Auto merge of #72504 - Dylan-DPC:rollup-6wi1ifz, r=Dylan-DPC

Rollup of 5 pull requests

Successful merges:

 - #72292 (Replace obligation construction with deref_steps())
 - #72431 (add warning sign to UB examples)
 - #72446 (Impl Ord for proc_macro::LineColumn)
 - #72492 (Add some regression tests)
 - #72496 (Correct small typo: 'not' -> 'note')

Failed merges:

r? @ghost

src/libcore/mem/maybe_uninit.rs

@@ -20,9 +20,9 @@ use crate::mem::ManuallyDrop;
 /// # #![allow(invalid_value)]
 /// use std::mem::{self, MaybeUninit};
 ///
-/// let x: &i32 = unsafe { mem::zeroed() }; // undefined behavior!
+/// let x: &i32 = unsafe { mem::zeroed() }; // undefined behavior! ⚠️
 /// // The equivalent code with `MaybeUninit<&i32>`:
-/// let x: &i32 = unsafe { MaybeUninit::zeroed().assume_init() }; // undefined behavior!
+/// let x: &i32 = unsafe { MaybeUninit::zeroed().assume_init() }; // undefined behavior! ⚠️
 /// ```
 ///
 /// This is exploited by the compiler for various optimizations, such as eliding
@@ -35,9 +35,9 @@ use crate::mem::ManuallyDrop;
 /// # #![allow(invalid_value)]
 /// use std::mem::{self, MaybeUninit};
 ///
-/// let b: bool = unsafe { mem::uninitialized() }; // undefined behavior!
+/// let b: bool = unsafe { mem::uninitialized() }; // undefined behavior! ⚠️
 /// // The equivalent code with `MaybeUninit<bool>`:
-/// let b: bool = unsafe { MaybeUninit::uninit().assume_init() }; // undefined behavior!
+/// let b: bool = unsafe { MaybeUninit::uninit().assume_init() }; // undefined behavior! ⚠️
 /// ```
 ///
 /// Moreover, uninitialized memory is special in that the compiler knows that
@@ -49,9 +49,9 @@ use crate::mem::ManuallyDrop;
 /// # #![allow(invalid_value)]
 /// use std::mem::{self, MaybeUninit};
 ///
-/// let x: i32 = unsafe { mem::uninitialized() }; // undefined behavior!
+/// let x: i32 = unsafe { mem::uninitialized() }; // undefined behavior! ⚠️
 /// // The equivalent code with `MaybeUninit<i32>`:
-/// let x: i32 = unsafe { MaybeUninit::uninit().assume_init() }; // undefined behavior!
+/// let x: i32 = unsafe { MaybeUninit::uninit().assume_init() }; // undefined behavior! ⚠️
 /// ```
 /// (Notice that the rules around uninitialized integers are not finalized yet, but
 /// until they are, it is advisable to avoid them.)
@@ -348,7 +348,7 @@ impl<T> MaybeUninit<T> {
     /// let x = MaybeUninit::<(u8, NotZero)>::zeroed();
     /// let x = unsafe { x.assume_init() };
     /// // Inside a pair, we create a `NotZero` that does not have a valid discriminant.
-    /// // This is undefined behavior.
+    /// // This is undefined behavior. ⚠️
     /// ```
     #[stable(feature = "maybe_uninit", since = "1.36.0")]
     #[inline]
@@ -400,7 +400,7 @@ impl<T> MaybeUninit<T> {
     ///
     /// let x = MaybeUninit::<Vec<u32>>::uninit();
     /// let x_vec = unsafe { &*x.as_ptr() };
-    /// // We have created a reference to an uninitialized vector! This is undefined behavior.
+    /// // We have created a reference to an uninitialized vector! This is undefined behavior. ⚠️
     /// ```
     ///
     /// (Notice that the rules around references to uninitialized data are not finalized yet, but
@@ -437,7 +437,7 @@ impl<T> MaybeUninit<T> {
     ///
     /// let mut x = MaybeUninit::<Vec<u32>>::uninit();
     /// let x_vec = unsafe { &mut *x.as_mut_ptr() };
-    /// // We have created a reference to an uninitialized vector! This is undefined behavior.
+    /// // We have created a reference to an uninitialized vector! This is undefined behavior. ⚠️
     /// ```
     ///
     /// (Notice that the rules around references to uninitialized data are not finalized yet, but
@@ -489,7 +489,7 @@ impl<T> MaybeUninit<T> {
     ///
     /// let x = MaybeUninit::<Vec<u32>>::uninit();
     /// let x_init = unsafe { x.assume_init() };
-    /// // `x` had not been initialized yet, so this last line caused undefined behavior.
+    /// // `x` had not been initialized yet, so this last line caused undefined behavior. ⚠️
     /// ```
     #[stable(feature = "maybe_uninit", since = "1.36.0")]
     #[inline(always)]
@@ -553,7 +553,7 @@ impl<T> MaybeUninit<T> {
     /// x.write(Some(vec![0,1,2]));
     /// let x1 = unsafe { x.read() };
     /// let x2 = unsafe { x.read() };
-    /// // We now created two copies of the same vector, leading to a double-free when
+    /// // We now created two copies of the same vector, leading to a double-free ⚠️ when
     /// // they both get dropped!
     /// ```
     #[unstable(feature = "maybe_uninit_extra", issue = "63567")]
@@ -603,7 +603,7 @@ impl<T> MaybeUninit<T> {
     ///
     /// let x = MaybeUninit::<Vec<u32>>::uninit();
     /// let x_vec: &Vec<u32> = unsafe { x.get_ref() };
-    /// // We have created a reference to an uninitialized vector! This is undefined behavior.
+    /// // We have created a reference to an uninitialized vector! This is undefined behavior. ⚠️
     /// ```
     ///
     /// ```rust,no_run
@@ -686,7 +686,7 @@ impl<T> MaybeUninit<T> {
     /// unsafe {
     ///     *b.get_mut() = true;
     ///     // We have created a (mutable) reference to an uninitialized `bool`!
-    ///     // This is undefined behavior.
+    ///     // This is undefined behavior. ⚠️
     /// }
     /// ```
     ///

