Auto merge of #101902 - jackh726:revert-static-hrtb-error, r=nikomatsakis

Partially revert #101433

reverts #101433 to fix #101844

We should get this into the beta cut, since the ICE is getting hit quite a bit.

13 files changed, 73 insertions, 200 deletions

diff --git a/src/test/ui/generic-associated-types/bugs/hrtb-implied-1.rs b/src/test/ui/generic-associated-types/bugs/hrtb-implied-1.rs
deleted file mode 100644
index 719d1bd5a4c..00000000000
--- a/src/test/ui/generic-associated-types/bugs/hrtb-implied-1.rs
+++ /dev/null
@@ -1,35 +0,0 @@
-// check-fail
-// known-bug
-
-// This gives us problems because `for<'a> I::Item<'a>: Debug` should mean "for
-// all 'a where I::Item<'a> is WF", but really means "for all 'a possible"
-
-use std::fmt::Debug;
-
-pub trait LendingIterator {
-    type Item<'this>
-    where
-        Self: 'this;
-}
-
-pub struct WindowsMut<'x> {
-    slice: &'x (),
-}
-
-impl<'y> LendingIterator for WindowsMut<'y> {
-    type Item<'this> = &'this mut () where 'y: 'this;
-}
-
-fn print_items<I>(_iter: I)
-where
-    I: LendingIterator,
-    for<'a> I::Item<'a>: Debug,
-{
-}
-
-fn main() {
-    let slice = &mut ();
-    //~^ temporary value dropped while borrowed
-    let windows = WindowsMut { slice };
-    print_items::<WindowsMut<'_>>(windows);
-}
diff --git a/src/test/ui/generic-associated-types/bugs/hrtb-implied-1.stderr b/src/test/ui/generic-associated-types/bugs/hrtb-implied-1.stderr
deleted file mode 100644
index 414999881d4..00000000000
--- a/src/test/ui/generic-associated-types/bugs/hrtb-implied-1.stderr
+++ /dev/null
@@ -1,20 +0,0 @@
-error[E0716]: temporary value dropped while borrowed
-  --> $DIR/hrtb-implied-1.rs:31:22
-   |
-LL |     let slice = &mut ();
-   |                      ^^ creates a temporary which is freed while still in use
-...
-LL |     print_items::<WindowsMut<'_>>(windows);
-   |     -------------------------------------- argument requires that borrow lasts for `'static`
-LL | }
-   | - temporary value is freed at the end of this statement
-   |
-note: due to current limitations in the borrow checker, this implies a `'static` lifetime
-  --> $DIR/hrtb-implied-1.rs:26:26
-   |
-LL |     for<'a> I::Item<'a>: Debug,
-   |                          ^^^^^
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0716`.
diff --git a/src/test/ui/generic-associated-types/bugs/hrtb-implied-2.rs b/src/test/ui/generic-associated-types/bugs/hrtb-implied-2.rs
deleted file mode 100644
index 8e6c5348e71..00000000000
--- a/src/test/ui/generic-associated-types/bugs/hrtb-implied-2.rs
+++ /dev/null
@@ -1,40 +0,0 @@
-// check-fail
-// known-bug
-
-// This gives us problems because `for<'a> I::Item<'a>: Debug` should mean "for
-// all 'a where I::Item<'a> is WF", but really means "for all 'a possible"
-
-trait LendingIterator: Sized {
-    type Item<'a>
-    where
-        Self: 'a;
-    fn next(&mut self) -> Self::Item<'_>;
-}
-fn fails<I: LendingIterator, F>(iter: &mut I, f: F) -> bool
-where
-    F: FnMut(I::Item<'_>),
-{
-    let mut iter2 = Eat(iter, f);
-    let _next = iter2.next();
-    //~^ borrowed data escapes
-    true
-}
-impl<I: LendingIterator> LendingIterator for &mut I {
-    type Item<'a> = I::Item<'a> where Self:'a;
-    fn next(&mut self) -> Self::Item<'_> {
-        (**self).next()
-    }
-}
-
-struct Eat<I, F>(I, F);
-impl<I: LendingIterator, F> Iterator for Eat<I, F>
-where
-    F: FnMut(I::Item<'_>),
-{
-    type Item = ();
-    fn next(&mut self) -> Option<Self::Item> {
-        None
-    }
-}
-
-fn main() {}
diff --git a/src/test/ui/generic-associated-types/bugs/hrtb-implied-2.stderr b/src/test/ui/generic-associated-types/bugs/hrtb-implied-2.stderr
deleted file mode 100644
index 1ee270398de..00000000000
--- a/src/test/ui/generic-associated-types/bugs/hrtb-implied-2.stderr
+++ /dev/null
@@ -1,22 +0,0 @@
-error[E0521]: borrowed data escapes outside of function
-  --> $DIR/hrtb-implied-2.rs:18:17
-   |
