Skip to content

Commit 0f4aba8

Browse files
oderskyodersky
committed
Introduce tracked class parameters
For a tracked class parameter we add a refinement in the constructor type that the class member is the same as the parameter. E.g. ```scala class C { type T } class D(tracked val x: C) { type T = x.T } ``` This will generate the constructor type: ```scala (x1: C): D { val x: x1.type } ``` Without `tracked` the refinement would not be added. This can solve several problems with dependent class types where previously we lost track of type dependencies.
1 parent bfebebd commit 0f4aba8

File tree

15 files changed

+63
-38
lines changed

15 files changed

+63
-38
lines changed

‎compiler/src/dotty/tools/dotc/ast/Desugar.scala

Lines changed: 18 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -437,13 +437,13 @@ object desugar {
437437
private def toDefParam(tparam: TypeDef, keepAnnotations: Boolean): TypeDef = {
438438
var mods = tparam.rawMods
439439
if (!keepAnnotations) mods = mods.withAnnotations(Nil)
440-
tparam.withMods(mods & (EmptyFlags | Sealed) | Param)
440+
tparam.withMods(mods & EmptyFlags | Param)
441441
}
442442
private def toDefParam(vparam: ValDef, keepAnnotations: Boolean, keepDefault: Boolean): ValDef = {
443443
var mods = vparam.rawMods
444444
if (!keepAnnotations) mods = mods.withAnnotations(Nil)
445445
val hasDefault = if keepDefault then HasDefault else EmptyFlags
446-
vparam.withMods(mods & (GivenOrImplicit | Erased | hasDefault) | Param)
446+
vparam.withMods(mods & (GivenOrImplicit | Erased | hasDefault | Tracked) | Param)
447447
}
448448

449449
def mkApply(fn: Tree, paramss: List[ParamClause])(using Context): Tree =
@@ -529,7 +529,7 @@ object desugar {
529529
// but not on the constructor parameters. The reverse is true for
530530
// annotations on class _value_ parameters.
531531
val constrTparams = impliedTparams.map(toDefParam(_, keepAnnotations = false))
532-
val constrVparamss =
532+
def defVparamss =
533533
if (originalVparamss.isEmpty) { // ensure parameter list is non-empty
534534
if (isCaseClass)
535535
report.error(CaseClassMissingParamList(cdef), namePos)
@@ -540,6 +540,7 @@ object desugar {
540540
ListOfNil
541541
}
542542
else originalVparamss.nestedMap(toDefParam(_, keepAnnotations = true, keepDefault = true))
543+
val constrVparamss = defVparamss
543544
val derivedTparams =
544545
constrTparams.zipWithConserve(impliedTparams)((tparam, impliedParam) =>
545546
derivedTypeParam(tparam).withAnnotations(impliedParam.mods.annotations))
@@ -614,6 +615,11 @@ object desugar {
614615
case _ => false
615616
}
616617

618+
def isRepeated(tree: Tree): Boolean = stripByNameType(tree) match {
619+
case PostfixOp(_, Ident(tpnme.raw.STAR)) => true
620+
case _ => false
621+
}
622+
617623
def appliedRef(tycon: Tree, tparams: List[TypeDef] = constrTparams, widenHK: Boolean = false) = {
618624
val targs = for (tparam <- tparams) yield {
619625
val targ = refOfDef(tparam)
@@ -630,10 +636,13 @@ object desugar {
630636
appliedTypeTree(tycon, targs)
631637
}
632638

633-
def isRepeated(tree: Tree): Boolean = stripByNameType(tree) match {
634-
case PostfixOp(_, Ident(tpnme.raw.STAR)) => true
635-
case _ => false
636-
}
639+
def addParamRefinements(core: Tree, paramss: List[List[ValDef]]): Tree =
640+
val refinements =
641+
for params <- paramss; param <- params; if param.mods.is(Tracked) yield
642+
ValDef(param.name, SingletonTypeTree(TermRefTree().watching(param)), EmptyTree)
643+
.withSpan(param.span)
644+
if refinements.isEmpty then core
645+
else RefinedTypeTree(core, refinements).showing(i"refined result: $result", Printers.desugar)
637646

