1 files changed, 39 insertions, 4 deletions
diff --git a/guava/src/com/google/common/collect/ImmutableMap.java b/guava/src/com/google/common/collect/ImmutableMap.java
index c370e5248..7a185b5d3 100644
--- a/guava/src/com/google/common/collect/ImmutableMap.java
+++ b/guava/src/com/google/common/collect/ImmutableMap.java
@@ -23,6 +23,7 @@ import static com.google.common.collect.CollectPreconditions.checkNonnegative;
 import static java.util.Objects.requireNonNull;
 
 import com.google.common.annotations.GwtCompatible;
+import com.google.common.annotations.GwtIncompatible;
 import com.google.common.annotations.J2ktIncompatible;
 import com.google.common.annotations.VisibleForTesting;
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
@@ -96,8 +97,11 @@ public abstract class ImmutableMap<K, V> implements Map<K, V>, Serializable {
    * and values are the result of applying the provided mapping functions to the input elements.
    *
    * <p>If the mapped keys contain duplicates (according to {@link Object#equals(Object)}), the
-   * values are merged using the specified merging function. Entries will appear in the encounter
-   * order of the first occurrence of the key.
+   * values are merged using the specified merging function. If the merging function returns {@code
+   * null}, then the collector removes the value that has been computed for the key thus far (though
+   * future occurrences of the key would reinsert it).
+   *
+   * <p>Entries will appear in the encounter order of the first occurrence of the key.
    *
    * @since 21.0
    */
@@ -754,6 +758,15 @@ public abstract class ImmutableMap<K, V> implements Map<K, V>, Serializable {
         public UnmodifiableIterator<Entry<K, V>> iterator() {
           return entryIterator();
         }
+
+        // redeclare to help optimizers with b/310253115
+        @SuppressWarnings("RedundantOverride")
+        @Override
+        @J2ktIncompatible // serialization
+        @GwtIncompatible // serialization
+        Object writeReplace() {
+          return super.writeReplace();
+        }
       }
       return new EntrySetImpl();
     }
@@ -762,6 +775,15 @@ public abstract class ImmutableMap<K, V> implements Map<K, V>, Serializable {
     ImmutableCollection<V> createValues() {
       return new ImmutableMapValues<>(this);
     }
+
+    // redeclare to help optimizers with b/310253115
+    @SuppressWarnings("RedundantOverride")
+    @Override
+    @J2ktIncompatible // serialization
+    @GwtIncompatible // serialization
+    Object writeReplace() {
+      return super.writeReplace();
+    }
   }
 
   ImmutableMap() {}
@@ -845,8 +867,9 @@ public abstract class ImmutableMap<K, V> implements Map<K, V>, Serializable {
   @Deprecated
   @Override
   @DoNotCall("Always throws UnsupportedOperationException")
+  @CheckForNull
   public final V computeIfPresent(
-      K key, BiFunction<? super K, ? super V, ? extends V> remappingFunction) {
+      K key, BiFunction<? super K, ? super V, ? extends @Nullable V> remappingFunction) {
     throw new UnsupportedOperationException();
   }
 
@@ -859,8 +882,9 @@ public abstract class ImmutableMap<K, V> implements Map<K, V>, Serializable {
   @Deprecated
   @Override
   @DoNotCall("Always throws UnsupportedOperationException")
+  @CheckForNull
   public final V compute(
-      K key, BiFunction<? super K, ? super @Nullable V, ? extends V> remappingFunction) {
+      K key, BiFunction<? super K, ? super @Nullable V, ? extends @Nullable V> remappingFunction) {
     throw new UnsupportedOperationException();
   }
 
@@ -1165,6 +1189,15 @@ public abstract class ImmutableMap<K, V> implements Map<K, V>, Serializable {
         }
       };
     }
+
+    // redeclare to help optimizers with b/310253115
+    @SuppressWarnings("RedundantOverride")
+    @Override
+    @J2ktIncompatible // serialization
+    @GwtIncompatible // serialization
+    Object writeReplace() {
+      return super.writeReplace();
+    }
   }
 
   @Override
@@ -1282,4 +1315,6 @@ public abstract class ImmutableMap<K, V> implements Map<K, V>, Serializable {
   private void readObject(ObjectInputStream stream) throws InvalidObjectException {
     throw new InvalidObjectException("Use SerializedForm");
   }
+
+  private static final long serialVersionUID = 0xcafebabe;
 }