Auto merge of #113902 - Enselic:lint-recursive-drop, r=oli-obk

Make `unconditional_recursion` warning detect recursive drops

Closes #55388

Also closes #50049 unless we want to keep it for the second example which this PR does not solve, but I think it is better to track that work in #57965.

r? `@oli-obk` since you are the mentor for #55388

Unresolved questions:
- [x] There are two false positives that must be fixed before merging (see diff). I suspect the best way to solve them is to perform analysis after drop elaboration instead of before, as now, but I have not explored that any further yet. Could that be an option? **Answer:** Yes, that solved the problem.

`@rustbot` label +T-compiler +C-enhancement +A-lint

2 files changed, 5 insertions, 0 deletions

diff --git a/compiler/rustc_mir_transform/Cargo.toml b/compiler/rustc_mir_transform/Cargo.toml
index eca5f98a2c0..f1198d9bfd3 100644
--- a/compiler/rustc_mir_transform/Cargo.toml
+++ b/compiler/rustc_mir_transform/Cargo.toml
@@ -18,6 +18,7 @@ rustc_hir = { path = "../rustc_hir" }
 rustc_index = { path = "../rustc_index" }
 rustc_middle = { path = "../rustc_middle" }
 rustc_const_eval = { path = "../rustc_const_eval" }
+rustc_mir_build = { path = "../rustc_mir_build" }
 rustc_mir_dataflow = { path = "../rustc_mir_dataflow" }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_session = { path = "../rustc_session" }
diff --git a/compiler/rustc_mir_transform/src/lib.rs b/compiler/rustc_mir_transform/src/lib.rs
index ccb67248822..f99a51fea0b 100644
--- a/compiler/rustc_mir_transform/src/lib.rs
+++ b/compiler/rustc_mir_transform/src/lib.rs
@@ -424,6 +424,10 @@ fn mir_drops_elaborated_and_const_checked(tcx: TyCtxt<'_>, def: LocalDefId) -> &
 
     run_analysis_to_runtime_passes(tcx, &mut body);
 
+    // Now that drop elaboration has been performed, we can check for
+    // unconditional drop recursion.
+    rustc_mir_build::lints::check_drop_recursion(tcx, &body);
+
     tcx.alloc_steal_mir(body)
 }