One AST is meant to be a target parser and tries to adhere as much as possible
to the spec. The other is a simplified version of that AST meant for execution.
Also newtypes have been replaced by type synonyms and NonEmpty lists are being
used where it makes sense.
The current parser will fail parsing floats because it parses an int,
and then stumbles on the dot.
To fix I interpret the value with the scientific library which already
is a dependency through attoparsec, so we're not introducing any extra
downloads or compiling.
I think this is still subtly wrong because "10.0" will be parsed as
ValueInt, but because input argument ints are allowed to be coerced
into doubles (according to the spec) this is probably acceptable.
Aside of making the definition of Schemas easier, it takes care of
issues like nested aliases which previously wasn't possible. The naming
of the DSL functions is still provisional.
The `Schema` has been overhauled to make `Output` monomorphic.
Traversing the `GraphQL` document is handled implicitly while defining
the `Schema`.
The 4th end-to-end test from `graphql-js` has been ported.
The first end-to-end test taken from `graphql-js` passes but this still
needs to be extended to support more general cases.
- `Data.GraphQL.Schema` has been heavily modified to support the
execution model. More drastic changes are expected in this module.
- When defining a `Schema` ordinary functions taking fields as input are
being used instead of maps. This makes the implementation of `execute`
easier, and, arguably, makes `Schema` definitions more *Haskellish*.
- Drop explicit `unordered-containers` dependency. `Aeson.Value`s and
field functions should be good enough for now.
This also includes a new type for Value String.
The tests fail now, although it parses successfully. I'll use a pretty
printer in next commit so that it's easier to spot the differences.
Onces this is working I'll add the rest of the escaped characters.
