static assert("nothing")

Tejas notrealemail at gmail.com
Tue May 31 10:45:30 UTC 2022


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?

This is what Zig does, actually:

https://ziglang.org/documentation/0.9.1/#compileError

```Zig
const std = @import("std");
const expect = std.testing.expect;

test "comptime vars" {
     var x: i32 = 1;
     comptime var y: i32 = 1;

     x += 1;
     y += 1;

     try expect(x == 2);
     try expect(y == 2);

     if (y != 2) {
         // This compile error never triggers because y is a 
comptime variable,
         // and so `y != 2` is a comptime value, and this if is 
statically evaluated.
         @compileError("wrong y value");
     }
}
```


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