Apanatshka
commented
2 years ago Sorry you ran into this.
Stratego 2 is a continuation of Stratego 1, which was originally designed and implemented within the world of C-like languages and therefore didn't have module discipline. There's a comment in the compiler code that suggests that the original implementors thought about it, but proper module discipline where you can have multiple distinct strategies with the same name in a project would require heavy modification in many parts of the compiler.
When I added the type system I wasn't aware of the bug you describe, and I implemented module discipline in the static semantics. I noticed this edge case during implementation, but it's been on my todo list ever since.
The first fix I'll likely implement for this is to make your example program illegal, i.e. you cannot have multiple distinct definitions of a strategy. In the long term, perhaps the compiler can refactored to allow for multiple distinct definitions of a strategy, but that's not something that can easily be done in the short term.
Thom747
eelcovisser
Describe the bug The Stratego 2 runtime bunches all definitions of a rule across different modules in one location, effectively removing the limited scope of rules within modules. The type-checker does respect module boundaries, so safe behavior according to the type-checker can result in unsafe behavior at run-time.
Project
Occurs when compiling and running Stratego 2.
Versions See Spoofax (Meta); Report Issue for information to copy here. No idea where to find this in Spoofax, looked for 15 minutes. Spoofax LWB 0.16.17.
To Reproduce
main.str2,A.str2,B.str2.mainimportAandB, but do nothing else.ruleinAandB.ruleinB.Observed behaviour
The usage of
ruleinBwill non-deterministically choose between theruleinAandB, even thoughAis not imported inB. Note that the type-checker will not error here, even if the signatures of the tworules are incompatible, as it does respect module boundaries.Expected behaviour
The usage of
ruleinBshould always use the definition inB, as the definition ofruleinAis not in scope.Additional context This problem causes completely unexpected behavior, which is not caught by the type-checker.