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Spurious "does not live long enough" for closure coerced to fn pointer in static item (AST borrowck only) #48540
Description
The test case below is reduced from a phf map.
rustc 1.26.0-nightly (28a1e4f 2018-02-24) with -Z borrowck=mir: OK
Without any -Z flag: error below, even though I believe the program to be valid. But maybe it’s not worth fixing if MIR-based borrow-checking will become the default soon? CC @nikomatsakis
A work-around is to have the closure in an intermediate const item.
fn main() {}
struct Static<T: 'static>(&'static [T]);
static FOO: Static<fn(&u32) -> &u32> = Static(&[|x| x]);error[E0597]: borrowed value does not live long enough
--> a.rs:5:52
|
5 | pub static FOO: Static<fn(&u32) -> &u32> = Static(&[|x| x]);
| ^^^^^^^- temporary value only lives until here
| |
| temporary value does not live long enough
|
= note: borrowed value must be valid for the static lifetime...
error: aborting due to previous errorfn main() {}
struct Static<T: 'static>(&'static [T]);
static FOO: Static<fn(&u32) -> &u32> = Static(&[
{
const F: fn(&u32) -> &u32 = |x| x; // work around
F
},
]);
Activity
nikomatsakis commentedon Feb 27, 2018
It's actually equivalent to
-Zborrowck=mir -Znll -Ztwo-phase-borrows, I thinknikomatsakis commentedon Feb 27, 2018
@SimonSapin is this a regression, do you know?
SimonSapin commentedon Feb 27, 2018
@nikomatsakis Not as far as I know. 1.24.0 stable gives the same error. Note that this is fixed by MIR-borrowck.
nikomatsakis commentedon Feb 27, 2018
OK. In that case I am inclined to wait, yes.
SimonSapin commentedon Nov 26, 2018
Adding the "fixed by NLL" label as an approximation of fixed by MIR borrowck
Auto merge of #59114 - matthewjasper:enable-migate-2015, r=<try>
Auto merge of #59114 - matthewjasper:enable-migate-2015, r=pnkfelix
Auto merge of #59114 - matthewjasper:enable-migate-2015, r=pnkfelix