Comparing Exceptions and Errors

[kdevel]

On Sunday, 5 June 2022 at 00:40:26 UTC, Ali Çehreli wrote:
[...]
> Errors are thrown when the program is discovered to be in an 
> invalid state.

The following program throws an `Error` in popFront:

    import std.range;

    void main ()
    {
       int [1] a;
       auto q = a[1..$]; // line 6
       q.popFront;       // line 7, throws 
core.exception.AssertError
    }

When the program counter (PC) is at line 6 the program is in a 
valid state.

At no time the program is in an invalid state and it would not 
pass into an invalid state if popFront threw an `Exception` 
instead of an `Error`.