primitivesList :: (MonadIO m) => [(MethodName, (Arity, [Value] -> m Value))]

I want to extract the method names in a separate list, so I write:

primitivesNames :: [MethodName]
primitivesNames = map fst primitivesList

We apply ghc, and the result is:

tingle-0.7.2.hs:408:26:
    Ambiguous type variable `m' in the constraint:
      `MonadIO m'
        arising from a use of `primitivesList' at tingle-0.7.2.hs:408:26-39
    Probable fix: add a type signature that fixes these type variable(s)

Line 408 is the "primitivesNames = ..." line.

Is there a way to fix this just by adding typing information ?  I do not
see how or where...

When a CAF has polymorphic type, it may be evaluated multiple times,
once per type.

: > primitivesList :: (MonadIO m) => [(MethodName, (Arity, [Value] -> m Value))]

: This is not permissible as a top-level declaration without
: -XNoMonomorphismRestriction / -fno-monomorphism-restriction.

: When a CAF has polymorphic type, it may be evaluated multiple times,
: once per type.

: > primitivesNames :: [MethodName]
: > primitivesNames = map fst primitivesList

: The evaluation of primitivesList depends on the choice of (MonadIO m).
: primitiveNames does not.  See the problem?

Thank you.  That makes lots of sense.  I was looking for the problem in
the newly added code, but the code that had been functioning for
weeks was the real culprit.

It does indeed work if I change the type to:

primitivesList :: M.Map MethodName
                        (Arity, [Value] -> ErrorT String (StateT MyState IO) Value)