Rollup merge of #103774 - compiler-errors:dyn-trait-in-type-name, r=eholk

Format `dyn Trait` better in `type_name` intrinsic

Noticed this in #103764 (though not related to that PR at all!)

```rust
trait Foo {
    type Bar;
}

fn main() {
    println!(
        "`dyn Fn(i32, i32) -> i32` => `{}`",
        std::any::type_name::<dyn Fn(i32, i32) -> i32>()
    );
    println!(
        "`dyn Foo<Bar = i32> + Send + Sync` => `{}`",
        std::any::type_name::<dyn Foo<Bar = i32> + Send + Sync>()
    );
}
```

```
`dyn Fn(i32, i32) -> i32` => `dyn core::ops::function::Fn<(i32, i32)>+Output = i32`
`dyn Foo<Bar = i32> + Send + Sync` => `dyn playground::Foo+Bar = i32+core::marker::Sync+core::marker::Send`
```

Just reuse `pretty_print_dyn_existential` which already makes an attempt to make its output stable.

2 files changed, 3 insertions, 11 deletions

diff --git a/compiler/rustc_const_eval/src/util/type_name.rs b/compiler/rustc_const_eval/src/util/type_name.rs
index 221efc6f981..08a6d69b8e4 100644
--- a/compiler/rustc_const_eval/src/util/type_name.rs
+++ b/compiler/rustc_const_eval/src/util/type_name.rs
@@ -73,18 +73,10 @@ impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
     }
 
     fn print_dyn_existential(
-        mut self,
+        self,
         predicates: &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>,
     ) -> Result<Self::DynExistential, Self::Error> {
-        let mut first = true;
-        for p in predicates {
-            if !first {
-                write!(self, "+")?;
-            }
-            first = false;
-            self = p.print(self)?;
-        }
-        Ok(self)
+        self.pretty_print_dyn_existential(predicates)
     }
 
     fn path_crate(mut self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index f07c60af248..fab85c39d25 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -1137,7 +1137,7 @@ pub trait PrettyPrinter<'tcx>:
         //
         // To avoid causing instabilities in compiletest
         // output, sort the auto-traits alphabetically.
-        auto_traits.sort_by_cached_key(|did| self.tcx().def_path_str(*did));
+        auto_traits.sort_by_cached_key(|did| with_no_trimmed_paths!(self.tcx().def_path_str(*did)));
 
         for def_id in auto_traits {
             if !first {