diff options
| -rw-r--r-- | src/librustc_typeck/check/coercion.rs | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/src/librustc_typeck/check/coercion.rs b/src/librustc_typeck/check/coercion.rs index 5b3484dcccb..76219c6971b 100644 --- a/src/librustc_typeck/check/coercion.rs +++ b/src/librustc_typeck/check/coercion.rs @@ -537,8 +537,9 @@ impl<'f, 'gcx, 'tcx> Coerce<'f, 'gcx, 'tcx> { let mut selcx = traits::SelectionContext::new(self); - // Use a FIFO queue for this custom fulfillment procedure. - let mut queue = VecDeque::new(); + // Use a FIFO queue for this custom fulfillment procedure. (The maximum + // length is almost always 1.) + let mut queue = VecDeque::with_capacity(1); // Create an obligation for `Source: CoerceUnsized<Target>`. let cause = ObligationCause::misc(self.cause.span, self.body_id); |