-LL | fn fails<I: LendingIterator, F>(iter: &mut I, f: F) -> bool
-   |                                 ----  - let's call the lifetime of this reference `'1`
-   |                                 |
-   |                                 `iter` is a reference that is only valid in the function body
-...
-LL |     let _next = iter2.next();
-   |                 ^^^^^^^^^^^^
-   |                 |
-   |                 `iter` escapes the function body here
-   |                 argument requires that `'1` must outlive `'static`
-   |
-   = note: requirement occurs because of a mutable reference to `Eat<&mut I, F>`
-   = note: mutable references are invariant over their type parameter
-   = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
-   = note: due to current limitations in the borrow checker, this implies a `'static` lifetime
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0521`.
diff --git a/src/test/ui/generic-associated-types/bugs/hrtb-implied-3.rs b/src/test/ui/generic-associated-types/bugs/hrtb-implied-3.rs
deleted file mode 100644
index bc9e6c8aea8..00000000000
--- a/src/test/ui/generic-associated-types/bugs/hrtb-implied-3.rs
+++ /dev/null
@@ -1,23 +0,0 @@
-trait LendingIterator {
-    type Item<'a>
-    where
-        Self: 'a;
-}
-
-impl LendingIterator for &str {
-    type Item<'a> = () where Self:'a;
-}
-
-fn trivial_bound<I>(_: I)
-where
-    I: LendingIterator,
-    for<'a> I::Item<'a>: Sized,
-{
-}
-
-fn fails(iter: &str) {
-    trivial_bound(iter);
-    //~^ borrowed data escapes
-}
-
-fn main() {}
diff --git a/src/test/ui/generic-associated-types/bugs/hrtb-implied-3.stderr b/src/test/ui/generic-associated-types/bugs/hrtb-implied-3.stderr
deleted file mode 100644
index c67e02437cd..00000000000
--- a/src/test/ui/generic-associated-types/bugs/hrtb-implied-3.stderr
+++ /dev/null
@@ -1,22 +0,0 @@
-error[E0521]: borrowed data escapes outside of function
-  --> $DIR/hrtb-implied-3.rs:19:5
-   |
-LL | fn fails(iter: &str) {
-   |          ----  - let's call the lifetime of this reference `'1`
-   |          |
-   |          `iter` is a reference that is only valid in the function body
-LL |     trivial_bound(iter);
-   |     ^^^^^^^^^^^^^^^^^^^
-   |     |
-   |     `iter` escapes the function body here
-   |     argument requires that `'1` must outlive `'static`
-   |
-note: due to current limitations in the borrow checker, this implies a `'static` lifetime
-  --> $DIR/hrtb-implied-3.rs:14:26
-   |
-LL |     for<'a> I::Item<'a>: Sized,
-   |                          ^^^^^
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0521`.
diff --git a/src/test/ui/generic-associated-types/trait-objects.extended.stderr b/src/test/ui/generic-associated-types/trait-objects.extended.stderr
index 45b64d2b024..086177cc106 100644
--- a/src/test/ui/generic-associated-types/trait-objects.extended.stderr
+++ b/src/test/ui/generic-associated-types/trait-objects.extended.stderr
@@ -11,8 +11,6 @@ LL |     x.size_hint().0
    |     |
    |     `x` escapes the function body here
    |     argument requires that `'1` must outlive `'static`
-   |
-   = note: due to current limitations in the borrow checker, this implies a `'static` lifetime
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/higher-rank-trait-bounds/hrtb-just-for-static.stderr b/src/test/ui/higher-rank-trait-bounds/hrtb-just-for-static.stderr
index 31e11e12835..b4312091edb 100644
--- a/src/test/ui/higher-rank-trait-bounds/hrtb-just-for-static.stderr
+++ b/src/test/ui/higher-rank-trait-bounds/hrtb-just-for-static.stderr
@@ -14,12 +14,6 @@ LL | fn give_some<'a>() {
    |              -- lifetime `'a` defined here
 LL |     want_hrtb::<&'a u32>()
    |     ^^^^^^^^^^^^^^^^^^^^ requires that `'a` must outlive `'static`
-   |
-note: due to current limitations in the borrow checker, this implies a `'static` lifetime
-  --> $DIR/hrtb-just-for-static.rs:9:15
-   |
-LL |     where T : for<'a> Foo<&'a isize>
-   |               ^^^^^^^^^^^^^^^^^^^^^^
 
