Under j2cl, make Maps.immutableEnumMap and toImmutableEnumMap work. Previously, they were present but failed at runtime.

RELNOTES=`collect`: Under j2cl, made `Maps.immutableEnumMap` and `toImmutableEnumMap` work.
PiperOrigin-RevId: 534145451

Author: cpovirk

android/guava/src/com/google/common/collect/Maps.java

@@ -22,6 +22,7 @@
 import static com.google.common.collect.CollectPreconditions.checkEntryNotNull;
 import static com.google.common.collect.CollectPreconditions.checkNonnegative;
 import static com.google.common.collect.NullnessCasts.uncheckedCastNullableTToT;
+import static java.util.Collections.singletonMap;
 import static java.util.Objects.requireNonNull;
 
 import com.google.common.annotations.GwtCompatible;
@@ -163,9 +164,8 @@ public static <K extends Enum<K>, V> ImmutableMap<K, V> immutableEnumMap(
     K key1 = entry1.getKey();
     V value1 = entry1.getValue();
     checkEntryNotNull(key1, value1);
-    Class<K> clazz = key1.getDeclaringClass();
-    EnumMap<K, V> enumMap = new EnumMap<>(clazz);
-    enumMap.put(key1, value1);
+    // Do something that works for j2cl, where we can't call getDeclaredClass():
+    EnumMap<K, V> enumMap = new EnumMap<>(singletonMap(key1, value1));
     while (entryItr.hasNext()) {
       Entry<K, ? extends V> entry = entryItr.next();
       K key = entry.getKey();

guava/src/com/google/common/collect/CollectCollectors.java

@@ -17,6 +17,7 @@
 package com.google.common.collect;
 
 import static com.google.common.base.Preconditions.checkNotNull;
+import static java.util.Collections.singletonMap;
 import static java.util.stream.Collectors.collectingAndThen;
 
 import com.google.common.annotations.GwtCompatible;
@@ -326,9 +327,10 @@ private static class EnumMapAccumulator<K extends Enum<K>, V> {
 
     void put(K key, V value) {
       if (map == null) {
-        map = new EnumMap<>(key.getDeclaringClass());
+        map = new EnumMap<>(singletonMap(key, value));
+      } else {
+        map.merge(key, value, mergeFunction);
       }
-      map.merge(key, value, mergeFunction);
     }
 
     EnumMapAccumulator<K, V> combine(EnumMapAccumulator<K, V> other) {

guava/src/com/google/common/collect/Maps.java

@@ -22,6 +22,7 @@
 import static com.google.common.collect.CollectPreconditions.checkEntryNotNull;
 import static com.google.common.collect.CollectPreconditions.checkNonnegative;
 import static com.google.common.collect.NullnessCasts.uncheckedCastNullableTToT;
+import static java.util.Collections.singletonMap;
 import static java.util.Objects.requireNonNull;
 
 import com.google.common.annotations.GwtCompatible;
@@ -170,9 +171,8 @@ public static <K extends Enum<K>, V> ImmutableMap<K, V> immutableEnumMap(
     K key1 = entry1.getKey();
     V value1 = entry1.getValue();
     checkEntryNotNull(key1, value1);
-    Class<K> clazz = key1.getDeclaringClass();
-    EnumMap<K, V> enumMap = new EnumMap<>(clazz);
-    enumMap.put(key1, value1);
+    // Do something that works for j2cl, where we can't call getDeclaredClass():
+    EnumMap<K, V> enumMap = new EnumMap<>(singletonMap(key1, value1));
     while (entryItr.hasNext()) {
       Entry<K, ? extends V> entry = entryItr.next();
       K key = entry.getKey();