Unexpected typer error with Scala 3.3.7

[plokhotnyuk]

Compiler version

3.3.7

Minimized code

No minimization yet, only steps to reproduce so far:

1. Clone reproducing sbt project:

git clone --depth 1 https://github.com/plokhotnyuk/jsoniter-scala

2. Switch to the affected branch:

git checkout scala-3.3.7

3. Run the following sbt command:

sbt ++3.3.7 jsoniter-scala-macrosJVM/test

Output

The following compilation error in the typer for the macro generated code:

[error]     |               |
[error]     |               |Error:
[error]     |               |assertion failed: Type Mismatch (while checking adapt):
[error]     |Found:    (com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight.Green :
[error]     |  com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight) |
[error]     |  (com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight.Green :
[error]     |    com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight)
[error]     |Required: (com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight.Green :
[error]     |  com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight)
[error]     |I tried to show that
[error]     |  (com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight.Green :
[error]     |  com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight) |
[error]     |  (com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight.Green :
[error]     |    com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight)
[error]     |conforms to
[error]     |  (com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight.Green :
[error]     |  com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight)
[error]     |but none of the attempts shown below succeeded:
[error]     |
[error]     |  ==> (com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight.Green :   com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight) |   (com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight.Green :     com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight)  <:  (com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight.Green :   com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight)
[error]     |  <== (com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight.Green :   com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight) |   (com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight.Green :     com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight)  <:  (com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight.Green :   com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight) = false
[error]     |
[error]     |The tests were made under the empty constraint
[error]     |tree = if in.isNextToken(123) then
[error]     |  {
[error]     |    in.rollbackToken()
[error]     |    in.skip()
[error]     |    com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight.Green
[error]     |  }
[error]     | else 
[error]     |  in.readNullOrTokenError[
[error]     |    
[error]     |      (com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight.Green :
[error]     |        com.github.plokhotnyuk.jsoniter_scala.macros.TrafficLight)
[error]     |    
[error]     |  ](default, 123)

Expectation

No compilation errors

[tgodzik]

Thanks for reporting! Curiously, this was working in the community build https://github.com/VirtusLab/community-build3/actions/runs/18031767030/job/51309613423

So I wonder why this broke only on update to 3.3.7

[tgodzik]

Looks like it's working on Next 3.7.3, so broken only on LTS

[plokhotnyuk]

The workaround is adding an extra .asInstanceOf[T], like here:
plokhotnyuk/jsoniter-scala@9e90a57#diff-2dd71e1f25e398ff5a215b7e53125b9d77f7744a1477c2f421789f29da33ccaeR2838

[tgodzik]

Looks like it was working in 2.37.11, which is why at that point the compilation passed.

[WojciechMazur]

So I wonder why this broke only on update to 3.3.7

It might be related to new version of jsoniter. The 3.3.7-RC2 was tested 2025-09-26 using the v2.37.11 of jsoniter.

The testing locally it successfully compiles against 2.38.1 but fails since 2.38.2
The OpenCB is now using the latest versions 2.38.3 released October 1
Configs are updated weekly (every Friday). That's probably why it was not caught earlier.

[tgodzik]

Yeah, the change here caused the bug to surface plokhotnyuk/jsoniter-scala@v2.38.1...v2.38.2

[plokhotnyuk]

Yeah, the change here caused the bug to surface plokhotnyuk/jsoniter-scala@v2.38.1...v2.38.2

Thanks, the regression was caught by the following change of Ref(sym).tpe to sym.termRef:
plokhotnyuk/jsoniter-scala@v2.38.1...v2.38.2#diff-2dd71e1f25e398ff5a215b7e53125b9d77f7744a1477c2f421789f29da33ccaeL1277

I've reverted it here already