MissingType crash for code completions

[prolativ]

Compiler version

Breaks with: 3.2.0, 3.nightly
Used to work with: 3.1.3

Minimized code

scala-cli repl --dep "com.softwaremill.sttp.client3::core:3.8.3" -S 3.2.0

scala> import sttp.client3.<TAB>

Output (click arrow to expand)

Oct 21, 2022 10:22:50 AM org.jline.utils.Log logr
INFO: Error while finding completion candidates
dotty.tools.dotc.core.TypeError: Could not read definition of class HttpClientAsyncBackend in /Users/mpalka/Library/Caches/Coursier/v1/https/repo1.maven.org/maven2/com/softwaremill/sttp/client3/core_3/3.8.3/core_3-3.8.3.jar(sttp/client3/HttpClientAsyncBackend.class)
An exception was encountered:
  dotty.tools.dotc.core.MissingType: 
Run with -Ydebug-unpickling to see full stack trace.
	at dotty.tools.dotc.core.tasty.TreeUnpickler.dotty$tools$dotc$core$tasty$TreeUnpickler$Completer$$_$fail$1(TreeUnpickler.scala:128)
	at dotty.tools.dotc.core.tasty.TreeUnpickler$Completer.liftedTree1$1(TreeUnpickler.scala:137)
	at dotty.tools.dotc.core.tasty.TreeUnpickler$Completer.complete(TreeUnpickler.scala:137)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.completeFrom(SymDenotations.scala:171)
	at dotty.tools.dotc.core.Denotations$Denotation.completeInfo$1(Denotations.scala:187)
	at dotty.tools.dotc.core.Denotations$Denotation.info(Denotations.scala:189)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.ensureCompleted(SymDenotations.scala:373)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.flags(SymDenotations.scala:64)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.is(SymDenotations.scala:110)
	at dotty.tools.dotc.interactive.Completion$Completer.dotty$tools$dotc$interactive$Completion$Completer$$include(Completion.scala:471)
	at dotty.tools.dotc.interactive.Completion$Completer$$anon$4.applyOrElse(Completion.scala:504)
	at dotty.tools.dotc.interactive.Completion$Completer$$anon$4.applyOrElse(Completion.scala:503)
	at scala.collection.immutable.List.collect(List.scala:275)
	at scala.collection.immutable.List.collect(List.scala:79)
	at dotty.tools.dotc.interactive.Completion$Completer.accessibleMembers(Completion.scala:505)
	at dotty.tools.dotc.interactive.Completion$Completer.directMemberCompletions(Completion.scala:339)
	at dotty.tools.dotc.interactive.Completion$.computeCompletions(Completion.scala:149)
	at dotty.tools.dotc.interactive.Completion$.completions(Completion.scala:48)
	at dotty.tools.repl.ReplDriver.completions$$anonfun$1(ReplDriver.scala:240)
	at scala.util.Either.map(Either.scala:382)
	at dotty.tools.repl.ReplDriver.completions(ReplDriver.scala:241)
	at dotty.tools.repl.ReplDriver.$anonfun$1(ReplDriver.scala:151)
	at org.jline.reader.impl.LineReaderImpl.doComplete(LineReaderImpl.java:4412)
	at org.jline.reader.impl.LineReaderImpl.doComplete(LineReaderImpl.java:4378)
	at org.jline.reader.impl.LineReaderImpl.expandOrComplete(LineReaderImpl.java:4317)
	at org.jline.reader.impl.LineReaderImpl$1.apply(LineReaderImpl.java:3809)
	at org.jline.reader.impl.LineReaderImpl.readLine(LineReaderImpl.java:679)
	at org.jline.reader.impl.LineReaderImpl.readLine(LineReaderImpl.java:468)
	at dotty.tools.repl.JLineTerminal.readLine(JLineTerminal.scala:74)
	at dotty.tools.repl.ReplDriver.readLine$1(ReplDriver.scala:156)
	at dotty.tools.repl.ReplDriver.loop$1(ReplDriver.scala:166)
	at dotty.tools.repl.ReplDriver.runUntilQuit$$anonfun$1(ReplDriver.scala:171)
	at dotty.tools.repl.ReplDriver.withRedirectedOutput(ReplDriver.scala:192)
	at dotty.tools.repl.ReplDriver.runBody$$anonfun$1(ReplDriver.scala:180)
	at dotty.tools.runner.ScalaClassLoader$.asContext(ScalaClassLoader.scala:80)
	at dotty.tools.repl.ReplDriver.runBody(ReplDriver.scala:180)
	at dotty.tools.repl.ReplDriver.runUntilQuit(ReplDriver.scala:171)
	at dotty.tools.repl.ReplDriver.tryRunning(ReplDriver.scala:133)
	at dotty.tools.repl.Main$.main(Main.scala:7)
	at dotty.tools.repl.Main.main(Main.scala)

