Add more tests

tests/ui/impl-trait/unsize_adt.rs

@@ -0,0 +1,14 @@
+//! Test that we do not allow unsizing `Foo<[Opaque; N]>` to `Foo<[Concrete]>`.
+
+struct Foo<T: ?Sized>(T);
+
+fn hello() -> Foo<[impl Sized; 2]> {
+    if false {
+        let x = hello();
+        let _: &Foo<[i32]> = &x;
+        //~^ ERROR: mismatched types
+    }
+    todo!()
+}
+
+fn main() {}

tests/ui/impl-trait/unsize_adt.stderr

@@ -0,0 +1,17 @@
+error[E0308]: mismatched types
+  --> $DIR/unsize_adt.rs:8:30
+   |
+LL | fn hello() -> Foo<[impl Sized; 2]> {
+   |                    ---------- the found opaque type
+...
+LL |         let _: &Foo<[i32]> = &x;
+   |                -----------   ^^ expected `&Foo<[i32]>`, found `&Foo<[impl Sized; 2]>`
+   |                |
+   |                expected due to this
+   |
+   = note: expected reference `&Foo<[i32]>`
+              found reference `&Foo<[impl Sized; 2]>`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.

tests/ui/impl-trait/unsize_slice.rs

@@ -0,0 +1,12 @@
+//! Test that we do not allow unsizing `[Opaque; N]` to `[Concrete]`.
+
+fn hello() -> [impl Sized; 2] {
+    if false {
+        let x = hello();
+        let _: &[i32] = &x;
+        //~^ ERROR: mismatched types
+    }
+    todo!()
+}
+
+fn main() {}

tests/ui/impl-trait/unsize_slice.stderr

@@ -0,0 +1,17 @@
+error[E0308]: mismatched types
+  --> $DIR/unsize_slice.rs:6:25
+   |
+LL | fn hello() -> [impl Sized; 2] {
+   |                ---------- the found opaque type
+...
+LL |         let _: &[i32] = &x;
+   |                ------   ^^ expected `&[i32]`, found `&[impl Sized; 2]`
+   |                |
+   |                expected due to this
+   |
+   = note: expected reference `&[i32]`
+              found reference `&[impl Sized; 2]`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.

tests/ui/impl-trait/unsize_tuple.rs

@@ -0,0 +1,14 @@
+//! Test that we do not allow unsizing `([Opaque; N],)` to `([Concrete],)`.
+
+#![feature(unsized_tuple_coercion)]
+
+fn hello() -> ([impl Sized; 2],) {
+    if false {
+        let x = hello();
+        let _: &([i32],) = &x;
+        //~^ ERROR: mismatched types
+    }
+    todo!()
+}
+
+fn main() {}

tests/ui/impl-trait/unsize_tuple.stderr

@@ -0,0 +1,17 @@
+error[E0308]: mismatched types
+  --> $DIR/unsize_tuple.rs:8:28
+   |
+LL | fn hello() -> ([impl Sized; 2],) {
+   |                 ---------- the found opaque type
+...
+LL |         let _: &([i32],) = &x;
+   |                ---------   ^^ expected `&([i32],)`, found `&([impl Sized; 2],)`
+   |                |
+   |                expected due to this
+   |
+   = note: expected reference `&([i32],)`
+              found reference `&([impl Sized; 2],)`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.

tests/ui/traits/trait-upcasting/illegal-upcast-to-impl-opaque.rs

@@ -0,0 +1,28 @@
+//@ revisions: current next
+//@[next] compile-flags: -Znext-solver
+//@[next] failure-status: 101
+//@[next] known-bug: unknown
+//@[next] normalize-stderr-test "note: .*\n\n" -> ""
+//@[next] normalize-stderr-test "thread 'rustc' panicked.*\n.*\n" -> ""
+//@[next] normalize-stderr-test "(error: internal compiler error: [^:]+):\d+:\d+: " -> "$1:LL:CC: "
+//@[next] normalize-stderr-test "delayed at .*" -> ""
+//@[next] rustc-env:RUST_BACKTRACE=0
+//@ check-pass
+
+#![feature(trait_upcasting)]
+
+trait Super {
+    type Assoc;
+}
+
+trait Sub: Super {}
+
+impl<T: ?Sized> Super for T {
+    type Assoc = i32;
+}
+
+fn illegal(x: &dyn Sub<Assoc = i32>) -> &dyn Super<Assoc = impl Sized> {
+    x
+}
+
+fn main() {}

tests/ui/traits/trait-upcasting/type-checking-test-4.rs

@@ -11,6 +11,10 @@ fn test_correct(x: &dyn Foo<'static>) {
     let _ = x as &dyn Bar<'static, 'static>;
 }
 
