[Dlang-internal] Detect CTFE in AssignExp:semantic

[Lucia Cojocaru via Dlang-internal]

The dmd code (e2ir.d and expression.d are of interest):
https://github.com/somzzz/dmd/commit/8bccc49ba661567c523545650aad30c01fd25090

The druntime template:
https://github.com/somzzz/druntime/commit/6cf9cbc6650697d8a038be7076e588601aefe954

The example which doesn't compile is a standalone code snippet 
which reproduces the error encountered. I started from the code 
in druntime and simplified it to that point. As of your 
suggestions, I will simplify it further and come back with 
another example.

Thanks!