• Per =?UTF-8?B?Tm9yZGzDtnc=?= (29/29) Nov 05 2018 Why does
• Stanislav Blinov (15/17) Nov 05 2018 ...Like a missing 'const' qualifier ;)
• Per =?UTF-8?B?Tm9yZGzDtnc=?= (3/5) Nov 05 2018 Fixed at
• Jacob Carlborg (8/40) Nov 06 2018 If the first example you declare a const variable of the type that

Per =?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:

Why does

 safe pure unittest
{
     import std.algorithm.searching : findSplit;
     if (const split = "a b".findSplit(" "))
     {
     }
}

error as

f.d(4,5): Error: mutable method 
`std.algorithm.searching.findSplit!("a == b", string, 
string).findSplit.Result!(string, 
string).Result.opCast!bool.opCast` is not callable using a 
`const` object
f.d(4,5):        Consider adding `const` or `inout` to 
std.algorithm.searching.findSplit!("a == b", string, 
string).findSplit.Result!(string, 
string).Result.opCast!bool.opCast

when

 safe pure unittest
{
     import std.algorithm.searching : findSplit;
     if (auto split = "a b".findSplit(" "))
     {
     }
}

doesn't?

AFAICT, it looks like a missing bool qualifier on `opCast!bool`, 
right?

Stanislav Blinov <stanislav.blinov gmail.com> writes:

On Monday, 5 November 2018 at 13:26:18 UTC, Per Nordlöw wrote:

 AFAICT, it looks like a missing bool qualifier on 
 `opCast!bool`, right?

...Like a missing 'const' qualifier ;)

auto findSplit(alias pred = "a == b", R1, R2)(R1 haystack, R2 
needle)
// ...
     static struct Result(S1, S2) if (isForwardRange!S1 &&
                                      isForwardRange!S2)
     {
// ...
         bool opCast(T : bool)()
         {
             return !asTuple[1].empty;
         }
// ...
     }

Per =?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:

On Monday, 5 November 2018 at 13:26:18 UTC, Per Nordlöw wrote:
 AFAICT, it looks like a missing bool qualifier on 
 `opCast!bool`, right?

Fixed at

https://github.com/dlang/phobos/pull/6749

Jacob Carlborg <doob me.com> writes:

On 2018-11-05 14:26, Per Nordlöw wrote:
 Why does
 
  safe pure unittest
 {
      import std.algorithm.searching : findSplit;
      if (const split = "a b".findSplit(" "))
      {
      }
 }
 
 error as
 
 f.d(4,5): Error: mutable method `std.algorithm.searching.findSplit!("a 
 == b", string, string).findSplit.Result!(string, 
 string).Result.opCast!bool.opCast` is not callable using a `const` object
 f.d(4,5):        Consider adding `const` or `inout` to 
 std.algorithm.searching.findSplit!("a == b", string, 
 string).findSplit.Result!(string, string).Result.opCast!bool.opCast
 
 when
 
  safe pure unittest
 {
      import std.algorithm.searching : findSplit;
      if (auto split = "a b".findSplit(" "))
      {
      }
 }
 
 doesn't?
 
 AFAICT, it looks like a missing bool qualifier on `opCast!bool`, right?

If the first example you declare a const variable of the type that 
"findSplit" returns. Then the compiler will call opCast since the 
variable is defined in the if condition. But you can only call methods 
marked as "const" if you have a const variable. The opCast method  in 
the struct returned by "findSplit" is missing a const attribute.

-- 
/Jacob Carlborg