Stop ConstraintCategory Ord impl from relying on Ty's Ord impl.

Author: oli-obk

Cargo.lock

@@ -4236,6 +4236,7 @@ name = "rustc_middle"
 version = "0.0.0"
 dependencies = [
  "bitflags 2.4.2",
+ "derivative",
  "either",
  "field-offset",
  "gsgdt",

compiler/rustc_middle/Cargo.toml

@@ -6,6 +6,7 @@ edition = "2021"
 [dependencies]
 # tidy-alphabetical-start
 bitflags = "2.4.1"
+derivative = "2.2.0"
 either = "1.5.0"
 field-offset = "0.3.5"
 gsgdt = "0.1.2"

compiler/rustc_middle/src/mir/query.rs

@@ -284,8 +284,15 @@ rustc_data_structures::static_assert_size!(ConstraintCategory<'_>, 16);
 /// order of the category, thereby influencing diagnostic output.
 ///
 /// See also `rustc_const_eval::borrow_check::constraints`.
-#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash)]
+#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
 #[derive(TyEncodable, TyDecodable, HashStable, TypeVisitable, TypeFoldable)]
+#[derive(derivative::Derivative)]
+#[derivative(
+    PartialOrd,
+    Ord,
+    PartialOrd = "feature_allow_slow_enum",
+    Ord = "feature_allow_slow_enum"
+)]
 pub enum ConstraintCategory<'tcx> {
     Return(ReturnConstraint),
     Yield,
@@ -295,6 +302,7 @@ pub enum ConstraintCategory<'tcx> {
     Cast {
         /// Whether this is an unsizing cast and if yes, this contains the target type.
         /// Region variables are erased to ReErased.
+        #[derivative(PartialOrd = "ignore", Ord = "ignore")]
         unsize_to: Option<Ty<'tcx>>,
     },
 
@@ -304,7 +312,7 @@ pub enum ConstraintCategory<'tcx> {
     ClosureBounds,
 
     /// Contains the function type if available.
-    CallArgument(Option<Ty<'tcx>>),
+    CallArgument(#[derivative(PartialOrd = "ignore", Ord = "ignore")] Option<Ty<'tcx>>),
     CopyBound,
     SizedBound,
     Assignment,

tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-comparing-against-free.stderr

@@ -53,17 +53,16 @@ LL | fn case2() {
 error[E0597]: `a` does not live long enough
   --> $DIR/propagate-approximated-shorter-to-static-comparing-against-free.rs:30:26
    |
-LL |       let a = 0;
-   |           - binding `a` declared here
-LL |       let cell = Cell::new(&a);
-   |                            ^^ borrowed value does not live long enough
+LL |     let a = 0;
+   |         - binding `a` declared here
+LL |     let cell = Cell::new(&a);
+   |                ----------^^-
+   |                |         |
+   |                |         borrowed value does not live long enough
+   |                argument requires that `a` is borrowed for `'static`
 ...
-LL | /     foo(cell, |cell_a, cell_x| {
-LL | |         cell_x.set(cell_a.get()); // forces 'a: 'x, implies 'a = 'static -> borrow error
-LL | |     })
-   | |______- argument requires that `a` is borrowed for `'static`
-LL |   }
-   |   - `a` dropped here while still borrowed
+LL | }
+   | - `a` dropped here while still borrowed
 
 error: aborting due to 2 previous errors
 

tests/ui/nll/user-annotations/adt-nullary-enums.stderr

@@ -1,16 +1,17 @@
 error[E0597]: `c` does not live long enough
   --> $DIR/adt-nullary-enums.rs:33:41
    |
-LL |       let c = 66;
-   |           - binding `c` declared here
-LL | /     combine(
-LL | |         SomeEnum::SomeVariant(Cell::new(&c)),
-   | |                                         ^^ borrowed value does not live long enough
-LL | |         SomeEnum::SomeOtherVariant::<Cell<&'static u32>>,
-LL | |     );
-   | |_____- argument requires that `c` is borrowed for `'static`
-LL |   }
-   |   - `c` dropped here while still borrowed
+LL |     let c = 66;
+   |         - binding `c` declared here
+LL |     combine(
+LL |         SomeEnum::SomeVariant(Cell::new(&c)),
+   |                               ----------^^-
+   |                               |         |
+   |                               |         borrowed value does not live long enough
+   |                               argument requires that `c` is borrowed for `'static`
+...
+LL | }
+   | - `c` dropped here while still borrowed
 
 error[E0597]: `c` does not live long enough
   --> $DIR/adt-nullary-enums.rs:41:41