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Linyxus opened this issue Aug 27, 2022 · 1 comment · Fixed by #16542
Closed

Capture checker triggers AssertionError on function application #15925

Linyxus opened this issue Aug 27, 2022 · 1 comment · Fixed by #16542
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@Linyxus
Labels
cc-experiment Intended to be merged with cc-experiment branch on origin itype:bug
Milestone
3.3.0

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@Linyxus
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Linyxus commented Aug 27, 2022 •
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Compiler version

cc-experiment

Minimized code

class Unit
object unit extends Unit

type Foo[X] = [T] -> (op: X => T) -> T
type Lazy[X] = {*} Unit -> X

def force[X](fx: Foo[Lazy[X]]): X =
  fx[X](f => f(unit))

Output

exception occurred while compiling issues/funargs-minimised.scala
java.lang.AssertionError: assertion failed while compiling issues/funargs-minimised.scala
Exception in thread "main" java.lang.AssertionError: assertion failed
	at scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:11)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckApply(Recheck.scala:203)
	at dotty.tools.dotc.cc.CheckCaptures$CaptureChecker.recheckApply(CheckCaptures.scala:306)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckUnnamed$1(Recheck.scala:367)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckStart(Recheck.scala:390)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheck(Recheck.scala:406)
	at dotty.tools.dotc.cc.CheckCaptures$CaptureChecker.recheck(CheckCaptures.scala:509)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckDefDef(Recheck.scala:173)
	at dotty.tools.dotc.cc.CheckCaptures$CaptureChecker.recheckDefDef(CheckCaptures.scala:443)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckDef(Recheck.scala:334)
	at dotty.tools.dotc.cc.CheckCaptures$CaptureChecker.checkUnit$$anonfun$1$$anonfun$1(CheckCaptures.scala:662)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at dotty.tools.dotc.cc.Setup$$anon$4.complete(Setup.scala:433)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.completeFrom(SymDenotations.scala:173)
	at dotty.tools.dotc.core.Denotations$Denotation.completeInfo$1(Denotations.scala:187)
	at dotty.tools.dotc.core.Denotations$Denotation.info(Denotations.scala:189)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.ensureCompleted(SymDenotations.scala:380)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckNamed$1(Recheck.scala:353)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckStart(Recheck.scala:389)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheck(Recheck.scala:406)
	at dotty.tools.dotc.cc.CheckCaptures$CaptureChecker.recheck(CheckCaptures.scala:509)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckStats$$anonfun$1(Recheck.scala:328)
	at scala.collection.immutable.List.foreach(List.scala:333)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckStats(Recheck.scala:328)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckBlock(Recheck.scala:240)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckBlock(Recheck.scala:248)
	at dotty.tools.dotc.cc.CheckCaptures$CaptureChecker.recheckBlock(CheckCaptures.scala:424)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckUnnamed$1(Recheck.scala:372)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckStart(Recheck.scala:390)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheck(Recheck.scala:406)
	at dotty.tools.dotc.cc.CheckCaptures$CaptureChecker.recheck(CheckCaptures.scala:509)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckArgs$1(Recheck.scala:209)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckApply(Recheck.scala:218)
	at dotty.tools.dotc.cc.CheckCaptures$CaptureChecker.recheckApply(CheckCaptures.scala:306)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckUnnamed$1(Recheck.scala:367)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckStart(Recheck.scala:390)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheck(Recheck.scala:406)
	at dotty.tools.dotc.cc.CheckCaptures$CaptureChecker.recheck(CheckCaptures.scala:509)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckDefDef(Recheck.scala:173)
	at dotty.tools.dotc.cc.CheckCaptures$CaptureChecker.recheckDefDef(CheckCaptures.scala:443)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckDef(Recheck.scala:334)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckNamed$1(Recheck.scala:355)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckStart(Recheck.scala:389)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheck(Recheck.scala:406)
	at dotty.tools.dotc.cc.CheckCaptures$CaptureChecker.recheck(CheckCaptures.scala:509)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckStats$$anonfun$1(Recheck.scala:328)
	at scala.collection.immutable.List.foreach(List.scala:333)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckStats(Recheck.scala:328)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckClassDef(Recheck.scala:183)
	at dotty.tools.dotc.cc.CheckCaptures$CaptureChecker.recheckClassDef(CheckCaptures.scala:464)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckNamed$1(Recheck.scala:361)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckStart(Recheck.scala:389)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheck(Recheck.scala:406)
	at dotty.tools.dotc.cc.CheckCaptures$CaptureChecker.recheck(CheckCaptures.scala:509)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckStats$$anonfun$1(Recheck.scala:328)
	at scala.collection.immutable.List.foreach(List.scala:333)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckStats(Recheck.scala:328)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckPackageDef(Recheck.scala:324)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckUnnamed$1(Recheck.scala:384)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheckStart(Recheck.scala:390)
	at dotty.tools.dotc.transform.Recheck$Rechecker.recheck(Recheck.scala:406)
	at dotty.tools.dotc.cc.CheckCaptures$CaptureChecker.recheck(CheckCaptures.scala:509)
	at dotty.tools.dotc.transform.Recheck$Rechecker.checkUnit(Recheck.scala:441)
	at dotty.tools.dotc.cc.CheckCaptures$CaptureChecker.checkUnit$$anonfun$2(CheckCaptures.scala:665)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at dotty.tools.dotc.cc.CaptureSet$.withCaptureSetsExplained(CaptureSet.scala:897)
	at dotty.tools.dotc.cc.CheckCaptures$CaptureChecker.checkUnit(CheckCaptures.scala:670)
	at dotty.tools.dotc.transform.Recheck.run(Recheck.scala:111)
	at dotty.tools.dotc.cc.CheckCaptures.run(CheckCaptures.scala:134)
	at dotty.tools.dotc.core.Phases$Phase.runOn$$anonfun$1(Phases.scala:316)
	at scala.collection.immutable.List.map(List.scala:246)
	at dotty.tools.dotc.core.Phases$Phase.runOn(Phases.scala:317)
	at dotty.tools.dotc.Run.runPhases$1$$anonfun$1(Run.scala:233)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:15)
	at scala.runtime.function.JProcedure1.apply(JProcedure1.java:10)
	at scala.collection.ArrayOps$.foreach$extension(ArrayOps.scala:1328)
	at dotty.tools.dotc.Run.runPhases$1(Run.scala:244)
	at dotty.tools.dotc.Run.compileUnits$$anonfun$1(Run.scala:252)
	at dotty.tools.dotc.Run.compileUnits$$anonfun$adapted$1(Run.scala:261)
	at dotty.tools.dotc.util.Stats$.maybeMonitored(Stats.scala:68)
	at dotty.tools.dotc.Run.compileUnits(Run.scala:261)
	at dotty.tools.dotc.Run.compileSources(Run.scala:185)
	at dotty.tools.dotc.Run.compile(Run.scala:169)
	at dotty.tools.dotc.Driver.doCompile(Driver.scala:35)
	at dotty.tools.dotc.Driver.process(Driver.scala:195)
	at dotty.tools.dotc.Driver.process(Driver.scala:163)
	at dotty.tools.dotc.Driver.process(Driver.scala:175)
	at dotty.tools.dotc.Driver.main(Driver.scala:205)
	at dotty.tools.dotc.Main.main(Main.scala)

