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August 03, 2010
TDPL: Function literals with missing argument type specifiers do not compile
The following example should compile according to TDPL. The compiler is supossed to automatically infer the type of the parameter in the function literal:

void main() { }

T[] find(alias pred, T)(T[] input)
   if (is(typeof(pred(input[0])) == bool))
{
   for (; input.length > 0; input = input[1 .. $])
   {
       if (pred(input[0]))
           break;
   }
   return input;
}

unittest {
   int[] a = [1, 2, 3, 4, -5, 3, -4];
   
   // find first negative number
   auto b = find!(function bool(int x) { return x < 0; })(a);
   auto c = find!(function (x) { return x < 0; })(a);
   auto d = find!((x) { return x < 0; })(a);
}

The auto c and auto d lines are not compiling:
higher_functions.d(55): Error: template higher_functions.find(alias pred,T) if (is(typeof(pred(input[0])) == bool)) does not match any function template declaration
higher_functions.d(55): Error: template higher_functions.find(alias pred,T) if (is(typeof(pred(input[0])) == bool)) cannot deduce template function from argument types !(__funcliteral2)(int[])
higher_functions.d(55): Error: template instance errors instantiating template
higher_functions.d(56): Error: template higher_functions.find(alias pred,T) if (is(typeof(pred(input[0])) == bool)) does not match any function template declaration
higher_functions.d(56): Error: template higher_functions.find(alias pred,T) if (is(typeof(pred(input[0])) == bool)) cannot deduce template function from argument types !(__dgliteral4)(int[])
higher_functions.d(56): Error: template instance errors instantiating template

Gotta love those error messages, a C++ programmer will feel right at home! ;)

If I add a type specifier like so:

   auto c = find!(function (int x) { return x < 0; })(a);
   auto d = find!((int x) { return x < 0; })(a);

Then it will compile. Should I report this to bugzilla?
August 03, 2010
Re: TDPL: Function literals with missing argument type specifiers do not compile
One other thing which is semi-relevant, from TDPL:

auto f = (int i) {};
assert(is(f == function));

f seems to be a delegate by default, not a function.

Andrej Mitrovic Wrote:

> The following example should compile according to TDPL. The compiler is supossed to automatically infer the type of the parameter in the function literal:
> 
> void main() { }
> 
> T[] find(alias pred, T)(T[] input)
>     if (is(typeof(pred(input[0])) == bool))
> {
>     for (; input.length > 0; input = input[1 .. $])
>     {
>         if (pred(input[0]))
>             break;
>     }
>     return input;
> }
> 
> unittest {
>     int[] a = [1, 2, 3, 4, -5, 3, -4];
>     
>     // find first negative number
>     auto b = find!(function bool(int x) { return x < 0; })(a);
>     auto c = find!(function (x) { return x < 0; })(a);
>     auto d = find!((x) { return x < 0; })(a);
> }
> 
> The auto c and auto d lines are not compiling:
> higher_functions.d(55): Error: template higher_functions.find(alias pred,T) if (is(typeof(pred(input[0])) == bool)) does not match any function template declaration
> higher_functions.d(55): Error: template higher_functions.find(alias pred,T) if (is(typeof(pred(input[0])) == bool)) cannot deduce template function from argument types !(__funcliteral2)(int[])
> higher_functions.d(55): Error: template instance errors instantiating template
> higher_functions.d(56): Error: template higher_functions.find(alias pred,T) if (is(typeof(pred(input[0])) == bool)) does not match any function template declaration
> higher_functions.d(56): Error: template higher_functions.find(alias pred,T) if (is(typeof(pred(input[0])) == bool)) cannot deduce template function from argument types !(__dgliteral4)(int[])
> higher_functions.d(56): Error: template instance errors instantiating template
> 
> Gotta love those error messages, a C++ programmer will feel right at home! ;)
> 
>  If I add a type specifier like so:
> 
>     auto c = find!(function (int x) { return x < 0; })(a);
>     auto d = find!((int x) { return x < 0; })(a);
> 
> Then it will compile. Should I report this to bugzilla?
August 21, 2010
Re: TDPL: Function literals with missing argument type specifiers do not compile
Update: This seems to have been fixed in 2.048. But I don't see it mentioned in the changelog, so I'm not sure if it was fixed for good or fixed by accident. :)

Andrej Mitrovic Wrote:

> The following example should compile according to TDPL. The compiler is supossed to automatically infer the type of the parameter in the function literal:
> 
> void main() { }
> 
> T[] find(alias pred, T)(T[] input)
>     if (is(typeof(pred(input[0])) == bool))
> {
>     for (; input.length > 0; input = input[1 .. $])
>     {
>         if (pred(input[0]))
>             break;
>     }
>     return input;
> }
> 
> unittest {
>     int[] a = [1, 2, 3, 4, -5, 3, -4];
>     
>     // find first negative number
>     auto b = find!(function bool(int x) { return x < 0; })(a);
>     auto c = find!(function (x) { return x < 0; })(a);
>     auto d = find!((x) { return x < 0; })(a);
> }
> 
> The auto c and auto d lines are not compiling:
> higher_functions.d(55): Error: template higher_functions.find(alias pred,T) if (is(typeof(pred(input[0])) == bool)) does not match any function template declaration
> higher_functions.d(55): Error: template higher_functions.find(alias pred,T) if (is(typeof(pred(input[0])) == bool)) cannot deduce template function from argument types !(__funcliteral2)(int[])
> higher_functions.d(55): Error: template instance errors instantiating template
> higher_functions.d(56): Error: template higher_functions.find(alias pred,T) if (is(typeof(pred(input[0])) == bool)) does not match any function template declaration
> higher_functions.d(56): Error: template higher_functions.find(alias pred,T) if (is(typeof(pred(input[0])) == bool)) cannot deduce template function from argument types !(__dgliteral4)(int[])
> higher_functions.d(56): Error: template instance errors instantiating template
> 
> Gotta love those error messages, a C++ programmer will feel right at home! ;)
> 
>  If I add a type specifier like so:
> 
>     auto c = find!(function (int x) { return x < 0; })(a);
>     auto d = find!((int x) { return x < 0; })(a);
> 
> Then it will compile. Should I report this to bugzilla?
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