Code:

===================================
import std.conv;
import std.regex;

struct A
{
	int field1;
	int field2;
	
	this(int field1, int field2)
	{
		if(field1 > field2)
			throw new Exception("This is illegal!");
	}
	
	this(string str)
	{
		if(str.match(ctRegex!(`^[0-9]{4}-[0-9]{2}`)))
			this(str[0..4].to!int, str[5..7].to!int);
		else
			throw new Exception("Invalid string");
	}
}

void main()
{
	A(2004, 43);
	A("2004-43");
}
===================================

This throws a compilation error:

main.d(17): Error: one path skips constructor
main.d(15): Error: return without calling constructor

Why do I need the constructor call, if I throw the exception anyway? Is this a bug?

On Thursday, 7 September 2017 at 16:08:53 UTC, Piotr Mitana wrote:
> Code:
>
> ===================================
> import std.conv;
> import std.regex;
>
> struct A

> This throws a compilation error:
>
> main.d(17): Error: one path skips constructor
> main.d(15): Error: return without calling constructor
>
> Why do I need the constructor call, if I throw the exception anyway? Is this a bug?

This seems likely a bug, my understanding of this error is for class inheritance, where it must call the super constructor for all code paths to create the base class. With a struct the compiler always has the means to create the base and so it just seems to be be saying, "hey you called the constructor maybe you still want to do that here."

And it would be a nice improvement to have control flow, but you may get away with it if you add assert(0); to the end of the constructor.

On Thursday, 7 September 2017 at 16:08:53 UTC, Piotr Mitana wrote:
>
> main.d(17): Error: one path skips constructor
> main.d(15): Error: return without calling constructor

http://www.digitalmars.com/d/archives/digitalmars/D/learn/Throwing_exception_in_constructor_28995.html