Re: Is there a way to get a template’s parameters and constraints?

[Steven Schveighoffer]

On 1/20/23 12:15 PM, Quirin Schroll wrote:
> Is there a trait (or a combination of traits) that gives me the 
> constraints of a template?
> 
> Example:
> ```D
> void f(T1 : long, T2 : const(char)[])(T x) { }
> template constraintsOf(alias templ) { /*Magic here*/ }
> alias constraints = constraintsOf!f; // tuple(long, const(char)[])
> ```
> 
> At the moment, I care about constraints that are types. I don’t care 
> about value or alias constraints (e.g. `opBinary(string op : "+")(..)` 
> or `f(alias x : something)()`, but if it works for types, it should 
> probably work for other constraints as well.
> 
> For what I want, `constraintsOf` may expect every template parameter to 
> be a type and to have a constraint.

No, there is no way to introspect anything about a template's details 
until its instantiated.

-Steve