[mulander]

> But with all that, as Joe Armstrong once jeered, no amount of type checking would catch the following bogus code:

It is worth to note that the stated problem, of accessing a file after it is closed was addressed in the Phd thesis by [1] Joe Armstrong in which he suggested a solution for exactly this problem by introducing a new testing & development methodology he named "protocol checkers" (9.1 Protocols, page 195). Relevant quote from the thesis:

> Given a protocol which is specified in a manner similar to the above it is possible to write a simple “protocol checking” program which can be placed between any pair of processes.

The protocol is a state machine, which would detect the attempt to write to a file after it was closed.

[1] - https://erlang.org/download/armstrong_thesis_2003.pdf

[sidpatil]

Another term for this is typestate analysis.

https://en.wikipedia.org/wiki/Typestate_analysis