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Add constructor proxies
Use synthetic apply methods instead of a fallback in Typer to implement creator applications
1 parent 40d5a36 commit d697007

33 files changed

+433
-223
lines changed

‎compiler/src/dotty/tools/dotc/config/Config.scala

Lines changed: 5 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -8,6 +8,11 @@ object Config {
88
inline val cacheImplicitScopes = true
99
inline val cacheMatchReduced = true
1010

11+
/** If true, we implement creator expressions by adding constructor proxies.
12+
* If false, we rely on fallbacks in Typer to try a constructor if everything else failed.
13+
*/
14+
inline val addConstructorProxies = true
15+
1116
/** If true, the `runWithOwner` operation uses a re-usable context,
1217
* similar to explore. This requires that the context does not escape
1318
* the call. If false, `runWithOwner` runs its operation argument

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

Lines changed: 13 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -300,14 +300,19 @@ class Definitions {
300300
cls.info = ClassInfo(cls.owner.thisType, cls, List(AnyType, MatchableType), newScope)
301301
cls.setFlag(NoInits | JavaDefined)
302302

303-
// The companion object doesn't really exist, so it needs to be marked as
304-
// absent. Here we need to set it before completing attempt to load Object's
305-
// classfile, which causes issue #1648.
306-
val companion = JavaLangPackageVal.info.decl(nme.Object).symbol
307-
companion.moduleClass.markAbsent()
308-
companion.markAbsent()
309-
310-
completeClass(cls)
303+
if config.Config.addConstructorProxies then
304+
ensureConstructor(cls, cls.denot.asClass, EmptyScope)
305+
val companion = JavaLangPackageVal.info.decl(nme.Object).symbol.asTerm
306+
NamerOps.makeConstructorCompanion(companion, cls)
307+
cls
308+
else
309+
// The companion object doesn't really exist, so it needs to be marked as
310+
// absent. Here we need to set it before completing attempt to load Object's
311+
// classfile, which causes issue #1648.
312+
val companion = JavaLangPackageVal.info.decl(nme.Object).symbol
313+
companion.moduleClass.markAbsent()
314+
companion.markAbsent()
315+
completeClass(cls)
311316
}
312317
def ObjectType: TypeRef = ObjectClass.typeRef
313318

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

Lines changed: 12 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -378,7 +378,7 @@ object Flags {
378378
val (Touched @ _, _, _) = newFlags(50, "<touched>")
379379

380380
/** Class has been lifted out to package level, local value has been lifted out to class level */
381-
val (Lifted @ _, _, _) = newFlags(51, "<lifted>")
381+
val (Lifted @ _, _, _) = newFlags(51, "<lifted>") // only used from lambda-lift (could be merged with ConstructorProxy)
382382

383383
/** Term member has been mixed in */
384384
val (MixedIn @ _, _, _) = newFlags(52, "<mixedin>")
@@ -420,6 +420,9 @@ object Flags {
420420
/** A denotation that is valid in all run-ids */
421421
val (Permanent @ _, _, _) = newFlags(61, "<permanent>")
422422

423+
/** Symbol is a constructor proxy (either companion, or apply method) */
424+
val (ConstructorProxy @ _, _, _) = newFlags(62, "<constructor proxy>") // (could be merged with Lifted)
425+
423426
// --------- Combined Flag Sets and Conjunctions ----------------------
424427

425428
/** All possible flags */
@@ -455,15 +458,16 @@ object Flags {
455458
Scala2SpecialFlags, MutableOrOpen, Opaque, Touched, JavaStatic,
456459
OuterOrCovariant, LabelOrContravariant, CaseAccessor,
457460
Extension, NonMember, Implicit, Given, Permanent, Synthetic,
458-
SuperParamAliasOrScala2x, Inline, Macro)
461+
SuperParamAliasOrScala2x, Inline, Macro, ConstructorProxy)
459462

460463
/** Flags that are not (re)set when completing the denotation, or, if symbol is
461464
* a top-level class or object, when completing the denotation once the class
462465
* file defining the symbol is loaded (which is generally before the denotation
463466
* is completed)
464467
*/
465468
val AfterLoadFlags: FlagSet = commonFlags(
466-
FromStartFlags, AccessFlags, Final, AccessorOrSealed, LazyOrTrait, SelfName, JavaDefined, Transparent)
469+
FromStartFlags, AccessFlags, Final, AccessorOrSealed,
470+
Abstract, LazyOrTrait, SelfName, JavaDefined, Transparent)
467471

