[beta] backports

compiler/rustc_infer/src/traits/project.rs

@@ -90,6 +90,7 @@ impl ProjectionCacheKey<'tcx> {
 pub enum ProjectionCacheEntry<'tcx> {
     InProgress,
     Ambiguous,
+    Recur,
     Error,
     NormalizedTy(NormalizedTy<'tcx>),
 }
@@ -143,7 +144,12 @@ impl<'tcx> ProjectionCache<'_, 'tcx> {
             "ProjectionCacheEntry::insert_ty: adding cache entry: key={:?}, value={:?}",
             key, value
         );
-        let fresh_key = self.map().insert(key, ProjectionCacheEntry::NormalizedTy(value));
+        let mut map = self.map();
+        if let Some(ProjectionCacheEntry::Recur) = map.get(&key) {
+            debug!("Not overwriting Recur");
+            return;
+        }
+        let fresh_key = map.insert(key, ProjectionCacheEntry::NormalizedTy(value));
         assert!(!fresh_key, "never started projecting `{:?}`", key);
     }
 
@@ -197,6 +203,14 @@ impl<'tcx> ProjectionCache<'_, 'tcx> {
         assert!(!fresh, "never started projecting `{:?}`", key);
     }
 
+    /// Indicates that while trying to normalize `key`, `key` was required to
+    /// be normalized again. Selection or evaluation should eventually report
+    /// an error here.
+    pub fn recur(&mut self, key: ProjectionCacheKey<'tcx>) {
+        let fresh = self.map().insert(key, ProjectionCacheEntry::Recur);
+        assert!(!fresh, "never started projecting `{:?}`", key);
+    }
+
     /// Indicates that trying to normalize `key` resulted in
     /// error.
     pub fn error(&mut self, key: ProjectionCacheKey<'tcx>) {

compiler/rustc_trait_selection/src/traits/project.rs

@@ -496,12 +496,6 @@ fn opt_normalize_projection_type<'a, 'b, 'tcx>(
             return Ok(None);
         }
         Err(ProjectionCacheEntry::InProgress) => {
-            // If while normalized A::B, we are asked to normalize
-            // A::B, just return A::B itself. This is a conservative
-            // answer, in the sense that A::B *is* clearly equivalent
-            // to A::B, though there may be a better value we can
-            // find.
-
             // Under lazy normalization, this can arise when
             // bootstrapping.  That is, imagine an environment with a
             // where-clause like `A::B == u32`. Now, if we are asked
@@ -512,6 +506,14 @@ fn opt_normalize_projection_type<'a, 'b, 'tcx>(
 
             debug!("found cache entry: in-progress");
 
+            // Cache that normalizing this projection resulted in a cycle. This
+            // should ensure that, unless this happens within a snapshot that's
+            // rolled back, fulfillment or evaluation will notice the cycle.
+
+            infcx.inner.borrow_mut().projection_cache().recur(cache_key);
+            return Err(InProgress);
+        }
+        Err(ProjectionCacheEntry::Recur) => {
             return Err(InProgress);
         }
         Err(ProjectionCacheEntry::NormalizedTy(ty)) => {
@@ -734,7 +736,14 @@ fn project_type<'cx, 'tcx>(
 
     if !selcx.tcx().sess.recursion_limit().value_within_limit(obligation.recursion_depth) {
         debug!("project: overflow!");
-        return Err(ProjectionTyError::TraitSelectionError(SelectionError::Overflow));
+        match selcx.query_mode() {
+            super::TraitQueryMode::Standard => {
+                selcx.infcx().report_overflow_error(&obligation, true);
+            }
+            super::TraitQueryMode::Canonical => {
+                return Err(ProjectionTyError::TraitSelectionError(SelectionError::Overflow));
+            }
+        }
     }
 
     let obligation_trait_ref = &obligation.predicate.trait_ref(selcx.tcx());

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -291,6 +291,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         self.infcx.tcx
     }
 
