@ declare_lint_pass! {
         FUZZY_PROVENANCE_CASTS,
         HIDDEN_GLOB_REEXPORTS,
         ILL_FORMED_ATTRIBUTE_INPUT,
-        ILLEGAL_FLOATING_POINT_LITERAL_PATTERN,
         INCOMPLETE_INCLUDE,
         INDIRECT_STRUCTURAL_MATCH,
         INEFFECTIVE_UNSTABLE_TRAIT_IMPL,
@@ -1873,55 +1872,6 @@ declare_lint! {
      };
 }
 
-declare_lint! {
-    /// The `illegal_floating_point_literal_pattern` lint detects
-    /// floating-point literals used in patterns.
-    ///
-    /// ### Example
-    ///
-    /// ```rust
-    /// let x = 42.0;
-    ///
-    /// match x {
-    ///     5.0 => {}
-    ///     _ => {}
-    /// }
-    /// ```
-    ///
-    /// {{produces}}
-    ///
-    /// ### Explanation
-    ///
-    /// Previous versions of the compiler accepted floating-point literals in
-    /// patterns, but it was later determined this was a mistake. The
-    /// semantics of comparing floating-point values may not be clear in a
-    /// pattern when contrasted with "structural equality". Typically you can
-    /// work around this by using a [match guard], such as:
-    ///
-    /// ```rust
-    /// # let x = 42.0;
-    ///
-    /// match x {
-    ///     y if y == 5.0 => {}
-    ///     _ => {}
-    /// }
-    /// ```
-    ///
-    /// This is a [future-incompatible] lint to transition this to a hard
-    /// error in the future. See [issue #41620] for more details.
-    ///
-    /// [issue #41620]: https://github.com/rust-lang/rust/issues/41620
-    /// [match guard]: https://doc.rust-lang.org/reference/expressions/match-expr.html#match-guards
-    /// [future-incompatible]: ../index.md#future-incompatible-lints
-    pub ILLEGAL_FLOATING_POINT_LITERAL_PATTERN,
-    Warn,
-    "floating-point literals cannot be used in patterns",
-    @future_incompatible = FutureIncompatibleInfo {
-        reason: FutureIncompatibilityReason::FutureReleaseErrorDontReportInDeps,
-        reference: "issue #41620 <https://github.com/rust-lang/rust/issues/41620>",
-    };
-}
-
 declare_lint! {
     /// The `unstable_name_collisions` lint detects that you have used a name
     /// that the standard library plans to add in the future.

compiler/rustc_middle/src/mir/interpret/value.rs

@@ -418,8 +418,8 @@ impl<'tcx, Prov: Provenance> Scalar<Prov> {
 
     #[inline]
     pub fn to_float<F: Float>(self) -> InterpResult<'tcx, F> {
-        // Going through `to_uint` to check size and truncation.
-        Ok(F::from_bits(self.to_uint(Size::from_bits(F::BITS))?))
+        // Going through `to_bits` to check size and truncation.
+        Ok(F::from_bits(self.to_bits(Size::from_bits(F::BITS))?))
     }
 
     #[inline]

compiler/rustc_middle/src/ty/consts/int.rs

@@ -249,11 +249,6 @@ impl ScalarInt {
         }
     }
 
-    #[inline]
-    pub fn try_to_target_usize(&self, tcx: TyCtxt<'_>) -> Result<u64, Size> {
-        Ok(self.to_bits(tcx.data_layout.pointer_size)? as u64)
-    }
-
     /// Tries to convert the `ScalarInt` to an unsigned integer of the given size.
     /// Fails if the size of the `ScalarInt` is not equal to `size` and returns the
     /// `ScalarInt`s size in that case.
@@ -262,56 +257,61 @@ impl ScalarInt {
         self.to_bits(size)
     }
 