638647
// a reference to the class type bound by `cdef`, with type parameters coming from the constructor
639648
val classTypeRef = appliedRef(classTycon)
@@ -854,18 +863,17 @@ object desugar {
854863
Nil
855864
}
856865
else {
857-
val defParamss = constrVparamss match {
866+
val defParamss = defVparamss match
858867
case Nil :: paramss =>
859868
paramss // drop leading () that got inserted by class
860869
// TODO: drop this once we do not silently insert empty class parameters anymore
861870
case paramss => paramss
862-
}
863871
val finalFlag = if ctx.settings.YcompileScala2Library.value then EmptyFlags else Final
864872
// implicit wrapper is typechecked in same scope as constructor, so
865873
// we can reuse the constructor parameters; no derived params are needed.
866874
DefDef(
867875
className.toTermName, joinParams(constrTparams, defParamss),
868-
classTypeRef, creatorExpr)
876+
addParamRefinements(classTypeRef, defParamss), creatorExpr)
869877
.withMods(companionMods | mods.flags.toTermFlags & (GivenOrImplicit | Inline) | finalFlag)
870878
.withSpan(cdef.span) :: Nil
871879
}

‎compiler/src/dotty/tools/dotc/ast/untpd.scala

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -231,6 +231,8 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
231231

232232
case class Infix()(implicit @constructorOnly src: SourceFile) extends Mod(Flags.Infix)
233233

234+
case class Tracked()(implicit @constructorOnly src: SourceFile) extends Mod(Flags.Tracked)
235+
234236
/** Used under pureFunctions to mark impure function types `A => B` in `FunctionWithMods` */
235237
case class Impure()(implicit @constructorOnly src: SourceFile) extends Mod(Flags.Impure)
236238
}

‎compiler/src/dotty/tools/dotc/core/Flags.scala

Lines changed: 4 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -242,7 +242,7 @@ object Flags {
242242
val (AccessorOrSealed @ _, Accessor @ _, Sealed @ _) = newFlags(11, "<accessor>", "sealed")
243243

244244
/** A mutable var, an open class */
245-
val (MutableOrOpen @ __, Mutable @ _, Open @ _) = newFlags(12, "mutable", "open")
245+
val (MutableOrOpen @ _, Mutable @ _, Open @ _) = newFlags(12, "mutable", "open")
246246

247247
/** Symbol is local to current class (i.e. private[this] or protected[this]
248248
* pre: Private or Protected are also set
@@ -377,6 +377,8 @@ object Flags {
377377
/** Symbol cannot be found as a member during typer */
378378
val (Invisible @ _, _, _) = newFlags(45, "<invisible>")
379379

380+
val (Tracked @ _, _, _) = newFlags(46, "tracked")
381+
380382
// ------------ Flags following this one are not pickled ----------------------------------
381383

382384
/** Symbol is not a member of its owner */
@@ -452,7 +454,7 @@ object Flags {
452454
CommonSourceModifierFlags.toTypeFlags | Abstract | Sealed | Opaque | Open
453455

454456
val TermSourceModifierFlags: FlagSet =
455-
CommonSourceModifierFlags.toTermFlags | Inline | AbsOverride | Lazy
457+
CommonSourceModifierFlags.toTermFlags | Inline | AbsOverride | Lazy | Tracked
456458

457459
/** Flags representing modifiers that can appear in trees */
458460
val ModifierFlags: FlagSet =

‎compiler/src/dotty/tools/dotc/core/NamerOps.scala

Lines changed: 6 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -15,7 +15,12 @@ object NamerOps:
1515
*/
1616
def effectiveResultType(ctor: Symbol, paramss: List[List[Symbol]])(using Context): Type =
1717
paramss match
18-
case TypeSymbols(tparams) :: _ => ctor.owner.typeRef.appliedTo(tparams.map(_.typeRef))
18+
case TypeSymbols(tparams) :: _ =>
19+
var resType = ctor.owner.typeRef.appliedTo(tparams.map(_.typeRef))
20+
for params <- paramss; param <- params do
21+
if param.is(Tracked) then
22+
resType = RefinedType(resType, param.name, param.termRef)
23+
resType
1924
case _ => ctor.owner.typeRef
2025

2126
/** If isConstructor, make sure it has at least one non-implicit parameter list

‎compiler/src/dotty/tools/dotc/core/StdNames.scala

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -623,6 +623,7 @@ object StdNames {
623623
val toString_ : N = "toString"
624624
val toTypeConstructor: N = "toTypeConstructor"
625625
val tpe : N = "tpe"
626+
val tracked: N = "tracked"
626627
val transparent : N = "transparent"
627628
val tree : N = "tree"
628629
val true_ : N = "true"

‎compiler/src/dotty/tools/dotc/core/tasty/TreePickler.scala

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -787,6 +787,7 @@ class TreePickler(pickler: TastyPickler) {
787787
if (flags.is(Extension)) writeModTag(EXTENSION)
788788
if (flags.is(ParamAccessor)) writeModTag(PARAMsetter)
789789
if (flags.is(SuperParamAlias)) writeModTag(PARAMalias)
790+
if (flags.is(Tracked)) writeModTag(TRACKED)
790791
assert(!(flags.is(Label)))
791792
}
792793
else {

