Update Tests

tests/ui/dyn-keyword/dyn-2021-edition-error.stderr

@@ -4,7 +4,15 @@ error[E0782]: trait objects must include the `dyn` keyword
 LL | fn function(x: &SomeTrait, y: Box<SomeTrait>) {
    |                 ^^^^^^^^^
    |
-help: add `dyn` keyword before this trait
+help: use a new generic type parameter, constrained by `SomeTrait`
+   |
+LL | fn function<T: SomeTrait>(x: &T, y: Box<SomeTrait>) {
+   |            ++++++++++++++     ~
+help: you can also use an opaque type, but users won't be able to specify the type parameter when calling the `fn`, having to rely exclusively on type inference
+   |
+LL | fn function(x: &impl SomeTrait, y: Box<SomeTrait>) {
+   |                 ++++
+help: alternatively, use a trait object to accept any type that implements `SomeTrait`, accessing its methods at runtime using dynamic dispatch
    |
 LL | fn function(x: &dyn SomeTrait, y: Box<SomeTrait>) {
    |                 +++

tests/ui/object-safety/reference-to-bare-trait-in-fn-inputs-and-outputs-issue-125139.rs

@@ -0,0 +1,142 @@
+//@ edition:2021
+
+trait Trait {}
+
+struct IceCream;
+
+impl IceCream {
+    fn foo(_: &Trait) {}
+    //~^ ERROR: trait objects must include the `dyn` keyword
+
+    fn bar(self, _: &'a Trait) {}
+    //~^ ERROR: trait objects must include the `dyn` keyword
+    //~| ERROR: use of undeclared lifetime name
+
+    fn alice<'a>(&self, _: &Trait) {}
+    //~^ ERROR: trait objects must include the `dyn` keyword
+
+    fn bob<'a>(_: &'a Trait) {}
+    //~^ ERROR: trait objects must include the `dyn` keyword
+
+    fn cat() -> &Trait {
+        //~^ ERROR: missing lifetime specifier
+        //~| ERROR: trait objects must include the `dyn` keyword
+        &Type
+    }
+
+    fn dog<'a>() -> &Trait {
+        //~^ ERROR: missing lifetime specifier
+        //~| ERROR: trait objects must include the `dyn` keyword
+        &Type
+    }
+
+    fn kitten() -> &'a Trait {
+        //~^ ERROR: use of undeclared lifetime name
+        //~| ERROR: trait objects must include the `dyn` keyword
+        &Type
+    }
+
+    fn puppy<'a>() -> &'a Trait {
+        //~^ ERROR: trait objects must include the `dyn` keyword
+        &Type
+    }
+
+    fn parrot() -> &mut Trait {
+        //~^ ERROR: missing lifetime specifier
+        //~| ERROR: cannot return a mutable reference to a bare trait
+        &mut Type
+        //~^ ERROR: cannot return reference to temporary value
+    }
+}
+
+trait Sing {
+    fn foo(_: &Trait);
+    //~^ ERROR: trait objects must include the `dyn` keyword
+
+    fn bar(_: &'a Trait);
+    //~^ ERROR: trait objects must include the `dyn` keyword
+    //~| ERROR: use of undeclared lifetime name
+
+    fn alice<'a>(_: &Trait);
+    //~^ ERROR: trait objects must include the `dyn` keyword
+
+    fn bob<'a>(_: &'a Trait);
+    //~^ ERROR: trait objects must include the `dyn` keyword
+
+    fn cat() -> &Trait;
+        //~^ ERROR: missing lifetime specifier
+        //~| ERROR: trait objects must include the `dyn` keyword
+
+    fn dog<'a>() -> &Trait {
+        //~^ ERROR: missing lifetime specifier
+        //~| ERROR: trait objects must include the `dyn` keyword
+        &Type
+    }
+
+    fn kitten() -> &'a Trait {
+        //~^ ERROR: use of undeclared lifetime name
+        //~| ERROR: trait objects must include the `dyn` keyword
+        &Type
+    }
+
+    fn puppy<'a>() -> &'a Trait {
+        //~^ ERROR: trait objects must include the `dyn` keyword
+        &Type
+    }
+
+    fn parrot() -> &mut Trait {
+        //~^ ERROR: missing lifetime specifier
+        //~| ERROR: cannot return a mutable reference to a bare trait
+        &mut Type
+        //~^ ERROR: cannot return reference to temporary value
+    }
+}
+
+fn foo(_: &Trait) {}
+//~^ ERROR: trait objects must include the `dyn` keyword
+
+fn bar(_: &'a Trait) {}
+//~^ ERROR: trait objects must include the `dyn` keyword
+//~| ERROR: use of undeclared lifetime name
+
+fn alice<'a>(_: &Trait) {}
+//~^ ERROR: trait objects must include the `dyn` keyword
+
+fn bob<'a>(_: &'a Trait) {}
+//~^ ERROR: trait objects must include the `dyn` keyword
+
+struct Type;
+
+impl Trait for Type {}
+
+fn cat() -> &Trait {
+//~^ ERROR: missing lifetime specifier
+//~| ERROR: trait objects must include the `dyn` keyword
+    &Type
+}
+
+fn dog<'a>() -> &Trait {
+//~^ ERROR: missing lifetime specifier
+//~| ERROR: trait objects must include the `dyn` keyword
+    &Type
+}
+
+fn kitten() -> &'a Trait {
+//~^ ERROR: use of undeclared lifetime name
+//~| ERROR: trait objects must include the `dyn` keyword
+    &Type
+}
+
+fn puppy<'a>() -> &'a Trait {
+//~^ ERROR: trait objects must include the `dyn` keyword
+    &Type
+}
+
+fn parrot() -> &mut Trait {
+    //~^ ERROR: missing lifetime specifier
+    //~| ERROR: cannot return a mutable reference to a bare trait
+    &mut Type
+    //~^ ERROR: cannot return reference to temporary value
+}
+
+fn main() {}