Output with -Ydebug-unpickling:

Oct 21, 2022 10:24:21 AM org.jline.utils.Log logr
INFO: Error while finding completion candidates
dotty.tools.dotc.core.MissingType: 
	at dotty.tools.dotc.core.TypeErasure.dotty$tools$dotc$core$TypeErasure$$sigName(TypeErasure.scala:815)
	at dotty.tools.dotc.core.TypeErasure$.sigName(TypeErasure.scala:204)
	at dotty.tools.dotc.core.Signature.$anonfun$2(Signature.scala:111)
	at scala.collection.immutable.List.map(List.scala:246)
	at dotty.tools.dotc.core.Signature.prependTermParams(Signature.scala:111)
	at dotty.tools.dotc.core.Types$MethodOrPoly.computeSignature$2(Types.scala:3565)
	at dotty.tools.dotc.core.Types$MethodOrPoly.signature(Types.scala:3582)
	at dotty.tools.dotc.core.Types$MethodOrPoly.computeSignature$2(Types.scala:3557)
	at dotty.tools.dotc.core.Types$MethodOrPoly.signature(Types.scala:3582)
	at dotty.tools.dotc.core.Denotations$SingleDenotation.signature(Denotations.scala:615)
	at dotty.tools.dotc.core.Denotations$SingleDenotation.signature(Denotations.scala:605)
	at dotty.tools.dotc.core.Denotations$SingleDenotation.atSignature(Denotations.scala:647)
	at dotty.tools.dotc.core.Denotations$SingleDenotation.atSignature(Denotations.scala:645)
	at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readLengthTerm$1(TreeUnpickler.scala:1299)
	at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTerm(TreeUnpickler.scala:1373)
	at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readLengthTerm$1(TreeUnpickler.scala:1215)
	at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTerm(TreeUnpickler.scala:1373)
	at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readLengthTerm$1(TreeUnpickler.scala:1210)
	at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTerm(TreeUnpickler.scala:1373)
	at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.$anonfun$19(TreeUnpickler.scala:962)
	at dotty.tools.tasty.TastyReader.collectWhile(TastyReader.scala:137)
	at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readTemplate(TreeUnpickler.scala:965)
	at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readNewDef(TreeUnpickler.scala:883)
	at dotty.tools.dotc.core.tasty.TreeUnpickler$TreeReader.readIndexedDef(TreeUnpickler.scala:802)
	at dotty.tools.dotc.core.tasty.TreeUnpickler$Completer.liftedTree1$1(TreeUnpickler.scala:133)
	at dotty.tools.dotc.core.tasty.TreeUnpickler$Completer.complete(TreeUnpickler.scala:137)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.completeFrom(SymDenotations.scala:171)
	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:373)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.flags(SymDenotations.scala:64)
	at dotty.tools.dotc.core.SymDenotations$SymDenotation.is(SymDenotations.scala:110)
	at dotty.tools.dotc.interactive.Completion$Completer.dotty$tools$dotc$interactive$Completion$Completer$$include(Completion.scala:471)
	at dotty.tools.dotc.interactive.Completion$Completer$$anon$4.applyOrElse(Completion.scala:504)
	at dotty.tools.dotc.interactive.Completion$Completer$$anon$4.applyOrElse(Completion.scala:503)
