Expose the loop that overwrites a variable still in use

[ondrejmirtes]

Needed by phpstan/phpstan-strict-rules#332 (also phpstan/phpstan#9940).

OverwriteVariablesWithForeachRule fires on any foreach whose key/value variable is already defined. Since #6380 tracks definedness precisely, that includes reusing a spent loop variable after a flag-then-check (if (!$found) return;). The rule needs a liveness answer: does the loop take over a variable that was assigned before it and is read after it, with nothing but the loop's own writes in between?

This adds VariableWritesNode::getVariableOverwritingLoop(VariableWrite $write): Foreach_|For_|null, answering exactly that for foreach key/value bindings and for-loop initial assignments (list targets included).

How it works:

• ForeachHandler / ForHandler wrap the statement's flow in a new VariableFlow::loopStatement() carrying the head bindings and the statement's own writes (bindings plus a for-loop's update, e.g. $i++).
• In VariableLivenessResolver, when the bound variable is live after the statement, a probe key (a \0-prefixed key no read can produce) enters the live set. It travels backwards through the statement: own writes let it through, other whole-variable writes kill it. Surviving to the statement entry it is armed; the first earlier assignment, by-reference alias, or offset write of the variable then records the loop. unset() kills it without recording.

Examples (see the fixture):

• foreach ($a as $x) {} foreach ($b as $x) {} — silent
• $found = false; foreach (...) { ... break; } if (!$found) return; foreach ($a as $x) {} — silent
• foreach ($outer as $x) { foreach ($inner as $x) {} use($x); } — inner loop reported
• function (string $x) { foreach ($a as $x) {} echo $x; } — reported
• for ($i = 0; ...) {} for ($i = 0; ...) {} — silent; reported only if $i is read after the second loop

Strict-rules side follows once this is in the dev phar.

🤖 Generated with Claude Code

https://claude.ai/code/session_01LYiPGg9cpsKLyK6X5BrJTT

[phpstan-bot]

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