Auto merge of rust-lang#116494 - compiler-errors:typeck-coinductive-a…

…mbig, r=<try> [crater only] Always make inductive cycles as ambig during typeck r? `@ghost`
rust-lang-ci · Oct 6, 2023 · 919137c · 919137c
2 parents 31be8cc + 1007c9c
commit 919137c
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diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -231,7 +231,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             freshener: infcx.freshener(),
             intercrate_ambiguity_causes: None,
             query_mode: TraitQueryMode::Standard,
-            treat_inductive_cycle: TreatInductiveCycleAs::Recur,
+            treat_inductive_cycle: TreatInductiveCycleAs::Ambig,
         }
     }
 

diff --git a/tests/ui/associated-type-bounds/bad-bounds-on-assoc-in-trait.stderr b/tests/ui/associated-type-bounds/bad-bounds-on-assoc-in-trait.stderr
@@ -1,3 +1,15 @@
+error[E0277]: `<Self as Case1>::C` is not an iterator
+  --> $DIR/bad-bounds-on-assoc-in-trait.rs:26:21
+   |
+LL |     type C: Clone + Iterator<Item: Send + Iterator<Item: for<'a> Lam<&'a u8, App: Debug>> + Sync>;
+   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `<Self as Case1>::C` is not an iterator
+   |
+   = help: the trait `Iterator` is not implemented for `<Self as Case1>::C`
+help: consider further restricting the associated type
+   |
+LL | trait Case1 where <Self as Case1>::C: Iterator {
+   |             ++++++++++++++++++++++++++++++++++
+
 error[E0277]: `<<Self as Case1>::C as Iterator>::Item` cannot be sent between threads safely
   --> $DIR/bad-bounds-on-assoc-in-trait.rs:26:36
    |
@@ -34,6 +46,6 @@ help: consider further restricting the associated type
 LL | trait Case1 where <<Self as Case1>::C as Iterator>::Item: Sync {
    |             ++++++++++++++++++++++++++++++++++++++++++++++++++
 
-error: aborting due to 3 previous errors
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/impl-trait/in-trait/specialization-broken.stderr b/tests/ui/impl-trait/in-trait/specialization-broken.stderr
@@ -1,31 +1,18 @@
-error[E0053]: method `bar` has an incompatible type for trait
-  --> $DIR/specialization-broken.rs:16:22
+error[E0391]: cycle detected when computing whether impls specialize one another
+  --> $DIR/specialization-broken.rs:12:1
    |
 LL | default impl<U> Foo for U
-   |              - this type parameter
-...
-LL |     fn bar(&self) -> U {
-   |                      ^
-   |                      |
-   |                      expected associated type, found type parameter `U`
-   |                      help: change the output type to match the trait: `impl Sized`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-note: type in trait
-  --> $DIR/specialization-broken.rs:9:22
+   = note: ...which requires evaluating trait selection obligation `i32: Foo`...
+   = note: ...which again requires computing whether impls specialize one another, completing the cycle
+note: cycle used when building specialization graph of trait `Foo`
+  --> $DIR/specialization-broken.rs:8:1
    |
-LL |     fn bar(&self) -> impl Sized;
-   |                      ^^^^^^^^^^
-   = note: expected signature `fn(&U) -> impl Sized`
-              found signature `fn(&U) -> U`
+LL | trait Foo {
+   | ^^^^^^^^^
+   = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
 
-error: method with return-position `impl Trait` in trait cannot be specialized
-  --> $DIR/specialization-broken.rs:16:5
-   |
-LL |     fn bar(&self) -> U {
-   |     ^^^^^^^^^^^^^^^^^^
-   |
-   = note: specialization behaves in inconsistent and surprising ways with `#![feature(return_position_impl_trait_in_trait)]`, and for now is disallowed
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0053`.
+For more information about this error, try `rustc --explain E0391`.
diff --git a/tests/ui/specialization/defaultimpl/specialization-no-default.stderr b/tests/ui/specialization/defaultimpl/specialization-no-default.stderr
@@ -8,61 +8,20 @@ LL | #![feature(specialization)]
    = help: consider using `min_specialization` instead, which is more stable and complete
    = note: `#[warn(incomplete_features)]` on by default
 