‎compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -733,6 +733,7 @@ class TreeUnpickler(reader: TastyReader,
733733
case INVISIBLE => addFlag(Invisible)
734734
case TRANSPARENT => addFlag(Transparent)
735735
case INFIX => addFlag(Infix)
736+
case TRACKED => addFlag(Tracked)
736737
case PRIVATEqualified =>
737738
readByte()
738739
privateWithin = readWithin

‎compiler/src/dotty/tools/dotc/parsing/Parsers.scala

Lines changed: 7 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -3100,6 +3100,7 @@ object Parsers {
31003100
case nme.open => Mod.Open()
31013101
case nme.transparent => Mod.Transparent()
31023102
case nme.infix => Mod.Infix()
3103+
case nme.tracked => Mod.Tracked()
31033104
}
31043105
}
31053106

@@ -3166,6 +3167,7 @@ object Parsers {
31663167
* | AccessModifier
31673168
* | override
31683169
* | opaque
3170+
* | tracked
31693171
* LocalModifier ::= abstract | final | sealed | open | implicit | lazy | erased | inline | transparent
31703172
*/
31713173
def modifiers(allowed: BitSet = modifierTokens, start: Modifiers = Modifiers()): Modifiers = {
@@ -3427,7 +3429,8 @@ object Parsers {
34273429
val isParams =
34283430
!impliedMods.is(Given)
34293431
|| startParamTokens.contains(in.token)
3430-
|| isIdent && (in.name == nme.inline || in.lookahead.isColon)
3432+
|| isIdent
3433+
&& (in.name == nme.inline || in.name == nme.tracked || in.lookahead.isColon)
34313434
(mods, isParams)
34323435
(if isParams then commaSeparated(() => param())
34333436
else contextTypes(paramOwner, numLeadParams, impliedMods)) match {
@@ -4005,7 +4008,9 @@ object Parsers {
40054008
paramss.nestedMap: param =>
40064009
if !param.mods.isAllOf(PrivateLocal) then
40074010
syntaxError(em"method parameter ${param.name} may not be `a val`", param.span)
4008-
param.withMods(param.mods &~ (AccessFlags | ParamAccessor | Mutable) | Param)
4011+
if param.mods.is(Tracked) then
4012+
syntaxError(em"method parameter ${param.name} may not be `tracked`", param.span)
4013+
param.withMods(param.mods &~ (AccessFlags | ParamAccessor | Tracked | Mutable) | Param)
40094014
.asInstanceOf[List[ParamClause]]
40104015

40114016
val gdef =

‎compiler/src/dotty/tools/dotc/parsing/Tokens.scala

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -294,7 +294,7 @@ object Tokens extends TokensCommon {
294294

295295
final val closingParens = BitSet(RPAREN, RBRACKET, RBRACE)
296296

297-
final val softModifierNames = Set(nme.inline, nme.into, nme.opaque, nme.open, nme.transparent, nme.infix)
297+
final val softModifierNames = Set(nme.inline, nme.into, nme.opaque, nme.open, nme.transparent, nme.infix, nme.tracked)
298298

299299
def showTokenDetailed(token: Int): String = debugString(token)
300300

‎compiler/src/dotty/tools/dotc/transform/PostTyper.scala

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -332,11 +332,11 @@ class PostTyper extends MacroTransform with InfoTransformer { thisPhase =>
332332
case Select(nu: New, nme.CONSTRUCTOR) if isCheckable(nu) =>
333333
// need to check instantiability here, because the type of the New itself
334334
// might be a type constructor.
335-
ctx.typer.checkClassType(tree.tpe, tree.srcPos, traitReq = false, stablePrefixReq = true)
335+
ctx.typer.checkClassType(tree.tpe, tree.srcPos, traitReq = false, stablePrefixReq = true, refinementOK = true)
336336
if !nu.tpe.isLambdaSub then
337337
// Check the constructor type as well; it could be an illegal singleton type
338338
// which would not be reflected as `tree.tpe`
339-
ctx.typer.checkClassType(nu.tpe, tree.srcPos, traitReq = false, stablePrefixReq = false)
339+
ctx.typer.checkClassType(nu.tpe, tree.srcPos, traitReq = false, stablePrefixReq = false, refinementOK = true)
340340
Checking.checkInstantiable(tree.tpe, nu.tpe, nu.srcPos)
341341
withNoCheckNews(nu :: Nil)(app1)
342342
case _ =>

0 commit comments

Comments
 (0)