8265253: javac -Xdoclint:all gives "no comment" warning for code that can't be commented

Reviewed-by: hannesw

src/jdk.javadoc/share/classes/jdk/javadoc/internal/doclint/Checker.java

@@ -45,9 +45,12 @@ import javax.lang.model.element.Element;
 import javax.lang.model.element.ElementKind;
 import javax.lang.model.element.ExecutableElement;
 import javax.lang.model.element.Name;
+import javax.lang.model.element.NestingKind;
+import javax.lang.model.element.TypeElement;
 import javax.lang.model.element.VariableElement;
 import javax.lang.model.type.TypeKind;
 import javax.lang.model.type.TypeMirror;
+import javax.lang.model.util.Elements;
 import javax.tools.Diagnostic.Kind;
 import javax.tools.JavaFileObject;
 
@@ -188,7 +191,7 @@ public class Checker extends DocTreePathScanner<Void, Void> {
                     if (isNormalClass(p.getParentPath())) {
                         reportMissing("dc.default.constructor");
                     }
-                } else if (!isOverridingMethod) {
+                } else if (!isOverridingMethod && !isSynthetic() && !isAnonymous()) {
                     reportMissing("dc.missing.comment");
                 }
                 return null;
@@ -1158,6 +1161,15 @@ public class Checker extends DocTreePathScanner<Void, Void> {
                 || env.types.isAssignable(t, env.java_lang_RuntimeException));
     }
 
+    private boolean isSynthetic() {
+        return env.elements.getOrigin(env.currElement) == Elements.Origin.SYNTHETIC;
+    }
+
+    private boolean isAnonymous() {
+        return (env.currElement instanceof TypeElement te)
+                && te.getNestingKind() == NestingKind.ANONYMOUS;
+    }
+
     private boolean isDefaultConstructor() {
         switch (env.currElement.getKind()) {
             case CONSTRUCTOR:

test/langtools/tools/doclint/AnonClassTest.java

@@ -0,0 +1,37 @@
+/*
+ * @test /nodynamiccopyright/
+ * @modules jdk.javadoc/jdk.javadoc.internal.doclint
+ * @build DocLintTester
+ * @run main DocLintTester -Xmsgs:-missing AnonClassTest.java
+ * @run main DocLintTester -Xmsgs:missing -ref AnonClassTest.out AnonClassTest.java
+ */
+
+/** Class comment. */
+public enum AnonClassTest {
+
+    /**
+     * E1 comment.
+     * This member uses an anonymous class, which should not trigger a warning.
+     */
+    E1 {
+        // no comment: should give warning
+        int field;
+
+        // no comment: should give warning
+        void m() { }
+
+        // no comment required: should not give warning
+        @java.lang.Override
+        public void m1() { }
+    },
+
+    // This member also uses an anonymous class,
+    // but there should only be a single warning for the member itself.
+    E2 { },
+
+    /** E3 comment. This member does not use an anonymous class. */
+    E3;
+
+    /** Method comment. */
+    public void m1() { }
+}

test/langtools/tools/doclint/AnonClassTest.out

@@ -0,0 +1,10 @@
+AnonClassTest.java:18: warning: no comment
+        int field;
+            ^
+AnonClassTest.java:21: warning: no comment
+        void m() { }
+             ^
+AnonClassTest.java:30: warning: no comment
+    E2 { },
+    ^
+3 warnings