http://d.puremagic.com/issues/show_bug.cgi?id=1698

           Summary: foreach auto type inference doesnt work properly
           Product: D
           Version: 2.008
          Platform: PC
        OS/Version: Windows
            Status: NEW
          Keywords: rejects-valid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla@digitalmars.com
        ReportedBy: spam@extrawurst.org


since the const/invariant changes in dmd2.008 the following valid code wont compile anymore, cause the compile is not able to infer the type for c correctly i think.

[CODE]
void bar(ref char c) {

}

void main() {

        string text;

        foreach(ref c; text) { // adding type char makes it work

                bar(c);
        }
}
[\CODE]

compiler message:
Error: cast(char)c is not an lvalue


-- 

d-bugmail@puremagic.com wrote:
> http://d.puremagic.com/issues/show_bug.cgi?id=1698
> 
>            Summary: foreach auto type inference doesnt work properly
>            Product: D
>            Version: 2.008
>           Platform: PC
>         OS/Version: Windows
>             Status: NEW
>           Keywords: rejects-valid
>           Severity: normal
>           Priority: P2
>          Component: DMD
>         AssignedTo: bugzilla@digitalmars.com
>         ReportedBy: spam@extrawurst.org
> 
> 
> since the const/invariant changes in dmd2.008 the following valid code wont
> compile anymore, cause the compile is not able to infer the type for c
> correctly i think.
> 
> [CODE]
> void bar(ref char c) {
> 
> }
> 
> void main() {
> 
>         string text;
> 
>         foreach(ref c; text) { // adding type char makes it work
> 
>                 bar(c);
>         }
> }
> [\CODE]
> 
> compiler message:
> Error: cast(char)c is not an lvalue
> 
> 

Since c inside of the foreach-loop is actually a "ref invariant(char)" (string = invariant(char)[]), it is correct that it cannot be passed to bar, taking a mutable "ref char".
Changing bar to "void bar( ref invariant(char) c ){}" makes it compile again.

http://d.puremagic.com/issues/show_bug.cgi?id=1698


spam@extrawurst.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |INVALID




------- Comment #2 from spam@extrawurst.org  2007-12-01 11:55 -------
you are right, my bad.


-- 

On 12/1/07, Sönke Ludwig <ludwig@informatik_dot_uni-luebeck.de> wrote:
> Since c inside of the foreach-loop is actually a "ref invariant(char)"
> (string = invariant(char)[]), it is correct that it cannot be passed to
> bar, taking a mutable "ref char".
> Changing bar to "void bar( ref invariant(char) c ){}" makes it compile
> again.

So... can you /assign/ a ref invariant(char)?

I'm confused as to why the code isn't just

    foreach(c;text)

Janice Caron schrieb:
> On 12/1/07, Sönke Ludwig <ludwig@informatik_dot_uni-luebeck.de> wrote:
>> Since c inside of the foreach-loop is actually a "ref invariant(char)"
>> (string = invariant(char)[]), it is correct that it cannot be passed to
>> bar, taking a mutable "ref char".
>> Changing bar to "void bar( ref invariant(char) c ){}" makes it compile
>> again.
> 
> So... can you /assign/ a ref invariant(char)?
> 
> I'm confused as to why the code isn't just
> 
>     foreach(c;text)
> 

You surprisingly can.. actually you can do:

import std.stdio;
void main()
{
	string text = "Hello, World!".idup;
	
	foreach( ref c; text )
		c = 'X';

	writefln(text); // prints "XXXX...
}

But you cannot do "text[0] = 'X';". So it seems to me arrays with the new const system are actually quite broken for now.