Self-host M5: native vendor invoker should surface parseAndCompile failure text (not silent null)

[PurHur]

Milestone

M5 (diagnostics) — parent #1492. Unblocks triage for #3028–#3031, #3035–#3036, #3041. Script UX slice: #3049. Complements #2988.

Problem

build/selfhost-native-compile-driver logs only:

helloworld_compile_smoke: parseAndCompile returned null (parser/CFG spine)
helloworld_compile_smoke: native emit failed at phase=parseAndCompile

Zend on the same bundle prints actionable errors (2026-05-29 probe):

Bundle	Zend parseAndCompile failure:
ircmaxell-php-cfg	Unknown type declaration found: */ (#3035)
ircmaxell-php-types	Unknown type declaration found: PHPTypes\Type The type (#3036)
ircmaxell-php-llvm	Unknown type declaration found: [type] [description] (#3041)

Implementers must re-run Zend lint manually; build/bootstrap-vendor/*.log tails are useless today.

Implementation plan (ready)

1. Capture last failure in lib/Runtime.php

• Add private static ?string $lastParseFailure = null (or thread-local) set in parse() / parseAndCompile() catch blocks when RuntimeException escapes PHPTypes/Compiler.
• Public accessor: Runtime::getLastParseFailure(): ?string for M3 emit bridge (no behavior change on success path).

2. M3 emit bridge (helloworld_compile_smoke.php and shared helper)

• Before return null on failed parseAndCompile, fprintf(STDERR, "parseAndCompile failure: target=%s: %s\n", $target, Runtime::getLastParseFailure() ?? 'unknown') — match Zend CLI prefix so bootstrap-vendor-objects.php can grep uniformly.
• Ensure PHP_COMPILER_VENDOR_PRELINK=1 path uses same helper (vendor bundles).

3. Native compiled driver path

• Confirm AOT-compiled Runtime::parseAndCompile lowering propagates exception message string (may need lib/AOT/runtime string export if currently swallowed) — bisect with BOOTSTRAP_M3_USE_INVENTORY_EMIT_DRIVER=1 on HelloWorld first.

4. script/bootstrap-vendor-objects.php

• On non-zero compile: if log lacks parseAndCompile failure:, append Runtime::getLastParseFailure from Zend re-run is not acceptable — fix native path only (#3049).

5. Regression

• Add test/real or script test: fixture PHP that throws known RuntimeException in parse → native M3 smoke stderr contains substring.

Path	Work
lib/Runtime.php	lastParseFailure + accessor
test/selfhost/compiler_helloworld_smoke/helloworld_compile_smoke.php	Stderr on null
lib/AOT/	If native path drops exception text
script/bootstrap-vendor-objects.php	Grep-friendly FAIL (#3049)

Repro

./script/docker-exec.sh --sync-back build/selfhost-native-compile-driver -- bash -lc '
  make bootstrap-selfhost-driver-smoke
  PHP_COMPILER_VENDOR_PRELINK=1 php script/bootstrap-vendor-objects.php --compile
'
# Native: null only; Zend -l shows Type.php:419 message

Done when

• Native vendor compile stderr/log includes same parseAndCompile failure: line as Zend -l for all three bundles (before fixing PHPTypes)
• bootstrap-vendor-objects.php --compile FAIL lines quote the declaration token (#3049)
• No manual php bin/compile.php -l required to start work on #3035+