Swift: Add convenience member predicates to 'TypeDecl'.

Author: MathiasVP

swift/ql/lib/codeql/swift/elements/decl/TypeDecl.qll

@@ -1,5 +1,15 @@
 private import codeql.swift.generated.decl.TypeDecl
+private import codeql.swift.generated.type.Type
+private import codeql.swift.elements.type.AnyGenericType
 
 class TypeDecl extends TypeDeclBase {
   override string toString() { result = this.getName() }
+
+  TypeDecl getBaseTypeDecl(int i) { result = this.getBaseType(i).(AnyGenericType).getDeclaration() }
+
+  TypeDecl getABaseTypeDecl() { result = this.getBaseTypeDecl(_) }
+
+  TypeDecl getDerivedTypeDecl(int i) { result.getBaseTypeDecl(i) = this }
+
+  TypeDecl getADerivedTypeDecl() { result = this.getDerivedTypeDecl(_) }
 }