Unit (and regression) tests for warning cycle code.

src/test/ui/impl-trait/issue-57979-impl-trait-in-path.rs

@@ -0,0 +1,37 @@
+// rust-lang/rust#57979 : the initial support for `impl Trait` didn't
+// properly check syntax hidden behind an associated type projection.
+// Here we test behavior of occurrences of `impl Trait` within a path
+// component in that context.
+
+mod allowed {
+    #![allow(nested_impl_trait)]
+
+    pub trait Bar { }
+    pub trait Quux<T> { type Assoc; }
+    pub fn demo(_: impl Quux<(), Assoc=<() as Quux<impl Bar>>::Assoc>) { }
+    impl<T> Quux<T> for () { type Assoc = u32; }
+}
+
+mod warned {
+    #![warn(nested_impl_trait)]
+
+    pub trait Bar { }
+    pub trait Quux<T> { type Assoc; }
+    pub fn demo(_: impl Quux<(), Assoc=<() as Quux<impl Bar>>::Assoc>) { }
+    //~^ WARN `impl Trait` is not allowed in path parameters
+    //~| WARN will become a hard error in a future release!
+    impl<T> Quux<T> for () { type Assoc = u32; }
+}
+
+mod denied {
+    #![deny(nested_impl_trait)]
+
+    pub trait Bar { }
+    pub trait Quux<T> { type Assoc; }
+    pub fn demo(_: impl Quux<(), Assoc=<() as Quux<impl Bar>>::Assoc>) { }
+    //~^ ERROR `impl Trait` is not allowed in path parameters
+    //~| WARN will become a hard error in a future release!
+    impl<T> Quux<T> for () { type Assoc = u32; }
+}
+
+fn main() { }

src/test/ui/impl-trait/issue-57979-impl-trait-in-path.stderr

@@ -0,0 +1,30 @@
+warning: `impl Trait` is not allowed in path parameters
+  --> $DIR/issue-57979-impl-trait-in-path.rs:20:52
+   |
+LL |     pub fn demo(_: impl Quux<(), Assoc=<() as Quux<impl Bar>>::Assoc>) { }
+   |                                                    ^^^^^^^^
+   |
+note: lint level defined here
+  --> $DIR/issue-57979-impl-trait-in-path.rs:16:13
+   |
+LL |     #![warn(nested_impl_trait)]
+   |             ^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #59014 <https://github.com/rust-lang/rust/issues/59014>
+
+error: `impl Trait` is not allowed in path parameters
+  --> $DIR/issue-57979-impl-trait-in-path.rs:31:52
+   |
+LL |     pub fn demo(_: impl Quux<(), Assoc=<() as Quux<impl Bar>>::Assoc>) { }
+   |                                                    ^^^^^^^^
+   |
+note: lint level defined here
+  --> $DIR/issue-57979-impl-trait-in-path.rs:27:13
+   |
+LL |     #![deny(nested_impl_trait)]
+   |             ^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #59014 <https://github.com/rust-lang/rust/issues/59014>
+
+error: aborting due to previous error
+

src/test/ui/impl-trait/issue-57979-nested-impl-trait-in-assoc-proj.rs

@@ -0,0 +1,37 @@
+// rust-lang/rust#57979 : the initial support for `impl Trait` didn't
+// properly check syntax hidden behind an associated type projection.
+// Here we test behavior of occurrences of `impl Trait` within an
+// `impl Trait` in that context.
+
+mod allowed {
+    #![allow(nested_impl_trait)]
+
+    pub trait Foo<T> { }
+    pub trait Bar { }
+    pub trait Quux { type Assoc; }
+    pub fn demo(_: impl Quux<Assoc=impl Foo<impl Bar>>) { }
+}
+
+mod warned {
+    #![warn(nested_impl_trait)]
+
+    pub trait Foo<T> { }
+    pub trait Bar { }
+    pub trait Quux { type Assoc; }
+    pub fn demo(_: impl Quux<Assoc=impl Foo<impl Bar>>) { }
+    //~^ WARN nested `impl Trait` is not allowed
+    //~| WARN will become a hard error in a future release!
+}
+
+mod denied {
+    #![deny(nested_impl_trait)]
+
+    pub trait Foo<T> { }
+    pub trait Bar { }
+    pub trait Quux { type Assoc; }
+    pub fn demo(_: impl Quux<Assoc=impl Foo<impl Bar>>) { }
+    //~^ ERROR nested `impl Trait` is not allowed
+    //~| WARN will become a hard error in a future release!
+}
+
+fn main() { }

src/test/ui/impl-trait/issue-57979-nested-impl-trait-in-assoc-proj.stderr

@@ -0,0 +1,36 @@
+warning: nested `impl Trait` is not allowed
+  --> $DIR/issue-57979-nested-impl-trait-in-assoc-proj.rs:21:45
+   |
+LL |     pub fn demo(_: impl Quux<Assoc=impl Foo<impl Bar>>) { }
+   |                                    ---------^^^^^^^^-
+   |                                    |        |
+   |                                    |        nested `impl Trait` here
+   |                                    outer `impl Trait`
+   |
+note: lint level defined here
+  --> $DIR/issue-57979-nested-impl-trait-in-assoc-proj.rs:16:13
+   |
+LL |     #![warn(nested_impl_trait)]
+   |             ^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #59014 <https://github.com/rust-lang/rust/issues/59014>
+
+error: nested `impl Trait` is not allowed
+  --> $DIR/issue-57979-nested-impl-trait-in-assoc-proj.rs:32:45
+   |
+LL |     pub fn demo(_: impl Quux<Assoc=impl Foo<impl Bar>>) { }
+   |                                    ---------^^^^^^^^-
+   |                                    |        |
+   |                                    |        nested `impl Trait` here
+   |                                    outer `impl Trait`
+   |
+note: lint level defined here
+  --> $DIR/issue-57979-nested-impl-trait-in-assoc-proj.rs:27:13
+   |
+LL |     #![deny(nested_impl_trait)]
+   |             ^^^^^^^^^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #59014 <https://github.com/rust-lang/rust/issues/59014>
+
+error: aborting due to previous error
+