Partials v2 gen

[arnaud-lb]

PFAs are created by generating the AST of a Closure at runtime and compiling it. The compiled op_array can be cached similarly to linked classes.

About caching

There are two levels of caching:

• The global opcache (ZCG(hash))
• The caller's run time cache

The cache key in ZCG(hash) is composed of the address of the declaring opline, the address of the function being called, and a prefix.

This scheme is not ideal because:

• The key used in ZCG(hash) may be a valid file name
• This takes a slot in ZCG(hash)
• When opcache is not enabled, only the run time cache is used. This cache stores only one entry, so cache misses will occur when the function being called changes.

A better solution might be to cache PFA op_arrays in the declaring op_array (similarly, the inheritance cache is stored in classes). This cache could store multiple PFAs, and could be used regardless of opcache being enabled.

Alternatively, use a global two-level map: First level is indexed by the "signature" of the PFA, second level by the function being called. This would lead to a better cache hit rate when the same function is partialled in multiple locations.

TODO

• Improve PFA caching when opcache is not enabled, and fix cases that are broken when opcache is not enabled
• Reorganize tests
• PFAs in constant expressions
• bindTo() is a no-op for PFA of closures