tasty error when declaring subclass field type and overriding (thrown when publishing) #12834

hughsimpson · 2021-06-15T14:44:16Z

Compiler version

3.0.0

Minimized code

class A(val ref: Option[B]) {}
class B(override val ref: Option[B]) extends A(ref = ref) {}

Output

runs fine, but when publishing with sbt publishLocal throws

[error] 8 |class B(override val ref: Option[B]) extends A(ref = ref) {}
[error]   |                                             ^^^^^^^^^^^
[error]   |undefined: new bug.A # -1: TermRef(TypeRef(TermRef(ThisType(TypeRef(NoPrefix,module class <root>)),object bug),A),<init>) at readTasty

Expectation

This should be fine (is a regression from scala 2)

The text was updated successfully, but these errors were encountered:

romanowski · 2021-06-15T21:51:16Z

It seems that this tasty inspector does not handle cycles well. The problem can be minimized even further:

class A(val ref: Option[B])
class B extends A(None)

smarter · 2021-06-15T22:26:17Z

This isn't specific to the inspector, it's also reproducible when compiling with -Ythrough-tasty, we can add something like this to find where the undefined TermRef is constructed:

diff --git compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala
index c8220d7e760..1e4d6d6235a 100644
--- compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala
+++ compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala
@@ -1290,6 +1290,11 @@ class TreeUnpickler(reader: TastyReader,
       }

       val tree = if (tag < firstLengthTreeTag) readSimpleTerm() else readLengthTerm()
+      tree.tpe match
+        case tp: TermRef =>
+          assert(tp.denot.exists, tp)
+        case _ =>
+
       if (!tree.isInstanceOf[TypTree]) // FIXME: Necessary to avoid self-type cyclic reference in tasty_tools
         tree.overwriteType(tree.tpe.simplified)
       setSpan(start, tree)

which gives us:

java.lang.AssertionError: assertion failed: TermRef(TypeRef(ThisType(TypeRef(ThisType(TypeRef(NoPrefix,module class <root>)),module class <empty>)),A),<init>)
        at scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8)
        at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTerm(TreeUnpickler.scala:1295)
        at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readLengthTerm$1(TreeUnpickler.scala:1132)
        at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTerm(TreeUnpickler.scala:1292)
        at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.$anonfun$4(TreeUnpickler.scala:927)
        at dotty.tools.tasty.TastyReader.collectWhile(TastyReader.scala:137)
        at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTemplate(TreeUnpickler.scala:930)
        at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readNewDef(TreeUnpickler.scala:857)
        at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readIndexedDef(TreeUnpickler.scala:776)
        at dotty.tools.dotc.core.tasty.TreeUnpickler$Completer.complete(TreeUnpickler.scala:122)
        at dotty.tools.dotc.core.SymDenotations$SymDenotation.completeFrom(SymDenotations.scala:167)
        at dotty.tools.dotc.core.Denotations$Denotation.completeInfo$1(Denotations.scala:188)
        at dotty.tools.dotc.core.Denotations$Denotation.info(Denotations.scala:190)
        at dotty.tools.dotc.core.Denotations$Denotation.completeInfo$1(Denotations.scala:188)
        at dotty.tools.dotc.core.Denotations$Denotation.info(Denotations.scala:190)
        at dotty.tools.dotc.core.SymDenotations$SymDenotation.ensureCompleted(SymDenotations.scala:369)
        at dotty.tools.dotc.core.SymDenotations$SymDenotation.flags(SymDenotations.scala:65)
        at dotty.tools.dotc.core.SymDenotations$SymDenotation.is(SymDenotations.scala:116)
        at dotty.tools.dotc.typer.Checking$NotPrivate$1.isLeaked(Checking.scala:569)
        at dotty.tools.dotc.typer.Checking$NotPrivate$1.apply(Checking.scala:580)
        at dotty.tools.dotc.core.Types$TypeMap.op$proxy16$1(Types.scala:5281)
        at dotty.tools.dotc.core.Types$TypeMap.mapArgs(Types.scala:5281)
        at dotty.tools.dotc.core.Types$TypeMap.mapOver(Types.scala:5316)
        at dotty.tools.dotc.typer.Checking$NotPrivate$1.apply(Checking.scala:610)
        at dotty.tools.dotc.typer.Checking$.checkNoPrivateLeaks(Checking.scala:614)
        at dotty.tools.dotc.typer.TypeAssigner.avoidPrivateLeaks(TypeAssigner.scala:47)
        at dotty.tools.dotc.typer.TypeAssigner.avoidPrivateLeaks$(TypeAssigner.scala:19)
        at dotty.tools.dotc.typer.Typer.avoidPrivateLeaks(Typer.scala:106)
        at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readNewDef(TreeUnpickler.scala:889)
        at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readIndexedDef(TreeUnpickler.scala:776)
        at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readIndexedParams$$anonfun$2(TreeUnpickler.scala:1037)
        at dotty.tools.tasty.TastyReader.collectWhile(TastyReader.scala:137)
        at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readIndexedParams(TreeUnpickler.scala:1037)
        at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTemplate(TreeUnpickler.scala:916)
        at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readNewDef(TreeUnpickler.scala:857)
        at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readIndexedDef(TreeUnpickler.scala:776)
        at dotty.tools.dotc.core.tasty.TreeUnpickler$Completer.complete(TreeUnpickler.scala:122)
        at dotty.tools.dotc.core.SymDenotations$SymDenotation.completeFrom(SymDenotations.scala:167)
        at dotty.tools.dotc.core.Denotations$Denotation.completeInfo$1(Denotations.scala:188)
        at dotty.tools.dotc.core.Denotations$Denotation.info(Denotations.scala:190)
        at dotty.tools.dotc.core.SymDenotations$SymDenotation.ensureCompleted(SymDenotations.scala:369)
        at dotty.tools.dotc.core.Symbols$ClassSymbol.rootTreeContaining(Symbols.scala:393)
        at dotty.tools.dotc.core.Symbols$ClassSymbol.rootTree(Symbols.scala:384)
        at dotty.tools.dotc.fromtasty.ReadTasty.compilationUnit$1(ReadTasty.scala:40)
        at dotty.tools.dotc.fromtasty.ReadTasty.readTASTY(ReadTasty.scala:70)
        at dotty.tools.dotc.fromtasty.ReadTasty.runOn$$anonfun$1(ReadTasty.scala:25)
        at scala.collection.immutable.List.flatMap(List.scala:293)
        at dotty.tools.dotc.fromtasty.ReadTasty.runOn(ReadTasty.scala:25)
        at dotty.tools.dotc.Run.runPhases$4$$anonfun$4(Run.scala:205)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
        at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
        at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1323)
        at dotty.tools.dotc.Run.runPhases$5(Run.scala:216)
        at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:224)
        at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.scala:18)
        at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:67)
        at dotty.tools.dotc.Run.compileUnits(Run.scala:231)
        at dotty.tools.dotc.Run.compileUnits(Run.scala:172)
        at dotty.tools.dotc.fromtasty.TASTYRun.compile(TASTYRun.scala:11)
        at dotty.tools.dotc.Driver.doCompile(Driver.scala:39)
        at dotty.tools.dotc.Driver.process(Driver.scala:199)
        at dotty.tools.dotc.Driver.process(Driver.scala:167)
        at dotty.tools.dotc.Driver.process(Driver.scala:179)
        at dotty.tools.dotc.fromtasty.Debug$.main(Debug.scala:52)
        at dotty.tools.dotc.fromtasty.Debug.main(Debug.scala)

