If you have a class Foo, and try to use decltype(*this) somewhere in a method (or constructor) of that class, the compiler crashes with C1001. Example:
decltype(*this) x(); // C1001
decltype(*this) x; // C1001
I am uncertain if this is valid C++, although I don't see why it wouldn't be. In any case, if it is invalid, it should report an appropriate error message rather than crash.
Also note that this only occurs on the this pointer, with any other pointer the decltype call works as expected.