AST: Properly disallow isa/cast/dyn_cast on Type
#85487
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Yeah, unless you want to declare a local |
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[stable/21.x][lldb] Swift: Fix `swift::Type` casts for swiftlang/swift#85487
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[next][lldb] Swift: Fix `swift::Type` casts for swiftlang/swift#85487
We currently disallow these by deleting them in the `swift` namespace. This approach has several loopholes, all of which ultimately work because we happen to define specializations of `simplify_type` for `swift::Type`: * `llvm::isa/cast/dyn_cast`. The deleted partial specializations will not be selected because they are not defined in the `llvm` namespace. * The argument is a non-const `Type`. The deleted function templates will not be selected because they all accept a `const Type &`, and there is a better `Y &Val` partial specialization in LLVM. * Other casting function templates such as `isa_and_nonull` and `cast_if_present` are not deleted. Eliminate these loopholes by instead triggering a static assertion failure with a helpful message upon instantiation of `CastInfo` for `swift::Type`.
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We currently disallow these by deleting them in the
swiftnamespace. This approach has several loopholes, all of which ultimately work because we happen to define specializations ofsimplify_typeforswift::Type:llvm::isa/cast/dyn_cast. The deleted partial specializations will not be selected because they are not defined in thellvmnamespace.Type. The deleted function templates will not be selected because they all accept aconst Type &, and there is a betterY &Valpartial specialization in LLVM.isa_and_nonullandcast_if_presentare not deleted.Eliminate these loopholes by instead triggering a static assertion failure with a helpful message upon instantiation of
CastInfoforswift::Type.