Every haskell expression has a type and types are always checked at \emph{compile-time}. Programs with errors will not compile and definitely not run. \vspace{\baselineskip} \\ It is possible to simulate dynamic types however, i.e. types which may be converted to the type you need them in, following rigid rules. In the end, they are still statically type-checked (as in: the compiler always knows what's going on).