cps: add limited exception handling support #94
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cps.nim
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| of nnkProcDef: | ||
| if not n.hasPragma("cpsContinuation"): | ||
| result = n | ||
| of nnkReturnStmt, nnkBreakStmt, nnkContinueStmt: |
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We only have to handle nnkReturnStmt, any nnkBreakStmt or nnkContinueStmt should be within the same continuation, thus finally won't trigger.
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As discussed, finally is rewritten into block, right?
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Nah, I just replicate it across all legs, with a tag letting us know whether the finally should be run. There might be a bug or two with that, but I haven't figured out any tests yet.
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The finally clause should always be run; that's the point. When you rewrite it into block statements, you produce two (or more) control-flow paths and all receive a copy of the finally code -- perhaps via a template. Any subsequent rewrite deals with these different paths via our normal block-handling logic, so the finally effectively evaporates.
It's kinda like your solution to if expressions... You dig down into the logic and say, "okay, now what are we really trying to say here..." and that statement is "treat this as an expression on the RHS of an assignment".
In this case, what we are really trying to say is, "do this stuff regardless of how you exit the scope".
cps.nim
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| desym cont | ||
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| # var ok {.inject.} = false | ||
| handlerWrapperBody.add newVarStmt( |
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We only need this stuff if there is a finally body, since it is an indicator for whether the finally branch should be executed
Experimental and not fully tested yet Splitting inside any `except` or `finally` bodies are not supported and will yield an error
- use workaroundRewrites at the end - make wrapper uses a typed body - move var decl to outside of wrapper - don't set ok for non-escaping control-flow
Experimental and not fully tested yet
Splitting inside any
exceptorfinallybodies arenot supported and will yield an error
/cc @disruptek I need you to break this