When parameter is added by addSimpleNamedParameter(), the type name
doesn't exist. Instead of printing empty strings, use short version of
editor placeholders.
rdar://83904268
Filter name for completion item is always used. Also, for cached items,
they are used multiple times for filtering. So precomputing and caching
it improves performance.
rdar://84036006
* "description" for override completion is now annotatable
* "description" doesn't include attributes and decl introducer, but it
includes generic paramters, effects specifiers, result type clause,
and generic where clauses
* "name" now only include the name and the parameter names
* "sourcetext" should be the same
rdar://63835352
Consolidate ThrowsKeyword, RethrowsKeyword, and AsyncKeyword to
EffectsSpecifierKeyword.
Abolish 'key.throwsoffset' and 'key.throwslength' as they aren't used.
When completing a single argument for a trailing closure, pre-expand the
closure expression syntax instead of using a placeholder. It's not valid
to pass a non-closure anyway.
rdar://62189182
