Auto merge of rust-lang#97642 - oli-obk:backport_undo_closure_wf_check, r=compiler-errors

Revert "Check that closures satisfy their where bounds"

This reverts commit 253408b from rust-lang#96899

This is only performed on beta to give us another few weeks to fix rust-lang#97607 on nightly. The planned fix is likely way too large to backport anyway.

r? `@compiler-errors`

Author: bors

compiler/rustc_trait_selection/src/traits/wf.rs

@@ -575,7 +575,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                     // generators don't take arguments.
                 }
 
-                ty::Closure(did, substs) => {
+                ty::Closure(_, substs) => {
                     // Only check the upvar types for WF, not the rest
                     // of the types within. This is needed because we
                     // capture the signature and it may not be WF
@@ -614,8 +614,10 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                     // can cause compiler crashes when the user abuses unsafe
                     // code to procure such a closure.
                     // See src/test/ui/type-alias-impl-trait/wf_check_closures.rs
-                    let obligations = self.nominal_obligations(did, substs);
-                    self.out.extend(obligations);
+                    // We should be checking the nominal_obligations here, but that caused
+                    // a regression in https://github.com/rust-lang/rust/issues/97607
+                    // The regression will be fixed on nightly, but the fix is too large
+                    // to be backported.
                 }
 
                 ty::FnPtr(_) => {

src/test/ui/const-generics/generic_const_exprs/closures.rs

@@ -1,6 +1,6 @@
 #![feature(generic_const_exprs)]
 #![allow(incomplete_features)]
 fn test<const N: usize>() -> [u8; N + (|| 42)()] {}
-//~^ ERROR cycle detected when building an abstract representation
+//~^ ERROR overly complex generic constant
 
 fn main() {}

src/test/ui/const-generics/generic_const_exprs/closures.stderr

@@ -1,26 +1,13 @@
-error[E0391]: cycle detected when building an abstract representation for test::{constant#0}
+error: overly complex generic constant
   --> $DIR/closures.rs:3:35
    |
 LL | fn test<const N: usize>() -> [u8; N + (|| 42)()] {}
-   |                                   ^^^^^^^^^^^^^
+   |                                   ^^^^-------^^
+   |                                       |
+   |                                       borrowing is not supported in generic constants
    |
-note: ...which requires building THIR for `test::{constant#0}`...
-  --> $DIR/closures.rs:3:35
-   |
-LL | fn test<const N: usize>() -> [u8; N + (|| 42)()] {}
-   |                                   ^^^^^^^^^^^^^
-note: ...which requires type-checking `test::{constant#0}`...
-  --> $DIR/closures.rs:3:35
-   |
-LL | fn test<const N: usize>() -> [u8; N + (|| 42)()] {}
-   |                                   ^^^^^^^^^^^^^
-   = note: ...which again requires building an abstract representation for test::{constant#0}, completing the cycle
-note: cycle used when checking that `test` is well-formed
-  --> $DIR/closures.rs:3:1
-   |
-LL | fn test<const N: usize>() -> [u8; N + (|| 42)()] {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = help: consider moving this anonymous constant into a `const` function
+   = note: this operation may be supported in the future
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0391`.

src/test/ui/higher-rank-trait-bounds/issue-59311.nll.stderr

@@ -1,11 +1,3 @@
-error: higher-ranked lifetime error
-  --> $DIR/issue-59311.rs:17:5
-   |
-LL |     v.t(|| {});
-   |     ^^^^^^^^^^
-   |
-   = note: could not prove [closure@$DIR/issue-59311.rs:17:9: 17:14] well-formed
-
 error: higher-ranked lifetime error
   --> $DIR/issue-59311.rs:17:9
    |
@@ -14,5 +6,5 @@ LL |     v.t(|| {});
    |
    = note: could not prove for<'a> &'a V: 'static
 
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 

src/test/ui/higher-rank-trait-bounds/issue-59311.rs

@@ -14,7 +14,7 @@ pub fn crash<V>(v: &V)
 where
     for<'a> &'a V: T + 'static,
 {
-    v.t(|| {}); //~ ERROR: `&'a V` does not fulfill the required lifetime
+    v.t(|| {}); //~ ERROR: higher-ranked lifetime error
 }
 
 fn main() {}

src/test/ui/higher-rank-trait-bounds/issue-59311.stderr

@@ -1,15 +1,10 @@
-error[E0477]: the type `&'a V` does not fulfill the required lifetime
-  --> $DIR/issue-59311.rs:17:5
+error: higher-ranked lifetime error
+  --> $DIR/issue-59311.rs:17:9
    |
 LL |     v.t(|| {});
-   |     ^^^^^^^^^^
+   |         ^^^^^
    |
-note: type must satisfy the static lifetime as required by this binding
-  --> $DIR/issue-59311.rs:15:24
-   |
-LL |     for<'a> &'a V: T + 'static,
-   |                        ^^^^^^^
+   = note: could not prove for<'a> &'a V: 'static
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0477`.

src/test/ui/type-alias-impl-trait/issue-53092.rs

@@ -1,12 +1,15 @@
 #![feature(type_alias_impl_trait)]
 #![allow(dead_code)]
 
+// check-pass
+// known-bug #53092 #90409
+
 type Bug<T, U> = impl Fn(T) -> U + Copy;
 
 const CONST_BUG: Bug<u8, ()> = unsafe { std::mem::transmute(|_: u8| ()) };
 
 fn make_bug<T, U: From<T>>() -> Bug<T, U> {
-    |x| x.into() //~ ERROR the trait bound `U: From<T>` is not satisfied
+    |x| x.into()
 }
 
 fn main() {

src/test/ui/type-alias-impl-trait/issue-53092.stderr

@@ -1,5 +1,8 @@
 #![feature(type_alias_impl_trait)]
 
+// check-pass
+// known-bug #53092 #90409
+
 trait Bar {
     fn bar(&self);
 }
@@ -8,7 +11,6 @@ type FooFn<B> = impl FnOnce();
 
 fn foo<B: Bar>(bar: B) -> FooFn<B> {
     move || { bar.bar() }
-    //~^ ERROR the trait bound `B: Bar` is not satisfied
 }
 
 fn main() {