47b068d445 output a diagnostic if a
deserialized decl was invalid (checking `Decl::isInvalid`). It had two
major issues:
1. It incorrectly output diagnostics for valid modules
2. It did not catch call invalid declarations
(1) is caused by `isInvalid` falling back to checking the storage for
accessors when the interface type hasn't already been computed (a
fallback to prevent a cycle due to `SimpleDidSetRequest` typechecking
the body). Since the `VarDecl` hasn't finished deserializing, it returns
`true` for its `isInvalid` check (even though it would later return
`false`).
For (2), only `ValueDecl`s would ever be invalid, since other
declarations use a bit in `Decl` to check for validity. As that's not
serialized, those would always be valid in deserialization.
To avoid both these issues, instead output a flag for each declaration
representing whether it is invalid (or not). Read that during
deserialization and output a diagnostic if it is invalid. To be extra
sure that a diagnostic is always output on an error, also output one
when deserializing any `ErrorType`. This ensures that SILGen does not
run when allowing errors (and an error is present), as it is likely to
crash when presented with an invalid AST.
Resolves rdar://74541834
When running in the allow errors mode
(-experimental-allow-module-with-compiler-errors), modules may contain
invalid declarations. The rest of the compiler pipeline, however,
expects to have valid declarations unless diagnostics have emitted an
error. Emit an error while deserializing to maintain this assumption.
Note that these errors will not have a useful location, unless there's a
corresponding `.swiftsourceinfo`. This isn't a problem for the intended
use case in IDEs, where diagnostics outside the current file would be
ignored anyway.
Since reading declarations is lazy, SILGen (and thus SIL diagnostics)
can still run as long as any invalid declarations weren't referenced in
the compiling module.
Resolves rdar://74325388
Adds a new frontend option
"-experimental-allow-module-with-compiler-errors". If any compilation
errors occur while generating the .swiftmodule, this mode will skip SIL
entirely and only serialize the (likey invalid) AST.
This existence of this option during generation is serialized into the
resulting .swiftmodule. Errors found in deserialization are only allowed
if it is set.
Primarily intended for IDE requests (eg. indexing and code completion)
to ensure robust cross-module results, despite possible errors.
Resolves rdar://69815975
