Missing String import with position tokens in Haskell backend

[MrQubo]

Minimal example:

position token Tok '_' ;
Entrypoint . Entrypoint ::= Tok ;

Save this under bug.cf in some temporary directory, run bnfc bug.cf, run runhaskell TestBug.hs. This is the error:

AbsBug.hs:18:36: error:
    Not in scope: type constructor or class ‘String’
   |
18 | newtype Tok = Tok ((C.Int, C.Int), String)
   |                                    ^^^^^^

I've only confirmed this bug with 2.9.1 release (from stackage) and not with master, but after quick look into code it seems like this wasn't fixed.

The cause of this bug is probably that here

bnfc/source/src/BNFC/Backend/Haskell/CFtoAbstract.hs

Line 154 in 94cc080

|| hasIdentLike && tokenText == StringToken && s == "String")

hasIdentLike is used, which only includes non-position tokens as described in this comment

bnfc/source/src/BNFC/CF.hs

Lines 758 to 759 in 94cc080

	-- Excludes position tokens.
	hasIdentLikeTokens :: CFG g -> Bool

.

[andreasabel]

Thanks for the report, @MrQubo, I can confirm that this is a regression in 2.9.1.