468472
/** A value that's unstable unless complemented with a Stable flag */
469473
val UnstableValueFlags: FlagSet = Mutable | Method
@@ -508,7 +512,7 @@ object Flags {
508512
val RetainedModuleValAndClassFlags: FlagSet =
509513
AccessFlags | Package | Case |
510514
Synthetic | JavaDefined | JavaStatic | Artifact |
511-
Lifted | MixedIn | Specialized
515+
Lifted | MixedIn | Specialized | ConstructorProxy
512516

513517
/** Flags that can apply to a module val */
514518
val RetainedModuleValFlags: FlagSet = RetainedModuleValAndClassFlags |
@@ -539,7 +543,10 @@ object Flags {
539543
val EnumCase: FlagSet = Case | Enum
540544
val CovariantLocal: FlagSet = Covariant | Local // A covariant type parameter
541545
val ContravariantLocal: FlagSet = Contravariant | Local // A contravariant type parameter
546+
val EffectivelyErased = ConstructorProxy | Erased
547+
val ConstructorProxyModule: FlagSet = ConstructorProxy | Module
542548
val DefaultParameter: FlagSet = HasDefault | Param // A Scala 2x default parameter
549+
val DeferredInline: FlagSet = Deferred | Inline
543550
val DeferredOrLazy: FlagSet = Deferred | Lazy
544551
val DeferredOrLazyOrMethod: FlagSet = Deferred | Lazy | Method
545552
val DeferredOrTermParamOrAccessor: FlagSet = Deferred | ParamAccessor | TermParam // term symbols without right-hand sides
@@ -548,7 +555,7 @@ object Flags {
548555
val FinalOrInline: FlagSet = Final | Inline
549556
val FinalOrModuleClass: FlagSet = Final | ModuleClass // A module class or a final class
550557
val EffectivelyFinalFlags: FlagSet = Final | Private
551-
val ExcludedForwarder: Flags.FlagSet = Specialized | Lifted | Protected | JavaStatic | Private | Macro
558+
val ExcludedForwarder: Flags.FlagSet = Specialized | Lifted | Protected | JavaStatic | Private | Macro | ConstructorProxy
552559
val FinalOrSealed: FlagSet = Final | Sealed
553560
val GivenOrImplicit: FlagSet = Given | Implicit
554561
val GivenOrImplicitVal: FlagSet = GivenOrImplicit.toTermFlags

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

Lines changed: 101 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -1,9 +1,12 @@
1-
package dotty.tools.dotc
1+
package dotty.tools
2+
package dotc
23
package core
34

4-
import Contexts._, Symbols._, Types._, Flags._, Scopes._, Decorators._, NameOps._
5+
import Contexts._, Symbols._, Types._, Flags._, Scopes._, Decorators._, Names._, NameOps._
56
import Denotations._
6-
import SymDenotations.LazyType, Names.Name, StdNames.nme
7+
import SymDenotations.{LazyType, SymDenotation}, StdNames.nme
8+
import config.Config
9+
import ast.untpd
710

811
/** Operations that are shared between Namer and TreeUnpickler */
912
object NamerOps:
@@ -57,4 +60,99 @@ object NamerOps:
5760
else NoSymbol.assertingErrorsReported(s"no companion $name in $scope")
5861
}
5962

