Re: One path skips constructor - is this a bug?

[Johan Engelen via Digitalmars-d-learn]

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

Re: One path skips constructor - is this a bug?

[Jesse Phillips via Digitalmars-d-learn]

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.

One path skips constructor - is this a bug?

[Piotr Mitana via Digitalmars-d-learn]

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?