	at scala.collection.immutable.List.collect(List.scala:275)
	at scala.collection.immutable.List.collect(List.scala:79)
	at dotty.tools.dotc.interactive.Completion$Completer.accessibleMembers(Completion.scala:505)
	at dotty.tools.dotc.interactive.Completion$Completer.directMemberCompletions(Completion.scala:339)
	at dotty.tools.dotc.interactive.Completion$.computeCompletions(Completion.scala:149)
	at dotty.tools.dotc.interactive.Completion$.completions(Completion.scala:48)
	at dotty.tools.repl.ReplDriver.completions$$anonfun$1(ReplDriver.scala:240)
	at scala.util.Either.map(Either.scala:382)
	at dotty.tools.repl.ReplDriver.completions(ReplDriver.scala:241)
	at dotty.tools.repl.ReplDriver.$anonfun$1(ReplDriver.scala:151)
	at org.jline.reader.impl.LineReaderImpl.doComplete(LineReaderImpl.java:4412)
	at org.jline.reader.impl.LineReaderImpl.doComplete(LineReaderImpl.java:4378)
	at org.jline.reader.impl.LineReaderImpl.expandOrComplete(LineReaderImpl.java:4317)
	at org.jline.reader.impl.LineReaderImpl$1.apply(LineReaderImpl.java:3809)
	at org.jline.reader.impl.LineReaderImpl.readLine(LineReaderImpl.java:679)
	at org.jline.reader.impl.LineReaderImpl.readLine(LineReaderImpl.java:468)
	at dotty.tools.repl.JLineTerminal.readLine(JLineTerminal.scala:74)
	at dotty.tools.repl.ReplDriver.readLine$1(ReplDriver.scala:156)
	at dotty.tools.repl.ReplDriver.loop$1(ReplDriver.scala:166)
	at dotty.tools.repl.ReplDriver.runUntilQuit$$anonfun$1(ReplDriver.scala:171)
	at dotty.tools.repl.ReplDriver.withRedirectedOutput(ReplDriver.scala:192)
	at dotty.tools.repl.ReplDriver.runBody$$anonfun$1(ReplDriver.scala:180)
	at dotty.tools.runner.ScalaClassLoader$.asContext(ScalaClassLoader.scala:80)
	at dotty.tools.repl.ReplDriver.runBody(ReplDriver.scala:180)
	at dotty.tools.repl.ReplDriver.runUntilQuit(ReplDriver.scala:171)
	at dotty.tools.repl.ReplDriver.tryRunning(ReplDriver.scala:133)
	at dotty.tools.repl.Main$.main(Main.scala:7)
	at dotty.tools.repl.Main.main(Main.scala)

[prolativ]

This also affects metals

[prolativ]

It seems the error doesn't occur if there's at least one character after the dot, e.g.

scala> import sttp.client3.q<TAB>

[prolativ]

On the other hand this does crash

import sttp.client3.H<TAB>

This might be more specifically connected with the HttpClientAsyncBackend class

[prolativ]

Also it seems that there's no crash if I set the java version to at least 11 (I'm using 8 by default). However in scala 3.1.3 this worked for any java version

[odersky]

Nothing obvious comes to mind when looking at the stacktraces. I think the best way forward would be a bisect.

[prolativ]

I tried to bisect this and it looks like the regression was introduced in this commit ee22b6a by incrementing TASTy minor version. I have no idea how this could have caused the bug but indeed, when I checked out to this branch, publishLocal'ed the compiler and used this version to run the REPL via scala-cli I got the error as in the bug report. When I downgraded MinorVersion from TastyFormat.scala and went through the same procedure, there was no crash.