The two GatherKinds no longer share any implementation, so there's
no point keeping the logic together. Doing this also allows removing
the acceptConstraintFn from gatherAllConstraints(), which further
simplifies depthFirstSearch().
The two GatherKinds no longer share any implementation, so there's
no point keeping the logic together. Doing this also allows removing
the acceptConstraintFn from gatherAllConstraints(), which further
simplifies depthFirstSearch().
Fixes a regression from commit 0c128e5db7.
The old depthFirstSearch() walked all adjacencies via the constraint graph,
and thus it would visit type variables that are currently inactive because
we're solving a conjunction element.
This was inconsistent with the new union-find which only formed the
connected components from the currently active type variables; adjacencies
involving inactive type variables are no longer considered.
Fix the inconsistency by changing gatherConstraints(), which used from
addTypeVariableConstraintsToWorkList(), to also skip inactive type
variables.
Fixes rdar://problem/143340082.
Instead of starting a depth-first search from each type variable
and marking all type variables that haven't been marked yet,
we can implement this as a union-find.
We can also store the temporary state directly inside the
TypeVariableType::Implementation, instead of creating large
DenseMaps whose keys range over all type variables.
PotentialBindings is part of ConstraintGraphNode and there's no need
to store the ConstraintSystem and TypeVariableType twice.
Also it doesn't need to be optional either, because we no longer need
to reset and recompute bindings.
All but two remaining call sites can be changed to just check for a
non-null solverState, because we want to assert if we're inside
of an active undo.
The two places inside binding inference can check isUndoActive()
directly.
Also, since we add a vertex immediately after introducing a new type
variable, the code path to handle the case where the type variable
had a parent or fixed type was actually dead.
If there is only one connected component, we don't actually have
to form the array of components at all. Re-organize the code so
that we can short-circuit this decision as soon as possible.
Previously, retractFromInference() was the last step in
unbindTypeVariable(). This doesn't really make sense,
because bindTypeVariable() doesn't call introduceToInference();
its two callers do it later.
Start untangling this by splitting off introduceToInference()
into its own Change, but for now, record this change at the
incorrect place to maintain the same behavior as before.
Although I don't plan to bring over new assertions wholesale
into the current qualification branch, it's entirely possible
that various minor changes in main will use the new assertions;
having this basic support in the release branch will simplify that.
(This is why I'm adding the includes as a separate pass from
rewriting the individual assertions)
