Language: declare(strict_types=1) — scalar parameter coercion and TypeError parity

[PurHur]

Category

language

Problem

PHP’s declare(strict_types=1) changes how scalar parameter type declarations behave at call sites. Zend enforces:

• With strict_types=1 in the caller file: scalar mismatches raise TypeError (no coercion).
• With strict_types=0 (default): scalar mismatches may coerce (e.g. '1' to 1) depending on target type.

Parity gap: this compiler must match Zend’s strictness rules (especially “caller controls strictness”), error types/messages, and behavior for int, float, string, bool parameters and return types.

php-src reference

• Zend/zend_execute.c — argument type verification / coercion paths
• Zend/zend_compile.c — declare(strict_types=1) compile-time flag propagation
• Tests: Zend/tests/type_declarations/strict_types/*

Repro

Create 3 files:

callee.php:

<?php
function takesInt(int $x): int { return $x; }

caller_weak.php:

<?php
require __DIR__.'/callee.php';
var_dump(takesInt('1'));

caller_strict.php:

<?php
declare(strict_types=1);
require __DIR__.'/callee.php';
try {
    takesInt('1');
    echo "NO ERROR\n";
} catch (Throwable $e) {
    echo get_class($e), "\n";
}

Run:

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php caller_weak.php
php caller_strict.php
php bin/vm.php caller_weak.php
php bin/vm.php caller_strict.php'

Expected (Zend):

• caller_weak.php prints int(1)
• caller_strict.php prints TypeError

Scope

• Compiler: ensure strict_types flag is stored per compilation unit and used at call sites
• VM: align scalar coercion + TypeError messages with Zend
• Tests: add test/compliance/cases/language/strict_types_scalar_args.phpt

Done when

• Repro matches Zend outputs for weak vs strict callers
• Caller-file strictness controls behavior even when callee is in a different file (Zend parity)
• Error type is TypeError with close-to-Zend message

[PurHur]

claim: cursor-agent — starting this run

[PurHur]

claim: cursor-agent-lane-c — continuation (repro green on master; adding compliance guard + closing)

[PurHur]

Merged via #9100.

Finding: cross-file caller strict_types parity was already green on master (VM + JIT); this PR adds the compliance guard requested in the issue scope.

Verification:
```bash
./script/docker-exec.sh -- bash -lc 'source script/php-env.sh
php test/repro/strict_types_9053/caller_weak.php # int(1)
php test/repro/strict_types_9053/caller_strict.php # TypeError
php bin/vm.php test/repro/strict_types_9053/caller_weak.php
php bin/vm.php test/repro/strict_types_9053/caller_strict.php
./vendor/bin/phpunit --filter strict_types_scalar_args # OK (2 tests)
```