THRIFT-6004: Emit native types on generated PHP service-level methods

[sveneld]

Update the PHP generator to emit native parameter and return types on every generated service-level method. Completes the typing pass on the generator side after THRIFT-5986 (declare strict_types), THRIFT-5990 (struct return types), and THRIFT-5991 (struct property types).

Generated signatures (before → after)

-public function testString($thing)                      // Interface
+public function testString(?string $thing): ?string

-public function __construct($input, $output = null)     // Client ctor
+public function __construct(TProtocol $input, ?TProtocol $output = null)

-public function send_testString($thing)                 // Client
+public function send_testString(?string $thing): void

-public function recv_testString()                       // Client
+public function recv_testString(): ?string

-public function __construct($handler)                   // Processor ctor
+public function __construct(object $handler)

-public function process($input, $output)                // Processor
+public function process(TProtocol $input, TProtocol $output): bool

-protected function process_testString($seqid, $input, $output)
+protected function process_testString(int $seqid, TProtocol $input, TProtocol $output): void

-public function __construct($impl)                      // Rest ctor
+public function __construct(object $impl)

-public function testString($request)                    // Rest method
+public function testString(array $request): ?string

Implementation

• New helper type_to_return(t_type*) returning : void or : ?T. Shares the existing type_to_native() mapping introduced by THRIFT-5991.
• function_signature() now appends type_to_return() for the return clause.
• argument_list() now emits ?type_to_native() on every parameter — previously only struct/container parameters were typed.
• send_* constructs a synthetic t_function(g_type_void, ...) so function_signature() produces the correct : void for the writer half.
• Processor process() early "method not found" path now return false; instead of bare return; to satisfy : bool.
• Rest method emission gates return on whether the underlying impl is void.

Drive-by cleanup

ThriftClassLoader::findFileInApcu() (merged in THRIFT-6001) was flagged by PHPStan: the trailing $file !== false ? $file : null was unreachable because the if-branch reassigns $file to findFile() (?string). Rewrote the body to a clear two-step fetch-or-recompute and narrowed the return via is_string().

Validation (Docker thrift-php-dev:local + thrift/thrift-build:ubuntu-focal)

• Built compiler with the patched generator.
• Regenerated all 6 fixture variants under lib/php/test/Resources/packages/ (gitignored — regen happens in CI).
• phpcs — 0 errors
• phpstan (level 5) — 0 errors
• phpunit Unit Suite — 637 tests, 0 failures
• phpunit Integration Suite — 108 tests, 0 failures

Part of umbrella THRIFT-5960.

• Apache Jira ticket — THRIFT-6004
• PR title follows the pattern "THRIFT-NNNN: …"
• Squashed to a single commit
• Did you do your best to avoid breaking changes? — third-party user code calling generated services with the wrong types will now fail loudly under strict types. Required regen of generated code against the new compiler.

Generated-by: Claude Opus 4.7