nicer error message for out-of-place _
#25001
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This was referenced May 7, 2024
Note that it's currently a syntax error in this context as well, e.g. var _ = 42;gives: I believe that today it's only permitted in de-tupling declaration contexts like: var (first, _) = myTupleExpr; |
DanilaFe
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May 7, 2024
Fixes #25000 (what a fun issue number!). This PR disallows writing `(_)`, to match the already-disallowed `_`. Prior to this PR, the following program did not parse: ```Chapel var x = _; ``` But the following alternate version did: ```Chapel var x = (_); ``` This was because the parenthesized-expression grammar rule used `tuple_component`, which allows `_` (`(_, )` can be used to unpack 1-tuples in loops). As a result, this fixes the odd issue in which writing a loop over `(_)` resulted in an internal error, while `_` resulted in a normal syntax error. This raised some follow-up concerns: 1. should we have a nicer error message when a user writes `_` where it doesn't belong? #25001 2. should we really allow `_` in all tuple expressions? currently we do. #25002 In the meantime, this PR turns the error in #25000 from an internal error into a syntax error. Reviewed by @vasslitvinov -- thanks! ## Testing - [x] paratest
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Today, writing
for _ in 1..10will lead to a generic "syntax error". This is not an ideal error message, but seems like it ought to be easy enough to make it a nice error message. For instance, it would be nice to note that_can only be used in declaration context likevar _ = ...and loop tuple-expressions.The text was updated successfully, but these errors were encountered: