enum of struct not calling constructor

[Andrej Mitrovic]

Example 1:

import std.stdio;

enum WindowSizes : QSize
{
Minimum = QSize(10)
}

struct QSize
{
int store;
this(int x)
{
store = x + 10;
}
}

void main()
{
auto foo = WindowSizes.Minimum;
assert(foo.store == 10);  // What?

auto bar = QSize(10);
assert(bar.store == 20);
}

It appears the constructor is never called for the enum. It does field by field 
assignments instead, just take a look at this case:

import std.stdio;

enum WindowSizes : Inverted
{
Minimum = Inverted(10, 20)
}

struct Inverted
{
int x;
int y;
this(int in_x, int in_y)
{
x = in_y;
y = in_x;
}
}

void main()
{
auto foo = WindowSizes.Minimum;
assert(foo.x == 10);
assert(foo.y == 20);

auto bar = Inverted(10, 20);
assert(bar.x == 20);
assert(bar.y == 10);
}

As can be seen, this could be a potential source of bugs. Should I file it?

Re: enum of struct not calling constructor

[Jonathan M Davis]

On Tuesday, January 18, 2011 08:44:02 Andrej Mitrovic wrote:
 Example 1:
 
 import std.stdio;
 
 enum WindowSizes : QSize
 {
 Minimum = QSize(10)
 }
 
 struct QSize
 {
 int store;
 this(int x)
 {
 store = x + 10;
 }
 }
 
 void main()
 {
 auto foo = WindowSizes.Minimum;
 assert(foo.store == 10);  // What?
 
 auto bar = QSize(10);
 assert(bar.store == 20);
 }
 
 It appears the constructor is never called for the enum. It does field by
 field assignments instead, just take a look at this case:
 
 import std.stdio;
 
 enum WindowSizes : Inverted
 {
 Minimum = Inverted(10, 20)
 }
 
 struct Inverted
 {
 int x;
 int y;
 this(int in_x, int in_y)
 {
 x = in_y;
 y = in_x;
 }
 }
 
 void main()
 {
 auto foo = WindowSizes.Minimum;
 assert(foo.x == 10);
 assert(foo.y == 20);
 
 auto bar = Inverted(10, 20);
 assert(bar.x == 20);
 assert(bar.y == 10);
 }
 
 As can be seen, this could be a potential source of bugs. Should I file it?

Absolutely.

- Jonathan M Davis

Re: enum of struct not calling constructor

[Andrej Mitrovic]

http://d.puremagic.com/issues/show_bug.cgi?id=5460