alphabetize marker traits when printed

This makes sure they are printed in a compiler-version-independent order, avoiding ui test instability.

Author: arielb1

src/librustc/util/ppaux.rs

@@ -729,13 +729,26 @@ define_print! {
  }
 
  // Builtin bounds.
- for did in self.auto_traits() {
+ let mut auto_traits: Vec<_> = self.auto_traits().map(|did| {
+ tcx.item_path_str(did)
+ }).collect();
+
+ // The auto traits come ordered by `DefPathHash`. While
+ // `DefPathHash` is *stable* in the sense that it depends on
+ // neither the host nor the phase of the moon, it depends
+ // "pseudorandomly" on the compiler version and the target.
+ //
+ // To avoid that causing instabilities in compiletest
+ // output, sort the auto-traits alphabetically.
+ auto_traits.sort();
+
+ for auto_trait in auto_traits {
  if !first {
  write!(f, " + ")?;
  }
  first = false;
 
- write!(f, "{}", tcx.item_path_str(did))?;
+ write!(f, "{}", auto_trait)?;
  }
 
  Ok(())

src/test/ui/issues/issue-33140-traitobject-crate.stderr

@@ -1,10 +1,10 @@
-warning: conflicting implementations of trait `Trait` for type `(dyn std::marker::Sync + std::marker::Send + 'static)`: (E0119)
+warning: conflicting implementations of trait `Trait` for type `(dyn std::marker::Send + std::marker::Sync + 'static)`: (E0119)
  --> $DIR/issue-33140-traitobject-crate.rs:85:1
  |
 LL | unsafe impl Trait for ::std::marker::Send + Sync { }
  | ------------------------------------------------ first implementation here
 LL | unsafe impl Trait for ::std::marker::Send + Send + Sync { }
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn std::marker::Sync + std::marker::Send + 'static)`
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn std::marker::Send + std::marker::Sync + 'static)`
  |
 note: lint level defined here
  --> $DIR/issue-33140-traitobject-crate.rs:3:9
@@ -14,25 +14,25 @@ LL | #![warn(order_dependent_trait_objects)]
  = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
  = note: for more information, see issue #56484 <https://github.com/rust-lang/rust/issues/56484>
 
-warning: conflicting implementations of trait `Trait` for type `(dyn std::marker::Sync + std::marker::Send + 'static)`: (E0119)
+warning: conflicting implementations of trait `Trait` for type `(dyn std::marker::Send + std::marker::Sync + 'static)`: (E0119)
  --> $DIR/issue-33140-traitobject-crate.rs:86:1
  |
 LL | unsafe impl Trait for ::std::marker::Send + Send + Sync { }
  | ------------------------------------------------------- first implementation here
 LL | unsafe impl Trait for ::std::marker::Sync + Send { }
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn std::marker::Sync + std::marker::Send + 'static)`
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn std::marker::Send + std::marker::Sync + 'static)`
  |
  = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
  = note: for more information, see issue #56484 <https://github.com/rust-lang/rust/issues/56484>
 
-warning: conflicting implementations of trait `Trait` for type `(dyn std::marker::Sync + std::marker::Send + 'static)`: (E0119)
+warning: conflicting implementations of trait `Trait` for type `(dyn std::marker::Send + std::marker::Sync + 'static)`: (E0119)
  --> $DIR/issue-33140-traitobject-crate.rs:88:1
  |
 LL | unsafe impl Trait for ::std::marker::Sync + Send { }
  | ------------------------------------------------ first implementation here
 LL | unsafe impl Trait for ::std::marker::Sync + Sync { }
 LL | unsafe impl Trait for ::std::marker::Sync + Send + Sync { }
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn std::marker::Sync + std::marker::Send + 'static)`
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn std::marker::Send + std::marker::Sync + 'static)`
  |
  = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
  = note: for more information, see issue #56484 <https://github.com/rust-lang/rust/issues/56484>

src/test/ui/issues/issue-33140.stderr

@@ -1,20 +1,20 @@
-error[E0119]: conflicting implementations of trait `Trait` for type `(dyn std::marker::Sync + std::marker::Send + 'static)`:
+error[E0119]: conflicting implementations of trait `Trait` for type `(dyn std::marker::Send + std::marker::Sync + 'static)`:
  --> $DIR/issue-33140.rs:9:1
  |
 LL | impl Trait for dyn Send + Sync {
  | ------------------------------ first implementation here
 ...
 LL | impl Trait for dyn Sync + Send {
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn std::marker::Sync + std::marker::Send + 'static)`
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn std::marker::Send + std::marker::Sync + 'static)`
 
-error[E0119]: conflicting implementations of trait `Trait2` for type `(dyn std::marker::Sync + std::marker::Send + 'static)`:
+error[E0119]: conflicting implementations of trait `Trait2` for type `(dyn std::marker::Send + std::marker::Sync + 'static)`:
  --> $DIR/issue-33140.rs:22:1
  |
 LL | impl Trait2 for dyn Send + Sync {
  | ------------------------------- first implementation here
 ...
 LL | impl Trait2 for dyn Sync + Send + Sync {
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn std::marker::Sync + std::marker::Send + 'static)`
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn std::marker::Send + std::marker::Sync + 'static)`
 
 error[E0592]: duplicate definitions with name `abc`
  --> $DIR/issue-33140.rs:29:5