2019-04-22 07:40:08 +00:00
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#![feature(dropck_eyepatch)]
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2016-10-17 14:14:25 +00:00
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// The point of this test is to test uses of `#[may_dangle]` attribute
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// where the formal declaration order (in the impl generics) does not
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// match the actual usage order (in the type instantiation).
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//
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// See also dropck-eyepatch.rs for more information about the general
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// structure of the test.
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use std::fmt;
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struct Dt<A: fmt::Debug>(&'static str, A);
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struct Dr<'a, B:'a+fmt::Debug>(&'static str, &'a B);
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struct Pt<A: fmt::Debug, B: fmt::Debug>(&'static str, A, B);
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struct Pr<'a, 'b, B:'a+'b+fmt::Debug>(&'static str, &'a B, &'b B);
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struct St<A: fmt::Debug>(&'static str, A);
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struct Sr<'a, B:'a+fmt::Debug>(&'static str, &'a B);
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impl<A: fmt::Debug> Drop for Dt<A> {
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fn drop(&mut self) { println!("drop {} {:?}", self.0, self.1); }
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}
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impl<'a, B: fmt::Debug> Drop for Dr<'a, B> {
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fn drop(&mut self) { println!("drop {} {:?}", self.0, self.1); }
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}
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unsafe impl<B: fmt::Debug, #[may_dangle] A: fmt::Debug> Drop for Pt<A, B> {
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// (unsafe to access self.1 due to #[may_dangle] on A)
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fn drop(&mut self) { println!("drop {} {:?}", self.0, self.2); }
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}
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unsafe impl<'b, #[may_dangle] 'a, B: fmt::Debug> Drop for Pr<'a, 'b, B> {
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// (unsafe to access self.1 due to #[may_dangle] on 'a)
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fn drop(&mut self) { println!("drop {} {:?}", self.0, self.2); }
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}
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2019-04-22 07:40:08 +00:00
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fn main() {
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2016-10-17 14:14:25 +00:00
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use std::cell::Cell;
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2019-04-22 07:40:08 +00:00
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// We use separate blocks with separate variable to prevent the error
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// messages from being deduplicated.
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{
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let c_long;
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let (mut dt, mut dr): (Dt<_>, Dr<_>);
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c_long = Cell::new(1);
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// No error: sufficiently long-lived state can be referenced in dtors
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dt = Dt("dt", &c_long);
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dr = Dr("dr", &c_long);
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}
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{
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let (c, mut dt, mut dr): (Cell<_>, Dt<_>, Dr<_>);
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c = Cell::new(1);
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// No Error: destructor order precisely modelled
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dt = Dt("dt", &c);
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dr = Dr("dr", &c);
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}
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{
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let (mut dt, mut dr, c_shortest): (Dt<_>, Dr<_>, Cell<_>);
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c_shortest = Cell::new(1);
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// Error: `c_shortest` dies too soon for the references in dtors to be valid.
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dt = Dt("dt", &c_shortest);
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//~^ ERROR `c_shortest` does not live long enough
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dr = Dr("dr", &c_shortest);
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}
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{
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let c_long;
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let (mut pt, mut pr, c_shortest): (Pt<_, _>, Pr<_>, Cell<_>);
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c_long = Cell::new(1);
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c_shortest = Cell::new(1);
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// No error: Drop impl asserts .1 (A and &'a _) are not accessed
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pt = Pt("pt", &c_shortest, &c_long);
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pr = Pr("pr", &c_shortest, &c_long);
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}
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{
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let c_long;
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let (mut pt, mut pr, c_shortest): (Pt<_, _>, Pr<_>, Cell<_>);
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c_long = Cell::new(1);
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c_shortest = Cell::new(1);
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// Error: Drop impl's assertion does not apply to `B` nor `&'b _`
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pt = Pt("pt", &c_long, &c_shortest);
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//~^ ERROR `c_shortest` does not live long enough
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pr = Pr("pr", &c_long, &c_shortest);
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}
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{
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let (st, sr, c_shortest): (St<_>, Sr<_>, Cell<_>);
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c_shortest = Cell::new(1);
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// No error: St and Sr have no destructor.
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st = St("st", &c_shortest);
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sr = Sr("sr", &c_shortest);
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}
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2016-10-17 14:14:25 +00:00
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}
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2018-11-05 15:19:51 +00:00
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fn use_imm<T>(_: &T) { }
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