Sema now type-checks the alternate ABI-providing decls inside of @abi attributes.
Making this work—particularly, making redeclaration checking work—required making name lookup aware of ABI decls. Name lookup now evaluates both API-providing and ABI-providing declarations. In most cases, it will filter ABI-only decls out unless a specific flag is passed, in which case it will filter API-only decls out instead. Calls that simply retrieve a list of declarations, like `IterableDeclContext::getMembers()` and friends, typically only return API-providing decls; you have to access the ABI-providing ones through those.
As part of that work, I have also added some basic compiler interfaces for working with the API-providing and ABI-providing variants. `ABIRole` encodes whether a declaration provides only API, only ABI, or both, and `ABIRoleInfo` combines that with a pointer to the counterpart providing the other role (for a declaration that provides both, that’ll just be a pointer to `this`).
Decl checking of behavior specific to @abi will come in a future commit.
Note that this probably doesn’t properly exercise some of the new code (ASTScope::lookupEnclosingABIAttributeScope(), for instance); I expect that to happen only once we can rename types using an @abi attribute, since that will create distinguishable behavior differences when resolving TypeReprs in other @abi attributes.
Both `try?` and `try!` are catch nodes, because they catch an error
thrown in their subexpression and handle it. Introduce an ASTScope for
all `try/try?/try1` expressions so we can find them, and model them as
catch nodes.
Fixes rdar://119216455.
Replace a number of virtual query functions like `getDeclIfAny`, which had
to be overridden at various points in the hierarchy, with simpler
implementations based on the scope kind and `dyn_cast`.
Macro-metaprogram whether each scope node is associated with a
particular declaration/statement/expression/attribute so these
implementations can be efficiently macro-metaprogrammed.
The ASTScope class hierarchy rooted at ASTScopeImpl is relying entirely
on overridden virtual functions and, in some cases, string comparisons
on the class name, to provide customization for the various classes.
Introduce proper LLVM dynamic casting support to this class hierarchy,
eliminating the string comparisons and the manually-specified
implementations of `getClassName` (which is now used only for printing).
We've been meaning to do this for years, but today I got angry enough.
