A brace block on a name that is also a local fails to parse inside parentheses #905

A brace block attached to a name that is also a local variable fails to parse when the call is inside parentheses. MRI calls the method and ignores the local.

def withblock; yield; end
withblock = 5
p(withblock { 7 })

$ /opt/homebrew/opt/ruby@4.0/bin/ruby probe.rb
7

$ rbgo probe.rb
parse error at line 3: expected ), got "{" ({)

Measured through scripts/conformance/rubyspec/cmd/oracle against
ruby 4.0.7 (2026-09-15 revision 229531a6cf) +PRISM [arm64-darwin25], with rbgo built from e5619211 (current main).

It needs all three lines

The brace block alone is fine — this is where the defect is not:

def withblock; yield; end
p(withblock { 7 })

=== 3 engines AGREED, byte for byte ===
7

The assignment withblock = 5 is what breaks it. Once the parser knows the name as a local, withblock { 7 } inside (...) stops parsing. A block makes a receiver-less name an FCALL regardless of any local of that name — primary: fcall brace_block (parse.y-ruby_4_0:4458-4463) — so MRI resolves withblock to the method, yields, and prints 7.

Whether the parenthesis is essential or merely how it surfaces here is not established; the three lines above are the smallest form I measured.

Not a regression

rbgo at e5619211 and the branch of #904 fail identically, so this predates #904. I found it while writing that PR's test and nearly asserted the MRI answer as a row from memory — the probe is what caught it.

Where it is likely to matter

Any DSL or test helper whose block-taking method shares a name with a local in
the same scope, written with parentheses. The shape is ordinary Ruby:

config = load_config
p(config { ... })

Scope

Parser-side (go-ruby-parser), not the compiler: the failure is at parse time
and no bytecode is produced. The compiler's own local-vs-method rule for the
parenthesised, blockless case is #904 and is separate from this.

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