Add some regression tests

src/test/ui/impl-trait/issue-69840.rs

@@ -0,0 +1,16 @@
+// check-pass
+
+#![feature(impl_trait_in_bindings)]
+#![allow(incomplete_features)]
+
+struct A<'a>(&'a ());
+
+trait Trait<T> {}
+
+impl<T> Trait<T> for () {}
+
+pub fn foo<'a>() {
+    let _x: impl Trait<A<'a>> = ();
+}
+
+fn main() {}

src/test/ui/never_type/issue-51506.rs

@@ -0,0 +1,41 @@
+#![feature(never_type, specialization)]
+#![allow(incomplete_features)]
+
+use std::iter::{self, Empty};
+
+trait Trait {
+    type Out: Iterator<Item = u32>;
+
+    fn f(&self) -> Option<Self::Out>;
+}
+
+impl<T> Trait for T {
+    default type Out = !; //~ ERROR: `!` is not an iterator
+
+    default fn f(&self) -> Option<Self::Out> {
+        None
+    }
+}
+
+struct X;
+
+impl Trait for X {
+    type Out = Empty<u32>;
+
+    fn f(&self) -> Option<Self::Out> {
+        Some(iter::empty())
+    }
+}
+
+fn f<T: Trait>(a: T) {
+    if let Some(iter) = a.f() {
+        println!("Some");
+        for x in iter {
+            println!("x = {}", x);
+        }
+    }
+}
+
+pub fn main() {
+    f(10);
+}

src/test/ui/never_type/issue-51506.stderr

@@ -0,0 +1,14 @@
+error[E0277]: `!` is not an iterator
+  --> $DIR/issue-51506.rs:13:5
+   |
+LL |     type Out: Iterator<Item = u32>;
+   |     ------------------------------- required by `Trait::Out`
+...
+LL |     default type Out = !;
+   |     ^^^^^^^^^^^^^^^^^^^^^ `!` is not an iterator
+   |
+   = help: the trait `std::iter::Iterator` is not implemented for `!`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.

src/test/ui/specialization/issue-44861.rs

@@ -0,0 +1,40 @@
+#![crate_type = "lib"]
+#![feature(specialization)]
+#![feature(unsize, coerce_unsized)]
+#![allow(incomplete_features)]
+
+use std::ops::CoerceUnsized;
+
+pub struct SmartassPtr<A: Smartass+?Sized>(A::Data);
+
+pub trait Smartass {
+    type Data;
+    type Data2: CoerceUnsized<*const [u8]>;
+}
+
+pub trait MaybeObjectSafe {}
+
+impl MaybeObjectSafe for () {}
+
+impl<T> Smartass for T {
+    type Data = <Self as Smartass>::Data2;
+    default type Data2 = ();
+    //~^ ERROR: the trait bound `(): std::ops::CoerceUnsized<*const [u8]>` is not satisfied
+}
+
+impl Smartass for () {
+    type Data2 = *const [u8; 1];
+}
+
+impl Smartass for dyn MaybeObjectSafe {
+    type Data = *const [u8];
+    type Data2 = *const [u8; 0];
+}
+
+impl<U: Smartass+?Sized, T: Smartass+?Sized> CoerceUnsized<SmartassPtr<T>> for SmartassPtr<U>
+    where <U as Smartass>::Data: std::ops::CoerceUnsized<<T as Smartass>::Data>
+{}
+
+pub fn conv(s: SmartassPtr<()>) -> SmartassPtr<dyn MaybeObjectSafe> {
+    s
+}

src/test/ui/specialization/issue-44861.stderr

@@ -0,0 +1,12 @@
+error[E0277]: the trait bound `(): std::ops::CoerceUnsized<*const [u8]>` is not satisfied
+  --> $DIR/issue-44861.rs:21:5
+   |
+LL |     type Data2: CoerceUnsized<*const [u8]>;
+   |     --------------------------------------- required by `Smartass::Data2`
+...
+LL |     default type Data2 = ();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::ops::CoerceUnsized<*const [u8]>` is not implemented for `()`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.

src/test/ui/specialization/issue-59435.rs

@@ -0,0 +1,17 @@
+#![feature(specialization)]
+#![allow(incomplete_features)]
+
+struct MyStruct {}
+
+trait MyTrait {
+    type MyType: Default;
+}
+
+impl MyTrait for i32 {
+    default type MyType = MyStruct;
+    //~^ ERROR: the trait bound `MyStruct: std::default::Default` is not satisfied
+}
+
+fn main() {
+    let _x: <i32 as MyTrait>::MyType = <i32 as MyTrait>::MyType::default();
+}

src/test/ui/specialization/issue-59435.stderr

@@ -0,0 +1,12 @@
+error[E0277]: the trait bound `MyStruct: std::default::Default` is not satisfied
+  --> $DIR/issue-59435.rs:11:5
+   |
+LL |     type MyType: Default;
+   |     --------------------- required by `MyTrait::MyType`
+...
+LL |     default type MyType = MyStruct;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::default::Default` is not implemented for `MyStruct`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.