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Update if-expr RFC with mid-block return interaction (#43) 

We don't have mid-block return support yet and it's not clear if we will due to similar grammatical issues with this wrt function calls, but noting this for completeness (thanks @alexmccord for bringing this up)
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Arseny Kapoulkine 2021-06-01 15:45:43 -07:00 committed by GitHub
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rfcs/syntax-if-expression.md
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@ -39,6 +39,8 @@ Studio's script editor autocomplete currently adds an indented block followed by
Parser recovery can also be more fragile due to leading `if` keyword - when `if` was encountered previously, it always meant an unfinished expression, but now it may start an `if-expr` that, when confused with `if-end` statement can lead to a substantially incorrect parse that is difficult to recover from. However, similar issues occur frequently due to function call statements and as such it's not clear that this makes the recovery materially worse.
While this is not a problem today, in the past we've contemplated adding support for mid-block `return` statements; these would create an odd grammatical quirk where an `if..then` statement following an empty `return` would parse as an `if` expression. This would happen even without `if` expressions though for function calls (e.g. `return` followed by `print(1)`), and is more of a problem with the potential `return` statement changes and less of a problem with this proposal.
## Alternatives
We've evaluated many alternatives for the proposed syntax.