[PATCH] D80981: [AST] Fix a crash on accessing a class without definition in constexpr function context.

[Haojian Wu via Phabricator via cfe-commits]

hokein marked an inline comment as done.
hokein added a subscriber: rsmith.
hokein added inline comments.


================
Comment at: clang/lib/AST/ExprConstant.cpp:4320
+    if (!RD->hasDefinition())
+      return APValue();
     APValue Struct(APValue::UninitStruct(), RD->getNumBases(),
----------------
sammccall wrote:
> This doesn't look all that safe - you're using a `None` value to indicate failure, but no current code path does that and none of the callers seem to check for failure.
> (e.g. `evaluateVarDecl` returns true instead of false).
> Presumably we're going to get a diagnostic somewhere (though it's not completely obvious to me) but can we be sure we won't assume this value has the right type somewhere down the line?
> 
> I get the feeling this is correct and I don't have enough context to understand why... how about you :-)
I don't have a promising explanation neither. 

I didn't find a better way to model failures in `getDefaultInitValue`. This function is used in multiple places of this file (and I'm not sure whether we should change it).

@rsmith any thoughts?


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https://reviews.llvm.org/D80981