src/libproc_macro/lib.rs

@@ -39,6 +39,7 @@ mod diagnostic;
 #[unstable(feature = "proc_macro_diagnostic", issue = "54140")]
 pub use diagnostic::{Diagnostic, Level, MultiSpan};
 
+use std::cmp::Ordering;
 use std::ops::{Bound, RangeBounds};
 use std::path::PathBuf;
 use std::str::FromStr;
@@ -420,6 +421,20 @@ impl !Send for LineColumn {}
 #[unstable(feature = "proc_macro_span", issue = "54725")]
 impl !Sync for LineColumn {}
 
+#[unstable(feature = "proc_macro_span", issue = "54725")]
+impl Ord for LineColumn {
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.line.cmp(&other.line).then(self.column.cmp(&other.column))
+    }
+}
+
+#[unstable(feature = "proc_macro_span", issue = "54725")]
+impl PartialOrd for LineColumn {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
 /// The source file of a given `Span`.
 #[unstable(feature = "proc_macro_span", issue = "54725")]
 #[derive(Clone)]

src/libproc_macro/tests/test.rs

@@ -0,0 +1,12 @@
+#![feature(proc_macro_span)]
+
+use proc_macro::LineColumn;
+
+#[test]
+fn test_line_column_ord() {
+    let line0_column0 = LineColumn { line: 0, column: 0 };
+    let line0_column1 = LineColumn { line: 0, column: 1 };
+    let line1_column0 = LineColumn { line: 1, column: 0 };
+    assert!(line0_column0 < line0_column1);
+    assert!(line0_column1 < line1_column0);
+}

src/librustc_typeck/check/coercion.rs

@@ -887,7 +887,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let coerce = Coerce::new(self, cause, AllowTwoPhase::No);
         coerce
             .autoderef(rustc_span::DUMMY_SP, expr_ty)
-            .find_map(|(ty, steps)| coerce.unify(ty, target).ok().map(|_| steps))
+            .find_map(|(ty, steps)| self.probe(|_| coerce.unify(ty, target)).ok().map(|_| steps))
     }
 
     /// Given some expressions, their known unified type and another expression,

src/librustc_typeck/check/demand.rs

@@ -1,16 +1,15 @@
 use crate::check::FnCtxt;
 use rustc_infer::infer::InferOk;
 use rustc_trait_selection::infer::InferCtxtExt as _;
-use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
-use rustc_trait_selection::traits::{self, ObligationCause};
+use rustc_trait_selection::traits::ObligationCause;
 
 use rustc_ast::util::parser::PREC_POSTFIX;
 use rustc_errors::{Applicability, DiagnosticBuilder};
 use rustc_hir as hir;
-use rustc_hir::lang_items::{CloneTraitLangItem, DerefTraitLangItem};
+use rustc_hir::lang_items::CloneTraitLangItem;
 use rustc_hir::{is_range_literal, Node};
 use rustc_middle::ty::adjustment::AllowTwoPhase;
-use rustc_middle::ty::{self, AssocItem, ToPredicate, Ty, TypeAndMut};
+use rustc_middle::ty::{self, AssocItem, Ty, TypeAndMut};
 use rustc_span::symbol::sym;
 use rustc_span::Span;
 
