The warnings that ClangImporter emits about issues it encounters while
importing declarations from Clang modules should all belong to a diagnostic
group so that users of `-warnings-as-errors` can control their behavior using
the compiler flags introduce with SE-0443. It's especially important that these
diagnostics be controllable since they are often caused by external
dependencies and therefore the developer may not have any control over whether
they are emitted.
The `#ClangDeclarationImport` diagnostic group is intentionally broad so that
developers have a way to control all of these diagnostics with a single
`-Wwarning` flag. I fully expect that we'll introduce finer-grained diagnostic
groups for some of these diagnostics in the future, but those groups should be
hierarchically nested under `#ClangDeclarationImport`, which is supported by
SE-0443.
Resolves rdar://150524204.
Lazy member loading has been in use and the default for several years
now. However, the lazy loading was disabled for any type whose primary
definition was parsed even though some of its extensions could have
been deserialized, e.g., from a Clang module. Moreover, the non-lazy
path walked all of the extensions of such a type for all member name
lookup operations. Faced with a large number of extensions to the same
type (in my example, 6,000), this walk of the list of the extensions
could dominate type-checking time.
Eliminate all effects of the `-disable-named-lazy-member-loading`
flag, and always use the "lazy" path, which effectively does no work
for parsed type definitions and extensions thereof. The example with
6,000 extensions of a single type goes from type checking in 6 seconds
down to type checking in 0.6 seconds, and name lookup completely
disappears from the profiling trace.
The deleted tests relied on the flag that is now inert. They aren't by
themselves providing much value nowadays, and it's better to have the
simpler (and more efficient) implementation of member name lookup be
the only one.
As per SR-14137 this caches entries in ImportedDecls even when the
import failed.
Also have to mention I did this based on Thomas's PR #36747.
This should help us better handle complex templates and dependant types.
If a swift_name attribute’s context referred to the same declaration it was attached to, or a different declaration whose own swift_name referred to the current one, we would recurse infinitely and eventually overflow the stack. This commit makes us instead detect the cycle, diagnose it with a warning, and drop the affected declaration.
Fixes rdar://79370809.
