These tests are using FileCheck to check the result of diagnostic
formatting in ways that don't match the new formatter. Force the old
formatter or, where possible, generalize so that they match both
formatters.
The error shown when the compiler fails to build a module from its
textual interface has been creating some confusion. This is a proposal
to make it more useful to the programmer not working in the SDK, insist
on looking at the previous errors first, put less emphasis on possible
compiler bugs, and always show alternatives to the incompatible
compilers issue as this is the most common case now.
When a swiftinterface fails to build for any of various reasons, we try to diagnose the failure at the site of the `import` declaration. But if the import is implicitly added—which happens for many SDK modules, like the standard library and ClangImporter overlays—there is no source location for the import, so the error ends up being diagnosed at <unknown>:0. This causes a number of issues; most notably, Xcode doesn’t display the diagnostic as prominently as others.
This change falls back to diagnosing the error at line 1, column 1 of the swiftinterface file itself. This is perhaps not an ideal location, and it won’t help with I/O errors where we can’t open the swiftinterface file (and therefore can’t diagnose an error in it), but it should improve the way we display most module interface building errors.
Currently, when a swiftinterface file fails to load, we emit the specific diagnostics for the failures, followed by a generic “failed to load module ‘Foo’” message. This PR improves that final diagnostic, particularly when the cause may be that the interface was emitted by a newer compiler using backwards-incompatible syntax.
...specifically, diagnosed in the parent DiagnosticEngine. This not
only provides a better user experience, but makes sure that the
compiler exits with a nonzero exit code even if the module goes
unused.
rdar://problem/50789839