63+
/** If a class has one of these flags, it does not get a constructor companion */
64+
private val NoConstructorProxyNeededFlags = Abstract | Trait | Case | Synthetic | Module
65+
66+
/** The flags of a constructor companion */
67+
private val ConstructorCompanionFlags = Synthetic | ConstructorProxy
68+
69+
/** The flags of an `apply` method that serves as a constructor proxy */
70+
val ApplyProxyFlags = Synthetic | ConstructorProxy | Inline | Method
71+
72+
/** Does symbol `cls` need constructor proxies to be generated? */
73+
def needsConstructorProxies(cls: Symbol)(using Context): Boolean =
74+
Config.addConstructorProxies
75+
&& cls.isClass
76+
&& !cls.flagsUNSAFE.isOneOf(NoConstructorProxyNeededFlags)
77+
&& !cls.isAnonymousClass
78+
79+
/** The completer of a constructor proxy apply method */
80+
class ApplyProxyCompleter(constr: Symbol)(using Context) extends LazyType:
81+
def complete(denot: SymDenotation)(using Context): Unit =
82+
denot.info = constr.info
83+
84+
/** Add constructor proxy apply methods to `scope`. Proxies are for constructors
85+
* in `cls` and they reside in `modcls`.
86+
*/
87+
def addConstructorApplies(scope: MutableScope, cls: ClassSymbol, modcls: ClassSymbol)(using Context): scope.type =
88+
def proxy(constr: Symbol): Symbol =
89+
newSymbol(
90+
modcls, nme.apply, ApplyProxyFlags | (constr.flagsUNSAFE & AccessFlags),
91+
ApplyProxyCompleter(constr), coord = constr.coord)
92+
if Config.addConstructorProxies then
93+
for dcl <- cls.info.decls do
94+
if dcl.isConstructor then scope.enter(proxy(dcl))
95+
scope
96+
end addConstructorApplies
97+
98+
/** The completer of a constructor companion for class `cls`, where
99+
* `modul` is the companion symbol and `modcls` is its class.
100+
*/
101+
def constructorCompanionCompleter(cls: ClassSymbol)(
102+
modul: TermSymbol, modcls: ClassSymbol)(using Context): LazyType =
103+
new LazyType with SymbolLoaders.SecondCompleter {
104+
def complete(denot: SymDenotation)(using Context): Unit =
105+
val prefix = modcls.owner.thisType
106+
denot.info = ClassInfo(
107+
prefix, modcls, defn.AnyType :: Nil,
108+
addConstructorApplies(newScope, cls, modcls), TermRef(prefix, modul))
109+
}.withSourceModule(modul)
110+
111+
/** A new symbol that is the constructor companion for class `cls` */
112+
def constructorCompanion(cls: ClassSymbol)(using Context): TermSymbol =
113+
val companion = newModuleSymbol(
114+
cls.owner, cls.name.toTermName,
115+
ConstructorCompanionFlags, ConstructorCompanionFlags,
116+
constructorCompanionCompleter(cls),
117+
coord = cls.coord,
118+
assocFile = cls.assocFile)
119+
companion.moduleClass.registerCompanion(cls)
120+
cls.registerCompanion(companion.moduleClass)
121+
companion
122+
123+
/** Add all necesssary constructor proxy symbols for members of class `cls`. This means:
124+
*
125+
* - if a member is a class that needs a constructor companion, add one,
126+
* provided no member with the same name exists.
127+
* - if `cls` is a companion object of a class that needs a constructor companion,
128+
* and `cls` does not already define or inherit an `apply` method,
129+
* add `apply` methods for all constructors of the companion class.
130+
*/
131+
def addConstructorProxies(cls: ClassSymbol)(using Context): Unit =
132+
133+
def memberExists(cls: ClassSymbol, name: TermName): Boolean =
134+
cls.baseClasses.exists(_.info.decls.lookupEntry(name) != null)
135+
for mbr <- cls.info.decls do
136+
if needsConstructorProxies(mbr)
137+
&& !mbr.asClass.unforcedRegisteredCompanion.exists
138+
&& !memberExists(cls, mbr.name.toTermName)
139+
then
140+
constructorCompanion(mbr.asClass).entered
141+
142+
if cls.is(Module)
143+
&& needsConstructorProxies(cls.linkedClass)
144+
&& !memberExists(cls, nme.apply)
145+
then
146+
addConstructorApplies(cls.info.decls.openForMutations, cls.linkedClass.asClass, cls)
147+
end addConstructorProxies
148+
149+
/** Turn `modul` into a constructor companion for class `cls` */
150+
def makeConstructorCompanion(modul: TermSymbol, cls: ClassSymbol)(using Context): Unit =
151+
val modcls = modul.moduleClass.asClass
152+
modul.setFlag(ConstructorCompanionFlags)
153+
modcls.setFlag(ConstructorCompanionFlags)
154+
modcls.info = constructorCompanionCompleter(cls)(modul, modcls)
155+
cls.registeredCompanion = modcls
156+
modcls.registeredCompanion = cls
157+
60158
end NamerOps

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

Lines changed: 13 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -951,7 +951,8 @@ object SymDenotations {
951951

952952
/** An erased value or an erased inline method or field */
953953
def isEffectivelyErased(using Context): Boolean =
954-
is(Erased) || is(Inline) && !isRetainedInline && !hasAnnotation(defn.ScalaStaticAnnot)
954+
isOneOf(EffectivelyErased)
955+
|| is(Inline) && !isRetainedInline && !hasAnnotation(defn.ScalaStaticAnnot)
955956

