[Issue 10999] Limited type matching

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=10999



--- Comment #7 from bearophile_hugs at eml.cc 2013-09-11 14:02:28 PDT ---
(In reply to comment #5)

> Please elaborate on which kind of
> type safety is broken by conversion from short to ushort (please with examples
> of system languages like C/C++).

"Type safety" is related to "strong typing". Strong typing means the compiler
refuses to use a type (like ushort) where you have specified another type (like
short), unless you also have explicitly specified what other types are accepted
(this for structural typing, subtyping, etc). And I don't care of C/C++,
thankfully D is not one of those two languages.


> (different ranges is not a problem because it
> is the same data reinterpreted in differen ways - which is not a surprise in
> low-level languages)

It's a problem because they are seen as potentially different values, so the
semantic of your program could change.


> This can't be an argument as similar situation can be created with other
> conversions in D. In other words, if you consider your example as an argument
> against implicit conversion, following should also be disallowed:
> 
> import std.stdio;
> 
> void bar(bool) { "bool".writeln; }
> void bar(long) { "long".writeln; }
> void main() {
>     int a;
>     bar(a); // long
>     bar(1); // bool
>     bar(2); // long
> }
> 
> import std.stdio;
> 
> void bar(int[]) { "int[]".writeln; }
> void bar(int[1]) { "int[1]".writeln; }
> void main() {
>     int[1] a;
>     bar(a);    // int[1]
>     bar([1]); // int[1]
>     bar([]);  // int[]
>     bar([1,1]); //int[]
> }
> 
> and some other conversion stuff.

There are indeed discussions about changing the semantics of booleans a little
in D, to refuse some dangerous implicit conversions. Recently there was a long
thread about this in the main D newsgroup.

-- 
Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email
------- You are receiving this mail because: -------