Revert "Revert "If an if or do statement always exits, following statements are dead.""

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 8f0038abd93fdb634df6c3596d64bb03e0241e69..5fefaad9fda6e258e5722a80c13597252854140f 100644
--- a/pkg/analyzer/lib/src/generated/resolver.dart
+++ b/pkg/analyzer/lib/src/generated/resolver.dart
@@ -2079,22 +2079,25 @@ class DeadCodeVerifier extends RecursiveAstVisitor<Object> {
 
   /**
    * Given some [NodeList] of [Statement]s, from either a [Block] or
-   * [SwitchMember], this loops through the list in reverse order searching for statements
-   * after a return, unlabeled break or unlabeled continue statement to mark them as dead code.
+   * [SwitchMember], this loops through the list searching for dead statements.
    *
    * @param statements some ordered list of statements in a [Block] or [SwitchMember]
    */
   void _checkForDeadStatementsInNodeList(NodeList<Statement> statements) {
+    bool statementExits(Statement statement) {
+      if (statement is BreakStatement) {
+        return statement.label == null;
+      } else if (statement is ContinueStatement) {
+        return statement.label == null;
+      }
+      return ExitDetector.exits(statement);
+    }
+
     int size = statements.length;
     for (int i = 0; i < size; i++) {
       Statement currentStatement = statements[i];
       currentStatement?.accept(this);
-      bool returnOrBreakingStatement = currentStatement is ReturnStatement ||
-          (currentStatement is BreakStatement &&
-              currentStatement.label == null) ||
-          (currentStatement is ContinueStatement &&
-              currentStatement.label == null);
-      if (returnOrBreakingStatement && i != size - 1) {
+      if (statementExits(currentStatement) && i != size - 1) {
         Statement nextStatement = statements[i + 1];
         Statement lastStatement = statements[size - 1];
         int offset = nextStatement.offset;