Bug 23297 – You Can Assign a dstring to a dchar[] if Both Sides of the Expression are Slices

The following code fails, like it should: ```d void main() { dchar[] a; //asset(typeof(a).stringof == "dchar[]") dstring b = "a"d; //assert(typeof(b).stringof == "immutable(dchar)[]"); a = b; //ERROR: VIOLATES THE TYPE SYSTEM } ``` However, the following code compiles and runs: ```d void main() { import std.stdio; dchar[] a = "ab".dup; writeln(typeof(a[0 .. $-1]).stringof); //Prints 'dchar[]' writeln(typeof(a[1 .. $]).stringof); //Prints 'immutable(dchar)[]' a[0 .. $-1] = a[1 .. $].idup; //Compiles, but WRONG --a.length; writeln(a); //Prints 'b' to stdout } ``` Given that the first example fails, the second example should also fail and output a similar error.

The second example should work, it's array copy - copies elements from one array to another. The first example is slice assignment that would refer to the same array.

I guess, documentation can be improved here, it mentions only array copy for static array and not for slices.

(In reply to anonymous4 from comment #1) > The second example should work, it's array copy - copies elements from one > array to another. The first example is slice assignment that would refer to > the same array. Can you be more clear? I think you got the two examples mixed up. Also, the second example compiles with wchar and char, not just dchar, and the following works: ```d void main() { wchar[] a = "ab"w.dup; wchar[]b = a.dup; import std.stdio; writeln("Type of a[0 .. $-1]: ", typeof(a[0 .. $-1]).stringof); writeln("Type of b[1 .. $].idup: ", typeof(b[1 .. $].idup).stringof); a[0 .. $-1] = b[1 .. $].idup; //See? Two completely different arrays. --a.length; writeln(a); writeln(typeof(a).stringof); } ``` This is assigning an array of immutable wchars to an array of mutable wchars. No matter how you put it, this is a violation of the type system.

(In reply to anonymous4 from comment #2) > I guess, documentation can be improved here, it mentions only array copy for > static array and not for slices. IMO fine: https://dlang.org/spec/arrays.html#array-copying

(In reply to kinke from comment #4) > (In reply to anonymous4 from comment #2) > > I guess, documentation can be improved here, it mentions only array copy for > > static array and not for slices. > > IMO fine: https://dlang.org/spec/arrays.html#array-copying Okay. Now I see why this isn't a bug.