[tannevaled]

Closes #41.

The gap

foo and foo() built identical ast.Calls, so nothing downstream could tell a VCALL from an FCALL, and ast.Call carries no position from which to re-read the source. Reproduction from the issue, against ruby 4.0.5:

nope_xyz     # NameError:     undefined local variable or method 'nope_xyz' for main
nope_xyz()   # NoMethodError: undefined method 'nope_xyz' for main

The grammar says where the information is

rule / function	line in parse.y-ruby_4_0	what it does
fcall : operation	3572-3577	NEW_FCALL($1, 0, &@$)
method_call : fcall paren_args	5242-5248	attaches the parenthesised list — this is the FCALL
gettable, case ID_LOCAL	13086	return NEW_VCALL(id, loc) — the VCALL
primary : tFID	4370-4374	NEW_FCALL for foo! / foo? — no parentheses, still an FCALL
operation : ident_or_const | tFID	6696-6698	why tFID reaches fcall at all
primary : fcall brace_block	4458-4463	a literal block makes an FCALL too
primary_value '[' opt_call_args rbracket	5292-5297	an index is a NEW_CALL, with brackets, not parens

Paren is set wherever the parser consumes a written ( … ) argument list: the bare-identifier call, a capitalised call (Integer("42")), a ./&. call, a :: call, and the .() shorthand.

The bit takes both values

Measured by the tests added here — Paren is neither always true nor always false, and each pair that must differ does:

spelling	Name	Paren	args
foo	foo	false	0
foo()	foo	true	0
foo(1)	foo	true	1
foo ()	foo	false	1
puts 1	puts	false	1
obj.foo	foo	false	0
obj.foo()	foo	true	0
obj.foo bar	foo	false	1
obj&.foo / obj&.foo()	foo	false / true	0
foo.() / foo.(1)	call	true	0 / 1
Foo::bar / Foo::bar(1)	bar	false / true	0 / 1
Integer("42")	Integer	true	1
a[0]	[]	false	1
foo! / foo?	foo! / foo?	false	0
x = 1; x	—	VarRef, not a Call	—
x = 1; x()	x	true	0

Two of those need saying out loud:

• foo () is Paren: false with one argument. The space means the () is a grouped expression passed as a command argument, not an argument list. MRI agrees it is an FCALL, and it stays one for a consumer, because a VCALL also requires zero arguments.
• foo! and foo? are Paren: false and yet FCALLs in MRI (primary: tFID), confirmed against the binary: both raise NoMethodError. So the bit alone does not decide VCALL, and the doc comment says so rather than letting a consumer guess. The rule is Recv == nil && !Paren && len(Args) == 0 && Block == nil on a plain identifier name, and TestCallParenVCallRule exercises exactly that rule over the whole edge set against MRI's answers.

Negative control: with every Paren forced to false, 12 assertions in the new tests fail. The tests measure the change.

One place the oracle and the binary disagree

The {x:} value-omitted shorthand. assoc : tLABEL (6669-6675) calls gettable, so the implied value is a VCALL, and our barewordValue builds a Call with Paren: false accordingly. The installed ruby 4.0.5 raises NoMethodError there, which would say FCALL — but that binary is +PRISM and runs the Prism parser by default; ruby --parser=parse.y raises NameError, agreeing with the oracle. The oracle wins, and this PR follows it. Flagging it because a consumer measuring against a stock ruby will see the Prism answer.

Existing consumers are unaffected

• No existing test was changed. git diff --name-only origin/main is ast/ast.go and parser.go only; the one new file is call_paren_test.go.
• Full suite green before and after (parser, ast, lexer, token), go vet ./... clean, gofmt -l clean on both changed files.
• gofmt -l . does report paren_singleton_def_test.go — pre-existing on main (verified against a pristine origin/main copy) and untouched here.

The zero value is false, so anyone who does not read the field sees nothing.

Why this is a separate PR from #40

No shared code: different structs, disjoint parser sites, no common helper. Same idea, same precedent (RangeLit.Exclusive), but nothing is reused by merging them, and split they review and merge independently.

What the consumer will need (separately)

Not in this PR — go-embedded-ruby/ruby needs a released parser version first, and a sibling wave is working there. When it picks this up: the existing FlagSendVCall should be set from Recv == nil && !Paren && len(Args) == 0 && Block == nil && Name a plain identifier (no trailing !, ? or =), which is what TestCallParenVCallRule here encodes. That flag then selects NameError over NoMethodError, covering language/send_spec.rb:235.

🤖 Generated with Claude Code