[Haskell-cafe] with -XOverloadedStrings, when is the implied fromString floated out?

[Johannes Waldmann]

Dear Cafe,


with OverloadedStrings, the compiler inserts `fromString` applications
at String literals. I was wondering - are these floated out?

{-# language OverloadedStrings #-}

import Data.String
import Debug.Trace

data Foo = Foo deriving Show

instance IsString Foo where
  fromString "Foo" = trace "**fromString**" Foo

main =
  let { f Foo = "Foo" :: Foo; g _ = "Foo" :: Foo }
  in print $ map (f . g) [0..1]


With ghc -O1, I get

**fromString**
[Foo,Foo]

That's good - not just floated out, but also interned
(? - both "Foo" are really the same, just one call)


With ghc -00, and in ghci, I get

**fromString**
**fromString**
**fromString**
**fromString**
[Foo,Foo]

no floating here. Is there a way to get this floated in ghci?


The background of my question is that overloaded strings,
and ghci, are heavily used in Tidal Cycles
https://hackage.haskell.org/package/tidal

I guess it's mostly fine, because it's rare (in live
coding performance) that application code contains function definitions.


- J.