Correct implementation of IdentityMostlySingleton

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

@@ -15,7 +15,7 @@
  */
 public abstract class AbstractMostlySingleton<T extends Object> implements Set<T> {
 
-    /** The possible states of the collection. */
+    /** The possible states of this set. */
     public enum State {
         /** An empty set. */
         EMPTY,
@@ -29,8 +29,8 @@ public enum State {
     protected State state;
     /** The current value, non-null when the state is SINGLETON. */
     protected @Nullable T value;
-    /** The wrapped collection, non-null when the state is ANY. */
-    protected @Nullable Collection<T> set;
+    /** The wrapped set, non-null when the state is ANY. */
+    protected @Nullable Set<T> set;
 
     /** Create an AbstractMostlySingleton. */
     protected AbstractMostlySingleton(State s) {

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

@@ -1,6 +1,8 @@
 package org.checkerframework.dataflow.util;
 
-import java.util.ArrayList;
+import java.util.Collections;
+import java.util.IdentityHashMap;
+import org.checkerframework.checker.interning.qual.FindDistinct;
 import org.checkerframework.javacutil.BugInCF;
 
 /**
@@ -21,15 +23,18 @@ public IdentityMostlySingleton(T value) {
 
     @Override
     @SuppressWarnings("fallthrough")
-    public boolean add(T e) {
+    public boolean add(@FindDistinct T e) {
         switch (state) {
             case EMPTY:
                 state = State.SINGLETON;
                 value = e;
                 return true;
             case SINGLETON:
+                if (value == e) {
+                    return false;
+                }
                 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;
+        }
+    }
+}