-    // Tries to convert the `ScalarInt` to `bool`. Fails if the `size` of the `ScalarInt`
-    // in not equal to `Size { raw: 1 }` or if the value is not 0 or 1 and returns the `size`
-    // value of the `ScalarInt` in that case.
-    #[inline]
-    pub fn try_to_bool(self) -> Result<bool, Size> {
-        match self.try_to_u8()? {
-            0 => Ok(false),
-            1 => Ok(true),
-            _ => Err(self.size()),
-        }
-    }
-
     // Tries to convert the `ScalarInt` to `u8`. Fails if the `size` of the `ScalarInt`
     // in not equal to `Size { raw: 1 }` and returns the `size` value of the `ScalarInt` in
     // that case.
     #[inline]
     pub fn try_to_u8(self) -> Result<u8, Size> {
-        self.to_bits(Size::from_bits(8)).map(|v| u8::try_from(v).unwrap())
+        self.try_to_uint(Size::from_bits(8)).map(|v| u8::try_from(v).unwrap())
     }
 
     /// Tries to convert the `ScalarInt` to `u16`. Fails if the size of the `ScalarInt`
     /// in not equal to `Size { raw: 2 }` and returns the `size` value of the `ScalarInt` in
     /// that case.
     #[inline]
     pub fn try_to_u16(self) -> Result<u16, Size> {
-        self.to_bits(Size::from_bits(16)).map(|v| u16::try_from(v).unwrap())
+        self.try_to_uint(Size::from_bits(16)).map(|v| u16::try_from(v).unwrap())
     }
 
     /// Tries to convert the `ScalarInt` to `u32`. Fails if the `size` of the `ScalarInt`
     /// in not equal to `Size { raw: 4 }` and returns the `size` value of the `ScalarInt` in
     /// that case.
     #[inline]
     pub fn try_to_u32(self) -> Result<u32, Size> {
-        self.to_bits(Size::from_bits(32)).map(|v| u32::try_from(v).unwrap())
+        self.try_to_uint(Size::from_bits(32)).map(|v| u32::try_from(v).unwrap())
     }
 
     /// Tries to convert the `ScalarInt` to `u64`. Fails if the `size` of the `ScalarInt`
     /// in not equal to `Size { raw: 8 }` and returns the `size` value of the `ScalarInt` in
     /// that case.
     #[inline]
     pub fn try_to_u64(self) -> Result<u64, Size> {
-        self.to_bits(Size::from_bits(64)).map(|v| u64::try_from(v).unwrap())
+        self.try_to_uint(Size::from_bits(64)).map(|v| u64::try_from(v).unwrap())
     }
 
     /// Tries to convert the `ScalarInt` to `u128`. Fails if the `size` of the `ScalarInt`
     /// in not equal to `Size { raw: 16 }` and returns the `size` value of the `ScalarInt` in
     /// that case.
     #[inline]
     pub fn try_to_u128(self) -> Result<u128, Size> {
-        self.to_bits(Size::from_bits(128))
+        self.try_to_uint(Size::from_bits(128))
+    }
+
+    #[inline]
+    pub fn try_to_target_usize(&self, tcx: TyCtxt<'_>) -> Result<u64, Size> {
+        self.try_to_uint(tcx.data_layout.pointer_size).map(|v| u64::try_from(v).unwrap())
+    }
+
+    // Tries to convert the `ScalarInt` to `bool`. Fails if the `size` of the `ScalarInt`
+    // in not equal to `Size { raw: 1 }` or if the value is not 0 or 1 and returns the `size`
+    // value of the `ScalarInt` in that case.
+    #[inline]
+    pub fn try_to_bool(self) -> Result<bool, Size> {
+        match self.try_to_u8()? {
+            0 => Ok(false),
+            1 => Ok(true),
+            _ => Err(self.size()),
+        }
     }
 
     /// Tries to convert the `ScalarInt` to a signed integer of the given size.
@@ -357,6 +357,27 @@ impl ScalarInt {
     pub fn try_to_i128(self) -> Result<i128, Size> {
         self.try_to_int(Size::from_bits(128))
     }
+
+    #[inline]
+    pub fn try_to_target_isize(&self, tcx: TyCtxt<'_>) -> Result<i64, Size> {
+        self.try_to_int(tcx.data_layout.pointer_size).map(|v| i64::try_from(v).unwrap())
+    }
+
+    #[inline]
+    pub fn try_to_float<F: Float>(self) -> Result<F, Size> {
+        // Going through `to_uint` to check size and truncation.
+        Ok(F::from_bits(self.to_bits(Size::from_bits(F::BITS))?))
+    }
+
+    #[inline]
+    pub fn try_to_f32(self) -> Result<Single, Size> {
+        self.try_to_float()
+    }
+
+    #[inline]
+    pub fn try_to_f64(self) -> Result<Double, Size> {
+        self.try_to_float()
+    }
 }
 
