Similar with @keyword, manifesting @recommended and @recommendedover content in code
completion results can help IDE users to choose the right API in the long candidate list.
This commit extract these two attributes from Clang doc comments and insert/cache them in
code completion results.
rdar://23101030 and rdar://23101029
Conventionally, code completion results are matched with user input solely by
names. However, names are limited in expressiveness. From this comments, we start to
decorate code completion results with @keywords fields extracted from Clang doc comments.
These fields are added by API authors to comment the decl with information that
is not manifested clear enough through names. Code completion users' typing of the
keyword leads to the corresponding code completion results being selected as well.
Keywords can be arbitrarily long and can be multiple.
For instance, a function called "index()" has "@keyword find" in its doc comment.
Users' typing of "find" leads to "index()" being selected in the code completion list.
When we miss the in-memory (libcache-based) code completion cache, we
can now chain to an on-disk code completion cache. This drastically
improves the time and peak memory usage it takes to do the first code
completion (ie. before the in-memory cache is warm) if we've done the
same lookup before.
The on-disk cache, like the in-memory cache is tied to the specific
compiled swift and clang module files (.swiftmodule and .pcm), and will
consider itself out of date if they are modified. Responsibility for
deleting completely dead/unreachable cache files falls to the client.
Most of this commit is adding a simple serialization and deserialization
for CodeCompletionResults and CodeCompletionStrings. The format is very
simple, using an array of fixed size CodeCompletionResults, with offsets
into two blobs: one for CodeCompletionString::Chunks, and one for
strings. Currently that gives us about 5.8 MB for all the results in
Cocoa, but it's very compressible if we decide we want to reduce it
(gzip'd it is ~1.2 MB for the same data).
Swift SVN r28369
