Correct implementation of IdentityMostlySingleton.

dataflow/src/main/java/org/checkerframework/dataflow/util/IdentityMostlySingleton.java

@@ -1,6 +1,7 @@
 package org.checkerframework.dataflow.util;
 
-import java.util.ArrayList;
+import java.util.Collections;
+import java.util.IdentityHashMap;
 import org.checkerframework.javacutil.BugInCF;
 
 /**
@@ -29,7 +30,7 @@ public boolean add(T e) {
                 return true;
             case SINGLETON:
                 state = State.ANY;
-                set = new ArrayList<>();
+                set = Collections.newSetFromMap(new IdentityHashMap<>());
                 assert value != null : "@AssumeAssertion(nullness): previous add is non-null";
                 set.add(value);
                 value = null;

framework/tests/nontopdefault/TestCasting.java

@@ -0,0 +1,20 @@
+import testlib.nontopdefault.qual.NTDMiddle;
+
+@SuppressWarnings("inconsistent.constructor.type") // Not the point of this test
+public class TestCasting {
+    void repro(@NTDMiddle long startTime) {
+        try {
+            System.out.println("Inside try");
+            return;
+        } catch (Exception ex) {
+            long timeTaken = startTime;
+            @NTDMiddle double dblTimeTaken = timeTaken;
+
+            throw new IllegalArgumentException();
+        } finally {
+            long timeTaken2 = startTime;
+            // This assignment used to fail.
+            @NTDMiddle double dblTimeTaken2 = timeTaken2;
+        }
+    }
+}