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Fix OrderingConstraint#order forgetting constraints; fix avoidLambdaParams #15077

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Merged
merged 1 commit into from
May 2, 2022
Merged

Fix OrderingConstraint#order forgetting constraints; fix avoidLambdaParams #15077

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11 changes: 6 additions & 5 deletions compiler/src/dotty/tools/dotc/core/ConstraintHandling.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -627,11 +627,7 @@ trait ConstraintHandling {
case x =>
// Happens if param was already solved while processing earlier params of the same TypeLambda.
// See #4720.

// Should propagate bounds even when param has been solved.
// See #11682.
lower.forall(addOneBound(_, x, isUpper = true)) &&
upper.forall(addOneBound(_, x, isUpper = false))
true
}
}
}
Expand Down Expand Up @@ -677,6 +673,11 @@ trait ConstraintHandling {
case t @ TypeParamRef(tl: TypeLambda, n) if comparedTypeLambdas contains tl =>
val bounds = tl.paramInfos(n)
range(bounds.lo, bounds.hi)
case tl: TypeLambda =>
val saved = comparedTypeLambdas
comparedTypeLambdas -= tl
try mapOver(tl)
finally comparedTypeLambdas = saved
case _ =>
mapOver(t)
}
Expand Down
20 changes: 13 additions & 7 deletions compiler/src/dotty/tools/dotc/core/OrderingConstraint.scala
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Expand Up @@ -354,13 +354,18 @@ class OrderingConstraint(private val boundsMap: ParamBounds,
* `<:<` relationships between parameters ("edges") but not bounds.
*/
def order(current: This, param1: TypeParamRef, param2: TypeParamRef, direction: UnificationDirection = NoUnification)(using Context): This =
if (param1 == param2 || current.isLess(param1, param2)) this
else {
assert(contains(param1), i"$param1")
assert(contains(param2), i"$param2")
// /!\ Careful here: we're adding constraints on `current`, not `this`, so
// think twice when using an instance method! We only need to pass `this` as
// the `prev` argument in methods on `ConstraintLens`.
// TODO: Refactor this code to take `prev` as a parameter and add
// constraints on `this` instead?
if param1 == param2 || current.isLess(param1, param2) then current
else
assert(current.contains(param1), i"$param1")
assert(current.contains(param2), i"$param2")
val unifying = direction != NoUnification
val newUpper = {
val up = exclusiveUpper(param2, param1)
val up = current.exclusiveUpper(param2, param1)
if unifying then
// Since param2 <:< param1 already holds now, filter out param1 to avoid adding
// duplicated orderings.
Expand All @@ -374,7 +379,7 @@ class OrderingConstraint(private val boundsMap: ParamBounds,
param2 :: up
}
val newLower = {
val lower = exclusiveLower(param1, param2)
val lower = current.exclusiveLower(param1, param2)
if unifying then
// Similarly, filter out param2 from lowerly-ordered parameters
// to avoid duplicated orderings.
Expand All @@ -390,7 +395,8 @@ class OrderingConstraint(private val boundsMap: ParamBounds,
val current1 = newLower.foldLeft(current)(upperLens.map(this, _, _, newUpper ::: _))
val current2 = newUpper.foldLeft(current1)(lowerLens.map(this, _, _, newLower ::: _))
current2
}
end if
end order

/** The list of parameters P such that, for a fresh type parameter Q:
*
Expand Down