"function reference" as a result of the function

Question

I have a function that returns the TFunc<Integer> reference to function:Integer , which reference to function:Integer . and I have a procedure that takes the TFunc<Integer> function as an argument, calls it and prints its result.

 program Project1; {$APPTYPE CONSOLE} {$R *.res} uses System.SysUtils; function GetFunction:TFunc<Integer>; begin result := function:Integer begin result := 42 end; end; procedure FunctionCall(AFunc:TFunc<Integer>); var i:Integer; begin i := AFunc; WriteLn(Format('Function Result = %d',[i])); end; begin // FunctionCall(GetFunction); // error FunctionCall(GetFunction()); // works as excpected end. 

this call ( FunctionCall(GetFunction); ) leads to an error. and a call with () works as intended.

my question is:
when in delphi I need marriages to call a function, and when not (I thought I never need them)
or
Shouldn't I need them and is that a mistake?

I am working with delphi xe5 on windows 7 dcc32.

Answer 1

If what you are reporting is correct (and see below to learn more about this), you would find a mistake, I suppose.

This code:

 FunctionCall(GetFunction); 

should not be compiled. Indeed, it does not compile when I try to compile it in XE3, XE4, XE5, XE6 and XE7. It does not compile, because in this particular context the compiler interprets GetFunction as a type of type

 function: TFunc<Integer> 

All of the above compilers with this error message:

  [dcc32 Error] E2010 Incompatible types: 'System.SysUtils.TFunc' and 'Procedure'

So, if you somehow (possibly with some compiler options) managed to make this code a compilation, then I can only assume that this is due to an error.

You should deal with this by using parentheses so that the compiler can understand that you want to call GetFunction , rather than referring to it.

 FunctionCall(GetFunction());