Create a separate `validateMoveStatementGraph` function so that
`ValidateMoves` and `ApplyMoves` both check the same conditions. Since
we're not using the builtin `graph.Validate` method, because we may have
multiple roots and want better cycle diagnostics, we need to add checks
for self references too. While multiple roots are an error enforced by
`Validate` for the concurrent walk, they are OK when using
`TransitiveReduction` and `ReverseDepthFirstWalk`, so we can skip that
check.
Apply moves must first use `TransitiveReduction` to reduce the graph,
otherwise nodes may be skipped if they are passed over by a transitive
edge.
This is a first pass at implementing refactoring.ValidateMoves, covering
the main validation rules.
This is not yet complete. A couple situations not yet covered are
represented by commented test cases in TestValidateMoves, although that
isn't necessarily comprehensive. We'll do a further pass of filling this
out with any other subtleties before we ship this feature.
As of this commit, refactoring.ValidateMoves doesn't actually do anything
yet (always returns nil) but the goal here is to wire in the set of all
declared instances so that refactoring.ValidateMoves will then have all
of the information it needs to encapsulate our validation rules.
The actual implementation of refactoring.ValidateMoves will follow in
subsequent commits.
This is a whole lot of nothing right now, just stubbing out some control
flow that ultimately just leads to TODOs that cause it to do nothing at
all.
My intent here is to get this cross-cutting skeleton in place and thus
make it easier for us to collaborate on adding the meat to it, so that
it's more likely we can work on different parts separately and still get
a result that tessellates.
James Bardin