note: external requirements --> $DIR/propagate-approximated-shorter-to-static-no-bound.rs:32:47 | LL | establish_relationships(&cell_a, &cell_b, |_outlives, x, y| { | ^^^^^^^^^^^^^^^^^ | = note: defining type: supply::{closure#0} with closure args [ i16, for extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) std::cell::Cell<&'?1 &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 2, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 4, kind: BrAnon(None) }) u32>)), (), ] = note: late-bound region is '?2 = note: late-bound region is '?3 = note: number of external vids: 4 = note: where '?1: '?0 note: no external requirements --> $DIR/propagate-approximated-shorter-to-static-no-bound.rs:31:1 | LL | fn supply<'a, 'b>(cell_a: Cell<&'a u32>, cell_b: Cell<&'b u32>) { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | = note: defining type: supply error[E0521]: borrowed data escapes outside of function --> $DIR/propagate-approximated-shorter-to-static-no-bound.rs:32:5 | LL | fn supply<'a, 'b>(cell_a: Cell<&'a u32>, cell_b: Cell<&'b u32>) { | -- ------ `cell_a` is a reference that is only valid in the function body | | | lifetime `'a` defined here LL | / establish_relationships(&cell_a, &cell_b, |_outlives, x, y| { LL | | LL | | LL | | // Only works if 'x: 'y: LL | | demand_y(x, y, x.get()) LL | | }); | | ^ | | | | |______`cell_a` escapes the function body here | argument requires that `'a` must outlive `'static` | = note: requirement occurs because of the type `Cell<&'?9 u32>`, which makes the generic argument `&'?9 u32` invariant = note: the struct `Cell` is invariant over the parameter `T` = help: see for more information about variance error: aborting due to previous error For more information about this error, try `rustc --explain E0521`.