Merge pull request #7988 from Marcono1234/marcono1234/sealed-types-predicates

Java: Add predicates for sealed classes

java/ql/lib/change-notes/2022-02-14-sealed-classes-predicates.md

@@ -0,0 +1,4 @@
+---
+category: feature
+---
+* Added predicates `ClassOrInterface.getAPermittedSubtype` and `isSealed` exposing information about sealed classes.

java/ql/lib/semmle/code/java/Type.qll

@@ -913,6 +913,12 @@ class ClassOrInterface extends RefType, @classorinterface {
     not this.isProtected() and
     not this.isPublic()
   }
+
+  /** Gets a permitted subtype in case this class or interface is a sealed class (Java 17 feature). */
+  ClassOrInterface getAPermittedSubtype() { permits(this, result) }
+
+  /** Holds if this class or interface is explicitly or implicitly a sealed class (Java 17 feature). */
+  predicate isSealed() { exists(this.getAPermittedSubtype()) }
 }
 
 private string getAPublicObjectMethodSignature() {

java/ql/test/library-tests/types/sealed-classes/SealedClasses.expected

@@ -0,0 +1,12 @@
+| SealedClasses.java:5:25:5:44 | ExplicitPermitsClass | SealedClasses.java:7:25:7:38 | SealedSubClass |
+| SealedClasses.java:5:25:5:44 | ExplicitPermitsClass | SealedClasses.java:10:29:10:45 | NonSealedSubClass |
+| SealedClasses.java:5:25:5:44 | ExplicitPermitsClass | SealedClasses.java:12:24:12:36 | FinalSubClass |
+| SealedClasses.java:7:25:7:38 | SealedSubClass | SealedClasses.java:8:24:8:39 | FinalSubSubClass |
+| SealedClasses.java:17:22:17:45 | ExplicitPermitsInterface | SealedClasses.java:7:25:7:38 | SealedSubClass |
+| SealedClasses.java:17:22:17:45 | ExplicitPermitsInterface | SealedClasses.java:19:22:19:39 | SealedSubInterface |
+| SealedClasses.java:17:22:17:45 | ExplicitPermitsInterface | SealedClasses.java:22:26:22:46 | NonSealedSubInterface |
+| SealedClasses.java:17:22:17:45 | ExplicitPermitsInterface | SealedClasses.java:24:12:24:22 | RecordClass |
+| SealedClasses.java:17:22:17:45 | ExplicitPermitsInterface | SealedClasses.java:26:10:26:18 | EnumClass |
+| SealedClasses.java:19:22:19:39 | SealedSubInterface | SealedClasses.java:20:24:20:42 | FinalInterfaceClass |
+| SealedClasses.java:32:22:32:45 | ImplicitPermitsInterface | SealedClasses.java:33:26:33:52 | ImplicitPermitsSubInterface |
+| SealedClasses.java:37:10:37:29 | ImplicitlySealedEnum | SealedClasses.java:38:9:38:9 | new ImplicitlySealedEnum(...) { ... } |

java/ql/test/library-tests/types/sealed-classes/SealedClasses.java

@@ -0,0 +1,40 @@
+class SealedClasses {
+    static class NonSealedClass { }
+    interface NonSealedInterface { }
+
+    static sealed class ExplicitPermitsClass permits SealedSubClass, NonSealedSubClass, FinalSubClass { }
+
+    static sealed class SealedSubClass extends ExplicitPermitsClass implements ExplicitPermitsInterface { }
+    static final class FinalSubSubClass extends SealedSubClass { }
+
+    static non-sealed class NonSealedSubClass extends ExplicitPermitsClass { }
+
+    static final class FinalSubClass extends ExplicitPermitsClass { }
+
+    static class ExtendingNonSealedClass extends NonSealedSubClass { }
+
+
+    sealed interface ExplicitPermitsInterface permits SealedSubClass, SealedSubInterface, NonSealedSubInterface, RecordClass, EnumClass { }
+
+    sealed interface SealedSubInterface extends ExplicitPermitsInterface { }
+    static final class FinalInterfaceClass implements SealedSubInterface { }
+
+    non-sealed interface NonSealedSubInterface extends ExplicitPermitsInterface { }
+
+    record RecordClass() implements ExplicitPermitsInterface { }
+
+    enum EnumClass implements ExplicitPermitsInterface { }
+
+    interface ExtendingNonSealedInterface extends NonSealedSubInterface { }
+
+
+    // `permits` clause may be omitted if all subtypes are in the same compilation unit
+    sealed interface ImplicitPermitsInterface { }
+    non-sealed interface ImplicitPermitsSubInterface extends ImplicitPermitsInterface { }
+
+
+    // Enum with anonymous subclass is implicitly sealed, see JLS 17 8.9
+    enum ImplicitlySealedEnum {
+        A { }
+    }
+}

java/ql/test/library-tests/types/sealed-classes/SealedClasses.ql

@@ -0,0 +1,5 @@
+import java
+
+from ClassOrInterface c
+where c.fromSource()
+select c, c.getAPermittedSubtype()

java/ql/test/library-tests/types/sealed-classes/options

@@ -0,0 +1 @@
+//semmle-extractor-options: --javac-args --enable-preview -source 16 -target 16