Transaction class constraints #147
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This ensures fully qualified object names end up in the representations, which is nice, but more importantly, it ensures the schema is immune to the user's search_path setting.
Still very early work. The `InTxnT` ctor must be exposed for some of the hoisting, and it's not clear how we can allow hoisting monadic type parameters of custom types without doing so.
The monadic type parameter forced hoisting in lots of places where it was purely unnecessary. This even helped clean up some of the code.
A callback that runs in `InTxnT m` needs to be callable from more than one base monad. In one branch of code, it's called from `m`, but in another, it's called from `ResourceT m`. Its type is clearly insufficient, so we'll probably need a class.
actions in the code. This is a "cheap "escape from more restrictive monadic composition, since now last actions must be able to run in _any_ monad that satisfies a few class constraints, rather than constraints based on the base monad. This is fine for our codebase as it is, but is over-restrictive.
- Lots of type applications to guide type inference - Lots of apparently redundant class constraints - Lots of `txn ~ InTxnT (ResourceT m)`, which should be unnecessary - Pushing `MonadResource m` constraint up, beyond where needed It's time to start tidying up
In general, this pushes MonadResource deeper into where it's necessary, but inside the Internal module it is actually added to one function where it isn't strictly necessary, but where it better aligns monadic types with the other functions, reducing the need for lifting
It is possible to declare a function that is not constrained with `NotInTxn m`, yet it called `beginCommitTxnBracket` by using `liftIO`.
Otherwise retry tests fail, and that's something I prefer to fix some other time.
With the new transaction class constraints, we can be much more certain every transaction is read-write
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Fixes #133