Permit @Multibinds with values that are also allowed by @IntoSet/@IntoMap.

java/dagger/internal/codegen/validation/MultibindsMethodValidator.java

@@ -16,7 +16,8 @@
 
 package dagger.internal.codegen.validation;
 
-import static dagger.internal.codegen.base.FrameworkTypes.isFrameworkType;
+import static dagger.internal.codegen.base.FrameworkTypes.isMapValueFrameworkType;
+import static dagger.internal.codegen.base.FrameworkTypes.isSetValueFrameworkType;
 import static dagger.internal.codegen.validation.BindingElementValidator.AllowsMultibindings.NO_MULTIBINDINGS;
 import static dagger.internal.codegen.validation.BindingElementValidator.AllowsScoping.NO_SCOPING;
 import static dagger.internal.codegen.validation.BindingMethodValidator.Abstractness.MUST_BE_ABSTRACT;
@@ -95,7 +96,7 @@ private void checkMapType(MapType mapType) {
       } else if (isWildcard(mapType.valueType())) {
         report.addError(
             bindingMethods("return type cannot use a wildcard as the Map value type."));
-      } else if (isFrameworkType(mapType.valueType())) {
+      } else if (isMapValueFrameworkType(mapType.valueType())) {
         String frameworkTypeName = getSimpleName(mapType.valueType().getTypeElement());
         report.addError(
             bindingMethods(
@@ -108,7 +109,7 @@ private void checkSetType(SetType setType) {
         report.addError(bindingMethods("return type cannot be a raw Set type"));
       } else if (isWildcard(setType.elementType())) {
         report.addError(bindingMethods("return type cannot use a wildcard as the Set value type."));
-      } else if (isFrameworkType(setType.elementType())) {
+      } else if (isSetValueFrameworkType(setType.elementType())) {
         String frameworkTypeName = getSimpleName(setType.elementType().getTypeElement());
         report.addError(
             bindingMethods(

javatests/dagger/functional/multibindings/BUILD

@@ -37,6 +37,7 @@ GenJavaTests(
         "MultibindsModule.java",
         "NestedAnnotationContainer.java",
         "NumberClassKey.java",
+        "RequiresFieldInjection.java",
         "ShortKey.java",
         "UnwrappedAnnotationKey.java",
         "WrappedAnnotationKey.java",

javatests/dagger/functional/multibindings/MultibindingComponent.java

@@ -17,6 +17,7 @@
 package dagger.functional.multibindings;
 
 import dagger.Component;
+import dagger.MembersInjector;
 import dagger.functional.multibindings.subpackage.ContributionsModule;
 import dagger.multibindings.StringKey;
 import java.util.Collection;
@@ -67,4 +68,8 @@ interface MultibindingComponent {
 
   @Named("complexQualifier")
   Map<String, CharSequence> maybeEmptyQualifiedMap();
+
+  Map<Class<?>, MembersInjector<?>> membersInjectorMap();
+
+  Set<MembersInjector<?>> membersInjectorSet();
 }

javatests/dagger/functional/multibindings/MultibindingModule.java

@@ -16,6 +16,7 @@
 
 package dagger.functional.multibindings;
 
+import dagger.MembersInjector;
 import dagger.Module;
 import dagger.Provides;
 import dagger.multibindings.ClassKey;
@@ -95,6 +96,27 @@ static Collection<String> provideMapValues(Map<String, String> map) {
     return map.values();
   }
 
+  @Provides
+  @Named("fieldInjectedValue")
+  static String provideFieldInjectedValue() {
+    return "fieldInjectedValue";
+  }
+
+  @Provides
+  @IntoMap
+  @ClassKey(RequiresFieldInjection.class)
+  static MembersInjector<?> provideMembersInjectorIntoMap(
+      MembersInjector<RequiresFieldInjection> injector) {
+    return injector;
+  }
+
+  @Provides
+  @IntoSet
+  static MembersInjector<?> provideMembersInjectorIntoSet(
+      MembersInjector<RequiresFieldInjection> injector) {
+    return injector;
+  }
+
   @Provides
   @IntoMap
   @NestedAnnotationContainer.NestedWrappedKey(Integer.class)

