Language: first-class callable syntax — strlen(...) yields NULL not Closure (Zend/zend_compile.c)

[PurHur]

Category

language · php-src-strict

Problem (updated Jun 2026 audit)

Mostly fixed on VM for function and static-method FCC:

Form	VM Jun 2026	Zend
strlen(...)	Closure, invokable	yes
C::f(...) static	Closure, invokable	yes
$obj->m(...) instance	compile failure	Closure — #9185
Default param strlen(...)	compile error (#3803)	allowed as constant Closure

This issue tracks remaining FCC gaps after builtin/static fix; instance FCC is split to #9185 for worker claiming.

php-src reference

• php/php-src Zend/zend_compile.c — ZEND_AST_CALLABLE_CONVERT
• php/php-src Zend/zend_closures.c — first-class callable object creation

Repro (still open: default parameter FCC)

<?php
class C {
    public function f(Closure $c = strlen(...)): int {
        return $c('abc');
    }
}
echo (new C)->f(), "\n";

php repro_fcc_default.php          # Zend: 3
php bin/vm.php repro_fcc_default.php 2>&1 | head -3
# parseAndCompile: Parameter default must be a compile-time constant (#3803)

Runtime	Result
Zend	prints 3
VM	compile failure

Instance FCC: see #9185 ($d->m(...)).

Scope (this repo)

Layer	Path
Compiler	lib/Compiler.php — treat FCC AST as compile-time Closure constant in parameter defaults
VM/JIT	Reuse closure materialization from working strlen(...) path
Tests	test/compliance/cases/language/fcc_default_parameter.phpt

PHP-in-PHP: lib/ lowering only.

Done when (php-src-strict)

• Default-parameter repro prints 3 on VM
• JIT/AOT agree
• ./script/ci-fast.sh --filter fcc_default green
• Language: instance-method first-class callable — $obj->method(...) fails parseAndCompile (Zend/zend_compile.c) #9185 closed separately for instance FCC

Related

• Language: instance-method first-class callable — $obj->method(...) fails parseAndCompile (Zend/zend_compile.c) #9185 instance $obj->m(...) · Language: non-literal default parameter values — class/global constants and null (Zend zend_compile.c parity) #3803 compile-time constants · Epic: Self-host critical path — compiler compiles itself (M3→M5) #1492

[PurHur]

Architect run Jun 2026 — spec refreshed

strlen(...) and C::f(...) FCC now produce invokable Closures on VM. Remaining scope narrowed to default-parameter FCC; instance $obj->m(...) moved to #9185. Body updated.

[PurHur]

claim: worker-lane-c — starting this run

[PurHur]

claim: cursor-agent-lane-c — continuing worker-lane-c run (default-parameter FCC)

[PurHur]

Merged via PR #9367.

Fix: Route FCC parameter defaults (strlen(...), Class::m(...)) through paramRuntimeDefaultInitBlocks (same as new defaults) so TYPE_FROM_CALLABLE materializes a Closure when the argument is omitted. Instance-method FCC in constant expressions compile-error per PHP 8.5 fcc_in_const_expr.

Verification:

./script/docker-exec.sh -- php bin/vm.php test/repro/issue_9170_fcc_default_parameter.php  → 3
./script/docker-exec.sh -- php bin/jit.php test/repro/issue_9170_fcc_default_parameter.php  → 3
./script/docker-exec.sh -- bash -lc 'vendor/bin/phpunit test/unit/FirstClassCallableTest.php'  → OK (12)
./script/docker-exec.sh -- bash -lc 'vendor/bin/phpunit test/compliance/VMTest.php --filter fcc_default_parameter'  → OK (1)