Use delayed bug for normalization errors in drop elaboration

Normalization can fail from errors from other items so use a delayed
bug instead of checking the body.

tests/ui/drop/drop_elaboration_with_errors2.rs

@@ -0,0 +1,33 @@
+// Regression test for #137287
+
+mod defining_scope {
+    use super::*;
+    pub type Alias<T> = impl Sized;
+    //~^ ERROR unconstrained opaque type
+    //~| ERROR `impl Trait` in type aliases is unstable
+
+    pub fn cast<T>(x: Container<Alias<T>, T>) -> Container<T, T> {
+        x
+        //~^ ERROR mismatched types
+    }
+}
+
+struct Container<T: Trait<U>, U> {
+    x: <T as Trait<U>>::Assoc,
+}
+
+trait Trait<T> {
+    type Assoc;
+}
+
+impl<T> Trait<T> for T {
+    type Assoc = Box<u32>;
+}
+impl<T> Trait<T> for defining_scope::Alias<T> {
+    //~^ ERROR conflicting implementations of trait `Trait<_>`
+    type Assoc = usize;
+}
+
+fn main() {
+    let x: Box<u32> = defining_scope::cast::<()>(Container { x: 0 }).x;
+}

tests/ui/drop/drop_elaboration_with_errors2.stderr

@@ -0,0 +1,47 @@
+error[E0658]: `impl Trait` in type aliases is unstable
+  --> $DIR/drop_elaboration_with_errors2.rs:5:25
+   |
+LL |     pub type Alias<T> = impl Sized;
+   |                         ^^^^^^^^^^
+   |
+   = note: see issue #63063 <https://github.com/rust-lang/rust/issues/63063> for more information
+   = help: add `#![feature(type_alias_impl_trait)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error[E0119]: conflicting implementations of trait `Trait<_>`
+  --> $DIR/drop_elaboration_with_errors2.rs:26:1
+   |
+LL | impl<T> Trait<T> for T {
+   | ---------------------- first implementation here
+...
+LL | impl<T> Trait<T> for defining_scope::Alias<T> {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation
+
+error: unconstrained opaque type
+  --> $DIR/drop_elaboration_with_errors2.rs:5:25
+   |
+LL |     pub type Alias<T> = impl Sized;
+   |                         ^^^^^^^^^^
+   |
+   = note: `Alias` must be used in combination with a concrete type within the same crate
+
+error[E0308]: mismatched types
+  --> $DIR/drop_elaboration_with_errors2.rs:10:9
+   |
+LL |     pub type Alias<T> = impl Sized;
+   |                         ---------- the found opaque type
+...
+LL |     pub fn cast<T>(x: Container<Alias<T>, T>) -> Container<T, T> {
+   |                 - expected this type parameter   --------------- expected `Container<T, T>` because of return type
+LL |         x
+   |         ^ expected `Container<T, T>`, found `Container<Alias<T>, T>`
+   |
+   = note: expected struct `Container<T, _>`
+              found struct `Container<Alias<T>, _>`
+   = help: type parameters must be constrained to match other types
+   = note: for more information, visit https://doc.rust-lang.org/book/ch10-02-traits.html#traits-as-parameters
+
+error: aborting due to 4 previous errors
+
+Some errors have detailed explanations: E0119, E0308, E0658.
+For more information about an error, try `rustc --explain E0119`.

tests/ui/drop/drop_elaboration_with_errors3.rs

@@ -0,0 +1,42 @@
+// Regression test for #135668
+//@ edition: 2021
+
+use std::future::Future;
+
+pub async fn foo() {
+    let _ = create_task().await;
+}
+
+async fn create_task() -> impl Sized {
+    bind(documentation)
+}
+
+async fn documentation() {
+    compile_error!("bonjour");
+    //~^ ERROR bonjour
+}
+
+fn bind<F>(_filter: F) -> impl Sized
+where
+    F: FilterBase,
+{
+    || -> <F as FilterBase>::Assoc { panic!() }
+}
+
+trait FilterBase {
+    type Assoc;
+}
+
+impl<F, R> FilterBase for F
+where
+    F: Fn() -> R,
+    // Removing the below line makes it correctly error on both stable and beta
+    R: Future,
+    // Removing the below line makes it ICE on both stable and beta
+    R: Send,
+    // Removing the above two bounds makes it ICE on stable but correctly error on beta
+{
+    type Assoc = F;
+}
+
+fn main() {}

tests/ui/drop/drop_elaboration_with_errors3.stderr

@@ -0,0 +1,8 @@
+error: bonjour
+  --> $DIR/drop_elaboration_with_errors3.rs:15:5
+   |
+LL |     compile_error!("bonjour");
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+