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47 lines
1.4 KiB
Rust
47 lines
1.4 KiB
Rust
// Similarly to escape-argument-callee, a test case where the closure
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// requires a relationship between 2 unrelated higher-ranked regions,
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// with no helpful relations between the HRRs and free regions.
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//
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// In this case, the error is reported by the closure itself. This is
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// because it is unable to approximate the higher-ranked region `'x`,
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// as it only knows of regions that `'x` is outlived by, and none that
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// `'x` outlives.
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// compile-flags:-Zverbose
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#![feature(rustc_attrs)]
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use std::cell::Cell;
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// Callee knows that:
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//
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// 'a: 'x
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// 'b: 'y
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//
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// but this doesn't really help us in proving that `'x: 'y`, so
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// closure gets an error. In particular, we would need to know that
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// `'x: 'a`, so that we could approximate `'x` "downwards" to `'a`.
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fn establish_relationships<'a, 'b, F>(_cell_a: &Cell<&'a u32>, _cell_b: &Cell<&'b u32>, _closure: F)
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where
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F: for<'x, 'y> FnMut(
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&Cell<&'x &'a u32>, // shows that 'a: 'x
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&Cell<&'y &'b u32>, // shows that 'b: 'y
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&Cell<&'x u32>,
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&Cell<&'y u32>,
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),
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{
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}
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fn demand_y<'x, 'y>(_cell_x: &Cell<&'x u32>, _cell_y: &Cell<&'y u32>, _y: &'y u32) {}
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#[rustc_regions]
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fn supply<'a, 'b>(cell_a: Cell<&'a u32>, cell_b: Cell<&'b u32>) {
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establish_relationships(&cell_a, &cell_b, |_outlives1, _outlives2, x, y| {
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// Only works if 'x: 'y:
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demand_y(x, y, x.get())
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//~^ ERROR
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});
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}
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fn main() {}
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