fix(parser): bind modifier rescue to whole paren-less command call - #15

Problem

A trailing modifier rescue after a paren-less command call bound to the last argument instead of the whole call:

raise "x" rescue 42   # parsed as raise("x" rescue 42)  -> raise ran unrescued

MRI parses this as (raise "x") rescue 42 (Ripper: rescue_mod(command(raise, ["x"]), 42)), so the value is 42. The parenthesised form method(args) rescue x was already correct.

Fix

The modifier rescue has lower precedence than a command call's paren-less argument list. A new noRescueMod flag (mirroring the existing noDo / noMasgn) suppresses the modifier rescue while parsing command arguments, so the enclosing expression wraps the whole Call in a Begin — identical to the parenthesised form. The flag is cleared inside any nested delimited context (a (…) group, a (…)/[…] argument list), so an inner modifier rescue there is still consumed (foo(bar rescue baz), p ("x" rescue 42)).

Also accepts a modifier rescue after a def…end statement (def foo; end rescue nil) — MRI accepts it, the parser previously errored — by handling rescue in applyModifiers.

AST proof

raise "x" rescue 42 now yields Begin{ Body:[ Call{raise, ["x"]} ], Rescues:[{ Body:[42] }] } — the rescue wraps the Call, and each argument stays a plain literal.

Unchanged (verified)

• modifier rescue on a plain expression / paren group ("x" rescue 42)
• assignment RHS x = expr rescue default
• parenthesised call method(args) rescue x

Verification

MRI ruby 4.0.x match for (raise "boom" rescue 99)=>99, (raise "x","y" rescue 7)=>7, puts "a" rescue nil (runs, no rescue), def foo; end rescue nil (accepted), assignment-RHS rescue=>9.

• 100% statement coverage
• go vet ./... clean
• GOWORK=off CGO_ENABLED=0

🤖 Generated with Claude Code