Bug report: Quartus Pro version 20.3/20.4 synthesis crashes on VHDL recursive function calls with...

Gladly.

For the workaround, instead of assigning the value to a constant, assign it to a variable, with the assignment done in the body of the function. See attached.

Note that the assignment of the value to the variable must be done in the body of the function, must not be done as an initial value assignment in the declarative part of the function, as the latter results in the same crash as setting a constant.