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Gadt unification #5611

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merged 8 commits into from
Dec 17, 2018
Merged

Gadt unification #5611

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225aabc
Revert "Handle higher-kinded GADT bounds"
abgruszecki Dec 14, 2018
08ac0a0
Move TyperState.instType
abgruszecki Dec 14, 2018
04503d9
Allow overriding ConstraintHandling logs
abgruszecki Dec 14, 2018
4c41fc4
Reuse ConstraintHandling for GADTMap
abgruszecki Dec 14, 2018
de795a9
Add caching to GADTMap
abgruszecki Dec 14, 2018
6cca0a6
Clean up GADTMap#ctx
abgruszecki Dec 14, 2018
f75f58f
Address review comments
abgruszecki Dec 16, 2018
d1fa5d7
Simplify TypeComparer.explaining
abgruszecki Dec 17, 2018
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17 changes: 6 additions & 11 deletions compiler/src/dotty/tools/dotc/core/TypeComparer.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -830,9 +830,9 @@ class TypeComparer(initctx: Context) extends ConstraintHandling {
* tp1 <:< tp2 using fourthTry (this might instantiate params in tp1)
* tp1 <:< app2 using isSubType (this might instantiate params in tp2)
*/
def compareLower(tycon2bounds: TypeBounds, followSuperType: Boolean): Boolean =
def compareLower(tycon2bounds: TypeBounds, tyconIsTypeRef: Boolean): Boolean =
if ((tycon2bounds.lo `eq` tycon2bounds.hi) && !tycon2bounds.isInstanceOf[MatchAlias])
if (followSuperType) recur(tp1, tp2.superType)
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It reverted commit fills a hole in the subtype checker. What tests failed before we reverted it? It would be good to find a root cause for the failure.

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@abgruszecki abgruszecki Dec 17, 2018 •
edited
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TypeSafeLambda failed. Since this PR anyway leaves GADTs using HKTs unsound, I wanted to focus first on solving #5630, and then to come back to this problem.

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OK, agreed. Maybe make an issue so that it is not forgotten?

if (tyconIsTypeRef) recur(tp1, tp2.superType)
else isSubApproxHi(tp1, tycon2bounds.lo.applyIfParameterized(args2))
else
fallback(tycon2bounds.lo)
Expand All @@ -841,15 +841,13 @@ class TypeComparer(initctx: Context) extends ConstraintHandling {
case param2: TypeParamRef =>
isMatchingApply(tp1) ||
canConstrain(param2) && canInstantiate(param2) ||
compareLower(bounds(param2), followSuperType = false)
compareLower(bounds(param2), tyconIsTypeRef = false)
case tycon2: TypeRef =>
isMatchingApply(tp1) ||
defn.isTypelevel_S(tycon2.symbol) && compareS(tp2, tp1, fromBelow = true) || {
tycon2.info match {
case info2: TypeBounds =>
val gbounds2 = ctx.gadt.bounds(tycon2.symbol)
if (gbounds2 == null) compareLower(info2, followSuperType = true)
else compareLower(gbounds2 & info2, followSuperType = false)
compareLower(info2, tyconIsTypeRef = true)
case info2: ClassInfo =>
tycon2.name.toString.startsWith("Tuple") &&
defn.isTupleType(tp2) && isSubType(tp1, tp2.toNestedPairs) ||
Expand Down Expand Up @@ -885,11 +883,8 @@ class TypeComparer(initctx: Context) extends ConstraintHandling {
case tycon1: TypeRef =>
val sym = tycon1.symbol
!sym.isClass && (
defn.isTypelevel_S(sym) && compareS(tp1, tp2, fromBelow = false) || {
val gbounds1 = ctx.gadt.bounds(tycon1.symbol)
if (gbounds1 == null) recur(tp1.superType, tp2)
else recur((gbounds1.hi & tycon1.info.bounds.hi).applyIfParameterized(args1), tp2)
})
defn.isTypelevel_S(sym) && compareS(tp1, tp2, fromBelow = false) ||
recur(tp1.superType, tp2))
case tycon1: TypeProxy =>
recur(tp1.superType, tp2)
case _ =>
Expand Down
2 changes: 1 addition & 1 deletion compiler/src/dotty/tools/dotc/core/Types.scala
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Expand Up @@ -563,7 +563,7 @@ object Types {
case _ =>
go(tp.superType)
}
case tp: ThisType =>
case tp: ThisType => // ??? inline
goThis(tp)
case tp: RefinedType =>
if (name eq tp.refinedName) goRefined(tp) else go(tp.parent)
Expand Down