add notes clarifying introduction of warnings for a pair of run-pass tests.

src/test/run-pass/hygienic-labels-in-let.rs

@@ -10,6 +10,14 @@
 
 // ignore-pretty: pprust doesn't print hygiene output
 
+// Test that labels injected by macros do not break hygiene.  This
+// checks cases where the macros invocations are under the rhs of a
+// let statement.
+
+// Issue #24278: The label/lifetime shadowing checker from #24162
+// conservatively ignores hygiene, and thus issues warnings that are
+// both true- and false-positives for this test.
+
 macro_rules! loop_x {
     ($e: expr) => {
         // $e shouldn't be able to interact with this 'x

src/test/run-pass/hygienic-labels.rs

@@ -8,6 +8,11 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// Test that labels injected by macros do not break hygiene.
+
+// Issue #24278: The label/lifetime shadowing checker from #24162
+// conservatively ignores hygiene, and thus issues warnings that are
+// both true- and false-positives for this test.
 
 macro_rules! loop_x {
     ($e: expr) => {