Summary: Make auto tail-const
           Product: D
           Version: unspecified
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: DMD

--- Comment #0 from Jonathan M Davis <> 2012-01-27 14:40:46 
PST ---
IFTI was recently changed with arrays to be tail-const. It would be useful if
we could do the same with auto. To quote dsimcha from the newsgroup (

The changes made to IFTI in DMD 2.057 are great, but they reveal another 
hassle with getting generic code to play nice with const.

import std.range, std.array;

ElementType!R sum(R)(R range) {
     if(range.empty) return 0;
     auto ans = range.front;

     foreach(elem; range) ans += elem;
     return ans;

void main() {
     const double[] nums = [1, 2, 3];

test.d(8): Error: variable test9.sum!(const(double)[]).sum.ans cannot 
modify const
test.d(14): Error: template instance test9.sum!(const(double)[]) error 

Of course this is fixable with an Unqual, but it requires the programmer 
to remember this every time and breaks for structs with indirection. 
Should we make `auto` also strip top-level const from primitives and 
arrays and, if const(Object)ref gets in, from objects?

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