[clang] [Clang][Sema] set declaration invalid earlier to prevent crash in calculating record layout (PR #87173)

[Shafik Yaghmour via cfe-commits]

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@@ -3899,6 +3899,9 @@ static QualType GetDeclSpecTypeForDeclarator(TypeProcessingState &state,
       SemaRef.Diag(OwnedTagDecl->getLocation(), DiagID)
           << SemaRef.Context.getTypeDeclType(OwnedTagDecl);
       D.setInvalidType(true);
+      OwnedTagDecl->setCompleteDefinition(false);
+      OwnedTagDecl->setInvalidDecl();
+      OwnedTagDecl->setCompleteDefinition();
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shafik wrote:

I am little uncomfortable with this change here, I see that you are calling `setCompleteDefinition(false)` in order to get around the `assert` that the decl is not complete in `Decl::setInvalidDecl(...)`. If this precondition is not true we need to understand why it break down or if this implies we should be handling this differently.

https://github.com/llvm/llvm-project/pull/87173