[llvm-bugs] [Bug 49668] New: Segfault on CRTP in consteval: `static_cast<Derived>(*this)`

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=49668

            Bug ID: 49668
           Summary: Segfault on CRTP in consteval:
                    `static_cast<Derived>(*this)`
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: C++2a
          Assignee: unassignedclangbugs at nondot.org
          Reporter: w-m at wmcode.nl
                CC: blitzrakete at gmail.com, erik.pilkington at gmail.com,
                    llvm-bugs at lists.llvm.org, richard-llvm at metafoo.co.uk

Created attachment 24667
  --> https://bugs.llvm.org/attachment.cgi?id=24667&action=edit
snippet.cpp

I encountered this problem while writing a small example snippet using CRTP in
consteval in Godbolt: https://godbolt.org/z/Ms3Gq5

The segfault happens both in Clang 11.0.1 and trunk.

Best as I can tell, the problem is related to doing something which is not
allowed:

Line 10 as written in the code snippet is

```
return static_cast<Derived>(*this).toFunImpl<F>();
```

but it turns out that in consteval expressions, only the form

```
return static_cast<Derived *>(this)->toFunImpl<F>();
```
is allowed.


Clang correctly gives a (rather cryptic?) error message here, but then suddenly
segfaults afterwards.

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