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?