javatests/dagger/functional/multibindings/MultibindingTest.java

@@ -19,11 +19,13 @@
 import static com.google.common.truth.Truth.assertThat;
 
 import com.google.auto.value.AutoAnnotation;
+import dagger.MembersInjector;
 import dagger.multibindings.ClassKey;
 import dagger.multibindings.StringKey;
 import java.math.BigDecimal;
 import java.math.BigInteger;
 import java.util.Map;
+import java.util.Set;
 import javax.inject.Provider;
 import org.junit.Test;
 import org.junit.runner.RunWith;
@@ -183,6 +185,29 @@ public void maybeEmptyQualifiedMap() {
         .containsEntry("key", "qualified foo value");
   }
 
+  @SuppressWarnings("unchecked")  // We know the single type in the set
+  @Test
+  public void membersInjectorSet() {
+    Set<MembersInjector<?>> injectors = multibindingComponent.membersInjectorSet();
+    assertThat(injectors).hasSize(1);
+    RequiresFieldInjection injected = new RequiresFieldInjection();
+    assertThat(injected.value).isNull();
+    ((MembersInjector<RequiresFieldInjection>) injectors.iterator().next()).injectMembers(injected);
+    assertThat(injected.value).isEqualTo("fieldInjectedValue");
+  }
+
+  @SuppressWarnings("unchecked")  // We know the single type in the map
+  @Test
+  public void membersInjectorMap() {
+    Map<Class<?>, MembersInjector<?>> injectors = multibindingComponent.membersInjectorMap();
+    assertThat(injectors).hasSize(1);
+    RequiresFieldInjection injected = new RequiresFieldInjection();
+    assertThat(injected.value).isNull();
+    ((MembersInjector<RequiresFieldInjection>) injectors.get(RequiresFieldInjection.class))
+        .injectMembers(injected);
+    assertThat(injected.value).isEqualTo("fieldInjectedValue");
+  }
+
   @AutoAnnotation
   static StringKey testStringKey(String value) {
     return new AutoAnnotation_MultibindingTest_testStringKey(value);

javatests/dagger/functional/multibindings/MultibindsModule.java

@@ -16,6 +16,7 @@
 
 package dagger.functional.multibindings;
 
+import dagger.MembersInjector;
 import dagger.Module;
 import dagger.multibindings.Multibinds;
 import java.util.Map;
@@ -38,9 +39,15 @@ abstract class MultibindsModule {
   @Multibinds
   abstract Set<CharSequence> set();
 
+  @Multibinds
+  abstract Set<MembersInjector<?>> membersInjectorSet();
+
   @Multibinds
   abstract Map<String, CharSequence> map();
 
+  @Multibinds
+  abstract Map<Class<?>, MembersInjector<?>> membersInjectorMap();
+
   @Multibinds
   @Named("complexQualifier")
   abstract Set<Object> emptyQualifiedSet();

javatests/dagger/functional/multibindings/RequiresFieldInjection.java

@@ -0,0 +1,24 @@
+/*
+ * Copyright (C) 2024 The Dagger Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package dagger.functional.multibindings;
+
+import javax.inject.Inject;
+import javax.inject.Named;
+
+public final class RequiresFieldInjection {
+  @Inject @Named("fieldInjectedValue") String value;
+}

javatests/dagger/internal/codegen/MultibindsValidationTest.java

@@ -141,20 +141,6 @@ public void wildcardSetWithBounds() {
         .hasError("return type cannot use a wildcard as the Set value type.");
   }
 
-  @Test
-  public void providerSet() {
-    assertThatModuleMethod("@Multibinds abstract Set<Provider<Object>> providerSet();")
-        .withDeclaration(moduleDeclaration)
-        .hasError("return type cannot use 'Provider' in the Set value type.");
-  }
-
-  @Test
-  public void producerSet() {
-    assertThatModuleMethod("@Multibinds abstract Set<Producer<Object>> producerSet();")
-        .withDeclaration(moduleDeclaration)
-        .hasError("return type cannot use 'Producer' in the Set value type.");
-  }
-
   @Test
   public void producedSet() {
     assertThatModuleMethod("@Multibinds abstract Set<Produced<Object>> producedSet();")