956957
/** ()T and => T types should be treated as equivalent for this symbol.
957958
* Note: For the moment, we treat Scala-2 compiled symbols as loose matching,
@@ -2165,6 +2166,8 @@ object SymDenotations {
21652166
if (companion.isClass && !isAbsent(canForce = false) && !companion.isAbsent(canForce = false))
21662167
myCompanion = companion
21672168

2169+
private[core] def unforcedRegisteredCompanion: Symbol = myCompanion
2170+
21682171
override def registeredCompanion(using Context) =
21692172
if !myCompanion.exists then
21702173
ensureCompleted()
@@ -2256,6 +2259,15 @@ object SymDenotations {
22562259
case d: DenotUnion => dropStale(d)
22572260
case d => d
22582261

2262+
/** Filter symbols making up a DenotUnion to remove alternatives from stale classfiles.
2263+
* This proceeds as follow:
2264+
*
2265+
* - prefer alternatives that are currently compiled over ones that have been compiled before.
2266+
* - if no alternative is compiled now, and they all come from the same file, keep all of them
2267+
* - if no alternative is compiled now, and they come from different files, keep the
2268+
* ones from the youngest file, but issue a warning that one of the class files
2269+
* should be removed from the classpath.
2270+
*/
22592271
def dropStale(multi: DenotUnion): PreDenotation =
22602272
val compiledNow = multi.filterWithPredicate(d =>
22612273
d.symbol.isDefinedInCurrentRun || d.symbol.associatedFile == null

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

Lines changed: 12 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -359,13 +359,19 @@ abstract class SymbolLoader extends LazyType { self =>
359359
throw ex
360360
}
361361
finally {
362-
def postProcess(denot: SymDenotation) =
363-
if (!denot.isCompleted &&
364-
!denot.completer.isInstanceOf[SymbolLoaders.SecondCompleter])
365-
denot.markAbsent()
366-
postProcess(root)
362+
def postProcess(denot: SymDenotation, other: Symbol) =
363+
if !denot.isCompleted &&
364+
!denot.completer.isInstanceOf[SymbolLoaders.SecondCompleter] then
365+
if denot.is(ModuleClass) && NamerOps.needsConstructorProxies(other) then
366+
NamerOps.makeConstructorCompanion(denot.sourceModule.asTerm, other.asClass)
367+
denot.resetFlag(Touched)
368+
else
369+
denot.markAbsent()
370+
371+
val other = if root.isRoot then NoSymbol else root.scalacLinkedClass
372+
postProcess(root, other)
367373
if (!root.isRoot)
368-
postProcess(root.scalacLinkedClass.denot)
374+
postProcess(other, root.symbol)
369375
}
370376
}
371377

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

Lines changed: 10 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -54,14 +54,17 @@ object Symbols {
5454
//assert(id != 723)
5555

5656
def coord: Coord = myCoord
57+
5758
/** Set the coordinate of this class, this is only useful when the coordinate is
5859
* not known at symbol creation. This is the case for root symbols
5960
* unpickled from TASTY.
6061
*
6162
* @pre coord == NoCoord
6263
*/
6364
private[core] def coord_=(c: Coord): Unit = {
64-
assert(myCoord == NoCoord)
65+
// assert(myCoord == NoCoord)
66+
// This assertion fails for CommentPickling test.
67+
// TODO: figure out what's wrong in the setup of CommentPicklingTest and re-enable assertion.
6568
myCoord = c
6669
}
6770

@@ -135,8 +138,12 @@ object Symbols {
135138
/** Does this symbol come from a currently compiled source file? */
136139
final def isDefinedInCurrentRun(using Context): Boolean =
137140
span.exists && defRunId == ctx.runId && {
138-
val file = associatedFile
139-
file != null && ctx.run.files.contains(file)
141+
try
142+
val file = associatedFile
143+
file != null && ctx.run.files.contains(file)
144+
catch case ex: StaleSymbol =>
145+
// can happen for constructor proxy companions. Test case is pos-macros/i9484.
146+
false
140147
}
141148

142149
/** Is symbol valid in current run? */

‎compiler/src/dotty/tools/dotc/core/classfile/ClassfileParser.scala

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -196,6 +196,7 @@ class ClassfileParser(
196196
addAnnotationConstructor(classInfo.asInstanceOf[TempClassInfoType])
197197