 macro_rules! from {
@@ -399,11 +420,7 @@ impl TryFrom<ScalarInt> for bool {
     type Error = Size;
     #[inline]
     fn try_from(int: ScalarInt) -> Result<Self, Size> {
-        int.to_bits(Size::from_bytes(1)).and_then(|u| match u {
-            0 => Ok(false),
-            1 => Ok(true),
-            _ => Err(Size::from_bytes(1)),
-        })
+        int.try_to_bool()
     }
 }
 

compiler/rustc_mir_build/messages.ftl

@@ -107,8 +107,6 @@ mir_build_extern_static_requires_unsafe_unsafe_op_in_unsafe_fn_allowed =
     .note = extern statics are not controlled by the Rust type system: invalid data, aliasing violations or data races will cause undefined behavior
     .label = use of extern static
 
-mir_build_float_pattern = floating-point types cannot be used in patterns
-
 mir_build_indirect_structural_match =
     to use a constant of type `{$non_sm_ty}` in a pattern, `{$non_sm_ty}` must be annotated with `#[derive(PartialEq)]`
 
@@ -232,6 +230,10 @@ mir_build_mutation_of_layout_constrained_field_requires_unsafe_unsafe_op_in_unsa
     .note = mutating layout constrained fields cannot statically be checked for valid values
     .label = mutation of layout constrained field
 
+mir_build_nan_pattern = cannot use NaN in patterns
+    .note = NaNs compare inequal to everything, even themselves, so this pattern would never match
+    .help = try using the `is_nan` method instead
+
 mir_build_non_const_path = runtime values cannot be referenced in patterns
 
 mir_build_non_empty_never_pattern =

compiler/rustc_mir_build/src/build/matches/simplify.rs

@@ -40,43 +40,39 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         &mut self,
         candidate: &mut Candidate<'pat, 'tcx>,
     ) -> bool {
-        // repeatedly simplify match pairs until fixed point is reached
         debug!("{candidate:#?}");
-
-        // existing_bindings and new_bindings exists to keep the semantics in order.
-        // Reversing the binding order for bindings after `@` changes the binding order in places
-        // it shouldn't be changed, for example `let (Some(a), Some(b)) = (x, y)`
+        // In order to please the borrow checker, in a pattern like `x @ pat` we must lower the
+        // bindings in `pat` before `x`. E.g. (#69971):
+        //
+        // struct NonCopyStruct {
+        //     copy_field: u32,
+        // }
+        //
+        // fn foo1(x: NonCopyStruct) {
+        //     let y @ NonCopyStruct { copy_field: z } = x;
+        //     // the above should turn into
+        //     let z = x.copy_field;
+        //     let y = x;
+        // }
         //
-        // To avoid this, the binding occurs in the following manner:
-        // * the bindings for one iteration of the following loop occurs in order (i.e. left to
-        // right)
-        // * the bindings from the previous iteration of the loop is prepended to the bindings from
-        // the current iteration (in the implementation this is done by mem::swap and extend)
-        // * after all iterations, these new bindings are then appended to the bindings that were
-        // preexisting (i.e. `candidate.binding` when the function was called).
+        // We can't just reverse the binding order, because we must preserve pattern-order
+        // otherwise, e.g. in `let (Some(a), Some(b)) = (x, y)`. Our rule then is: deepest-first,
+        // and bindings at the same depth stay in source order.
+        //
+        // To do this, every time around the loop we prepend the newly found bindings to the
+        // bindings we already had.
         //
         // example:
         // candidate.bindings = [1, 2, 3]
-        // binding in iter 1: [4, 5]
-        // binding in iter 2: [6, 7]
+        // bindings in iter 1: [4, 5]
+        // bindings in iter 2: [6, 7]
         //
-        // final binding: [1, 2, 3, 6, 7, 4, 5]
-        let mut existing_bindings = mem::take(&mut candidate.bindings);
-        let mut new_bindings = Vec::new();
+        // final bindings: [6, 7, 4, 5, 1, 2, 3]
+        let mut accumulated_bindings = mem::take(&mut candidate.bindings);
+        // Repeatedly simplify match pairs until fixed point is reached
         loop {
-            let match_pairs = mem::take(&mut candidate.match_pairs);
-
-            if let [MatchPair { pattern: Pat { kind: PatKind::Or { pats }, .. }, place }] =
-                &*match_pairs
-            {
-                existing_bindings.extend_from_slice(&new_bindings);
-                mem::swap(&mut candidate.bindings, &mut existing_bindings);
-                candidate.subcandidates = self.create_or_subcandidates(candidate, place, pats);
-                return true;
-            }
-
             let mut changed = false;
-            for match_pair in match_pairs {
+            for match_pair in mem::take(&mut candidate.match_pairs) {
                 match self.simplify_match_pair(match_pair, candidate) {
                     Ok(()) => {
                         changed = true;
@@ -86,36 +82,39 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     }
                 }
             }
-            // Avoid issue #69971: the binding order should be right to left if there are more
-            // bindings after `@` to please the borrow checker
-            // Ex
-            // struct NonCopyStruct {
-            //     copy_field: u32,
-            // }
-            //
-            // fn foo1(x: NonCopyStruct) {
-            //     let y @ NonCopyStruct { copy_field: z } = x;
-            //     // the above should turn into
-            //     let z = x.copy_field;
-            //     let y = x;
-            // }
-            candidate.bindings.extend_from_slice(&new_bindings);
-            mem::swap(&mut candidate.bindings, &mut new_bindings);
+
+            // This does: accumulated_bindings = candidate.bindings.take() ++ accumulated_bindings
+            candidate.bindings.extend_from_slice(&accumulated_bindings);
+            mem::swap(&mut candidate.bindings, &mut accumulated_bindings);
             candidate.bindings.clear();
 
