Allow static provider methods to be deduped

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=308639369

Author: lukesandberg

core/src/com/google/inject/internal/ProviderMethodsModule.java

@@ -325,7 +325,7 @@ private <T> ProviderMethod<T> createProviderMethod(
     return ProviderMethod.create(
         key,
         method,
-        isStaticModule() ? null : delegate,
+        isStaticModule() || Modifier.isStatic(method.getModifiers()) ? null : delegate,
         ImmutableSet.copyOf(point.getDependencies()),
         scopeAnnotation,
         skipFastClassGeneration,

core/test/com/google/inject/spi/ProviderMethodsTest.java

@@ -1047,6 +1047,44 @@ Integer fail() {
     }
   }
 
+  static final class DeduplicateModule extends AbstractModule {
+    @Provides
+    String provideString() {
+      return "";
+    }
+  }
+
+  public void testDeduplicateProviderMethodsBindings_sameInstance() {
+    Module module = new DeduplicateModule();
+    Guice.createInjector(Stage.PRODUCTION, module, module);
+  }
+
+  public void testDeduplicateProviderMethodsBindings_differentInstances() {
+    try {
+      Guice.createInjector(Stage.PRODUCTION, new DeduplicateModule(), new DeduplicateModule());
+      fail();
+    } catch (CreationException expected) {
+      assertContains(expected.getMessage(), "A binding to java.lang.String was already configured");
+    }
+  }
+
+  static final class DeduplicateStaticModule extends AbstractModule {
+    @Provides
+    static String provideString() {
+      return "";
+    }
+  }
+
+  public void testDeduplicateProviderMethodsBindings_sameInstance_staticMethod() {
+    Module module = new DeduplicateStaticModule();
+    Guice.createInjector(Stage.PRODUCTION, module, module);
+  }
+
+  public void testDeduplicateProviderMethodsBindings_differentInstances_staticMethod() {
+    Guice.createInjector(
+        Stage.PRODUCTION, new DeduplicateStaticModule(), new DeduplicateStaticModule());
+  }
+
   private void runNullableTest(Injector injector, Dependency<?> dependency, Module module) {
     switch (InternalFlags.getNullableProvidesOption()) {
       case ERROR: