The current `AttrTypeReplacer` does not allow for custom handling of
replacer functions that may cause self-recursion. For example, the
replacement of one attr/type may depend on the replacement of another
attr/type (by calling into the replacer manually again), which in turn
may depend on the replacement of the original attr/type.
To enable this functionality, this PR broke out the original
AttrTypeReplacer into two parts:
- An uncached base version (`detail::AttrTypeReplacerBase`) that allows
registering replacer functions and has logic for invoking it on
attr/types & their sub-elements
- A cached version (`AttrTypeReplacer`) that provides the same caching
as the original one. This is still the one used everywhere and behavior
is unchanged.
On top of the uncached base version, a `CyclicAttrTypeReplacer` is
introduced that provides caching & cycle-handling for replacer logic
that is cyclic. Cycle-breaking & caching is provided by the
`CyclicReplacerCache` from
https://github.com/llvm/llvm-project/pull/98202.
Both concrete implementations of the uncached base version use CRTP to
avoid dynamic dispatch. The base class merely provides replacer
registration & invocation, and is not meant to be used, or otherwise
extended elsewhere.
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