             if !changed {
-                existing_bindings.extend_from_slice(&new_bindings);
-                mem::swap(&mut candidate.bindings, &mut existing_bindings);
-                // Move or-patterns to the end, because they can result in us
-                // creating additional candidates, so we want to test them as
-                // late as possible.
-                candidate
-                    .match_pairs
-                    .sort_by_key(|pair| matches!(pair.pattern.kind, PatKind::Or { .. }));
-                debug!(simplified = ?candidate, "simplify_candidate");
-                return false; // if we were not able to simplify any, done.
+                // If we were not able to simplify anymore, done.
+                break;
             }
         }
+
+        // Store computed bindings back in `candidate`.
+        mem::swap(&mut candidate.bindings, &mut accumulated_bindings);
+
+        let did_expand_or =
+            if let [MatchPair { pattern: Pat { kind: PatKind::Or { pats }, .. }, place }] =
+                &*candidate.match_pairs
+            {
+                candidate.subcandidates = self.create_or_subcandidates(candidate, place, pats);
+                candidate.match_pairs.clear();
+                true
+            } else {
+                false
+            };
+
+        // Move or-patterns to the end, because they can result in us
+        // creating additional candidates, so we want to test them as
+        // late as possible.
+        candidate.match_pairs.sort_by_key(|pair| matches!(pair.pattern.kind, PatKind::Or { .. }));
+        debug!(simplified = ?candidate, "simplify_candidate");
+
+        did_expand_or
     }
 
     /// Given `candidate` that has a single or-pattern for its match-pairs,

compiler/rustc_mir_build/src/errors.rs

@@ -780,9 +780,14 @@ pub struct UnsizedPattern<'tcx> {
     pub non_sm_ty: Ty<'tcx>,
 }
 
-#[derive(LintDiagnostic)]
-#[diag(mir_build_float_pattern)]
-pub struct FloatPattern;
+#[derive(Diagnostic)]
+#[diag(mir_build_nan_pattern)]
+#[note]
+#[help]
+pub struct NaNPattern {
+    #[primary_span]
+    pub span: Span,
+}
 
 #[derive(LintDiagnostic)]
 #[diag(mir_build_pointer_pattern)]