ruby.git/test/prism/fixtures/case_in_in.txt, branch master The Ruby Programming Language [ruby/prism] Fix in handling 2026-03-02T17:07:05+00:00 Kevin Newton kddnewton@gmail.com 2026-03-02T16:49:29+00:00 c7ed328cd569a258aa949f78f721195e2be15e9e in is a unique keyword because it can be the start of a clause or an infix keyword. We need to be explicitly sure that even though in _could_ close an expression context (the body of another in clause) that we are not also parsing an inline in. The exception is the case of a command call, which can never be the LHS of an expression, and so we must immediately exit. [Bug #21925] [Bug #21674] https://github.com/ruby/prism/commit/20374ced51 
in is a unique keyword because it can be the start of a clause or
an infix keyword. We need to be explicitly sure that even though in
_could_ close an expression context (the body of another in clause)
that we are not also parsing an inline in. The exception is the
case of a command call, which can never be the LHS of an expression,
and so we must immediately exit.

[Bug #21925]
[Bug #21674]

https://github.com/ruby/prism/commit/20374ced51