Rollup merge of #142671 - davidtwco:no-default-bounds-attr, r=lcnr

add #![rustc_no_implicit_bounds]

Follow-up from rust-lang/rust#137944.

Adds a new `rustc_attrs` attribute that stops rustc from adding any default bounds. Useful for tests where default bounds just add noise and make debugging harder.

After reviewing all tests with `?Sized`, these tests seem like they could probably benefit from `#![rustc_no_implicit_bounds]`.

- Skipping most of `tests/ui/unsized` as these seem to want to test `?Sized`
- Skipping tests that used `Box<T>` because it's still bound by `T: MetaSized`
- Skipping parsing or other tests that cared about `?Sized` syntactically
- Skipping tests for `derive(CoercePointee)` because this appears to check that the pointee type is relaxed with `?Sized` explicitly

r? `@lcnr`

1 files changed, 5 insertions, 3 deletions

diff --git a/tests/ui/traits/next-solver/overflow/recursion-limit-normalizes-to-constraints.rs b/tests/ui/traits/next-solver/overflow/recursion-limit-normalizes-to-constraints.rs
index dee5500aadd..e5a57a44d49 100644
--- a/tests/ui/traits/next-solver/overflow/recursion-limit-normalizes-to-constraints.rs
+++ b/tests/ui/traits/next-solver/overflow/recursion-limit-normalizes-to-constraints.rs
@@ -1,5 +1,7 @@
 //@ compile-flags: -Znext-solver=coherence
 //@ check-pass
+#![feature(rustc_attrs)]
+#![rustc_no_implicit_bounds]
 
 // A regression test for trait-system-refactor-initiative#70.
 
@@ -7,8 +9,8 @@ trait Trait {
     type Assoc;
 }
 
-struct W<T: ?Sized>(*mut T);
-impl<T: ?Sized> Trait for W<W<T>>
+struct W<T>(*mut T);
+impl<T> Trait for W<W<T>>
 where
     W<T>: Trait,
 {
@@ -20,6 +22,6 @@ impl<T: Trait<Assoc = u32>> NoOverlap for T {}
 // `Projection(<W<_> as Trait>::Assoc, u32)` should result in error even
 // though applying the impl results in overflow. This is necessary to match
 // the behavior of the old solver.
-impl<T: ?Sized> NoOverlap for W<T> {}
+impl<T> NoOverlap for W<T> {}
 
 fn main() {}