@@ -633,48 +632,29 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 }
             }
             _ if sp == expr.span && !is_macro => {
-                // Check for `Deref` implementations by constructing a predicate to
-                // prove: `<T as Deref>::Output == U`
-                let deref_trait = self.tcx.require_lang_item(DerefTraitLangItem, Some(sp));
-                let item_def_id = self
-                    .tcx
-                    .associated_items(deref_trait)
-                    .in_definition_order()
-                    .find(|item| item.kind == ty::AssocKind::Type)
-                    .unwrap()
-                    .def_id;
-                let predicate =
-                    ty::PredicateKind::Projection(ty::Binder::bind(ty::ProjectionPredicate {
-                        // `<T as Deref>::Output`
-                        projection_ty: ty::ProjectionTy {
-                            // `T`
-                            substs: self.tcx.intern_substs(&[checked_ty.into()]),
-                            // `Deref::Output`
-                            item_def_id,
-                        },
-                        // `U`
-                        ty: expected,
-                    }))
-                    .to_predicate(self.tcx);
-                let obligation = traits::Obligation::new(self.misc(sp), self.param_env, predicate);
-                let impls_deref = self.infcx.predicate_may_hold(&obligation);
-
-                // For a suggestion to make sense, the type would need to be `Copy`.
-                let is_copy = self.infcx.type_is_copy_modulo_regions(self.param_env, expected, sp);
-
-                if is_copy && impls_deref {
-                    if let Ok(code) = sm.span_to_snippet(sp) {
-                        let message = if checked_ty.is_region_ptr() {
-                            "consider dereferencing the borrow"
-                        } else {
-                            "consider dereferencing the type"
-                        };
-                        let suggestion = if is_struct_pat_shorthand_field {
-                            format!("{}: *{}", code, code)
-                        } else {
-                            format!("*{}", code)
-                        };
-                        return Some((sp, message, suggestion, Applicability::MachineApplicable));
+                if let Some(steps) = self.deref_steps(checked_ty, expected) {
+                    if steps == 1 {
+                        // For a suggestion to make sense, the type would need to be `Copy`.
+                        if self.infcx.type_is_copy_modulo_regions(self.param_env, expected, sp) {
+                            if let Ok(code) = sm.span_to_snippet(sp) {
+                                let message = if checked_ty.is_region_ptr() {
+                                    "consider dereferencing the borrow"
+                                } else {
+                                    "consider dereferencing the type"
+                                };
+                                let suggestion = if is_struct_pat_shorthand_field {
+                                    format!("{}: *{}", code, code)
+                                } else {
+                                    format!("*{}", code)
+                                };
+                                return Some((
+                                    sp,
+                                    message,
+                                    suggestion,
+                                    Applicability::MachineApplicable,
+                                ));
+                            }
+                        }
                     }
                 }
             }

src/libstd/f32.rs

@@ -882,7 +882,7 @@ impl f32 {
     /// Returns `max` if `self` is greater than `max`, and `min` if `self` is
     /// less than `min`. Otherwise this returns `self`.
     ///
-    /// Not that this function returns NaN if the initial value was NaN as
+    /// Note that this function returns NaN if the initial value was NaN as
     /// well.
     ///
     /// # Panics

src/libstd/f64.rs

@@ -884,7 +884,7 @@ impl f64 {
     /// Returns `max` if `self` is greater than `max`, and `min` if `self` is
     /// less than `min`. Otherwise this returns `self`.
     ///
-    /// Not that this function returns NaN if the initial value was NaN as
+    /// Note that this function returns NaN if the initial value was NaN as
     /// well.
     ///
     /// # Panics

src/test/ui/feature-gates/feature-gate-associated_type_bounds.rs

@@ -1,3 +1,6 @@
+// compile-flags: -Zsave-analysis
+// This is also a regression test for #69415 and the above flag is needed.
+
 #![feature(untagged_unions)]
 
 trait Tr1 { type As1: Copy; }