Today I stumbled across three issues with partial initialization of "static" arrays:

void main ()
{
   char [7] b = [ 1: 'x' ]; // okay
   char [7] a = [ 0: 'x' ]; // i1.d(4): Error: mismatched array lengths, 7 and 1
}

import std.stdio;

void main ()
{
   char [7] c7 = [ 1: 'x' ];
   writeln (cast (ubyte [7]) c7); // [255, 120, 255, 255, 255, 255, 255] okay
   char [7] d7 = "x";
   writeln (cast (ubyte [7]) d7); // [120, 0, 0, 0, 0, 0, 0] would have expected
                                  // [120, 255, 255, 255, 255, 255, 255]
}

// i3.d
void main ()
{
   string s = "x";
   static assert (is (typeof (s) == typeof ("x")));
   assert (s == "x");
   char [7] c7 = s; // throws RangeError
}

$ dmd -g i3
$ ./i3
core.exception.RangeError@i3.d(7): Range violation
----------------
??:? _d_arrayboundsp [...]
i3.d:7 _Dmain [...]

Shall I file them to bugzilla?

On Saturday, 14 August 2021 at 09:40:54 UTC, kdevel wrote:

void main ()
{
   char [7] b = [ 1: 'x' ]; // okay
   char [7] a = [ 0: 'x' ]; // i1.d(4): Error: mismatched array lengths, 7 and 1
}

import std.stdio;

void main ()
{
   char [7] c7 = [ 1: 'x' ];
   writeln (cast (ubyte [7]) c7); // [255, 120, 255, 255, 255, 255, 255] okay
   char [7] d7 = "x";
   writeln (cast (ubyte [7]) d7); // [120, 0, 0, 0, 0, 0, 0] would have expected
                                  // [120, 255, 255, 255, 255, 255, 255]
}

// i3.d
void main ()
{
   string s = "x";
   static assert (is (typeof (s) == typeof ("x")));
   assert (s == "x");
   char [7] c7 = s; // throws RangeError
}

$ dmd -g i3
$ ./i3
core.exception.RangeError@i3.d(7): Range violation
----------------
??:? _d_arrayboundsp [...]
i3.d:7 _Dmain [...]

Static arrays really don't get any love :(

I also recently filed a bug:
https://issues.dlang.org/show_bug.cgi?id=22198

I think you should also file these ones.
If they're wrong, it'll just get RESOLVED INVALID. Even better, someone here can tell why the above mentioned behaviours aren't bugs and you can just do it yourself.

On Saturday, 14 August 2021 at 09:40:54 UTC, kdevel wrote:

I would say case 2 and 3 are not bugs. It's just the element type conversion and mismatched lengths of the ranges.

Not sure about the first one.

On Saturday, 14 August 2021 at 13:01:13 UTC, frame wrote:

Yeah, I jumped the train :(

Replace string with char and double quotes with single quotes then case 2 and 3 give the expected output

1 is 100% a bug, please report that.

On Saturday, 14 August 2021 at 13:01:13 UTC, frame wrote:

   char [7] d7 = "x"; // okay

   string s = "x";
   char [7] c7 = s; // throws RangeError

What justifies that the compiler behaves differently on two terms ('s', '"x"') which are of equal size, type, length and value?

On Saturday, 14 August 2021 at 14:04:47 UTC, kdevel wrote:

   char [7] d7 = "x"; // okay

   string s = "x";
   char [7] c7 = s; // throws RangeError

They are not.

assert(string.sizeof != char.sizeof);

On Saturday, 14 August 2021 at 14:18:57 UTC, Tejas wrote:

   char [7] d7 = "x"; // okay

   string s = "x";
   char [7] c7 = s; // throws RangeError

The terms are s and "x":

void main ()
{
   string s = "x";
   assert (s.sizeof == "x".sizeof);
}

On Saturday, 14 August 2021 at 14:33:42 UTC, kdevel wrote:

   char [7] d7 = "x"; // okay

   string s = "x";
   char [7] c7 = s; // throws RangeError

void main ()
{
   string s = "x";
   assert (s.sizeof == "x".sizeof);
}

It did implicit conversion on the literal but not the variable.
Basically,

char[7] a = cast(char[7])"x"; // works
string s = "x";
char[7] b = cast(char[7])s; //fails

That's my best guess.

Hopefully someone more experienced chimes in.

On Saturday, 14 August 2021 at 14:04:47 UTC, kdevel wrote:

   char [7] d7 = "x"; // okay

   string s = "x";
   char [7] c7 = s; // throws RangeError

One is pure initialization, CTFE magic for strings or something like that. The other one is an assignment of an already created range where length check kicks in. The compiler is fine with that as it compiles. It's the bound checker at runtime level that bails out.

On Saturday, 14 August 2021 at 14:04:47 UTC, kdevel wrote:

   char [7] d7 = "x"; // okay

   string s = "x";
   char [7] c7 = s; // throws RangeError

Literals in D can have different types in different contexts. For example:

byte b = 16; // 16 is treated as a byte literal
int n = 16; // 16 is treated as an int literal
b = n; // Error: cannot convert int to byte

Similarly, the string literal "x" can be treated either as a string (a dynamic array of immutable(char)) or as a static array of char, depending on the type of variable it's assigned to.