Check if dependencies are modified since the last checking.
Dependencies:
- Other source files in the current module
- Dependent files collected by the dependency tracker
When:
- If the last dependency check was over N (defaults to 5) seconds ago
Invalidate if:
- The dependency file is missing
- The modification time of the dependecy is greater than the last check
- If the modification time is zero, compare the content using the file
system from the previous completion and the current completion
rdar://problem/62336432
SwiftSourceInfo files provide source location information for decls coming from
loaded modules. For most IDE use cases it either has an undesirable impact on
performance with no benefit (code completion), results in stale locations being
used instead of more up-to-date indexer locations (cursor info), or has no
observable effect (live diagnostics, which are filtered to just those with a
location in the primary file).
For non-IDE clients of SourceKit though, cursor info providing declaration
locations for symbols from other modules is useful, so add a global
configuration option (and a new request to set it) to control whether
.swiftsourceinfo files are loaded or not based on use case (they are loaded by
default).
The code goes into its own sub-tree under 'tools' but tests go under 'test',
so that running 'check-swift' will also run all the SourceKit tests.
SourceKit is disabled on non-darwin platforms.
