0fa1c1662f
This change is worrisome to me, both because: 1. I thought the rules in RFC 599 imply that the `Box<Trait>` without `'static` in the first case would expand to the second case, but their behaviors here differ. And, 2. The explicit handling of `'static` should mean `dropck` has no application here and thus we should have seen no change to the expected error messages. Nonetheless, the error messages changed.
46 lines
1.6 KiB
Rust
46 lines
1.6 KiB
Rust
// Copyright 2015 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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// Various unsuccessful attempts to put the unboxed closure kind
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// inference into an awkward position that might require fixed point
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// iteration (basically where inferring the kind of a closure `c`
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// would require knowing the kind of `c`). I currently believe this is
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// impossible.
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fn a() {
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// This case of recursion wouldn't even require fixed-point
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// iteration, but it still doesn't work. The weird structure with
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// the `Option` is to avoid giving any useful hints about the `Fn`
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// kind via the expected type.
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let mut factorial: Option<Box<Fn(u32) -> u32>> = None;
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let f = |x: u32| -> u32 {
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//~^ ERROR `factorial` does not live long enough
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let g = factorial.as_ref().unwrap();
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if x == 0 {1} else {x * g(x-1)}
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};
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factorial = Some(Box::new(f));
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}
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fn b() {
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let mut factorial: Option<Box<Fn(u32) -> u32 + 'static>> = None;
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let f = |x: u32| -> u32 {
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//~^ ERROR closure may outlive the current function, but it borrows `factorial`
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let g = factorial.as_ref().unwrap();
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if x == 0 {1} else {x * g(x-1)}
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};
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factorial = Some(Box::new(f));
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}
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fn main() { }
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