swift234

[Name lookup] Introduce a lookup table into each nominal type declaration.

The lookup table for a nominal type declaration provides efficient
(O(1)) access to all of the declarations with a given name in a
nominal type and its extensions. This is architecturally different
from Clang's handling of Objective-C classes and
categories/extensions, where each category/extension has its own
lookup table, and is meant to reduce the number of hash table lookups
required, especially once these hash tables are stored in the module.

The lookup table is built and updated lazily as extensions and members
are introduced, similarly to Clang's lookup tables. However, the
simpler name lookup rules in Swift (vs. C/C++/Objective-C) make this
approach actually semantically correct.



Swift SVN r5874