diff --git a/src/librustc_mir/dataflow/impls/borrowed_locals.rs b/src/librustc_mir/dataflow/impls/borrowed_locals.rs
index f929b2ddde0..b61dc56407e 100644
--- a/src/librustc_mir/dataflow/impls/borrowed_locals.rs
+++ b/src/librustc_mir/dataflow/impls/borrowed_locals.rs
@@ -99,6 +99,9 @@ impl<K> GenKillAnalysis<'tcx> for MaybeBorrowedLocals<K>
 where
     K: BorrowAnalysisKind<'tcx>,
 {
+    // The generator transform relies on the fact that this analysis does **not** use "before"
+    // effects.
+
     fn statement_effect(
         &self,
         trans: &mut impl GenKill<Self::Idx>,
diff --git a/src/librustc_mir/dataflow/impls/init_locals.rs b/src/librustc_mir/dataflow/impls/init_locals.rs
index 01cb794a2e0..726330b1f03 100644
--- a/src/librustc_mir/dataflow/impls/init_locals.rs
+++ b/src/librustc_mir/dataflow/impls/init_locals.rs
@@ -33,6 +33,9 @@ fn initialize_start_block(&self, body: &mir::Body<'tcx>, entry_set: &mut BitSet<
 }
 
 impl dataflow::GenKillAnalysis<'tcx> for MaybeInitializedLocals {
+    // The generator transform relies on the fact that this analysis does **not** use "before"
+    // effects.
+
     fn statement_effect(
         &self,
         trans: &mut impl GenKill<Self::Idx>,