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38 lines
1.5 KiB
Rust
38 lines
1.5 KiB
Rust
// revisions: nll_target
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// The following revisions are disabled due to missing support for two_phase_beyond_autoref
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//[nll_beyond] compile-flags: -Z two_phase_beyond_autoref
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// This is the second counter-example from Niko's blog post
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// smallcultfollowing.com/babysteps/blog/2017/03/01/nested-method-calls-via-two-phase-borrowing/
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//
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// It is "artificial". It is meant to illustrate directly that we
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// should allow an aliasing access during reservation, but *not* while
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// the mutable borrow is active.
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//
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// The convention for the listed revisions: "lxl" means lexical
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// lifetimes (which can be easier to reason about). "nll" means
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// non-lexical lifetimes. "nll_target" means the initial conservative
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// two-phase borrows that only applies to autoref-introduced borrows.
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// "nll_beyond" means the generalization of two-phase borrows to all
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// `&mut`-borrows (doing so makes it easier to write code for specific
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// corner cases).
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fn main() {
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/*0*/ let mut i = 0;
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/*1*/ let p = &mut i; // (reservation of `i` starts here)
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/*2*/ let j = i; // OK: `i` is only reserved here
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//[nll_target]~^ ERROR cannot use `i` because it was mutably borrowed [E0503]
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/*3*/ *p += 1; // (mutable borrow of `i` starts here, since `p` is used)
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/*4*/ let k = i; //[nll_beyond]~ ERROR cannot use `i` because it was mutably borrowed [E0503]
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//[nll_target]~^ ERROR cannot use `i` because it was mutably borrowed [E0503]
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/*5*/ *p += 1;
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let _ = (j, k, p);
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}
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