Removal of UniqMap module

[Richard Eisenberg]

> On May 10, 2020, at 11:22 AM, Matthew Pickering <matthewtpickering at gmail.com> wrote:
> 
> Hi,
> 
> I noticed that the UniqMap module was removed from the tree
> 
> See 1c7c6f1afc8e7f7ba5d256780bc9d5bb5f3e7601
> 
> Why was it removed?

From the commit message: "This module isn't used anywhere in GHC." That seems like a good reason to remove, to me. While I can understand the frustration at having this disappear when you need it, we can't quite just keep whole unused modules around in the hope that someone someday will use them.

> I needed it today and now I am unsure what the
> suitable replacement is.

A UniqFM whose range includes the domain element would work fine, I think.

> 
> As a general point, please can we stop with these annoying
> refactorings which delete unused code

I disagree here. A codebase as large and sprawling as GHC's needs constant pruning. The alternative is not to control the sprawl, and that seems considerably worse than refactorings and churn.

Richard