Is there a way to statically assert compilation of an expression failed *with a certain message*? I want to check my static asserts trip when they should.

-- 
Tomek

Tomek Sowiñski:

> Is there a way to statically assert compilation of an expression failed *with a certain message*? I want to check my static asserts trip when they should.

I have asked something like this a lot of time ago, but I don't know a way to do it. You are able to statically assert that some code doesn't compile, but I don't know how to assert that a certain message gets produced. You are asking for a specific static catch :-)

Bye,
bearophile

On Thursday, February 10, 2011 16:12:01 Tomek Sowiński wrote:
> Is there a way to statically assert compilation of an expression failed *with a certain message*? I want to check my static asserts trip when they should.

You mean like

static assert(0, "We have a failure, Captain!");

If a static assert fails, it's obvious. Compilation fails. Now, if you're trying to assert something like that a particular template instantiation fails, the use static assert(!__traits(compiles, exp)); where exp is the expression being tested.

- Jonathan M Davis

bearophile napisał:

> > Is there a way to statically assert compilation of an expression failed *with a certain message*? I want to check my static asserts trip when they should.
> 
> I have asked something like this a lot of time ago, but I don't know a way to do it. You are able to statically assert that some code doesn't compile, but I don't know how to assert that a certain message gets produced. You are asking for a specific static catch :-)

Static catch, yeah. But I'd be content with traits__(fails, expr, msg) which seems tractable.

-- 
Tomek

How's this?

import std.stdio;
import std.conv;

void staticAssert(alias exp, string message, string file = __FILE__,
int line = __LINE__)()
{
    static if (!exp)
    {
        pragma(msg, file ~ ":(" ~ to!string(line) ~ ") " ~
"staticAssert: " ~  to!string(message));
        assert(0);
    }
}

void main()
{
    enum x = false;
    staticAssert!(x, "Oh no we failed!");

    int y;
}

I've managed to screw up the colon placement though, here's a quick fix:

import std.stdio;
import std.conv;

void staticAssert(alias exp, string message, string file = __FILE__,
int line = __LINE__)()
{
    static if (!exp)
    {
        pragma(msg, file ~ "(" ~ to!string(line) ~ "): " ~
"staticAssert: " ~  to!string(message));
        assert(0);
    }
}

void main()
{
    enum x = false;
    staticAssert!(x, "Oh no we failed!");

    int y;
}

Tomek S.:

> Static catch, yeah. But I'd be content with traits__(fails, expr, msg) which seems tractable.

Asking for new features in this newsgroup is not so useful. You may add it to bugzilla...

Bye,
bearophile

Andrej Mitrovic napisał:

> I've managed to screw up the colon placement though, here's a quick fix:
> 
> import std.stdio;
> import std.conv;
> 
> void staticAssert(alias exp, string message, string file = __FILE__,
> int line = __LINE__)()
> {
>     static if (!exp)
>     {
>         pragma(msg, file ~ "(" ~ to!string(line) ~ "): " ~
> "staticAssert: " ~  to!string(message));
>         assert(0);
>     }
> }
> 
> void main()
> {
>     enum x = false;
>     staticAssert!(x, "Oh no we failed!");
> 
>     int y;
> }

How does it help to find out that compilation tripped on a specific static assertion?

-- 
Tomek

I thought you were just looking for a static assert with a custom message?