09783d1dab
explicit form `Fn<A,B>` and now should use `Fn(A) -> B` or `Fn<A,Output=B>`, but in some cases we get duplicate error reports. This is mildly annoying and arises because of the main error and another error from the projection. Might be worth squashing those, but seems like a separate problem.
38 lines
959 B
Rust
38 lines
959 B
Rust
// Copyright 2014 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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#![feature(unboxed_closures)]
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// A basic test of using a higher-ranked trait bound.
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trait FnLike<A,R> {
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fn call(&self, arg: A) -> R;
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}
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type FnObject<'b> = for<'a> FnLike<(&'a i32,), &'a i32> + 'b;
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struct Identity;
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impl<'a, T> FnLike<(&'a T,), &'a T> for Identity {
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fn call(&self, (arg,): (&'a T,)) -> &'a T {
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arg
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}
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}
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fn call_repeatedly(f: &FnObject) {
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let x = 3;
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let y = f.call((&x,));
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assert_eq!(3, *y);
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}
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fn main() {
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call_repeatedly(&Identity);
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}
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