The "buffer ID" in a SourceFile, which is used to find the source file's
contents in the SourceManager, has always been optional. However, the
effectively every SourceFile actually does have a buffer ID, and the
vast majority of accesses to this information dereference the optional
without checking.
Update the handful of call sites that provided `nullopt` as the buffer
ID to provide a proper buffer instead. These were mostly unit tests
and testing programs, with a few places that passed a never-empty
optional through to the SourceFile constructor.
Then, remove optionality from the representation and accessors. It is
now the case that every SourceFile has a buffer ID, simplying a bunch
of code.
Although I don't plan to bring over new assertions wholesale
into the current qualification branch, it's entirely possible
that various minor changes in main will use the new assertions;
having this basic support in the release branch will simplify that.
(This is why I'm adding the includes as a separate pass from
rewriting the individual assertions)
The `NameMatcher` implemented in swift-syntax as slightly different semantics because it consideres `(callable.|callAsFunction)(x: 78)` as a reference to `callAsFunction` instead of a call with argument labels `(x: 78)`, which means that one test needs to be updated.
This allows building sourcekitd and swift-refactor with `SWIFT_BUILD_SWIFT_SYNTAX=NO`. In these builds, the `relatedidents` and `find-syntactic-rename-ranges` requests will always return an error.
With the local refactoring being removed, all production refactoring paths return a set of ranges to rename and don’t apply edits to the file. Thus, the `syntactic-rename` action also doesn’t make sense anymore.
We should (and do) have one new name for the entire rename operation, not a separate new name for different positions at which the renamed symbol occurs.