-error[E0520]: `foo` specializes an item from a parent `impl`, but that item is not marked `default`
-  --> $DIR/specialization-no-default.rs:20:5
+error[E0391]: cycle detected when computing whether impls specialize one another
+  --> $DIR/specialization-no-default.rs:46:1
    |
-LL | impl<T> Foo for T {
-   | ----------------- parent `impl` is here
-...
-LL |     fn foo(&self) {}
-   |     ^^^^^^^^^^^^^ cannot specialize default item `foo`
+LL | default impl<T> Baz for T {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: to specialize, `foo` in the parent `impl` must be marked `default`
-
-error[E0520]: `bar` specializes an item from a parent `impl`, but that item is not marked `default`
-  --> $DIR/specialization-no-default.rs:23:5
-   |
-LL | impl<T> Foo for T {
-   | ----------------- parent `impl` is here
-...
-LL |     fn bar(&self) {}
-   |     ^^^^^^^^^^^^^ cannot specialize default item `bar`
-   |
-   = note: to specialize, `bar` in the parent `impl` must be marked `default`
-
-error[E0520]: `T` specializes an item from a parent `impl`, but that item is not marked `default`
-  --> $DIR/specialization-no-default.rs:37:5
-   |
-LL | impl<T> Bar for T {
-   | ----------------- parent `impl` is here
-...
-LL |     type T = ();
-   |     ^^^^^^ cannot specialize default item `T`
-   |
-   = note: to specialize, `T` in the parent `impl` must be marked `default`
-
-error[E0520]: `baz` specializes an item from a parent `impl`, but that item is not marked `default`
-  --> $DIR/specialization-no-default.rs:55:5
-   |
-LL | impl<T: Clone> Baz for T {
-   | ------------------------ parent `impl` is here
-...
-LL |     fn baz(&self) {}
-   |     ^^^^^^^^^^^^^ cannot specialize default item `baz`
-   |
-   = note: to specialize, `baz` in the parent `impl` must be marked `default`
-
-error[E0520]: `redundant` specializes an item from a parent `impl`, but that item is not marked `default`
-  --> $DIR/specialization-no-default.rs:74:5
-   |
-LL | impl<T: Clone> Redundant for T {
-   | ------------------------------ parent `impl` is here
-...
-LL |     fn redundant(&self) {}
-   |     ^^^^^^^^^^^^^^^^^^^ cannot specialize default item `redundant`
+   = note: ...which immediately requires computing whether impls specialize one another again
+note: cycle used when building specialization graph of trait `Baz`
+  --> $DIR/specialization-no-default.rs:42:1
    |
-   = note: to specialize, `redundant` in the parent `impl` must be marked `default`
+LL | trait Baz {
+   | ^^^^^^^^^
+   = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
 
-error: aborting due to 5 previous errors; 1 warning emitted
+error: aborting due to previous error; 1 warning emitted
 
-For more information about this error, try `rustc --explain E0520`.
+For more information about this error, try `rustc --explain E0391`.
diff --git a/tests/ui/specialization/defaultimpl/specialization-trait-item-not-implemented.stderr b/tests/ui/specialization/defaultimpl/specialization-trait-item-not-implemented.stderr
@@ -8,15 +8,21 @@ LL | #![feature(specialization)]
    = help: consider using `min_specialization` instead, which is more stable and complete
    = note: `#[warn(incomplete_features)]` on by default
 
-error[E0046]: not all trait items implemented, missing: `foo_two`
-  --> $DIR/specialization-trait-item-not-implemented.rs:18:1
+error[E0391]: cycle detected when computing whether impls specialize one another
+  --> $DIR/specialization-trait-item-not-implemented.rs:12:1
    |
-LL |     fn foo_two(&self) -> &'static str;
-   |     ---------------------------------- `foo_two` from trait
-...
-LL | impl Foo for MyStruct {}
-   | ^^^^^^^^^^^^^^^^^^^^^ missing `foo_two` in implementation
+LL | default impl<T> Foo for T {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: ...which requires evaluating trait selection obligation `MyStruct: Foo`...
+   = note: ...which again requires computing whether impls specialize one another, completing the cycle
+note: cycle used when building specialization graph of trait `Foo`
+  --> $DIR/specialization-trait-item-not-implemented.rs:5:1
+   |
+LL | trait Foo {
+   | ^^^^^^^^^
+   = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
 