+fn test_correct2<'a>(x: &dyn Foo<'a>) {
+    let _ = x as &dyn Bar<'_, '_>;
+}
+
 fn test_wrong1<'a>(x: &dyn Foo<'static>, y: &'a u32) {
     let _ = x as &dyn Bar<'static, 'a>; // Error
                                         //~^ ERROR lifetime may not live long enough

tests/ui/traits/trait-upcasting/type-checking-test-4.stderr

@@ -1,21 +1,21 @@
 error: lifetime may not live long enough
-  --> $DIR/type-checking-test-4.rs:15:13
+  --> $DIR/type-checking-test-4.rs:19:13
    |
 LL | fn test_wrong1<'a>(x: &dyn Foo<'static>, y: &'a u32) {
    |                -- lifetime `'a` defined here
 LL |     let _ = x as &dyn Bar<'static, 'a>; // Error
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^ type annotation requires that `'a` must outlive `'static`
 
 error: lifetime may not live long enough
-  --> $DIR/type-checking-test-4.rs:20:13
+  --> $DIR/type-checking-test-4.rs:24:13
    |
 LL | fn test_wrong2<'a>(x: &dyn Foo<'static>, y: &'a u32) {
    |                -- lifetime `'a` defined here
 LL |     let _ = x as &dyn Bar<'a, 'static>; // Error
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^ type annotation requires that `'a` must outlive `'static`
 
 error: lifetime may not live long enough
-  --> $DIR/type-checking-test-4.rs:26:5
+  --> $DIR/type-checking-test-4.rs:30:5
    |
 LL | fn test_wrong3<'a>(x: &dyn Foo<'a>) -> Option<&'static u32> {
    |                -- lifetime `'a` defined here
@@ -24,23 +24,23 @@ LL |     y.get_b() // ERROR
    |     ^^^^^^^^^ returning this value requires that `'a` must outlive `'static`
 
 error: lifetime may not live long enough
-  --> $DIR/type-checking-test-4.rs:31:5
+  --> $DIR/type-checking-test-4.rs:35:5
    |
 LL | fn test_wrong4<'a>(x: &dyn Foo<'a>) -> Option<&'static u32> {
    |                -- lifetime `'a` defined here
 LL |     <_ as Bar>::get_b(x) // ERROR
    |     ^^^^^^^^^^^^^^^^^^^^ returning this value requires that `'a` must outlive `'static`
 
 error: lifetime may not live long enough
-  --> $DIR/type-checking-test-4.rs:36:5
+  --> $DIR/type-checking-test-4.rs:40:5
    |
 LL | fn test_wrong5<'a>(x: &dyn Foo<'a>) -> Option<&'static u32> {
    |                -- lifetime `'a` defined here
 LL |     <_ as Bar<'_, '_>>::get_b(x) // ERROR
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ returning this value requires that `'a` must outlive `'static`
 
 error: lifetime may not live long enough
-  --> $DIR/type-checking-test-4.rs:44:5
+  --> $DIR/type-checking-test-4.rs:48:5
    |
 LL | fn test_wrong6<'a>(x: &dyn Foo<'a>) -> Option<&'static u32> {
    |                -- lifetime `'a` defined here

tests/ui/traits/trait-upcasting/type-checking-test-opaques.rs

@@ -0,0 +1,21 @@
+#![feature(trait_upcasting, type_alias_impl_trait)]
+
+type Tait = impl Sized;
+
+trait Foo<'a>: Bar<'a, 'a, Tait> {}
+trait Bar<'a, 'b, T> {}
+
+fn test_correct(x: &dyn Foo<'static>) {
+    let _ = x as &dyn Bar<'static, 'static, Tait>;
+}
+
+fn test_correct2<'a>(x: &dyn Foo<'a>) {
+    let _ = x as &dyn Bar<'_, '_, Tait>;
+}
+
+fn test_correct3<'a>(x: &dyn Foo<'a>, _: Tait) {
+    let _ = x as &dyn Bar<'_, '_, ()>;
+    //~^ ERROR: non-primitive cast
+}
+
+fn main() {}

tests/ui/traits/trait-upcasting/type-checking-test-opaques.stderr

@@ -0,0 +1,9 @@
+error[E0605]: non-primitive cast: `&dyn Foo<'a>` as `&dyn Bar<'_, '_, ()>`
+  --> $DIR/type-checking-test-opaques.rs:17:13
+   |
+LL |     let _ = x as &dyn Bar<'_, '_, ()>;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^ an `as` expression can only be used to convert between primitive types or to coerce to a specific trait object
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0605`.

