Implemented MonadST Aff (#213)

Author: prescientmoon

CHANGELOG.md

@@ -7,6 +7,7 @@ Notable changes to this project are documented in this file. The format is based
 Breaking changes:
 
 New features:
+- MonadST instance for Aff
 
 Bugfixes:
 

packages.dhall

@@ -1,4 +1,5 @@
 let upstream =
-      https://raw.githubusercontent.com/purescript/package-sets/prepare-0.15/src/packages.dhall
+      https://github.com/purescript/package-sets/releases/download/psc-0.15.4-20220725/packages.dhall
+        sha256:e56fbdf33a5afd2a610c81f8b940b413a638931edb41532164e641bb2a9ec29c
 
 in  upstream

spago.dhall

@@ -18,6 +18,7 @@
   , "partial"
   , "prelude"
   , "refs"
+  , "st"
   , "tailrec"
   , "transformers"
   , "unsafe-coerce"

src/Effect/Aff.purs

@@ -40,6 +40,8 @@ import Control.Lazy (class Lazy)
 import Control.Monad.Error.Class (class MonadError, class MonadThrow, throwError, catchError, try)
 import Control.Monad.Error.Class (try, throwError, catchError) as Exports
 import Control.Monad.Rec.Class (class MonadRec, Step(..))
+import Control.Monad.ST.Class (class MonadST, liftST)
+import Control.Monad.ST.Global (Global)
 import Control.Parallel (parSequence_, parallel)
 import Control.Parallel.Class (class Parallel)
 import Control.Parallel.Class (sequential, parallel) as Exports
@@ -115,6 +117,9 @@ instance monadEffectAff :: MonadEffect Aff where
 instance lazyAff :: Lazy (Aff a) where
   defer f = pure unit >>= f
 
+instance monadSTAff :: MonadST Global Aff where
+  liftST = liftST >>> liftEffect
+
 -- | Applicative for running parallel effects. Any `Aff` can be coerced to a
 -- | `ParAff` and back using the `Parallel` class.
 foreign import data ParAff :: Type -> Type