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Skip dropck::check_drop_impl in is_const_item_without_destructor
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adt_destructor by default also validates the Drop impl using
dropck::check_drop_impl, which contains an expect_local(). This
leads to ICE in check_const_item_mutation if the const's type is
not a local type.

    thread 'rustc' panicked at 'DefId::expect_local: `DefId(5:4805 ~ alloc[d7e9]::vec::{impl#50})` isn't local', compiler/rustc_span/src/def_id.rs:174:43
    stack backtrace:
       0: rust_begin_unwind
       1: rustc_span::def_id::DefId::expect_local::{{closure}}
       2: rustc_typeck::check::dropck::check_drop_impl
       3: rustc_middle::ty::util::<impl rustc_middle::ty::context::TyCtxt>::calculate_dtor::{{closure}}
       4: rustc_middle::ty::trait_def::<impl rustc_middle::ty::context::TyCtxt>::for_each_relevant_impl
       5: rustc_middle::ty::util::<impl rustc_middle::ty::context::TyCtxt>::calculate_dtor
       6: rustc_typeck::check::adt_destructor
       7: rustc_middle::ty::query::<impl rustc_query_system::query::config::QueryAccessors<rustc_middle::ty::context::TyCtxt> for rustc_middle::ty::query::queries::adt_destructor>::compute
       8: rustc_query_system::dep_graph::graph::DepGraph<K>::with_task_impl
       9: rustc_query_system::query::plumbing::get_query_impl
      10: rustc_mir::transform::check_const_item_mutation::ConstMutationChecker::is_const_item_without_destructor
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dtolnay committed Oct 1, 2020
1 parent 352ce8b commit 41baa09
Showing 1 changed file with 2 additions and 1 deletion.
Expand Up @@ -34,6 +34,7 @@ impl<'a, 'tcx> ConstMutationChecker<'a, 'tcx> {

fn is_const_item_without_destructor(&self, local: Local) -> Option<DefId> {
let def_id = self.is_const_item(local)?;
let mut any_dtor = |_tcx, _def_id| Ok(());

// We avoid linting mutation of a const item if the const's type has a
// Drop impl. The Drop logic observes the mutation which was performed.
Expand All @@ -46,7 +47,7 @@ impl<'a, 'tcx> ConstMutationChecker<'a, 'tcx> {
//
// LOG.msg = "wow"; // prints "wow"
//
match self.tcx.adt_destructor(def_id) {
match self.tcx.calculate_dtor(def_id, &mut any_dtor) {
Some(_) => None,
None => Some(def_id),
}
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