Issue 22188. Verify that none or all execution flows return.

pkg/analyzer/lib/src/generated/resolver.dart

Index: pkg/analyzer/lib/src/generated/resolver.dart
diff --git a/pkg/analyzer/lib/src/generated/resolver.dart b/pkg/analyzer/lib/src/generated/resolver.dart
index 9f3ab6db8bc4e02b0522cb0702245e1e9c2fc947..5dcbcfb806ba26ffddb919f83f0b292a41d6ca49 100644
--- a/pkg/analyzer/lib/src/generated/resolver.dart
+++ b/pkg/analyzer/lib/src/generated/resolver.dart
@@ -4331,6 +4331,13 @@ class ExitDetector extends GeneralizingAstVisitor<bool> {
     }
     return false;
   }
+
+  /**
+   * Return `true` if the given [node] exits.
+   */
+  static bool exits(AstNode node) {
+    return new ExitDetector()._nodeExits(node);
+  }
 }
 
 /**