 error: implementation of `Foo` is not general enough
   --> $DIR/hrtb-just-for-static.rs:30:5
diff --git a/src/test/ui/higher-rank-trait-bounds/hrtb-perfect-forwarding.stderr b/src/test/ui/higher-rank-trait-bounds/hrtb-perfect-forwarding.stderr
index 5e75a4cc8af..1461e7fd2dd 100644
--- a/src/test/ui/higher-rank-trait-bounds/hrtb-perfect-forwarding.stderr
+++ b/src/test/ui/higher-rank-trait-bounds/hrtb-perfect-forwarding.stderr
@@ -46,12 +46,6 @@ LL | fn foo_hrtb_bar_not<'b, T>(mut t: T)
 ...
 LL |     foo_hrtb_bar_not(&mut t);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^ requires that `'b` must outlive `'static`
-   |
-note: due to current limitations in the borrow checker, this implies a `'static` lifetime
-  --> $DIR/hrtb-perfect-forwarding.rs:37:8
-   |
-LL |     T: for<'a> Foo<&'a isize> + Bar<&'b isize>,
-   |        ^^^^^^^^^^^^^^^^^^^^^^
 
 error: implementation of `Bar` is not general enough
   --> $DIR/hrtb-perfect-forwarding.rs:43:5
diff --git a/src/test/ui/issues/issue-26217.stderr b/src/test/ui/issues/issue-26217.stderr
index 73c772205c3..c7601caacdc 100644
--- a/src/test/ui/issues/issue-26217.stderr
+++ b/src/test/ui/issues/issue-26217.stderr
@@ -5,12 +5,6 @@ LL | fn bar<'a>() {
    |        -- lifetime `'a` defined here
 LL |     foo::<&'a i32>();
    |     ^^^^^^^^^^^^^^ requires that `'a` must outlive `'static`
-   |
-note: due to current limitations in the borrow checker, this implies a `'static` lifetime
-  --> $DIR/issue-26217.rs:1:30
-   |
-LL | fn foo<T>() where for<'a> T: 'a {}
-   |                              ^^
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/mir/issue-101844.rs b/src/test/ui/mir/issue-101844.rs
new file mode 100644
index 00000000000..da8a25f5f82
--- /dev/null
+++ b/src/test/ui/mir/issue-101844.rs
@@ -0,0 +1,73 @@
+// check-pass
+
+pub trait FirstTrait {
+    type Item;
+    type Extra: Extra<(), Error = Self::Item>;
+}
+
+trait SecondTrait {
+    type Item2;
+}
+
+trait ThirdTrait: SecondTrait {
+    type Item3;
+}
+
+trait FourthTrait {
+    type Item4;
+}
+
+impl<First> SecondTrait for First
+where
+    First: FirstTrait,
+{
+    type Item2 = First::Extra;
+}
+
+impl<Second, T> ThirdTrait for Second
+where
+    Second: SecondTrait<Item2 = T>,
+{
+    type Item3 = T;
+}
+
+impl<S, Third: ?Sized> FourthTrait for Third
+where
+    Third: ThirdTrait<Item3 = S>,
+{
+    type Item4 = S;
+}
+
+pub trait Extra<Request> {
+    type Error;
+}
+
+struct ImplShoulExist<D, Req> {
+    _gen: (D, Req),
+}
+
