Order of evaluation for named arguments

[Timon Gehr]

On 3/29/25 19:38, Steven Schveighoffer wrote:
> In the D spec, the function parameter [section on order of evaluation] 
> (https://dlang.org/spec/expression.html#order-calls) says:
> 
>> Arguments are evaluated left to right.
> 
> So a question was raised, what about named arguments, since those might 
> not match the order of parameters?
> 
> I decided to test:
> 
> ```d
> import std.stdio;
> void foo(int a, int b) {
>     writeln(i"a: $(a), b: $(b)");
> }
> 
> void main() {
>     int x;
>     foo(b: ++x, a: ++x);
> }
> ```
> 
> According to the spec, this should print "a: 2, b: 1", as the order of 
> evaluation of the expression should go left to right. But the actual 
> printout is "a: 1, b: 2".
> 
> So the question is, should we modify the spec to reflect this, or would 
> it be better to change the compiler to enforce this left-to-right 
> evaluation rule?
> 
> -Steve

Fixing the compiler is better. Changing the spec is slightly easier.