60 lines
1.7 KiB
Rust
60 lines
1.7 KiB
Rust
// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// Test that when we write `x.foo()`, we do not have to know the
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// complete type of `x` in order to type-check the method call. In
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// this case, we know that `x: Vec<_1>`, but we don't know what type
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// `_1` is (because the call to `push` comes later). To pick between
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// the impls, we would have to know `_1`, since we have to know
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// whether `_1: MyCopy` or `_1 == Box<i32>`. However (and this is the
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// point of the test), we don't have to pick between the two impls --
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// it is enough to know that `foo` comes from the `Foo` trait. We can
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// translate the call as `Foo::foo(&x)` and let the specific impl get
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// chosen later.
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#![allow(unknown_features)]
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#![feature(box_syntax)]
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trait Foo {
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fn foo(&self) -> isize;
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}
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trait MyCopy { fn foo(&self) { } }
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impl MyCopy for i32 { }
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impl<T:MyCopy> Foo for Vec<T> {
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fn foo(&self) -> isize {1}
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}
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impl Foo for Vec<Box<i32>> {
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fn foo(&self) -> isize {2}
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}
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fn call_foo_copy() -> isize {
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let mut x = Vec::new();
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let y = x.foo();
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x.push(0_i32);
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y
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}
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fn call_foo_other() -> isize {
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let mut x: Vec<_> = Vec::new();
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let y = x.foo();
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let z: Box<i32> = box 0;
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x.push(z);
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y
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}
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fn main() {
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assert_eq!(call_foo_copy(), 1);
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assert_eq!(call_foo_other(), 2);
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}
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