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