tests: add #![rustc_no_implicit_bounds]

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

Author: davidtwco

tests/ui/cast/cast-rfc0401-vtable-kinds.rs

@@ -1,4 +1,8 @@
 //@ run-pass
+
+#![feature(rustc_attrs)]
+#![rustc_no_implicit_bounds]
+
 // Check that you can cast between different pointers to trait objects
 // whose vtable have the same kind (both lengths, or both trait pointers).
 
@@ -9,11 +13,11 @@ trait Bar { //~ WARN trait `Bar` is never used
 impl Bar for () {}
 
 #[repr(C)]
-struct FooS<T:?Sized>(T);
+struct FooS<T>(T);
 #[repr(C)]
-struct BarS<T:?Sized>(T);
+struct BarS<T>(T);
 
-fn foo_to_bar<T:?Sized>(u: *const FooS<T>) -> *const BarS<T> {
+fn foo_to_bar<T>(u: *const FooS<T>) -> *const BarS<T> {
     u as *const BarS<T>
 }
 

tests/ui/cast/cast-rfc0401-vtable-kinds.stderr

@@ -1,5 +1,5 @@
 warning: trait `Bar` is never used
-  --> $DIR/cast-rfc0401-vtable-kinds.rs:5:7
+  --> $DIR/cast-rfc0401-vtable-kinds.rs:9:7
    |
 LL | trait Bar {
    |       ^^^

tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.current.stderr

@@ -1,5 +1,5 @@
 error: lifetime may not live long enough
-  --> $DIR/ptr-to-trait-obj-different-regions-id-trait.rs:24:27
+  --> $DIR/ptr-to-trait-obj-different-regions-id-trait.rs:26:27
    |
 LL | fn m<'a>() {
    |      -- lifetime `'a` defined here

tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.next.stderr

@@ -1,5 +1,5 @@
 error: lifetime may not live long enough
-  --> $DIR/ptr-to-trait-obj-different-regions-id-trait.rs:24:27
+  --> $DIR/ptr-to-trait-obj-different-regions-id-trait.rs:26:27
    |
 LL | fn m<'a>() {
    |      -- lifetime `'a` defined here

tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.rs

@@ -2,20 +2,22 @@
 //@ ignore-compare-mode-next-solver (explicit revisions)
 //@[next] compile-flags: -Znext-solver
 //@ check-fail
-//
+#![feature(rustc_attrs)]
+#![rustc_no_implicit_bounds]
+
 // Make sure we can't trick the compiler by using a projection.
 
 trait Cat<'a> {}
 impl Cat<'_> for () {}
 
 trait Id {
-    type Id: ?Sized;
+    type Id;
 }
-impl<T: ?Sized> Id for T {
+impl<T> Id for T {
     type Id = T;
 }
 
-struct S<T: ?Sized> {
+struct S<T> {
     tail: <T as Id>::Id,
 }
 

tests/ui/coercion/codegen-smart-pointer-with-alias.rs

@@ -8,20 +8,22 @@
 // system, which isn't guaranteed to be normalized after substitution.
 
 #![feature(coerce_unsized)]
+#![feature(rustc_attrs)]
+#![rustc_no_implicit_bounds]
 
 use std::ops::CoerceUnsized;
 
 trait Mirror {
-    type Assoc: ?Sized;
+    type Assoc;
 }
-impl<T: ?Sized> Mirror for T {
+impl<T> Mirror for T {
     type Assoc = T;
 }
 
 trait Any {}
 impl<T> Any for T {}
 
-struct Signal<'a, T: ?Sized>(<&'a T as Mirror>::Assoc);
+struct Signal<'a, T>(<&'a T as Mirror>::Assoc);
 
 // This `CoerceUnsized` impl isn't special; it's a bit more restricted than we'd see in the wild,
 // but this ICE also reproduces if we were to make it general over `Signal<T> -> Signal<U>`.

tests/ui/coercion/issue-26905-rpass.rs

@@ -1,17 +1,19 @@
 //@ run-pass
 #![feature(unsize, coerce_unsized)]
+#![feature(rustc_attrs)]
+#![rustc_no_implicit_bounds]
 
 // Verfies that PhantomData is ignored for DST coercions
 
 use std::marker::{Unsize, PhantomData};
 use std::ops::CoerceUnsized;
 
-struct MyRc<T: ?Sized> {
+struct MyRc<T> {
     _ptr: *const T,
     _boo: PhantomData<T>,
 }
 
-impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<MyRc<U>> for MyRc<T>{ }
+impl<T: Unsize<U>, U> CoerceUnsized<MyRc<U>> for MyRc<T>{ }
 
 fn main() {
     let data = [1, 2, 3];

tests/ui/coercion/issue-26905.rs

@@ -1,19 +1,21 @@
 #![feature(unsize, coerce_unsized)]
+#![feature(rustc_attrs)]
+#![rustc_no_implicit_bounds]
 
 // Verfies that non-PhantomData ZSTs still cause coercions to fail.
 // They might have additional semantics that we don't want to bulldoze.
 
 use std::marker::{Unsize, PhantomData};
 use std::ops::CoerceUnsized;
 
-struct NotPhantomData<T: ?Sized>(PhantomData<T>);
+struct NotPhantomData<T>(PhantomData<T>);
 
-struct MyRc<T: ?Sized> {
+struct MyRc<T> {
     _ptr: *const T,
     _boo: NotPhantomData<T>,
 }
 
-impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<MyRc<U>> for MyRc<T>{ } //~ERROR
+impl<T: Unsize<U>, U> CoerceUnsized<MyRc<U>> for MyRc<T>{ } //~ERROR
 
 fn main() {
     let data = [1, 2, 3];

tests/ui/coercion/issue-26905.stderr

@@ -1,11 +1,11 @@
 error[E0375]: implementing `CoerceUnsized` does not allow multiple fields to be coerced
-  --> $DIR/issue-26905.rs:16:40
+  --> $DIR/issue-26905.rs:18:23
    |
-LL | impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<MyRc<U>> for MyRc<T>{ }
-   |                                        ^^^^^^^^^^^^^^^^^^^^^^
+LL | impl<T: Unsize<U>, U> CoerceUnsized<MyRc<U>> for MyRc<T>{ }
+   |                       ^^^^^^^^^^^^^^^^^^^^^^
    |
 note: the trait `CoerceUnsized` may only be implemented when a single field is being coerced
-  --> $DIR/issue-26905.rs:12:5
+  --> $DIR/issue-26905.rs:14:5
    |
 LL |     _ptr: *const T,
    |     ^^^^^^^^^^^^^^

tests/ui/coercion/sub-principals.rs

@@ -7,10 +7,12 @@
 // a non-higer-ranked instantiation.
 
 #![feature(unsize)]
+#![feature(rustc_attrs)]
+#![rustc_no_implicit_bounds]
 
 use std::marker::Unsize;
 
-fn test<T: ?Sized, U: ?Sized>()
+fn test<T, U>()
 where
     T: Unsize<U>,
 {