+impl<D, Req> ImplShoulExist<D, Req>
+where
+    D: FourthTrait,
+    D::Item4: Extra<Req>,
+    <D::Item4 as Extra<Req>>::Error: Into<()>,
+{
+    fn access_fn(_: D) {
+        todo!()
+    }
+}
+
+impl<D, Req> Extra<Req> for ImplShoulExist<D, Req> {
+    type Error = ();
+}
+
+pub fn broken<MS>(ms: MS)
+where
+    MS: FirstTrait,
+    MS::Item: Into<()>,
+{
+    // Error: Apparently Balance::new doesn't exist during MIR validation
+    let _ = ImplShoulExist::<MS, ()>::access_fn(ms);
+}
+
+fn main() {}
diff --git a/src/test/ui/nll/local-outlives-static-via-hrtb.stderr b/src/test/ui/nll/local-outlives-static-via-hrtb.stderr
index f5c10f3ddea..61009da49ff 100644
--- a/src/test/ui/nll/local-outlives-static-via-hrtb.stderr
+++ b/src/test/ui/nll/local-outlives-static-via-hrtb.stderr
@@ -9,12 +9,6 @@ LL |     assert_static_via_hrtb(&local);
 LL |     assert_static_via_hrtb_with_assoc_type(&&local);
 LL | }
    | - `local` dropped here while still borrowed
-   |
-note: due to current limitations in the borrow checker, this implies a `'static` lifetime
-  --> $DIR/local-outlives-static-via-hrtb.rs:15:53
-   |
-LL | fn assert_static_via_hrtb<G>(_: G) where for<'a> G: Outlives<'a> {}
-   |                                                     ^^^^^^^^^^^^
 
 error[E0597]: `local` does not live long enough
   --> $DIR/local-outlives-static-via-hrtb.rs:25:45
@@ -26,12 +20,6 @@ LL |     assert_static_via_hrtb_with_assoc_type(&&local);
    |     argument requires that `local` is borrowed for `'static`
 LL | }
    | - `local` dropped here while still borrowed
-   |
-note: due to current limitations in the borrow checker, this implies a `'static` lifetime
-  --> $DIR/local-outlives-static-via-hrtb.rs:19:20
-   |
-LL |     for<'a> &'a T: Reference<AssociatedType = &'a ()>,
-   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/nll/type-test-universe.stderr b/src/test/ui/nll/type-test-universe.stderr
index 31e17d64b8c..242486c360a 100644
--- a/src/test/ui/nll/type-test-universe.stderr
+++ b/src/test/ui/nll/type-test-universe.stderr
@@ -11,12 +11,6 @@ LL | fn test2<'a>() {
    |          -- lifetime `'a` defined here
 LL |     outlives_forall::<Value<'a>>();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ requires that `'a` must outlive `'static`
-   |
-note: due to current limitations in the borrow checker, this implies a `'static` lifetime
-  --> $DIR/type-test-universe.rs:6:16
-   |
-LL |     for<'u> T: 'u,
-   |                ^^
 
 error: aborting due to 2 previous errors