[Issue 1698] New: foreach auto type inference doesnt work properly

[Sönke Ludwig]

d-bugmail at 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 at digitalmars.com
>         ReportedBy: spam at 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.