Java: Add MemberType

java/change-notes/2021-04-14-membertype.md

@@ -0,0 +1,2 @@
+lgtm,codescanning
+* A CodeQL class `MemberType` is introduced to describe nested classes. Its `getQualifiedName` method returns `$`-delimited nested type names (for example, `mypackage.Outer$Middle$Inner`), where previously the same type would be named differently depending on whether it was addressed as a `NestedType` or a `Member`.

java/ql/src/Performance/InnerClassCouldBeStatic.ql

@@ -100,8 +100,7 @@ predicate potentiallyStatic(InnerClass c) {
     m = a.getEnclosingCallable() and
     m.getDeclaringType() = c
   ) and
-  not c instanceof AnonymousClass and
-  not c instanceof LocalClass and
+  c instanceof MemberType and
   forall(
     InnerClass other // If nested and non-static, ...
   |

java/ql/src/semmle/code/java/PrintAst.qll

@@ -433,9 +433,7 @@ final class ClassInterfaceNode extends ElementNode {
     or
     result.(FieldDeclaration).getAField().getDeclaringType() = ty
     or
-    result.(NestedType).getEnclosingType().getSourceDeclaration() = ty and
-    not result instanceof AnonymousClass and
-    not result instanceof LocalClass
+    result.(MemberType).getEnclosingType().getSourceDeclaration() = ty
     or
     isInitBlock(ty, result)
   }

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

@@ -517,7 +517,12 @@ class RefType extends Type, Annotatable, Modifiable, @reftype {
   /** Holds if this is a top-level type, which is not nested inside any other types. */
   predicate isTopLevel() { this instanceof TopLevelType }
 
-  /** Holds if this type is declared in a specified package with the specified name. */
+  /**
+   * Holds if this type is declared in a specified package with the specified name.
+   *
+   * For nested types the name of the nested type is prefixed with a `$` and appended
+   * to the name of the enclosing type, which might be a nested type as well.
+   */
   predicate hasQualifiedName(string package, string type) {
     this.getPackage().hasName(package) and type = this.nestedName()
   }
@@ -532,15 +537,26 @@ class RefType extends Type, Annotatable, Modifiable, @reftype {
   }
 
   /**
-   * Gets the qualified name of this type.
+   * Gets the qualified name of this type, consisting of the package name followed by
+   * a `.` and the name of this type.
+   *
+   * For nested types the name of the nested type is prefixed with a `$` and appended
+   * to the name of the enclosing type, which might be a nested type as well. For example:
+   * `java.lang.Thread$State`.
    */
   string getQualifiedName() {
     exists(string pkgName | pkgName = getPackage().getName() |
       if pkgName = "" then result = nestedName() else result = pkgName + "." + nestedName()
     )
   }
 
-  /** Gets the nested name of this type. */
+  /**
+   * Gets the nested name of this type.
+   *
+   * If this type is not a nested type, the result is the same as `getName()`.
+   * Otherwise the name of the nested type is prefixed with a `$` and appended to
+   * the name of the enclosing type, which might be a nested type as well.
+   */
   string nestedName() {
     not this instanceof NestedType and result = this.getName()
     or
@@ -788,6 +804,21 @@ class NestedType extends RefType {
   }
 }
 
+/**
+ * A nested type which is a direct member of the enclosing type,
+ * that is, neither an anonymous nor local class.
+ */
+class MemberType extends NestedType, Member {
+  /**
+   * Gets the qualified name of this member type.
+   *
+   * The qualified name consists of the package name, a `.`, the name of the declaring
+   * type (which might be a nested or member type as well), followed by a `$` and the
+   * name of this member type. For example: `java.lang.Thread$State`.
+   */
+  override string getQualifiedName() { result = NestedType.super.getQualifiedName() }
+}
+
 /**
  * A class declared within another type.
  *
@@ -797,8 +828,9 @@ class NestedType extends RefType {
 class NestedClass extends NestedType, Class { }
 
 /**
- * An inner class is a nested class that is neither
- * explicitly nor implicitly declared static.
+ * An inner class is a nested class that is neither explicitly nor
+ * implicitly declared static. This includes anonymous and local
+ * classes.
  */
 class InnerClass extends NestedClass {
   InnerClass() { not this.isStatic() }

java/ql/src/semmle/code/java/frameworks/play/Play.qll

@@ -44,14 +44,8 @@ class PlayAddCsrfTokenAnnotation extends Annotation {
 /**
  * The type `play.libs.F.Promise<Result>`.
  */
-class PlayAsyncResultPromise extends Member {
-  PlayAsyncResultPromise() {
-    exists(Class c |
-      c.hasQualifiedName("play.libs", "F") and
-      this = c.getAMember() and
-      this.getQualifiedName() = "F.Promise<Result>"
-    )
-  }
+class PlayAsyncResultPromise extends MemberType {
+  PlayAsyncResultPromise() { hasQualifiedName("play.libs", "F$Promise<Result>") }
 }
 
 /**