[analyzer] Mark switch expression's matched expression as used

Fixes unused_result being incorrectly reported.

Change-Id: Ifcf06bdb3e2134cdd738f3f880290e5c1be7e16b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/448224
Reviewed-by: Paul Berry <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>
Reviewed-by: Samuel Rawlins <[email protected]>
Commit-Queue: Paul Berry <[email protected]>

Author: parlough

pkg/analyzer/lib/src/error/use_result_verifier.dart

@@ -253,6 +253,7 @@ class UseResultVerifier {
         parent is RecordLiteral ||
         parent is ReturnStatement ||
         parent is SetOrMapLiteral ||
+        parent is SwitchExpression ||
         parent is SwitchExpressionCase ||
         parent is SwitchStatement ||
         parent is ThrowExpression ||

pkg/analyzer/test/src/diagnostics/unused_result_test.dart

@@ -1444,11 +1444,27 @@ class C {
 ''');
   }
 
-  /// https://github.com/dart-lang/sdk/issues/52314
   test_switchExpression() async {
     await assertNoErrorsInCode(r'''
 import 'package:meta/meta.dart';
 
+void main() {
+  print(switch (methodWithAnnotation()) {
+    true => true,
+    _ => false,
+  });
+}
+
+@useResult
+bool methodWithAnnotation() => true;
+''');
+  }
+
+  /// https://github.com/dart-lang/sdk/issues/52314
+  test_switchExpressionCase() async {
+    await assertNoErrorsInCode(r'''
+import 'package:meta/meta.dart';
+
 class C {
   bool m(Object o) {
     return switch (o) {