Fix treatment of hi-boot files and dfuns
Trac Trac #16038 exposed the fact that TcRnDriver.checkHiBootIface
was creating a binding, in the module being compiled, for
$fxBlah = $fBlah
but $fxBlah was a /GlobalId/. But all bindings should be for
/LocalIds/ else dependency analysis goes down the tubes.
- I added a CoreLint check that an occurrence of a GlobalId is not bound by an binding of a LocalId. (There is already a binding-site check that no binding binds a GlobalId.)
- I refactored (and actually signficantly simplified) the tricky code for dfuns in checkHiBootIface to ensure that we get LocalIds for those boot-dfuns.
Alas, I then got "duplicate instance" messages when compiling
HsExpr. It turns out that this is a long-standing, but extremely
delicate, bug: even before this patch, if you compile HsExpr
with -ddump-tc-trace, you get "duplicate instance". Without
-ddump-tc-trace, it's OK. What a mess!
The reason for the duplicate-instance is now explained in
Note [Loading your own hi-boot file] in LoadIface. I fixed
it by a Gross Hack in LoadIface.loadInterface. This is at
least no worse than before.
But there should be a better way. I have opened Trac #16081 for this.