 error: aborting due to previous error; 1 warning emitted
 
-For more information about this error, try `rustc --explain E0046`.
+For more information about this error, try `rustc --explain E0391`.
diff --git a/tests/ui/specialization/defaultimpl/specialization-trait-not-implemented.stderr b/tests/ui/specialization/defaultimpl/specialization-trait-not-implemented.stderr
@@ -8,37 +8,12 @@ LL | #![feature(specialization)]
    = help: consider using `min_specialization` instead, which is more stable and complete
    = note: `#[warn(incomplete_features)]` on by default
 
-error[E0599]: the method `foo_one` exists for struct `MyStruct`, but its trait bounds were not satisfied
+error[E0275]: overflow evaluating the requirement `MyStruct: Foo`
   --> $DIR/specialization-trait-not-implemented.rs:22:29
    |
-LL | struct MyStruct;
-   | ---------------
-   | |
-   | method `foo_one` not found for this struct
-   | doesn't satisfy `MyStruct: Foo`
-...
 LL |     println!("{}", MyStruct.foo_one());
-   |                             ^^^^^^^ method cannot be called on `MyStruct` due to unsatisfied trait bounds
-   |
-note: trait bound `MyStruct: Foo` was not satisfied
-  --> $DIR/specialization-trait-not-implemented.rs:14:1
-   |
-LL | default impl<T> Foo for T {
-   | ^^^^^^^^^^^^^^^^---^^^^^-
-   | |
-   | unsatisfied trait bound introduced here
-note: the trait `Foo` must be implemented
-  --> $DIR/specialization-trait-not-implemented.rs:7:1
-   |
-LL | trait Foo {
-   | ^^^^^^^^^
-   = help: items from traits can only be used if the trait is implemented and in scope
-note: `Foo` defines an item `foo_one`, perhaps you need to implement it
-  --> $DIR/specialization-trait-not-implemented.rs:7:1
-   |
-LL | trait Foo {
-   | ^^^^^^^^^
+   |                             ^^^^^^^
 
 error: aborting due to previous error; 1 warning emitted
 
-For more information about this error, try `rustc --explain E0599`.
+For more information about this error, try `rustc --explain E0275`.
diff --git a/tests/ui/specialization/issue-39448.stderr b/tests/ui/specialization/issue-39448.stderr
@@ -8,28 +8,21 @@ LL | #![feature(specialization)]
    = help: consider using `min_specialization` instead, which is more stable and complete
    = note: `#[warn(incomplete_features)]` on by default
 
-error[E0275]: overflow evaluating the requirement `T: FromA<U>`
-  --> $DIR/issue-39448.rs:45:13
-   |
-LL |     x.foo(y.to()).to()
-   |             ^^
-   |
-note: required for `T` to implement `FromA<U>`
-  --> $DIR/issue-39448.rs:24:29
+error[E0391]: cycle detected when computing whether impls specialize one another
+  --> $DIR/issue-39448.rs:24:1
    |
 LL | impl<T: A, U: A + FromA<T>> FromA<T> for U {
-   |                   --------  ^^^^^^^^     ^
-   |                   |
-   |                   unsatisfied trait bound introduced here
-note: required for `U` to implement `ToA<T>`
-  --> $DIR/issue-39448.rs:34:12
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: ...which requires evaluating trait selection obligation `u16: FromA<u8>`...
+   = note: ...which again requires computing whether impls specialize one another, completing the cycle
+note: cycle used when building specialization graph of trait `FromA`
+  --> $DIR/issue-39448.rs:20:1
    |
-LL | impl<T, U> ToA<U> for T
-   |            ^^^^^^     ^
-LL | where
-LL |     U: FromA<T>,
-   |        -------- unsatisfied trait bound introduced here
+LL | trait FromA<T> {
+   | ^^^^^^^^^^^^^^
+   = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
 
 error: aborting due to previous error; 1 warning emitted
 
-For more information about this error, try `rustc --explain E0275`.
+For more information about this error, try `rustc --explain E0391`.