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Instantiate constraint entries when updated to equal bounds #20208

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Instantiate constraint entries when updated to equal bounds #20208

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191885c
Instantiate constraint entries when updated to equal bounds
EugeneFlesselle Apr 22, 2024
3d35817
Pass current OrderingConstraint to stripParams
EugeneFlesselle Apr 22, 2024
6cb6d38
Revert to equal bounds when typeVarOfParam is unknown
EugeneFlesselle Apr 22, 2024
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2 changes: 1 addition & 1 deletion compiler/src/dotty/tools/dotc/core/ConstraintHandling.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -327,7 +327,7 @@ trait ConstraintHandling {
(c1 eq constraint)
|| {
constraint = c1
val TypeBounds(lo, hi) = constraint.entry(param): @unchecked
val TypeBounds(lo, hi) = constraint.nonParamBounds(param)
isSub(lo, hi)
}
end addOneBound
Expand Down
29 changes: 21 additions & 8 deletions compiler/src/dotty/tools/dotc/core/OrderingConstraint.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -104,6 +104,18 @@ object OrderingConstraint {
def updateEntries(c: OrderingConstraint, poly: TypeLambda, entries: Array[Type])(using Context): OrderingConstraint =
c.newConstraint(boundsMap = c.boundsMap.updated(poly, entries))
def initial = NoType

override def update(prev: OrderingConstraint, current: OrderingConstraint,
poly: TypeLambda, idx: Int, entry: Type)(using Context): OrderingConstraint =
entry match
case TypeBounds(lo, hi) if lo eq hi =>
val replaceParams = new TypeMap:
def apply(tp: Type): Type = tp match
case tp: TypeParamRef => current.typeVarOfParam(tp).orElse(tp)
case _ => mapOver(tp)
super.update(prev, current, poly, idx, replaceParams(hi))
case _ =>
super.update(prev, current, poly, idx, entry)
}

private val lowerLens: ConstraintLens[List[TypeParamRef]] = new ConstraintLens[List[TypeParamRef]] {
Expand Down Expand Up @@ -477,26 +489,27 @@ class OrderingConstraint(private val boundsMap: ParamBounds,
* @param isUpper If true, `bound` is an upper bound, else a lower bound.
*/
private def stripParams(
current: OrderingConstraint,
tp: Type,
todos: mutable.ListBuffer[(OrderingConstraint, TypeParamRef) => OrderingConstraint],
isUpper: Boolean)(using Context): Type = tp match {
case param: TypeParamRef if contains(param) =>
case param: TypeParamRef if current.contains(param) =>
todos += (if isUpper then order(_, _, param) else order(_, param, _))
NoType
case tp: TypeBounds =>
val lo1 = stripParams(tp.lo, todos, !isUpper).orElse(defn.NothingType)
val hi1 = stripParams(tp.hi, todos, isUpper).orElse(tp.topType)
val lo1 = stripParams(current, tp.lo, todos, !isUpper).orElse(defn.NothingType)
val hi1 = stripParams(current, tp.hi, todos, isUpper).orElse(tp.topType)
tp.derivedTypeBounds(lo1, hi1)
case tp: AndType if isUpper =>
val tp1 = stripParams(tp.tp1, todos, isUpper)
val tp2 = stripParams(tp.tp2, todos, isUpper)
val tp1 = stripParams(current, tp.tp1, todos, isUpper)
val tp2 = stripParams(current, tp.tp2, todos, isUpper)
if (tp1.exists)
if (tp2.exists) tp.derivedAndType(tp1, tp2)
else tp1
else tp2
case tp: OrType if !isUpper =>
val tp1 = stripParams(tp.tp1, todos, isUpper)
val tp2 = stripParams(tp.tp2, todos, isUpper)
val tp1 = stripParams(current, tp.tp1, todos, isUpper)
val tp2 = stripParams(current, tp.tp2, todos, isUpper)
if (tp1.exists)
if (tp2.exists) tp.derivedOrType(tp1, tp2)
else tp1
Expand Down Expand Up @@ -527,7 +540,7 @@ class OrderingConstraint(private val boundsMap: ParamBounds,
while (i < poly.paramNames.length) {
val param = poly.paramRefs(i)
val bounds = dropWildcards(nonParamBounds(param))
val stripped = stripParams(bounds, todos, isUpper = true)
val stripped = stripParams(current, bounds, todos, isUpper = true)
current = boundsLens.update(this, current, param, stripped)
while todos.nonEmpty do
current = todos.head(current, param)
Expand Down
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