Expectation

The code should compile successfully.

According to the backtrace, the assertion fails because the number of arguments of the function type mismatches with actual arguments when rechecking f.apply(unit).
@Linyxus Linyxus added itype:bug stat:needs triage Every issue needs to have an "area" and "itype" label labels Aug 27, 2022
@Linyxus Linyxus changed the title Capture checker triggers AssertionError for function application Capture checker triggers AssertionError on function application Aug 27, 2022
@Linyxus
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Linyxus commented Aug 27, 2022

Note: the failure is related to the type definition Lazy, since the following code compiles:

class Unit
object unit extends Unit

type Foo[X] = [T] -> (op: X => T) -> T
// type Lazy[X] = {*} Unit -> X

def force[X](fx: Foo[{*} Unit -> X]): X =
  fx[X](f => f(unit))

@Linyxus Linyxus added cc-experiment Intended to be merged with cc-experiment branch on origin and removed stat:needs triage Every issue needs to have an "area" and "itype" label labels Aug 27, 2022
@Linyxus Linyxus self-assigned this Oct 19, 2022
@Linyxus Linyxus mentioned this issue Dec 16, 2022
Merged
odersky added a commit that referenced this issue Dec 20, 2022
@odersky
Fix dependent function setup for capture checking (#16542)
0397de1 
Fixes #15925.

This issue is caused by a bug in `mapInferred` during CC `Setup`. In
this function we convert all top-level non-dependent functions to its
dependent counterpart. However, it does not correctly handle the case
when the type is an alias to function types. The problematic case in the
pattern matching:
```scala
case tp @ AppliedType(tycon, args) =>
  val tycon1 = this(tycon)
  if defn.isNonRefinedFunction(tp) then
    // Convert toplevel generic function types to dependent functions
    val args0 = args.init
    var res0 = args.last
    val args1 = mapNested(args0)
    val res1 = this(res0)
    // ... do the conversion
```
It retrieves the argument and the result type of the function directly
from the applied type arguments. This works for function classes.
However, if the type here is a type alias to the function, e.g. `type
Lazy[X] = Unit => X`, it is still recognized as a function (since
`defn.isNonRefinedFunction` does dealiasing) but it is incorrect to get
the argument and result type of the function from the type parameter
list here (which is just `X :: Nil`).

To fix this, we will dealias the type and recurse when it is an alias to
the function type.
@Kordyjan Kordyjan added this to the 3.3.0 milestone Aug 1, 2023
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@Linyxus Linyxus

Labels
cc-experiment Intended to be merged with cc-experiment branch on origin itype:bug
Projects
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Milestone
3.3.0
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Fix dependent function setup for capture checking dotty-staging/dotty
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@Linyxus @Kordyjan