AST Transformation in Groovy 4.0.x VS 3.0.x

Is there any guideline to port AST Transformations for Groovy 4.0 ?

I am porting Taack-UI to Groovy 4.0, and I am stuck with errors like:
[. . . ]
  General error during instruction selection: size==0
[. . .]

At the moment I just added casts at ReturnStatements. (See
https://github.com/Taack/infra/blob/main/taack-ui/src/main/groovy/taack/ast/model/TaackFieldEnumASTTransformation.groovy
)

Thanks !

--
Adrien Guichard
+ 33 6 10 78 75 88
https://taack.org
29 Boulevard Edgar Quinet
75014 Paris
France