[clang] [clang] Allow C-style casts in constexpr in MS compatible mode (PR #197005)

[Eli Friedman via cfe-commits]

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@@ -812,6 +813,7 @@ class ASTContext : public RefCountedBase<ASTContext> {
   mutable DeclarationNameTable DeclarationNames;
   IntrusiveRefCntPtr<ExternalASTSource> ExternalSource;
   ASTMutationListener *Listener = nullptr;
+  SmallVector<PartialDiagnosticAt> *MSConstExprDiag = nullptr;
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efriedma-quic wrote:

How many steps would it be to pass this down explicitly instead of going through ASTContext?  I think I'd prefer to pass down explicitly; it's more code, but implicit stacks like this are really terrible to reason about.

https://github.com/llvm/llvm-project/pull/197005