speculative_ctfe.d

/// Returns true iff $(D func(args)) can be evaluated at compile-time
/// and doesn't error when evaluated.
template runsWithoutError(alias func, args...)
	if(__traits(compiles, func(args)))
{
	// Wrapper anon func so it works with `func`s that have void return type
	enum exec() = () { func(args); return true; /* never used */ }();
	//enum runsWithoutError = exec!();
	enum runsWithoutError = __traits(compiles, exec!());
}

void test(string s)
{
	assert(s == "foo");
}

static assert(runsWithoutError!(test, "foo"));
static assert(!runsWithoutError!(test, "bar"));

import std.conv : to;
static assert(runsWithoutError!(to!int, "42"));
static assert(!runsWithoutError!(to!int, "foo"));