diff options
| -rw-r--r-- | src/librustc/middle/ty/util.rs | 15 |
1 files changed, 12 insertions, 3 deletions
diff --git a/src/librustc/middle/ty/util.rs b/src/librustc/middle/ty/util.rs index 3d1eb66287f..a8f7a4db133 100644 --- a/src/librustc/middle/ty/util.rs +++ b/src/librustc/middle/ty/util.rs @@ -566,9 +566,18 @@ impl<'tcx> ty::ctxt<'tcx> { } } - /// Returns true if this ADT is a dtorck type, i.e. whether it - /// being safe for destruction requires all borrowed pointers - /// reachable by it to have lifetimes strictly greater than self. + /// Returns true if this ADT is a dtorck type. + /// + /// Invoking the destructor of a dtorck type during usual cleanup + /// (e.g. the glue emitted for stack unwinding) requires all + /// lifetimes in the type-structure of `adt` to strictly outlive + /// the adt value itself. + /// + /// If `adt` is not dtorck, then the adt's destructor can be + /// invoked even when there are lifetimes in the type-structure of + /// `adt` that do not strictly outlive the adt value itself. + /// (This allows programs to make cyclic structures without + /// resorting to unasfe means; see RFCs 769 and 1238). pub fn is_adt_dtorck(&self, adt: ty::AdtDef<'tcx>) -> bool { let dtor_method = match adt.destructor() { Some(dtor) => dtor, |