Fix RBS syntax error

[hakanensari]

The newly-released RBS 4.0 rejects void in union types at the parser level. The (Integer | void) return type on Readable#rewind now causes a hard parse error.

Change to void, consistent with CompositeIO#rewind and the YARD @return annotation.

[Copilot]

Pull request overview

Updates the RBS for HTTP::FormData::Readable#rewind to avoid an RBS 4.0 parser error caused by using void inside a union type, aligning the signature with Ruby’s IO#rewind/StringIO#rewind behavior.

Changes:

• Replace def rewind: () -> (Integer | void) with def rewind: () -> Integer in HTTP::FormData::Readable.

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[Copilot]

Readable#rewind now returns Integer, but @io is declared as StringIO | CompositeIO and CompositeIO#rewind is currently typed as () -> void later in this same RBS file. With Steep checking lib/ against sig/, this will likely produce a type mismatch for lib/http/form_data/readable.rb#rewind (it delegates to @io.rewind). Consider also updating CompositeIO#rewind’s signature to () -> Integer (it returns 0 in Ruby because the last expression is @index = 0), so the types are consistent and Steep can type-check the implementation.

[hakanensari]

Good catch. Changed to void instead of Integer to stay consistent with CompositeIO#rewind. The integer return was, in any case, just a side effect of the implementation.

Steep and rbs parse pass either way.