A longstanding shortcoming of the AST-transformation system is the minimal guarantees provided when multiple ASTTs target the same area of code. While comprehensive support for this seems like it would require a redesign or at least major rework, I have a suggestion for a small change that might get a large segment of use cases working.
I propose adding "order" directives to transforms akin to Spring's @Ordered and @AutoConfigureBefore/After. The sole effect of these directives would be to instruct the compiler to run identified transformations in sorted sequence. As a specific hands-on use case, there's been a feature request open against Spock for 5 years to support stateful traits (https://github.com/spockframework/spock/issues/83); the impediment is that both Spock and traits are implemented as SEMANTIC_ANALYSIS ASTTs, so that Spock doesn't see the trait fields with their @Shared annotations when it runs. Is something like this feasible, or does it conflict with existing sequencing or traversal requirements inside the compiler processing?