+    pub(super) fn query_mode(&self) -> TraitQueryMode {
+        self.query_mode
+    }
+
     ///////////////////////////////////////////////////////////////////////////
     // Selection
     //

library/alloc/src/rc.rs

@@ -1749,7 +1749,7 @@ struct WeakInner<'a> {
     strong: &'a Cell<usize>,
 }
 
-impl<T: ?Sized> Weak<T> {
+impl<T> Weak<T> {
     /// Returns a raw pointer to the object `T` pointed to by this `Weak<T>`.
     ///
     /// The pointer is valid only if there are some strong references. The pointer may be dangling,
@@ -1882,7 +1882,9 @@ impl<T: ?Sized> Weak<T> {
         // SAFETY: we now have recovered the original Weak pointer, so can create the Weak.
         Weak { ptr: unsafe { NonNull::new_unchecked(ptr) } }
     }
+}
 
+impl<T: ?Sized> Weak<T> {
     /// Attempts to upgrade the `Weak` pointer to an [`Rc`], delaying
     /// dropping of the inner value if successful.
     ///

library/alloc/src/rc/tests.rs

@@ -208,30 +208,6 @@ fn into_from_weak_raw() {
     }
 }
 
-#[test]
-fn test_into_from_weak_raw_unsized() {
-    use std::fmt::Display;
-    use std::string::ToString;
-
-    let arc: Rc<str> = Rc::from("foo");
-    let weak: Weak<str> = Rc::downgrade(&arc);
-
-    let ptr = Weak::into_raw(weak.clone());
-    let weak2 = unsafe { Weak::from_raw(ptr) };
-
-    assert_eq!(unsafe { &*ptr }, "foo");
-    assert!(weak.ptr_eq(&weak2));
-
-    let arc: Rc<dyn Display> = Rc::new(123);
-    let weak: Weak<dyn Display> = Rc::downgrade(&arc);
-
-    let ptr = Weak::into_raw(weak.clone());
-    let weak2 = unsafe { Weak::from_raw(ptr) };
-
-    assert_eq!(unsafe { &*ptr }.to_string(), "123");
-    assert!(weak.ptr_eq(&weak2));
-}
-
 #[test]
 fn get_mut() {
     let mut x = Rc::new(3);

library/alloc/src/sync.rs

@@ -1535,7 +1535,7 @@ struct WeakInner<'a> {
     strong: &'a atomic::AtomicUsize,
 }
 
-impl<T: ?Sized> Weak<T> {
+impl<T> Weak<T> {
     /// Returns a raw pointer to the object `T` pointed to by this `Weak<T>`.
     ///
     /// The pointer is valid only if there are some strong references. The pointer may be dangling,
@@ -1668,7 +1668,9 @@ impl<T: ?Sized> Weak<T> {
         // SAFETY: we now have recovered the original Weak pointer, so can create the Weak.
         unsafe { Weak { ptr: NonNull::new_unchecked(ptr) } }
     }
+}
 
+impl<T: ?Sized> Weak<T> {
     /// Attempts to upgrade the `Weak` pointer to an [`Arc`], delaying
     /// dropping of the inner value if successful.
     ///

library/alloc/src/sync/tests.rs

@@ -158,30 +158,6 @@ fn into_from_weak_raw() {
     }
 }
 
-#[test]
-fn test_into_from_weak_raw_unsized() {
-    use std::fmt::Display;
-    use std::string::ToString;
-
-    let arc: Arc<str> = Arc::from("foo");
-    let weak: Weak<str> = Arc::downgrade(&arc);
-
-    let ptr = Weak::into_raw(weak.clone());
-    let weak2 = unsafe { Weak::from_raw(ptr) };
-
-    assert_eq!(unsafe { &*ptr }, "foo");
-    assert!(weak.ptr_eq(&weak2));
-
-    let arc: Arc<dyn Display> = Arc::new(123);
-    let weak: Weak<dyn Display> = Arc::downgrade(&arc);
-
-    let ptr = Weak::into_raw(weak.clone());
-    let weak2 = unsafe { Weak::from_raw(ptr) };
-
-    assert_eq!(unsafe { &*ptr }.to_string(), "123");
-    assert!(weak.ptr_eq(&weak2));
-}
-
 #[test]
 fn test_cowarc_clone_make_mut() {
     let mut cow0 = Arc::new(75);