tests/ui/type-alias-impl-trait/constrain_in_projection.current.stderr

@@ -0,0 +1,11 @@
+error[E0277]: the trait bound `Foo: Trait<Bar>` is not satisfied
+  --> $DIR/constrain_in_projection.rs:24:14
+   |
+LL |     let x = <Foo as Trait<Bar>>::Assoc::default();
+   |              ^^^ the trait `Trait<Bar>` is not implemented for `Foo`
+   |
+   = help: the trait `Trait<()>` is implemented for `Foo`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0277`.

tests/ui/type-alias-impl-trait/constrain_in_projection.rs

@@ -0,0 +1,28 @@
+//! Check that projections will constrain opaque types while looking for
+//! matching impls.
+
+//@ revisions: current next
+//@ ignore-compare-mode-next-solver (explicit revisions)
+//@[next] compile-flags: -Znext-solver
+//@[next]check-pass
+
+#![feature(type_alias_impl_trait)]
+
+struct Foo;
+
+type Bar = impl Sized;
+
+trait Trait<T> {
+    type Assoc: Default;
+}
+
+impl Trait<()> for Foo {
+    type Assoc = u32;
+}
+
+fn bop(_: Bar) {
+    let x = <Foo as Trait<Bar>>::Assoc::default();
+    //[current]~^ `Foo: Trait<Bar>` is not satisfied
+}
+
+fn main() {}

tests/ui/type-alias-impl-trait/constrain_in_projection2.current.stderr

@@ -0,0 +1,13 @@
+error[E0277]: the trait bound `Foo: Trait<Bar>` is not satisfied
+  --> $DIR/constrain_in_projection2.rs:27:14
+   |
+LL |     let x = <Foo as Trait<Bar>>::Assoc::default();
+   |              ^^^ the trait `Trait<Bar>` is not implemented for `Foo`
+   |
+   = help: the following other types implement trait `Trait<T>`:
+             <Foo as Trait<()>>
+             <Foo as Trait<u32>>
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0277`.

tests/ui/type-alias-impl-trait/constrain_in_projection2.next.stderr

@@ -0,0 +1,19 @@
+error[E0283]: type annotations needed: cannot satisfy `Foo: Trait<Bar>`
+  --> $DIR/constrain_in_projection2.rs:27:14
+   |
+LL |     let x = <Foo as Trait<Bar>>::Assoc::default();
+   |              ^^^ help: use the fully qualified path to an implementation: `<Type as Trait>::Assoc`
+   |
+note: multiple `impl`s satisfying `Foo: Trait<Bar>` found
+  --> $DIR/constrain_in_projection2.rs:18:1
+   |
+LL | impl Trait<()> for Foo {
+   | ^^^^^^^^^^^^^^^^^^^^^^
+...
+LL | impl Trait<u32> for Foo {
+   | ^^^^^^^^^^^^^^^^^^^^^^^
+   = note: associated types cannot be accessed directly on a `trait`, they can only be accessed through a specific `impl`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0283`.

tests/ui/type-alias-impl-trait/constrain_in_projection2.rs

@@ -0,0 +1,32 @@
+//! Check that projections will constrain opaque types while looking for
+//! matching impls and error if ambiguous.
+
+//@ revisions: current next
+//@ ignore-compare-mode-next-solver (explicit revisions)
+//@[next] compile-flags: -Znext-solver
+
+#![feature(type_alias_impl_trait)]
+
+struct Foo;
+
+type Bar = impl Sized;
+
+trait Trait<T> {
+    type Assoc: Default;
+}
+
+impl Trait<()> for Foo {
+    type Assoc = u32;
+}
+
+impl Trait<u32> for Foo {
+    type Assoc = u32;
+}
+
+fn bop(_: Bar) {
+    let x = <Foo as Trait<Bar>>::Assoc::default();
+    //[next]~^ ERROR: cannot satisfy `Foo: Trait<Bar>`
+    //[current]~^^ ERROR: `Foo: Trait<Bar>` is not satisfied
+}
+
+fn main() {}