Add tests for dyn-incompatible cases

tests/ui/dyn-keyword/inferred-type-in-qualified-path-for-with-one-impl.rs

@@ -0,0 +1,10 @@
+trait Trait {
+    fn function() {}
+}
+
+impl Trait for () {}
+
+fn main() {
+    Trait::function();
+    //~^ ERROR cannot call associated function on trait without specifying the corresponding `impl` type
+}

tests/ui/dyn-keyword/inferred-type-in-qualified-path-for-with-one-impl.stderr

@@ -0,0 +1,17 @@
+error[E0790]: cannot call associated function on trait without specifying the corresponding `impl` type
+  --> $DIR/inferred-type-in-qualified-path-for-with-one-impl.rs:8:5
+   |
+LL |     fn function() {}
+   |     ---------------- `Trait::function` defined here
+...
+LL |     Trait::function();
+   |     ^^^^^^^^^^^^^^^^^ cannot call associated function of trait
+   |
+help: use the fully-qualified path to the only available implementation
+   |
+LL |     <() as Trait>::function();
+   |     ++++++      +
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0790`.

tests/ui/dyn-keyword/trait-dyn-in-qualified-path-for-object-safe-function-with-one-impl.rs

@@ -0,0 +1,9 @@
+trait Trait {
+    fn function() {}
+}
+
+impl Trait for () {}
+
+fn main() {
+    <dyn Trait>::function(); //~ ERROR the trait `Trait` is not dyn compatible
+}

tests/ui/dyn-keyword/trait-dyn-in-qualified-path-for-object-safe-function-with-one-impl.stderr

@@ -0,0 +1,27 @@
+error[E0038]: the trait `Trait` is not dyn compatible
+  --> $DIR/trait-dyn-in-qualified-path-for-object-safe-function-with-one-impl.rs:8:6
+   |
+LL |     <dyn Trait>::function();
+   |      ^^^^^^^^^ `Trait` is not dyn compatible
+   |
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+  --> $DIR/trait-dyn-in-qualified-path-for-object-safe-function-with-one-impl.rs:2:8
+   |
+LL | trait Trait {
+   |       ----- this trait is not dyn compatible...
+LL |     fn function() {}
+   |        ^^^^^^^^ ...because associated function `function` has no `self` parameter
+   = help: only type `()` implements `Trait`; consider using it directly instead.
+help: consider turning `function` into a method by giving it a `&self` argument
+   |
+LL |     fn function(&self) {}
+   |                 +++++
+help: alternatively, consider constraining `function` so it does not apply to trait objects
+   |
+LL |     fn function() where Self: Sized {}
+   |                   +++++++++++++++++
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0038`.

tests/ui/dyn-keyword/trait-dyn-in-qualified-path-for-object-safe-function.rs

@@ -0,0 +1,14 @@
+//@ run-pass
+
+trait Trait {
+    fn function(&self) {}
+}
+
+impl dyn Trait {
+}
+
+impl Trait for () {}
+
+fn main() {
+    Trait::function(&());
+}

tests/ui/dyn-keyword/trait-dyn-in-qualified-path-for-object-unsafe-trait.rs

@@ -0,0 +1,13 @@
+trait Trait: Sized {}
+
+impl dyn Trait { //~ ERROR the trait `Trait` is not dyn compatible
+    fn function(&self) {} //~ ERROR the trait `Trait` is not dyn compatible
+}
+
+impl Trait for () {}
+
+fn main() {
+    <dyn Trait>::function(&());
+    //~^ ERROR the trait `Trait` is not dyn compatible
+    //~| ERROR the trait `Trait` is not dyn compatible
+}

