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//@ run-pass
// Test that when we write `x.foo()`, we do not have to know the
// complete type of `x` in order to type-check the method call. In
// this case, we know that `x: Vec<_1>`, but we don't know what type
// `_1` is (because the call to `push` comes later). To pick between
// the impls, we would have to know `_1`, since we have to know
// whether `_1: MyCopy` or `_1 == Box<i32>`. However (and this is the
// point of the test), we don't have to pick between the two impls --
// it is enough to know that `foo` comes from the `Foo` trait. We can
// codegen the call as `Foo::foo(&x)` and let the specific impl get
// chosen later.
trait Foo {
fn foo(&self) -> isize;
}
trait MyCopy { fn foo(&self) { } } //~ WARN method `foo` is never used
impl MyCopy for i32 { }
impl<T:MyCopy> Foo for Vec<T> {
fn foo(&self) -> isize {1}
}
impl Foo for Vec<Box<i32>> {
fn foo(&self) -> isize {2}
}
fn call_foo_copy() -> isize {
let mut x = Vec::new();
let y = x.foo();
x.push(0_i32);
y
}
fn call_foo_other() -> isize {
let mut x: Vec<_> = Vec::new();
let y = x.foo();
let z: Box<i32> = Box::new(0);
x.push(z);
y
}
fn main() {
assert_eq!(call_foo_copy(), 1);
assert_eq!(call_foo_other(), 2);
}
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