View non-exposed library functions while developing in Haskell

Question

I made a mistake in another question that could have been solved by viewing

:t myfunctionofinterest

for a function I was using in a librar

Answer 1

Quoting the GHCi docs:

The :module command provides a way to do two things that cannot be done with ordinary import declarations:

• :module supports the * modifier on modules, which opens the full top-level scope of a module, rather than just its exports.

The additional * makes GHCi load the bytecode version of the module. This will not be as performant, but you'll get access to unexported bindings.

Example:

λ> :m *MyLib
λ> :t myfunctionofinterest

If you get

module 'MyLib' is not interpreted; try ':add *MyLib' first

you may have to do :load first (the advice about :add doesn't always do the trick):

λ> :l *MyLib
λ> :m *MyLib
λ> :t myfunctionofinterest