198198
setClassInfo(classRoot, classInfo, fromScala2 = false)
199+
NamerOps.addConstructorProxies(moduleRoot.classSymbol)
199200
}
200201
else if (result == Some(NoEmbedded))
201202
for (sym <- List(moduleRoot.sourceModule, moduleRoot.symbol, classRoot.symbol)) {

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

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -940,6 +940,7 @@ class TreeUnpickler(reader: TastyReader,
940940
tparams ++ vparams ++ stats
941941
})
942942
defn.patchStdLibClass(cls)
943+
NamerOps.addConstructorProxies(cls)
943944
setSpan(start,
944945
untpd.Template(constr, mappedParents, Nil, self, lazyStats)
945946
.withType(localDummy.termRef))

‎compiler/src/dotty/tools/dotc/core/unpickleScala2/Scala2Unpickler.scala

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -582,6 +582,7 @@ class Scala2Unpickler(bytes: Array[Byte], classRoot: ClassDenotation, moduleClas
582582
case denot: ClassDenotation if !isRefinementClass(denot.symbol) =>
583583
val selfInfo = if (atEnd) NoType else readTypeRef()
584584
setClassInfo(denot, tp, fromScala2 = true, selfInfo)
585+
NamerOps.addConstructorProxies(denot.classSymbol)
585586
case denot =>
586587
val tp1 = translateTempPoly(tp)
587588
denot.info =

‎compiler/src/dotty/tools/dotc/semanticdb/ExtractSemanticDB.scala

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -89,6 +89,7 @@ class ExtractSemanticDB extends Phase:
8989

9090
private def excludeSymbol(sym: Symbol)(using Context): Boolean =
9191
!sym.exists
92+
|| sym.is(ConstructorProxy)
9293
|| sym.name.isWildcard
9394
|| excludeQual(sym)
9495

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

Lines changed: 17 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -976,6 +976,23 @@ object Erasure {
976976
override def typedTypeDef(tdef: untpd.TypeDef, sym: Symbol)(using Context): Tree =
977977
EmptyTree
978978

979+
/** Drop all constructor proxies of members of class `cls`.
980+
* If `cls` is itself a constructor proxy, mark it as absent after erasure.
981+
*/
982+
private def dropConstructorProxies(cls: ClassSymbol)(using Context) =
983+
import Flags._
984+
if cls.linkedClass.is(ConstructorProxy) then
985+
if cls.owner.is(PackageClass) && cls.isDefinedInCurrentRun then
986+
cls.linkedClass.copySymDenotation(initFlags = EmptyFlags, info = NoType)
987+
.installAfter(erasurePhase)
988+
cls.registeredCompanion = NoSymbol
989+
for mbr <- cls.info.decls do
990+
if mbr.is(ConstructorProxy) then mbr.dropAfter(erasurePhase)
991+
992+
override def typedClassDef(cdef: untpd.TypeDef, cls: ClassSymbol)(using Context): Tree =
993+
try super.typedClassDef(cdef, cls)
994+
finally dropConstructorProxies(cls)
995+
979996
override def typedAnnotated(tree: untpd.Annotated, pt: Type)(using Context): Tree =
980997
typed(tree.arg, pt)
981998

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

Lines changed: 4 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -253,7 +253,10 @@ class Mixin extends MiniPhase with SymTransformer { thisPhase =>
253253

254254
for
255255
getter <- mixin.info.decls.toList
256-
if getter.isGetter && !wasOneOf(getter, Deferred) && !getter.isConstExprFinalVal
256+
if getter.isGetter
257+
&& !getter.isEffectivelyErased
258+
&& !wasOneOf(getter, Deferred)
259+
&& !getter.isConstExprFinalVal
257260
yield
258261
if (isCurrent(getter) || getter.name.is(ExpandedName)) {
259262
val rhs =

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

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -143,10 +143,10 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer { thisPhase
143143
}
144144

145145
private def processValOrDefDef(tree: Tree)(using Context): tree.type =
146+
val sym = tree.symbol
146147
tree match
147-
case tree: ValOrDefDef if !tree.symbol.is(Synthetic) =>
148+
case tree: ValOrDefDef if !sym.is(Synthetic) =>
148149
checkInferredWellFormed(tree.tpt)
149-
val sym = tree.symbol
150150
if sym.is(Method) then
151151
if sym.isSetter then
152152
removeUnwantedAnnotations(sym, defn.SetterMetaAnnot, NoSymbol, keepIfNoRelevantAnnot = false)

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