We were verifying the Swift full version information from the module
file extension metadata for the Swift name lookup tables, but not
actually putting it in the hash, which meant that having an older
module cache around would cause spurious failures when Swift name
lookup tables were enabled. Instead, use just the major/minor version
numbers of the lookup tables. When the lookup table format or contents
of the lookup table change, we'll bump the version number.
The recently-introduced module file extensions functionality in Clang
allows us to piggy-back the Swift name lookup tables in Clang's module
files. When the Swift name lookup tables are enabled, introduce such a
module file extension, and wire it into the SwiftLookupTable.
The actual contents of the extension block are simple: a single
on-disk hash table mapping base names to "full entries", which store
the context (e.g., a class, protocol, tag, or TU) and the set of
declarations.
Allow lazy resolution of declaration IDs deserialized from the
extension block to Clang declarations, to try to minimize the set of
declarations we must deserialize. Name lookup itself is only used to
dump the Swift name lookup tables and ensure we're round-tripping
properly.
The base name -> full name mapping really isn't interesting; index
based on the base name and filter by context instead. This makes the
lookup table dumper less interesting for testing purposes
(unfortunately), but test coverage will improve greatly once we can
turn on these lookup tables.
This is needed for member lookup via the Swift lookup tables, although
the lookup part is not yet implemented. Note also that the results are
currently wrong for C enumerations mapped into Swift enums or option
sets. That will come shortly.
When we parse a bridging header, start building a mapping from Swift
names (both base names and full names) to the Clang declarations that
have those names in particular Clang contexts. For now, just provide
the ability to build the table (barely) and dump it out; we'll grow
it's contents in time.
