QL: Merge pull request #15 from github/inheritance

Resolve inheritable members (fields and member predicates)

ql/src/codeql_ql/ast/Ast.qll

@@ -106,6 +106,8 @@ class Predicate extends TPredicate, AstNode {
    */
   VarDecl getParameter(int i) { none() }
 
+  int getArity() { result = count(getParameter(_)) }
+
   // TODO: ReturnType.
   override AstNode getAChild(string pred) {
     pred = "getBody" and result = this.getBody()
@@ -212,11 +214,22 @@ class ClassPredicate extends TClassPredicate, Predicate {
 
   override Class getParent() { result.getAClassPredicate() = this }
 
+  predicate isPrivate() {
+    exists(Generated::ClassMember member |
+      pred = member.getChild(_) and
+      member.getAFieldOrChild().(Generated::Annotation).getName().getValue() = "private"
+    )
+  }
+
   override VarDecl getParameter(int i) {
     toGenerated(result) =
       rank[i](Generated::VarDecl decl, int index | decl = pred.getChild(index) | decl order by index)
   }
 
+  ClassType getDeclaringType() { result.getDeclaration() = getParent() }
+
+  predicate overrides(ClassPredicate other) { predOverrides(this, other) }
+
   override AstNode getAChild(string pred_name) {
     pred_name = "getBody" and result = this.getBody()
     or
@@ -270,6 +283,18 @@ class VarDecl extends TVarDecl, AstNode {
 
   TypeExpr getType() { toGenerated(result) = var.getChild(0) }
 
+  predicate isPrivate() {
+    exists(Generated::ClassMember member |
+      var = member.getChild(_).(Generated::Field).getChild() and
+      member.getAFieldOrChild().(Generated::Annotation).getName().getValue() = "private"
+    )
+  }
+
+  /** If this is a field, returns the class type that declares it. */
+  ClassType getDeclaringType() { result.getDeclaration().getAField() = this }
+
+  predicate overrides(VarDecl other) { fieldOverrides(this, other) }
+
   override AstNode getAChild(string pred) { pred = "getType" and result = this.getType() }
 }
 
@@ -451,6 +476,9 @@ class Class extends TClass, TypeDeclaration, ModuleDeclaration {
     toGenerated(result) = cls.getChild(_).(Generated::TypeUnionBody).getChild(_)
   }
 
+  /** Gets the class type defined by this class declaration. */
+  Type getType() { result.getDeclaration() = this }
+
   override AstNode getAChild(string pred) {
     pred = "getAliasType" and result = this.getAliasType()
     or

ql/src/codeql_ql/ast/internal/Type.qll

@@ -77,6 +77,63 @@ class ClassType extends Type, TClass {
     or
     result = super.getAnInternalSuperType()
   }
+
+  ClassPredicate getClassPredicate(string name, int arity) {
+    result = classPredCandidate(this, name, arity) and
+    not exists(ClassPredicate other | other = classPredCandidate(this, name, arity) |
+      other.getDeclaringType().getASuperType+() = result.getDeclaringType()
+    )
+  }
+
+  VarDecl getField(string name) {
+    result = fieldCandidate(this, name) and
+    not exists(VarDecl other | other = fieldCandidate(this, name) |
+      other.getDeclaringType().getASuperType+() = result.getDeclaringType()
+    )
+  }
+}
+
+private ClassPredicate declaredPred(ClassType ty, string name, int arity) {
+  result = ty.getDeclaration().getAClassPredicate() and
+  result.getName() = name and
+  result.getArity() = arity
+}
+
+private ClassPredicate classPredCandidate(ClassType ty, string name, int arity) {
+  result = declaredPred(ty, name, arity)
+  or
+  not exists(declaredPred(ty, name, arity)) and
+  result = inherClassPredCandidate(ty, name, arity)
+}
+
+private ClassPredicate inherClassPredCandidate(ClassType ty, string name, int arity) {
+  result = classPredCandidate(ty.getASuperType(), name, arity) and
+  not result.isPrivate()
+}
+
+predicate predOverrides(ClassPredicate sub, ClassPredicate sup) {
+  sup = inherClassPredCandidate(sub.getDeclaringType(), sub.getName(), sub.getArity())
+}
+
+private VarDecl declaredField(ClassType ty, string name) {
+  result = ty.getDeclaration().getAField() and
+  result.getName() = name
+}
+
+private VarDecl fieldCandidate(ClassType ty, string name) {
+  result = declaredField(ty, name)
+  or
+  not exists(declaredField(ty, name)) and
+  result = inherFieldCandidate(ty, name)
+}
+
+private VarDecl inherFieldCandidate(ClassType ty, string name) {
+  result = fieldCandidate(ty.getASuperType(), name) and
+  not result.isPrivate()
+}
+
+predicate fieldOverrides(VarDecl sub, VarDecl sup) {
+  sup = inherFieldCandidate(sub.getDeclaringType(), sub.getName())
 }
 
 class ClassCharType extends Type, TClassChar {