Language: closure use($a, $a) compiles — Zend "Cannot use variable $a twice" (Zend/zend_compile.c)

[PurHur]

Category

language · php-src-strict · closures · compile-time fatal

Problem

php-src rejects a closure that lists the same variable twice in use. This compiler accepts use ($a, $a) and runs the body. Distinct from use ($this) (illegal name); this is a duplicate lexical binding.

Repro	Zend 8.2+	VM/JIT (2026-08-18 @ 8d228396dc)
$a=1; $f=function() use ($a, $a) { return $a; }; echo "accepted\n";	Fatal: Cannot use variable $a twice (rc=255)	accepted (rc=0)

php-src reference

• php/php-src Zend/zend_compile.c — closure use list uniqueness (zend_compile_closure, lexical variable table)

PHP implementation target

• lib/ closure compile — duplicate use names must compile-fatal with Zend's message including the variable name
• JIT/AOT share the compile path; no C runtime branches

Repro

./script/docker-exec.sh -- bash -lc 'php bin/vm.php test/repro/maintainer_gap_use_dup.php 2>&1 | head -5'
./script/docker-exec.sh -- bash -lc 'php bin/jit.php test/repro/maintainer_gap_use_dup.php 2>&1 | head -5'

Done when

• VM and JIT compile-abort with Zend substring Cannot use variable $a twice (rc≠0, no accepted output)
• Compliance .phpt guard under test/compliance/cases/language/closure_use_duplicate*.phpt
• php-src-strict; no php-compiler-strict shortcut

[PurHur]

claim: Worker lane C — starting this run

[PurHur]

Merged #32164

php-src-strict: VM and JIT compile-abort with Cannot use variable $a twice (rc=255), no accepted output. Shared compile path (lib/Compiler/ClosureUseDuplicateCompileCheck.php + compileAnonymousFunctionExpr); no C runtime change. php-src Zend/zend_compile.c zend_compile_closure_binding.

Verification:

• php bin/vm.php test/repro/maintainer_gap_use_dup.php → PHP Fatal error: Cannot use variable $a twice VM_RC=255
• php bin/jit.php test/repro/maintainer_gap_use_dup.php → same message JIT_RC=255
• ./script/phpunit.sh --filter ClosureUseDuplicate → OK (7 tests, 13 assertions)
• php script/bootstrap-inventory.php --check → OK 7579/7579

Not covered: full VMTest/JITTest suites, differential sweep.