remove local fixity declarations

[Doaitse Swierstra]

On page 38 the language definition allows local fixity declarations. Since no-one seems to be using these, not to be aware of the possibility to do so, I propose to remove them. The necessity to inspect every block to see whether there are fixity declarations, and the necessity to parse all expressions twice is cumbersome.

[simonmar@…]

Haskell 98 only has top-level fixity declarations, and fixity declarations in a class declaration (which are essentially top-level too). What do you mean by "local"?

See also FixityResolution.

[simonmar@…]

I just looked again, and you're quite right, there are local fixity declarations! And GHC even implements them.

I'm not convinced they should be removed, because it's no harder to deal with local fixity declarations than it is to deal with fixity of imported identifiers. On the other hand, it is certainly a small feature that we could remove.