src/bootstrap/tarball.rs

@@ -241,10 +241,16 @@ impl<'a> Tarball<'a> {
     }
 
     pub(crate) fn bare(self) -> PathBuf {
+        // Bare tarballs should have the top level directory match the package
+        // name, not "image". We rename the image directory just before passing
+        // into rust-installer.
+        let dest = self.temp_dir.join(self.package_name());
+        t!(std::fs::rename(&self.image_dir, &dest));
+
         self.run(|this, cmd| {
             cmd.arg("tarball")
                 .arg("--input")
-                .arg(&this.image_dir)
+                .arg(&dest)
                 .arg("--output")
                 .arg(crate::dist::distdir(this.builder).join(this.package_name()));
         })

src/stage0.txt

@@ -12,7 +12,7 @@
 # stable release's version number. `date` is the date where the release we're
 # bootstrapping off was released.
 
-date: 2020-12-29
+date: 2020-12-31
 rustc: 1.49.0
 
 # We use a nightly rustfmt to format the source because it solves some
@@ -39,4 +39,4 @@ rustc: 1.49.0
 # looking at a beta source tarball and it's uncommented we'll shortly comment it
 # out.
 
-dev: 1
+#dev: 1

src/test/ui/associated-types/defaults-cyclic-fail-1.rs

@@ -24,13 +24,13 @@ impl Tr for u32 {
 // ...but not in an impl that redefines one of the types.
 impl Tr for bool {
     type A = Box<Self::B>;
-    //~^ ERROR type mismatch resolving `<bool as Tr>::B == _`
+    //~^ ERROR overflow evaluating the requirement `<bool as Tr>::B == _`
 }
 // (the error is shown twice for some reason)
 
 impl Tr for usize {
     type B = &'static Self::A;
-    //~^ ERROR type mismatch resolving `<usize as Tr>::A == _`
+    //~^ ERROR overflow evaluating the requirement `<usize as Tr>::A == _`
 }
 
 fn main() {

src/test/ui/associated-types/defaults-cyclic-fail-1.stderr

@@ -1,15 +1,15 @@
-error[E0271]: type mismatch resolving `<bool as Tr>::B == _`
+error[E0275]: overflow evaluating the requirement `<bool as Tr>::B == _`
   --> $DIR/defaults-cyclic-fail-1.rs:26:5
    |
 LL |     type A = Box<Self::B>;
-   |     ^^^^^^^^^^^^^^^^^^^^^^ cyclic type of infinite size
+   |     ^^^^^^^^^^^^^^^^^^^^^^
 
-error[E0271]: type mismatch resolving `<usize as Tr>::A == _`
+error[E0275]: overflow evaluating the requirement `<usize as Tr>::A == _`
   --> $DIR/defaults-cyclic-fail-1.rs:32:5
    |
 LL |     type B = &'static Self::A;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^ cyclic type of infinite size
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0271`.
+For more information about this error, try `rustc --explain E0275`.

src/test/ui/associated-types/defaults-cyclic-fail-2.rs

@@ -25,13 +25,13 @@ impl Tr for u32 {
 
 impl Tr for bool {
     type A = Box<Self::B>;
-    //~^ ERROR type mismatch resolving `<bool as Tr>::B == _`
+    //~^ ERROR overflow evaluating the requirement `<bool as Tr>::B == _`
 }
 // (the error is shown twice for some reason)
 
 impl Tr for usize {
     type B = &'static Self::A;
-    //~^ ERROR type mismatch resolving `<usize as Tr>::A == _`
+    //~^ ERROR overflow evaluating the requirement `<usize as Tr>::A == _`
 }
 
 fn main() {

src/test/ui/associated-types/defaults-cyclic-fail-2.stderr

@@ -1,15 +1,15 @@
-error[E0271]: type mismatch resolving `<bool as Tr>::B == _`
+error[E0275]: overflow evaluating the requirement `<bool as Tr>::B == _`
   --> $DIR/defaults-cyclic-fail-2.rs:27:5
    |
 LL |     type A = Box<Self::B>;
-   |     ^^^^^^^^^^^^^^^^^^^^^^ cyclic type of infinite size
+   |     ^^^^^^^^^^^^^^^^^^^^^^
 
