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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-17 12:02:58 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-17 12:02:58 +0000
commit698f8c2f01ea549d77d7dc3338a12e04c11057b9 (patch)
tree173a775858bd501c378080a10dca74132f05bc50 /src/test/ui/nll/closure-requirements/propagate-fail-to-approximate-longer-wrong-bounds.rs
parentInitial commit. (diff)
downloadrustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.tar.xz
rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.zip
Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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diff --git a/src/test/ui/nll/closure-requirements/propagate-fail-to-approximate-longer-wrong-bounds.rs b/src/test/ui/nll/closure-requirements/propagate-fail-to-approximate-longer-wrong-bounds.rs
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+// Similarly to escape-argument-callee, a test case where the closure
+// requires a relationship between 2 unrelated higher-ranked regions,
+// with no helpful relations between the HRRs and free regions.
+//
+// In this case, the error is reported by the closure itself. This is
+// because it is unable to approximate the higher-ranked region `'x`,
+// as it only knows of regions that `'x` is outlived by, and none that
+// `'x` outlives.
+
+// compile-flags:-Zverbose
+
+#![feature(rustc_attrs)]
+
+use std::cell::Cell;
+
+// Callee knows that:
+//
+// 'a: 'x
+// 'b: 'y
+//
+// but this doesn't really help us in proving that `'x: 'y`, so
+// closure gets an error. In particular, we would need to know that
+// `'x: 'a`, so that we could approximate `'x` "downwards" to `'a`.
+fn establish_relationships<'a, 'b, F>(_cell_a: &Cell<&'a u32>, _cell_b: &Cell<&'b u32>, _closure: F)
+where
+ F: for<'x, 'y> FnMut(
+ &Cell<&'x &'a u32>, // shows that 'a: 'x
+ &Cell<&'y &'b u32>, // shows that 'b: 'y
+ &Cell<&'x u32>,
+ &Cell<&'y u32>,
+ ),
+{
+}
+
+fn demand_y<'x, 'y>(_cell_x: &Cell<&'x u32>, _cell_y: &Cell<&'y u32>, _y: &'y u32) {}
+
+#[rustc_regions]
+fn supply<'a, 'b>(cell_a: Cell<&'a u32>, cell_b: Cell<&'b u32>) {
+ establish_relationships(&cell_a, &cell_b, |_outlives1, _outlives2, x, y| {
+ // Only works if 'x: 'y:
+ demand_y(x, y, x.get())
+ //~^ ERROR
+ });
+}
+
+fn main() {}