HaskellWiki:Syntax highlighting/Breakage

This page is an attempt to find a minimal criminal for the bugs in GeSHi, the syntax highlighter that powers <haskell> and <hask> on the Haskell wiki.

x == '-' || True

That breaks.

x :: String
x = map toUpper "hello"

Subsequent <haskell> blocks seem to independant of the breakages.

False || True

Looks like the (||) operator is causing the problems.

a || b

However, that works. Perhaps it only breaks when using literals?

'a' || 'b'

No, characters work too.

'a' || True

True || 'a'

5 || 'a'

'a' || 5

5 || True

True || 5

Any kind of attempt to mix literals of different types breaks.

'a' || 'b' -- chars work

 "a" || "b" -- strings work

I think any number or constructor on either side of the || makes it break.

 f 5 || g 6

 f 'a' || g 6

Function application with numbers fails too.

Mixing "a", 'a', or a on one side and a function taking the same on the other works:

"a" || isDigit 'a'

However, with a numeric argument, it's wrong:

"a" || isDigit 5

Possible counterexample to 'constructors don't work':

a || A

Specifically, if they have two or more letters, they seem to fail:

a || Ab

More evidence:

Ab || a

a || Ab

Ab || 'a'

'a' || Ab

Ab || "a"

"a" || Ab

"a" || True