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#![feature(specialization, associated_type_defaults)]
//~^ WARN the feature `specialization` is incomplete
// Test that attempting to override a non-default method or one not in the
// parent impl causes an error.
trait Foo {
type Ty = ();
const CONST: u8 = 123;
fn foo(&self) -> bool { true }
}
// Specialization tree for Foo:
//
// Box<T> Vec<T>
// / \ / \
// Box<i32> Box<i64> Vec<()> Vec<bool>
impl<T> Foo for Box<T> {
type Ty = bool;
const CONST: u8 = 0;
fn foo(&self) -> bool { false }
}
// Allowed
impl Foo for Box<i32> {}
// Can't override a non-`default` fn
impl Foo for Box<i64> {
type Ty = Vec<()>;
//~^ error: `Ty` specializes an item from a parent `impl`, but that item is not marked `default`
const CONST: u8 = 42;
//~^ error: `CONST` specializes an item from a parent `impl`, but that item is not marked `default`
fn foo(&self) -> bool { true }
//~^ error: `foo` specializes an item from a parent `impl`, but that item is not marked `default`
}
// Doesn't mention the item = provided body/value is used and the method is final.
impl<T> Foo for Vec<T> {}
// Allowed
impl Foo for Vec<()> {}
impl Foo for Vec<bool> {
type Ty = Vec<()>;
//~^ error: `Ty` specializes an item from a parent `impl`, but that item is not marked `default`
const CONST: u8 = 42;
//~^ error: `CONST` specializes an item from a parent `impl`, but that item is not marked `default`
fn foo(&self) -> bool { true }
//~^ error: `foo` specializes an item from a parent `impl`, but that item is not marked `default`
}
fn main() {}
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