FBRetainCycleDetector

What This fixes struct parsing when a struct contains a union, and hardens the struct-offset scan against type encodings cannot handle. 1. Union parsing () - fixes #21 ObjC runtime type encodings represent a union as , or for anonymous unions. The parser did not recognize as a grouping character: it fell through to the literal branch and stopped at the first quoted member name inside the union. For a union with named members such as , the parser previously produced: …treating overlapping union members as sequential struct fields and leaving a malformed encoding. Every subsequent field's offset inside the struct was then wrong, so an object reference stored after the union was located at a garbage index (read of the wrong memory during cycle detection). The fix adds and consumes the whole union as one opaque , keeping the offsets of the types that follow it correct. 2. Layout scan hardening () - related to #126 does not throw on encodings it cannot size (bitfields , C++ types, …): it logs the "unsupported type encoding spec" warning and returns . The code ignored the return value and then computed / from zero or garbage values. The scan now checks the return value and bails out (same intent as the existing branch) instead of producing misaligned references. Tests Added to : literal encoding regression test asserting the exact parsed types. real ivar encoding with a named union. real ivar encoding with an anonymous union. Verified with a standalone C++ build of the parser (ObjC bits mechanically stubbed) that runs the new union cases plus all pre-existing parser cases (primitives, objects, nested structs, bitfields, type paths) with no regressions.

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FIX: "FBRetainCycleDetector/FBRetainCycleDetector-Swift.h file not found" in Xcode 16