Resolve isset/empty/?? chains from handler-built descriptors

[ondrejmirtes]

Rules\IssetCheck was a hand-maintained mirror of MutatingScope::issetCheck()'s chain walk (variable / offset / property / leaf), re-walking the AST and re-resolving types and property reflections with its own drifting copy of the logic (the scope side even carried a // mirrored in ... comment).

This lands the resolve-type-rewrite branch's architecture for the rule side, with MutatingScope untouched:

• the chain-link handlers (VariableHandler / ArrayDimFetchHandler / PropertyFetchHandler / StaticPropertyFetchHandler) attach an IssetabilityDescriptor to their ExpressionResult, built from the child results they already have in hand;
• IssetHandler, EmptyHandler, CoalesceHandler and AssignOpHandler (??=) emit virtual nodes (IssetExpressionNode / EmptyExpressionNode / CoalesceExpressionNode) carrying the subject ExpressionResults;
• IssetRule / EmptyRule / NullCoalesceRule listen on those nodes, and Rules\IssetCheck folds the resolved links of an IssetabilityResolution instead of walking the AST.

IssetabilityDescriptor, IssetabilityLinkInfo, the three virtual nodes and the three rules are byte-identical to the branch; IssetabilityResolution and Rules\IssetCheck differ only by omitting branch-only leftovers (notEmpty() is dead until the branch's EmptyHandler conversion, plus a debug block). For ??=, AssignOpHandler prices the left side once as a Noop-callback read, mirroring CoalesceHandler's left-side processing — that is the branch's own shape for carrying the descriptor to the rule.

The engine side (MutatingScope::issetCheck() and the handlers' resolveType/specifyTypes) is deliberately untouched; it converges with the branch's sweep, at which point issetCheck() is deleted and no duplicated chain-walk logic remains.

Verification:

• full test suite green with zero expectation churn (17778 tests)
• --error-format=raw output identical to 2.2.x on an isset-saturated stress file
• user CPU neutral on both self-analysis and a synthetic file that is 100% isset/??/empty() chains (ABBA pairs, +0.6% on the stress file, within noise)

🤖 Generated with Claude Code

https://claude.ai/code/session_01DaBZjgksga4c5s6Q9FniY7