Can’t parse “a-b”, whereas “a - b” is fine

[dato]

Hello! This might be a bug for HSE… but perhaps there’s an explanation or restriction that I’m missing.

Consider the following code:

module Foo where

test a b = a - b

This is correctly parsed:

% structured-haskell-mode check decl < foo.hs
% echo $?
0

However, if I change a - b to a-b (without surrounding spaces), I get:

% structured-haskell-mode check decl < foo.hs
structured-haskell-mode: Parse error: a-b

Any tips?

Many thanks in advance!

[chrisdone]

No idea. :-)

[alanz]

I suspect the parser is seeing "a-b" as an identifier or operator and it is invalid.