Generics.SYB.GHC

Custom SYB traversals explicitly designed for operating over the GHC AST.

Documentation

genericIsSubspan

Arguments

:: forall ast. Typeable ast

=> Proxy (Located ast)

The type of nodes we'd like to consider.

-> SrcSpan

-> GenericQ (Maybe (Bool, ast))

A generic query intended to be used for calling smallestM and largestM. If the current node is a Located, returns whether or not the given SrcSpan is a subspan. For all other nodes, returns Nothing, which indicates uncertainty. The search strategy in smallestM et al. will continue searching uncertain nodes.

mkBindListT :: forall b m. (Data b, Monad m) => (Int -> b -> m [b]) -> GenericM m

Lift a function that replaces a value with several values into a generic function. The result doesn't perform any searching, so should be driven via everywhereM or friends.

The Int argument is the index in the list being bound.

everywhereM' :: forall m. Monad m => GenericM m -> GenericM m

Apply a monadic transformation everywhere in a top-down manner.

smallestM :: forall m a. Monad m => GenericQ (Maybe (Bool, a)) -> (a -> GenericM m) -> GenericM m

Apply the given GenericM at all every node whose children fail the GenericQ, but which passes the query itself.

The query must be a monotonic function when it returns Just. That is, if s is a subtree of t, q t should return Just True if q s does. It is the True-to-false edge of the query that triggers the transformation.

Why is the query a Maybe Bool? The GHC AST intersperses Located nodes with data nodes, so for any given node we can only definitely return an answer if it's a Located. See genericIsSubspan for how this parameter is used.

largestM :: forall m a. Monad m => GenericQ (Maybe (Bool, a)) -> (a -> GenericM m) -> GenericM m

Apply the given GenericM at every node that passes the GenericQ, but don't descend into children if the query matches. Because this traversal is root-first, this policy will find the largest subtrees for which the query holds true.

Why is the query a Maybe Bool? The GHC AST intersperses Located nodes with data nodes, so for any given node we can only definitely return an answer if it's a Located. See genericIsSubspan for how this parameter is used.