Add a first version of the check for incorrect method signature

error-prone-contrib/src/main/java/tech/picnic/errorprone/bugpatterns/MissingRefasterAnnotationCheck.java

@@ -0,0 +1,53 @@
+package tech.picnic.errorprone.bugpatterns;
+
+import static com.google.errorprone.matchers.ChildMultiMatcher.MatchType.AT_LEAST_ONE;
+import static com.google.errorprone.matchers.Matchers.annotations;
+import static com.google.errorprone.matchers.Matchers.anyOf;
+import static com.google.errorprone.matchers.Matchers.isType;
+
+import com.google.auto.service.AutoService;
+import com.google.errorprone.BugPattern;
+import com.google.errorprone.BugPattern.LinkType;
+import com.google.errorprone.BugPattern.SeverityLevel;
+import com.google.errorprone.BugPattern.StandardTags;
+import com.google.errorprone.VisitorState;
+import com.google.errorprone.bugpatterns.BugChecker;
+import com.google.errorprone.bugpatterns.BugChecker.ClassTreeMatcher;
+import com.google.errorprone.matchers.Description;
+import com.google.errorprone.matchers.MultiMatcher;
+import com.sun.source.tree.AnnotationTree;
+import com.sun.source.tree.ClassTree;
+import com.sun.source.tree.MethodTree;
+import com.sun.source.tree.Tree;
+
+/** A {@link BugChecker} that flags likely missing Refaster annotations. */
+@AutoService(BugChecker.class)
+@BugPattern(
+    name = "MissingRefasterAnnotation",
+    summary = "The Refaster template contains a method without any Refaster annotations",
+    linkType = LinkType.NONE,
+    severity = SeverityLevel.WARNING,
+    tags = StandardTags.LIKELY_ERROR)
+public final class MissingRefasterAnnotationCheck extends BugChecker implements ClassTreeMatcher {
+  private static final long serialVersionUID = 1L;
+  private static final MultiMatcher<Tree, AnnotationTree> HAS_REFASTER_ANNOTATION =
+      annotations(
+          AT_LEAST_ONE,
+          anyOf(
+              isType("com.google.errorprone.refaster.annotation.Placeholder"),
+              isType("com.google.errorprone.refaster.annotation.BeforeTemplate"),
+              isType("com.google.errorprone.refaster.annotation.AfterTemplate")));
+
+  @Override
+  public Description matchClass(ClassTree tree, VisitorState state) {
+    long methodTypes =
+        tree.getMembers().stream()
+            .filter(member -> member.getKind() == Tree.Kind.METHOD)
+            .map(MethodTree.class::cast)
+            .map(method -> HAS_REFASTER_ANNOTATION.matches(method, state))
+            .distinct()
+            .count();
+
+    return methodTypes < 2 ? Description.NO_MATCH : buildDescription(tree).build();
+  }
+}

error-prone-contrib/src/main/java/tech/picnic/errorprone/refastertemplates/ImmutableListTemplates.java

@@ -67,8 +67,8 @@ final class ImmutableListTemplates {
     }
 
     @AfterTemplate
-    ImmutableList<T> after(T element) {
-      return ImmutableList.of(element);
+    ImmutableList<T> after(T secondName) {
+      return ImmutableList.of(secondName);
     }
   }
 

error-prone-contrib/src/test/java/tech/picnic/errorprone/bugpatterns/MissingRefasterAnnotationCheckTest.java

@@ -0,0 +1,78 @@
+package tech.picnic.errorprone.bugpatterns;
+
+import com.google.common.base.Predicates;
+import com.google.errorprone.CompilationTestHelper;
+import org.junit.jupiter.api.Test;
+
+public final class MissingRefasterAnnotationCheckTest {
+  private final CompilationTestHelper compilationTestHelper =
+      CompilationTestHelper.newInstance(MissingRefasterAnnotationCheck.class, getClass())
+          .expectErrorMessage(
+              "X",
+              Predicates.containsPattern(
+                  "The Refaster template contains a method without any Refaster annotations"));
+
+  @Test
+  public void testIdentification() {
+    compilationTestHelper
+        .addSourceLines(
+            "A.java",
+            "import com.google.errorprone.refaster.annotation.AfterTemplate;",
+            "import com.google.errorprone.refaster.annotation.AlsoNegation;",
+            "import com.google.errorprone.refaster.annotation.BeforeTemplate;",
+            "import java.util.Map;",
+            "",
+            "class A {",
+            "  // BUG: Diagnostic matches: X",
+            "  static final class MethodLacksBeforeTemplateAnnotation {",
+            "    @BeforeTemplate",
+            "    boolean before1(String string) {",
+            "      return string.equals(\"\");",
+            "    }",
+            "",
+            "    // @BeforeTemplate is missing",
+            "    boolean before2(String string) {",
+            "      return string.length() == 0;",
+            "    }",
+            "",
+            "    @AfterTemplate",
+            "    @AlsoNegation",
+            "    boolean after(String string) {",
+            "      return string.isEmpty();",
+            "    }",
+            "  }",
+            "",
+            "  // BUG: Diagnostic matches: X",
+            "  static final class MethodLacksAfterTemplateAnnotation {",
+            "    @BeforeTemplate",
+            "    boolean before(String string) {",
+            "      return string.equals(\"\");",
+            "    }",
+            "",
+            "    // @AfterTemplate is missing",
+            "    boolean after(String string) {",
+            "      return string.isEmpty();",
+            "    }",
+            "  }",
+            "",
+            "  // BUG: Diagnostic matches: X",
+            "  abstract class MethodLacksPlaceholderAnnotation<K, V> {",
+            "    // @Placeholder is missing",
+            "    abstract V function(K key);",
+            "",
+            "    @BeforeTemplate",
+            "    void before(Map<K, V> map, K key) {",
+            "      if (!map.containsKey(key)) {",
+            "        map.put(key, function(key));",
+            "      }",
+            "    }",
+            "",
+            "    @AfterTemplate",
+            "    void after(Map<K, V> map, K key) {",
+            "      map.computeIfAbsent(key, k -> function(k));",
+            "    }",
+            "  }",
+            "}")
+        .doTest();
+  }
+}