From the documentation : The difference between using do ... end and { ... } is that do ... end binds to the left-most call, while { ... } binds to the right-most call However, this doesn’t match the actual behavior I see: def a(*args) end def a(*args) puts "a received block" yield end def b…

Also, for context, I’m working on GitHub - crystal-lang-tools/tree-sitter-crystal: tree sitter parser for crystal lang, fork of keidax/tree-sitter-crystal . The parser currently assumes Crystal’s block precedence rules match Ruby, and I just realized it doesn’t :scream:

wired behavior: def a(*args) puts "a" end def a(*args, &) puts "a received block" yield end def b(*args) puts "b" end def b(*args, &) puts "b received block" yield end def c(*args) puts "c" end def c(*args, &) puts "c received block" yield end a b c do puts "in block" end …

I’d report it on the github issue tracker, as at the very least it is a bug in the documentation. Though the behavior seems weird so it is probably not intended.

I always felt this difference in behaviour is quite extraordinary. And probably more confusing than helpful. :person_shrugging: It’s a good recommendation to always use parenthesis when there is doubt. Maybe the formatter should do that? :thinking: Anyway while looking briefly at the parser code, …

I’m still hoping to get some feedback on the Github issue. I’m working on the tree-sitter implementation for Crystal, and need to reconsider some choices about how block precedence is handled. Knowing whether this behavior might change in the future would be very helpful!

Do/end block behavior differs from Ruby

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keidax December 21, 2024, 1:14am 6

Github issue created: Possible bug: binding of do/end blocks is surprising and doesn't match the documentation · Issue #15303 · crystal-lang/crystal · GitHub

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RFC: `with ... yield` replacement Crystal Contrib	57	4111	May 14, 2025
Proposal: New "ends" keyword Community	46	1474	April 18, 2021
Verifying what an 'end' goes with Help & Support	4	502	December 10, 2019
RFC: `&.` within a block Crystal Contrib	61	3954	December 9, 2023

Do/end block behavior differs from Ruby

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