so basically when we unpickle A we first unpickle the class parameters like ref, once we have a symbol for that we run avoidPrivateLeaks on it which forces the symbol info, which forces B, which forces the parents of B which contain a reference to the constructor of A which hasn't been unpickled yet, hence the error. If we could avoid running avoidPrivateLeaks we wouldn't run into this issue. The job of avoidPrivateLeaks in the unpickler is to get rid of any inaccessible type alias by de-aliasing them, as in:

class Foo {
  private type T = Int
  val x: T // dealiased to Int when unpickling
}

but I don't think that class parameters can refer to type aliases defined in the class, since they're always of the form class Foo(val someParam: ...), so we might be able to get away with just not running avoidPrivateLeaks at all on them:

diff --git compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala
index c8220d7e760..2c32e3c5648 100644
--- compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala
+++ compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala
@@ -885,7 +885,7 @@ class TreeUnpickler(reader: TastyReader,
       }
       goto(end)
       setSpan(start, tree)
-      if (!sym.isType) // Only terms might have leaky aliases, see the documentation of `checkNoPrivateLeaks`
+      if (!sym.isType && !sym.is(ParamAccessor)) // Only terms might have leaky aliases, see the documentation of `checkNoPrivateLeaks`
         sym.info = ta.avoidPrivateLeaks(sym)

       if (ctx.settings.YreadComments.value) {

smarter · 2021-06-16T09:26:58Z

By the way, as a work around you can disable scaladoc generation:

Compile / doc / sources := Seq()

When unpickling a template like `A` in i12834.scala, the first thing we do is to unpickle its class parameters, here that's `ref`. While unpickling `ref` we run `avoidPrivateLeaks` on it which forces its info and requires unpickling `B` which refers to `A.<init>` which leads to a crash because we haven't entered `<init>` in `A` yet. We can avoid this cycle by simply not running `avoidPrivateLeaks` on param accessors, this should be safe since a primary constructor parameter cannot refer to a type member of the class. Fixes scala#12834.

hughsimpson added the itype:bug label Jun 15, 2021

griggt added the area:doctool label Jun 15, 2021

hughsimpson mentioned this issue Jun 15, 2021

Initial scala 3 support babylonhealth/lit-fhir#27

Merged

romanowski added the area:tasty-inspector issues relating to the TASTy inspector label Jun 15, 2021

romanowski assigned nicolasstucki Jun 15, 2021

smarter assigned smarter and unassigned nicolasstucki Jun 15, 2021

smarter mentioned this issue Jun 16, 2021

TreeUnpickler: fix cycle involving param accessor #12844

Merged

bishabosha closed this as completed in #12844 Jun 18, 2021

bishabosha mentioned this issue Jun 18, 2021

cyclic reference crash with -from-tasty with parents/params loop #12872

Open

bishabosha added area:pickling and removed area:tasty-inspector issues relating to the TASTy inspector area:doctool labels Jun 18, 2021

Kordyjan added this to the 3.0.2 milestone Aug 2, 2023

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tasty error when declaring subclass field type and overriding (thrown when publishing) #12834

tasty error when declaring subclass field type and overriding (thrown when publishing) #12834

hughsimpson commented Jun 15, 2021

romanowski commented Jun 15, 2021

smarter commented Jun 15, 2021 •

edited

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smarter commented Jun 16, 2021

tasty error when declaring subclass field type and overriding (thrown when publishing) #12834

tasty error when declaring subclass field type and overriding (thrown when publishing) #12834

Comments

hughsimpson commented Jun 15, 2021

Compiler version

Minimized code

Output

Expectation

romanowski commented Jun 15, 2021

smarter commented Jun 15, 2021 • edited Loading

smarter commented Jun 16, 2021

smarter commented Jun 15, 2021 •

edited

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