public static Expr Create(TypeName typeName) => new SizeofType(typeName);
public static Expr Create(TypeName typeName, Expr expr) => new TypeCast(typeName, expr);
public SizeofType(TypeName typeName) { this.TypeName = typeName; }
public TypeCast(TypeName typeName, Expr expr) { this.TypeName = typeName; this.Expr = expr; }