6084 – Impossible to instantiate local template with TypeTuple-foreach iterator variable.

The following code is rejected by DMD:
import std.typetuple;
void main(){
 int foo(int x)(){return x;}
 foreach(i;TypeTuple!(0)) foo!(i);
}
Error: template instance cannot use local 'i' as parameter to non-global template foo(int x)
'i' is only a compile-time constant integral value at the point of instantiation, therefore there is no reason why this should not work.

Workaround:
import std.typetuple;
void main(){
 int foo(int x)(){return x;}
 foreach(_i;TypeTuple!(0)){
 enum i=_i;
 foo!i;
 }
}

Another workaround:
import std.typetuple;
void main(){
 int foo(int x)(){return x;}
 foreach(i;TypeTuple!(0)){
 foo!(i+0);
 }
}

patch:
In statement.c, ~line 1443:
- v->storage_class |= STCconst;
+ v->storage_class |= STCmanifest; // issue 6084 

https://github.com/D-Programming-Language/dmd/pull/406 

https://github.com/D-Programming-Language/dmd/commit/573e6124795e3197182c38c4c12a68e3bf81dfca
https://github.com/D-Programming-Language/dmd/commit/2df0a1802eaf6d28374b1c5c1cbeda0737e34a72