On Tuesday, 31 May 2022 at 09:11:41 UTC, JG wrote:
On Tuesday, 31 May 2022 at 08:51:45 UTC, realhet wrote:
Hi,
In my framework I just found a dozen of compile time error
handling like:
...else static assert("Invalid type");
This compiles without error. And it was useless for detecting
errors because I forgot the first "false" or "0" parameter.
I think it is because of the weird case of "every string
casted to bool is true".
There is an example in Phobos also:
https://github.com/dlang/phobos/blob/master/std/uni/package.d
at line 8847: static assert("Unknown normalization form
"~norm);
It is easy to make this mistake, but does static
assert(string) has any meaningful use cases?
I was going to suggest to do something like:
```d
import std;
string compileError(string msg) {
import std.format;
return format("static assert(0,%(%s%));",[msg]);
}
auto doGreatThings(T)(T x)
{
static if(is(T==int))
{
return "great things!";
}
else mixin(compileError("Invalid type."));
}
void main()
{
doGreatThings!int(123).writeln;
doGreatThings!string("oh dear").writeln;
}
```
But (a) why should you need to and (b) this makes the message
more obscure.
onlineapp.d-mixin-14(14): Error: static assert: "Invalid type."
onlineapp.d(20): instantiated from here:
`doGreatThings!string`
And then suddenly everyone has their own version of compileError.
There's no reason the compiler can't check whether the first
expression given evaluates to string and if so then the first
argument moves to the second argument and the first argument
becomes 0.
`extern (D) this(const ref Loc loc, Expression exp, Expression
msg)`
