SrcLoc/SrcSpan/Located naming

[Isaac Dupree]

is a confusing mess!
The most important module is named SrcLoc, which is acceptable.
It contains three types,
SrcLoc,
SrcSpan, which approximately is two SrcLocs (begin and end),
and Located, which combines a SrcSpan (not a SrcLoc!) with an arbitrary 
other type.

In practice (well, in my case at least) you almost always want a SrcSpan 
and not a SrcLoc.
Many of the functions on SrcLoc have "srcLoc" in their names, which is good.

However, so do many of the functions on Located-and-SrcSpan, which is 
terrible.  It gets a little worse when you combine with the (fairly 
sensibly named functions) at Name.NamedThing
noLoc, getLoc, addCLoc, combineLocs work on Locateds.
noSrcLoc, getSrcLoc, work on SrcLocs.  Instead, noSrcSpan and getSrcSpan 
are the ones you want.

Okay it's not quite as bad as I thought.  You want to avoid a function 
iff it contains the whole phrase "srcLoc".  But I still got confused a 
lot of times.  I wonder if we could rename something so that SrcLoc and 
Located don't have the same word-part in them, because they aren't 
really closely enough related?  Even if it's just renaming "SrcLoc" to 
"SrcSpot" or something.

It's also annoying that Name.getSrcSpan doesn't work on Locateds 
(inevitable I guess since it's type-different from NamedThing), but the 
function you have to use instead is called getLoc, even though it also 
produces a SrcSpan (only the argument-type is different).  Hmm.

-Isaac