-error[E0271]: type mismatch resolving `<usize as Tr>::A == _`
+error[E0275]: overflow evaluating the requirement `<usize as Tr>::A == _`
   --> $DIR/defaults-cyclic-fail-2.rs:33:5
    |
 LL |     type B = &'static Self::A;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^ cyclic type of infinite size
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0271`.
+For more information about this error, try `rustc --explain E0275`.

src/test/ui/associated-types/impl-wf-cycle-1.rs

@@ -0,0 +1,29 @@
+// Regression test for #79714
+
+trait Baz {}
+impl Baz for () {}
+impl<T> Baz for (T,) {}
+
+trait Fiz {}
+impl Fiz for bool {}
+
+trait Grault {
+    type A;
+    type B;
+}
+
+impl<T: Grault> Grault for (T,)
+where
+    Self::A: Baz,
+    Self::B: Fiz,
+{
+    type A = ();
+    //~^ ERROR overflow evaluating the requirement `<(T,) as Grault>::A == _`
+    type B = bool;
+    //~^ ERROR overflow evaluating the requirement `<(T,) as Grault>::A == _`
+}
+//~^^^^^^^^^^ ERROR overflow evaluating the requirement `<(T,) as Grault>::A == _`
+
+fn main() {
+    let x: <(_,) as Grault>::A = ();
+}

src/test/ui/associated-types/impl-wf-cycle-1.stderr

@@ -0,0 +1,39 @@
+error[E0275]: overflow evaluating the requirement `<(T,) as Grault>::A == _`
+  --> $DIR/impl-wf-cycle-1.rs:15:1
+   |
+LL | / impl<T: Grault> Grault for (T,)
+LL | | where
+LL | |     Self::A: Baz,
+LL | |     Self::B: Fiz,
+...  |
+LL | |
+LL | | }
+   | |_^
+   |
+   = note: required because of the requirements on the impl of `Grault` for `(T,)`
+   = note: 1 redundant requirements hidden
+   = note: required because of the requirements on the impl of `Grault` for `(T,)`
+
+error[E0275]: overflow evaluating the requirement `<(T,) as Grault>::A == _`
+  --> $DIR/impl-wf-cycle-1.rs:20:5
+   |
+LL |     type A = ();
+   |     ^^^^^^^^^^^^
+   |
+   = note: required because of the requirements on the impl of `Grault` for `(T,)`
+   = note: 1 redundant requirements hidden
+   = note: required because of the requirements on the impl of `Grault` for `(T,)`
+
+error[E0275]: overflow evaluating the requirement `<(T,) as Grault>::A == _`
+  --> $DIR/impl-wf-cycle-1.rs:22:5
+   |
+LL |     type B = bool;
+   |     ^^^^^^^^^^^^^^
+   |
+   = note: required because of the requirements on the impl of `Grault` for `(T,)`
+   = note: 1 redundant requirements hidden
+   = note: required because of the requirements on the impl of `Grault` for `(T,)`
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0275`.

src/test/ui/associated-types/impl-wf-cycle-2.rs

@@ -0,0 +1,16 @@
+// Regression test for #79714
+
+trait Grault {
+    type A;
+}
+
+impl<T: Grault> Grault for (T,)
+where
+    Self::A: Copy,
+{
+    type A = ();
+    //~^ ERROR overflow evaluating the requirement `<(T,) as Grault>::A == _`
+}
+//~^^^^^^^ ERROR overflow evaluating the requirement `<(T,) as Grault>::A == _`
+
+fn main() {}