Regression: return-type TypeError getTrace() empty — missing callee function frame (Zend/zend_exceptions.c) #14369

Summary

When a user function or method violates its declared return type, Zend populates TypeError::getTrace() with a frame for the failing callable (g, m, …). VM returns an empty trace array ([]), breaking Exception::getTrace(), getTraceAsString(), and debug tooling that expects the innermost frame.

Repro covers generator return-type violations and ordinary method return-type violations.

php-src reference

• Zend/zend_exceptions.c — zend_throw_return_type_error, trace frame assembly
• Zend/zend_execute.c — return-type enforcement sites

PHP implementation target

• lib/VM.php / exception throw path — ensure return-type TypeError captures callee frame before unwinding
• Shared with debug_backtrace() frame list (Stdlib: debug_backtrace() frame line always 0 — must report source line (ext/standard/basic_functions.c) #9323) where possible; PHP-in-PHP first

Repro

php bin/vm.php test/repro/maintainer_gap_return_type_error_trace.php
# VM: fail generator trace: [] / fail method trace: []
# Zend: ok

test/repro/maintainer_gap_return_type_error_trace.php

Expected (php-src-strict)

• getTrace()[0]['function'] is the violating callable name
• Fatal uncaught stack trace lists caller frame (g() / C->m()), not only {main}

Done when

• Repro green on VM
• JIT/AOT agree when those backends enforce return types
• No new C beyond thin ABI if trace data already exists in VM frames