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ac922245f0
The SCCs of the region graph are not a reliable heuristic to use for blaming an interesting constraint for diagnostics. For region errors, if the outlived region is `'static`, or the involved types are invariant in their lifetiems, there will be cycles in the constraint graph containing both the target region and the most interesting constraints to blame. To get better diagnostics in these cases, this commit removes that heuristic.
45 lines
1.1 KiB
Rust
45 lines
1.1 KiB
Rust
// A simpler variant of `outlives-from-argument` where cells are
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// passed by value.
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//
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// This is simpler because there are no "extraneous" region
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// relationships. In the 'main' variant, there are a number of
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// anonymous regions as well.
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//@ compile-flags:-Zverbose-internals
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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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// 'x: 'a
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// 'b: 'y
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//
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// so if we are going to ensure that `'x: 'y`, then `'a: 'b` must
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// hold.
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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<&'a &'x u32>, // shows that 'x: 'a
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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>(_outlives1: Cell<&&'x u32>, _outlives2: Cell<&'y &u32>, _y: &'y u32) {}
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#[rustc_regions]
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fn test<'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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//~^ ERROR lifetime may not live long enough
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// Only works if 'x: 'y:
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demand_y(outlives1, outlives2, x.get())
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});
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}
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fn main() {}
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