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Fix cyclic reference errors in collection strawman #2914

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Merged
merged 4 commits into from
Aug 2, 2017
Merged

Fix cyclic reference errors in collection strawman #2914

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725ccdd
Pickle LazyRefs
odersky Jul 25, 2017
bcbd456
Be more careful reading applied types from Tasty
odersky Jul 25, 2017
b765b95
Survive cyclic reference errors when printing an error message.
odersky Jul 25, 2017
dd661bf
Make LazyRef completers take a context
odersky Jul 26, 2017
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5 changes: 4 additions & 1 deletion compiler/src/dotty/tools/dotc/core/tasty/TastyFormat.scala
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Expand Up @@ -164,6 +164,7 @@ Standard-Section: "ASTs" TopLevelStat*
BIND Length boundName_NameRef bounds_Type
// for type-variables defined in a type pattern
BYNAMEtype underlying_Type
LAZYref underlying_Type
POLYtype Length result_Type NamesTypes
METHODtype Length result_Type NamesTypes // needed for refinements
TYPELAMBDAtype Length result_Type NamesTypes // variance encoded in front of name: +/-/(nothing)
Expand Down Expand Up @@ -256,7 +257,7 @@ object TastyFormat {
final val OBJECTCLASS = 40

final val SIGNED = 63

final val firstInternalTag = 64
final val IMPLMETH = 64

Expand Down Expand Up @@ -322,6 +323,7 @@ object TastyFormat {
final val PROTECTEDqualified = 105
final val RECtype = 106
final val SINGLETONtpt = 107
final val LAZYref = 108

final val IDENT = 112
final val IDENTtpt = 113
Expand Down Expand Up @@ -512,6 +514,7 @@ object TastyFormat {
case DOUBLEconst => "DOUBLEconst"
case STRINGconst => "STRINGconst"
case RECtype => "RECtype"
case LAZYref => "LAZYref"

case IDENT => "IDENT"
case IDENTtpt => "IDENTtpt"
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1 change: 1 addition & 0 deletions compiler/src/dotty/tools/dotc/core/tasty/TreePickler.scala
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Expand Up @@ -246,6 +246,7 @@ class TreePickler(pickler: TastyPickler) {
case tpe: ParamRef =>
assert(pickleParamRef(tpe), s"orphan parameter reference: $tpe")
case tpe: LazyRef =>
writeByte(LAZYref)
pickleType(tpe.ref)
}

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12 changes: 11 additions & 1 deletion compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala
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Expand Up @@ -293,6 +293,11 @@ class TreeUnpickler(reader: TastyReader, nameAtRef: NameRef => TermName, posUnpi
RecType(rt => registeringType(rt, readType()))
case RECthis =>
RecThis(readTypeRef().asInstanceOf[RecType])
case LAZYref =>
val rdr = fork
def readUnderlying() = rdr.readType()
skipTree()
LazyRef(readUnderlying)
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This means LazyRefs will keep the context from which they were unpickled around, if these LazyRefs are subsequently stored in some cache, that could lead to space leaks, no?

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@odersky odersky Jul 25, 2017 •
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Yes, correct. Maybe the best option is to allow a context to be passed into a LazyRef completer. In the case of unpickling, this is fine; we don't need to hang on to more than the reader (I think, at least that's what we do for the other completers).

case SHARED =>
val ref = readAddr()
typeAtAddr.getOrElseUpdate(ref, forkAt(ref).readType())
Expand Down Expand Up @@ -991,7 +996,12 @@ class TreeUnpickler(reader: TastyReader, nameAtRef: NameRef => TermName, posUnpi
val refinements = readStats(refineCls, end)(localContext(refineCls))
RefinedTypeTree(parent, refinements, refineCls)
case APPLIEDtpt =>
AppliedTypeTree(readTpt(), until(end)(readTpt()))
// If we do directly a tpd.AppliedType tree we might get a
// wrong number of arguments in some scenarios reading F-bounded
// types. This came up in #137 of collection strawman.
val tycon = readTpt()
val args = until(end)(readTpt())
untpd.AppliedTypeTree(tycon, args).withType(tycon.tpe.safeAppliedTo(args.tpes))
case ANDtpt =>
val tpt1 = readTpt()
val tpt2 = readTpt()
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14 changes: 10 additions & 4 deletions compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala
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Expand Up @@ -23,6 +23,7 @@ import dotty.tools.dotc.ast.Trees
import dotty.tools.dotc.ast.untpd.Modifiers
import dotty.tools.dotc.core.Flags.{FlagSet, Mutable}
import dotty.tools.dotc.core.SymDenotations.SymDenotation
import scala.util.control.NonFatal

object messages {

Expand Down Expand Up @@ -708,10 +709,15 @@ object messages {

private val actualArgString = actual.map(_.show).mkString("[", ", ", "]")

private val prettyName = fntpe.termSymbol match {
case NoSymbol => fntpe.show
case symbol => symbol.showFullName
}
private val prettyName =
try
fntpe.termSymbol match {
case NoSymbol => fntpe.show
case symbol => symbol.showFullName
}
catch {
case NonFatal(ex) => fntpe.show
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If this is only for cyclic references, could we do case ex: CyclicReference instead?

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I think we by default we should not throw any exception from printing. It detracts from the underlying cause.

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Sure, but we shouldn't be throwing any kind of exceptions, and silently catching them all might hide issues.

}

val msg =
hl"""|${NoColor(msgPrefix)} type arguments for $prettyName$expectedArgString
Expand Down