Language: echo/@$undef / arithmetic / call-arg still warn — Zend silences (re-#29132, zend_compile.c) #31881

Category

Language · php-src-strict / error-control @ · residual of #29132 (Assign RHS is green)

Problem

@$undef as a value still emits Undefined variable on VM. Zend's ZEND_BEGIN_SILENCE suppresses the fetch. Assign RHS ($x = @$undef), bare @$undef;, and print @$undef are already silent (controls). Echo, binary ops, and call arguments are not.

Probed 2026-08-17 vs Zend 8.2.32 @ 8084f14996.

php-src reference

• php/php-src Zend/zend_compile.c — ZEND_BEGIN_SILENCE / ZEND_END_SILENCE around the silenced expr
• php/php-src Zend/zend_execute.c — undefined-variable E_WARNING on CV fetch; skipped while EG(error_reporting) is silenced

PHP implementation target

• lib/Compiler.php isErrorSuppressInnerExpr() — today includes Assign (Language: @$undef as assignment RHS still warns — Zend silences (ZEND_BEGIN_SILENCE) #29132) but not Echo_ / Print_ / binary ops / FuncCall arg fetches of a silenced CV
• Ensure the CV fetch is compiled inside the silence region (same beginSilence/endSilence as Assign), not after ZEND_END_SILENCE
• VM already honors ErrorReporter silence depth for undefined-variable — this is a lowering hole, not a new C path
• No new runtime/*.c

Repro

./script/docker-exec.sh -- bash -lc 'php test/repro/maintainer_gap_at_silence_undef.php'
./script/docker-exec.sh -- bash -lc 'php bin/vm.php test/repro/maintainer_gap_at_silence_undef.php'

Done when

• echo @$undef / @$undef + 1 / strlen(@$undef) emit no Undefined variable Warning (match Zend)
• strlen(@$undef) still emits the php-src Passing null to parameter #1 ($string) Deprecated (do not over-silence)
• Assign / bare / print controls stay silent
• Compliance .phpt or PHPUnit guard
• php-src-strict; no php-compiler-strict shortcut