Ben Gamari authored Dec 16, 2016 and Ben Gamari committed Dec 16, 2016

It already has access to the current package's UnitId via the Module.
Edward Yang pointed out that there is one wrinkle, however: the
following invariant isn't true at all stages of compilation,

    if I am compiling the module (this_mod :: Module), then
    thisPackage dflags == moduleUnitId this_mod.

Specifically, this is only true after desugaring; it may be broken when
typechecking an indefinite signature.

However, it's safe to assume this in the native codegen. I've updated
Note to state this invariant more directly.

Test Plan: Validate

Reviewers: austin, ezyang, simonmar

Reviewed By: ezyang, simonmar

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2863