Error on component methods with type variables.

These will always lead to a missing binding error, but the processor sometimes also throws (e.g. in InjectBindingRegistry.getOrFindMembersInjectionBinding, which assumes a valid key for members injection).

RELNOTES=Adds a new error for component methods with type variables

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=175732905

java/dagger/internal/codegen/ComponentValidator.java

@@ -173,6 +173,10 @@ public ComponentValidationReport validate(
               List<? extends VariableElement> parameters = method.getParameters();
               TypeMirror returnType = resolvedMethod.getReturnType();
 
+              if (!resolvedMethod.getTypeVariables().isEmpty()) {
+                builder.addError("Component methods cannot have type variables", method);
+              }
+
               // abstract methods are ones we have to implement, so they each need to be validated
               // first, check the return type. if it's a subcomponent, validate that method as such.
               Optional<AnnotationMirror> subcomponentAnnotation =

javatests/dagger/internal/codegen/GenericMethodsTest.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright (C) 2017 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.internal.codegen;
+
+import static com.google.testing.compile.CompilationSubject.assertThat;
+import static dagger.internal.codegen.Compilers.daggerCompiler;
+
+import com.google.testing.compile.Compilation;
+import com.google.testing.compile.JavaFileObjects;
+import javax.tools.JavaFileObject;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+@RunWith(JUnit4.class)
+public class GenericMethodsTest {
+  @Test
+  public void parameterizedComponentMethods() {
+    JavaFileObject component =
+        JavaFileObjects.forSourceLines(
+            "test.TestComponent",
+            "package test;",
+            "",
+            "import dagger.Component;",
+            "import dagger.MembersInjector;",
+            "import java.util.Set;",
+            "",
+            "@Component",
+            "interface TestComponent {",
+            "  <T1> void injectTypeVariable(T1 type);",
+            "  <T2> MembersInjector<T2> membersInjector();",
+            "  <T3> Set<T3> setOfT();",
+            "  <UNUSED> TestComponent unused();",
+            "}");
+    Compilation compilation = daggerCompiler().compile(component);
+    assertThat(compilation).failed();
+    assertThat(compilation)
+        .hadErrorContaining("cannot have type variables")
+        .inFile(component)
+        .onLineContaining("<T1>");
+    assertThat(compilation)
+        .hadErrorContaining("cannot have type variables")
+        .inFile(component)
+        .onLineContaining("<T2>");
+    assertThat(compilation)
+        .hadErrorContaining("cannot have type variables")
+        .inFile(component)
+        .onLineContaining("<T3>");
+    assertThat(compilation)
+        .hadErrorContaining("cannot have type variables")
+        .inFile(component)
+        .onLineContaining("<UNUSED>");
+  }
+}