tests/ui/dyn-keyword/trait-dyn-in-qualified-path-for-object-unsafe-trait.stderr

@@ -0,0 +1,68 @@
+error[E0038]: the trait `Trait` is not dyn compatible
+  --> $DIR/trait-dyn-in-qualified-path-for-object-unsafe-trait.rs:3:6
+   |
+LL | impl dyn Trait {
+   |      ^^^^^^^^^ `Trait` is not dyn compatible
+   |
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+  --> $DIR/trait-dyn-in-qualified-path-for-object-unsafe-trait.rs:1:14
+   |
+LL | trait Trait: Sized {}
+   |       -----  ^^^^^ ...because it requires `Self: Sized`
+   |       |
+   |       this trait is not dyn compatible...
+   = help: only type `()` implements `Trait`; consider using it directly instead.
+
+error[E0038]: the trait `Trait` is not dyn compatible
+  --> $DIR/trait-dyn-in-qualified-path-for-object-unsafe-trait.rs:4:18
+   |
+LL |     fn function(&self) {}
+   |                  ^^^^ `Trait` is not dyn compatible
+   |
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+  --> $DIR/trait-dyn-in-qualified-path-for-object-unsafe-trait.rs:1:14
+   |
+LL | trait Trait: Sized {}
+   |       -----  ^^^^^ ...because it requires `Self: Sized`
+   |       |
+   |       this trait is not dyn compatible...
+   = help: only type `()` implements `Trait`; consider using it directly instead.
+
+error[E0038]: the trait `Trait` is not dyn compatible
+  --> $DIR/trait-dyn-in-qualified-path-for-object-unsafe-trait.rs:10:27
+   |
+LL |     <dyn Trait>::function(&());
+   |                           ^^^ `Trait` is not dyn compatible
+   |
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+  --> $DIR/trait-dyn-in-qualified-path-for-object-unsafe-trait.rs:1:14
+   |
+LL | trait Trait: Sized {}
+   |       -----  ^^^^^ ...because it requires `Self: Sized`
+   |       |
+   |       this trait is not dyn compatible...
+   = help: only type `()` implements `Trait`; consider using it directly instead.
+   = note: required for the cast from `&()` to `&(dyn Trait + 'static)`
+
+error[E0038]: the trait `Trait` is not dyn compatible
+  --> $DIR/trait-dyn-in-qualified-path-for-object-unsafe-trait.rs:10:6
+   |
+LL |     <dyn Trait>::function(&());
+   |      ^^^^^^^^^ `Trait` is not dyn compatible
+   |
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+  --> $DIR/trait-dyn-in-qualified-path-for-object-unsafe-trait.rs:1:14
+   |
+LL | trait Trait: Sized {}
+   |       -----  ^^^^^ ...because it requires `Self: Sized`
+   |       |
+   |       this trait is not dyn compatible...
+   = help: only type `()` implements `Trait`; consider using it directly instead.
+
+error: aborting due to 4 previous errors
+
+For more information about this error, try `rustc --explain E0038`.

tests/ui/dyn-keyword/trait-dyn-in-qualified-path-with-collision.rs

@@ -0,0 +1,11 @@
+trait Trait {
+    fn function(&self) {}
+}
+impl dyn Trait {
+    fn function(&self) {}
+}
+impl Trait for () {}
+fn main() {
+    <dyn Trait>::function(&());
+    //~^ ERROR multiple applicable items in scope
+}

tests/ui/dyn-keyword/trait-dyn-in-qualified-path-with-collision.stderr

@@ -0,0 +1,22 @@
+error[E0034]: multiple applicable items in scope
+  --> $DIR/trait-dyn-in-qualified-path-with-collision.rs:9:18
+   |
+LL |     <dyn Trait>::function(&());
+   |     -------------^^^^^^^^ multiple `function` found
+   |     |
+   |     help: use fully-qualified syntax to disambiguate: `Trait::`
+   |
+note: candidate #1 is defined in the trait `Trait`
+  --> $DIR/trait-dyn-in-qualified-path-with-collision.rs:2:5
+   |
+LL |     fn function(&self) {}
+   |     ^^^^^^^^^^^^^^^^^^
+note: candidate #2 is defined in an impl for the type `(dyn Trait + 'static)`
+  --> $DIR/trait-dyn-in-qualified-path-with-collision.rs:5:5
+   |
+LL |     fn function(&self) {}
+   |     ^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0034`.

tests/ui/dyn-keyword/trait-dyn-in-qualified-path.rs

@@ -0,0 +1,8 @@
+trait Trait: Sized {
+    fn function() {}
+}
+fn main() {
+    <dyn Trait>::function();
+    //~^ ERROR trait `Trait` is not dyn compatible
+    //~| ERROR the size for values of type `dyn Trait` cannot be known at compilation time
+}

tests/ui/dyn-keyword/trait-dyn-in-qualified-path.stderr

@@ -0,0 +1,34 @@
+error[E0038]: the trait `Trait` is not dyn compatible
+  --> $DIR/trait-dyn-in-qualified-path.rs:5:6
+   |
+LL |     <dyn Trait>::function();
+   |      ^^^^^^^^^ `Trait` is not dyn compatible
+   |
+note: for a trait to be dyn compatible it needs to allow building a vtable
+      for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+  --> $DIR/trait-dyn-in-qualified-path.rs:1:14
+   |
+LL | trait Trait: Sized {
+   |       -----  ^^^^^ ...because it requires `Self: Sized`
+   |       |
+   |       this trait is not dyn compatible...
+
+error[E0277]: the size for values of type `dyn Trait` cannot be known at compilation time
+  --> $DIR/trait-dyn-in-qualified-path.rs:5:6
+   |
+LL |     <dyn Trait>::function();
+   |      ^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `dyn Trait`
+note: required by a bound in `Trait::function`
+  --> $DIR/trait-dyn-in-qualified-path.rs:1:14
+   |
+LL | trait Trait: Sized {
+   |              ^^^^^ required by this bound in `Trait::function`
+LL |     fn function() {}
+   |        -------- required by a bound in this associated function
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0038, E0277.
+For more information about an error, try `rustc --explain E0038`.

tests/ui/dyn-keyword/trait-missing-dyn-in-qualified-path.edition2018.stderr

@@ -0,0 +1,69 @@
+warning: trait objects without an explicit `dyn` are deprecated
+  --> $DIR/trait-missing-dyn-in-qualified-path.rs:5:19
+   |
+LL |     let x: u32 = <Default>::default();
+   |                   ^^^^^^^
+   |
+   = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
+   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
+   = note: `#[warn(bare_trait_objects)]` on by default
+help: if this is a dyn-compatible trait, use `dyn`
+   |
+LL |     let x: u32 = <dyn Default>::default();
+   |                   +++
+
+error[E0038]: the trait `Default` is not dyn compatible
+  --> $DIR/trait-missing-dyn-in-qualified-path.rs:5:19
+   |
+LL |     let x: u32 = <Default>::default();
+   |                   ^^^^^^^ `Default` is not dyn compatible
+   |
+   = note: the trait is not dyn compatible because it requires `Self: Sized`
+   = note: for a trait to be dyn compatible it needs to allow building a vtable
+           for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+
+error[E0277]: the size for values of type `dyn Default` cannot be known at compilation time
+  --> $DIR/trait-missing-dyn-in-qualified-path.rs:5:19
+   |
+LL |     let x: u32 = <Default>::default();
+   |                   ^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `dyn Default`
+note: required by a bound in `default`
+  --> $SRC_DIR/core/src/default.rs:LL:COL
+
+error[E0308]: mismatched types
+  --> $DIR/trait-missing-dyn-in-qualified-path.rs:5:18
+   |
+LL |     let x: u32 = <Default>::default();
+   |            ---   ^^^^^^^^^^^^^^^^^^^^ expected `u32`, found `dyn Default`
+   |            |
+   |            expected due to this
+   |
+   = note:      expected type `u32`
+           found trait object `dyn Default`
+   = help: `u32` implements `Default` so you could change the expected type to `Box<dyn Default>`
+
+error[E0038]: the trait `Default` is not dyn compatible
+  --> $DIR/trait-missing-dyn-in-qualified-path.rs:5:18
+   |
+LL |     let x: u32 = <Default>::default();
+   |                  ^^^^^^^^^^^^^^^^^^^^ `Default` is not dyn compatible
+   |
+   = note: the trait is not dyn compatible because it requires `Self: Sized`
+   = note: for a trait to be dyn compatible it needs to allow building a vtable
+           for more information, visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+
+error[E0277]: the size for values of type `dyn Default` cannot be known at compilation time
+  --> $DIR/trait-missing-dyn-in-qualified-path.rs:5:18
+   |
+LL |     let x: u32 = <Default>::default();
+   |                  ^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `dyn Default`
+   = note: the return type of a function must have a statically known size
+
+error: aborting due to 5 previous errors; 1 warning emitted
+
+Some errors have detailed explanations: E0038, E0277, E0308.
+For more information about an error, try `rustc --explain E0038`.

tests/ui/dyn-keyword/trait-missing-dyn-in-qualified-path.edition2021.stderr

@@ -0,0 +1,14 @@
+error[E0782]: expected a type, found a trait
+  --> $DIR/trait-missing-dyn-in-qualified-path.rs:5:19
+   |
+LL |     let x: u32 = <Default>::default();
+   |                   ^^^^^^^
+   |
+help: you can add the `dyn` keyword if you want a trait object
+   |
+LL |     let x: u32 = <dyn Default>::default();
+   |                   +++
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0782`.

tests/ui/dyn-keyword/trait-missing-dyn-in-qualified-path.rs

@@ -0,0 +1,14 @@
+//@revisions: edition2018 edition2021
+//@[edition2018] edition:2018
+//@[edition2021] edition:2021
+fn main() {
+    let x: u32 = <Default>::default();
+    //[edition2021]~^ ERROR expected a type, found a trait
+    //[edition2018]~^^ WARNING trait objects without an explicit `dyn` are deprecated
+    //[edition2018]~| WARNING this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
+    //[edition2018]~| ERROR trait `Default` is not dyn compatible
+    //[edition2018]~| ERROR trait `Default` is not dyn compatible
+    //[edition2018]~| ERROR the size for values of type `dyn Default` cannot be known at compilation time
+    //[edition2018]~| ERROR mismatched types
+    //[edition2018]~| ERROR the size for values of type `dyn Default` cannot be known at compilation time
+}