Unresolved symbol while pickling quote

[nicolasstucki]

Compiler version

3.1.0

Minimized code

import scala.quoted.*

def generateImpl(using q: Quotes): Expr[Unit] =
  '{ def runEffect[T]: T = ${ runEffectImpl[T] } }

inline def runEffectImpl[T: Type]: Expr[T] = ???

Related to #13563

Output

java.lang.AssertionError: assertion failed: unresolved symbols: type T (line 3) #13947 when pickling tests/pos-macros/i13563b.scala
        at scala.runtime.Scala3RunTime$.assertFailed(Scala3RunTime.scala:8)
        at dotty.tools.dotc.core.tasty.TreePickler.pickle(TreePickler.scala:777)
        at dotty.tools.dotc.quoted.PickledQuotes$.pickle(PickledQuotes.scala:167)
        at dotty.tools.dotc.quoted.PickledQuotes$.pickleQuote(PickledQuotes.scala:36)
        ...

Expectation

Should compile

[nicolasstucki]

Workaround

- inline def runEffectImpl[T: Type]: Expr[T] = ???
+ def runEffectImpl[T: Type]: Expr[T] = ???

[griggt]

@deniszo and I looked at this during today's spree. Some observations:

• The workaround above does not seem to help on 3.1.0 or master
• The example compiles with Re-architecture quote pickling #12540, but fails -Ycheck
• The workaround above does seem to work on the Re-architecture quote pickling #12540 branch, with -Ycheck
• The example compiles if the Type context bound is on both runEffect and runEffectImpl, or on neither
• The example compiles if runEffectImpl is called with a type parameter of Nothing (inferred or explicit)

It seems that for some reason in this case, transformQuotation

https://github.com/lampepfl/dotty/blob/b311b4ecf84bf33dd387353a7dfb989e73f236ca/compiler/src/dotty/tools/dotc/transform/PickleQuotes.scala#L129-L141

wants to pickle a quote whose body consists solely of TypeTree[TypeRef(NoPrefix,type T)], and I get the impression that is somewhat nonsensical to pickle in isolation?

[griggt]

Is it expected that this issue can be solved separately from / without #12540 (or a similar reworking of quote pickling)?