Allow TypeApplications syntax to be used to instantiate type variables in SPECIALISE pragmas

Currently the SPECIALISE pragma requires that the user repeat the entire type of a binding to instantiate its types. This is often needlessly verbose and quite tiresome. Instead, why not allow the user to write the desired type as an application with TypeApplications?

For instance, currently we might write,

foldWithOptionsAndParser :: forall m params. ( MonadIO m, MonadMask m, ToRow params )
                         => FoldOptions
                         -> RowParser row
                         -> Connection
                         -> Query
                         -> params
                         -> a
                         -> (a -> row -> m a)
                         -> m a
foldWithOptionsAndParser opts parser conn template qs a f = ...
{-# SPECIALISE
    foldWithOptionsAndParser :: FoldOptions -> RowParser row -> Connection -> Query -> params -> a
                             -> (a -> row -> IO a) -> IO a #-}

Instead we might want to write,

{-# SPECIALISE foldWithOptionsAndParser @IO #-}

Trac metadata

Trac field	Value
Version	8.0.1
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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