Potential Refactors

Summary

Name	Short description	Estimated time	Estimated difficulty	Estimated risk
UnresolvedPkgLoc	Remove some maybes from PackageLocation, since in some places Nothing never gets used	2-3h	2/5	2/5
Dependency as constraint			3/5	4/5
Maybe UnqualComponentName			1/5	1/5

Details

UnresolvedPkgLoc

In ElaboratedConfiguredPackage.elabPkgSourceLocation, RemoteSourceRepoPackage cannot have a Nothing, but PackageLocation often has Maybe Filepath as local, leading to impossible cases like this one and silly code like this one.

We should remove the maybe wherever is possible.

@fgaz attempted this refactor here (remember to grep for undefined)

Maybe PackageLocation should have two type params: one for RepoTarballPackage (which can be Nothing) and one for the rest. Or just one for RepoTarballPackage.

Dependency as constraint

See https://github.com/fgaz/gsoc/blob/master/2018/final-report.md#the-dependency-as-constraint-problem

Maybe UnqualComponentName

See https://github.com/fgaz/gsoc/blob/master/2018/final-report.md#the-pervasive-maybe-unqualcomponentname