function - "Identifier Expected" or "Invalid Prototype" when implementing a scripted constant in Inno Setup

Question

So given this function, I get the error "Identifier Expected" on the GetRoot := ROOTPage.Values[0]; line. I expect it is telling me that the ROOTPage is not defined?

const
  DefaultRoot = 'C:IAmGRoot';
Var
  ROOTPage : TInputQueryWizardPage;

procedure SetupRoot;
begin
  ROOTPage := CreateInputQueryPage(wpUserInfo,
    ExpandConstant('{cm:RootTitle}'), 
    ExpandConstant('{cm:RootInstructions}'),
    ExpandConstant('{cm:RootDescription}') + ' "' + DefaultRoot + '"'
    );
  
  ROOTPage.Add(ExpandConstant('{cm:SSRoot}') + ':', False);
  ROOTPage.Values[0] := ExpandConstant('{DefaultRoot}');

  // add SSROOT to path
end;

function GetRoot : string;
begin
  GetRoot := ROOTPage.Values[0];
end;

How should I interpret this error. What is an identifier in Pascal?

This page tells me that identifiers are variable names. Perhaps I need to expand the ROOTPage.Values[0] in some way since I am referencing an array from an Inno Setup object?

Or maybe I need to return the value differently. I saw one page on Pascal that said that you needed to avoid assigning to the function value on parameter less functions to avoid a recursive loop. Does this mean I should pass in a dummy value? or is there a different syntax? That page did not explain.

I secretly think my real issue is that I am not defining my function correctly... but well. That much compiles at least. This question could become: How do you handle a parameter-less function in Pascal?

I do not think Inno Setup is part of the issue, but I am working with Inno Setup in case that is important.

---

Update: It doesn't seem to be the array because this gets the same error:

const
  DefaultRoot = 'C:IAmGRoot';

function GetRoot : string;
begin
  GetRoot := DefaultRoot;
end;

---

Update: This link has said that the function name can be replaced/ should be replaced with the key word Result such as the following code. I actually knew this, but the Inno Setup compiler does not recognize this as valid syntax. It then tells me my function is an invalid prototype.

function GetRoot : string;
begin
  Result := DefaultRoot;
end;

---

Update: If I do this I get "Invalid Prototype for GetRoot"

function GetRoot : boolean;
begin
  Result := False;
end;

---

Update for @Martin Prikryl:

Well I use it a few places but the typical use would be like this:

[Files]
Source: "C:ValidPathRelease*"; DestDir: "{app}in"; Components: DefinedComponent
Source: "C:ValidPathDeployment*"; DestDir: "{code:GetRoot}"; Flags: ignoreversion recursesubdirs; Components: DefinedComponent

Answer 1

Identifier expected

Your code would be correct in a Pascal, but it does not compile in Pascal Script.

In Pascal, when you want to assign a return value of a function, you either assign the value to a "variable" with a name of the function or to Result variable.

So this is correct:

function GetRoot: string;
begin
  GetRoot := ROOTPage.Values[0];
end;

And this too (both are equivalent):

function GetRoot: string;
begin
  Result := ROOTPage.Values[0];
end;

In the Pascal Script, only the Result works. When you use the name of the function, you get the "Identifier expected."

---

Invalid prototype

You get this when the function is called from outside of the Code section and a specific parameter list/return value is required. But you didn't tell us, what you use the GetRoot function for.

There are two places, where you can use a custom function in Inno Setup:

• Check parameter: For this the function must return a Boolean and take either no parameter or one parameter (the parameter type is determined by a value you provide in the Check parameter).

  function MyProgCheck(): Boolean;
  
  function MyDirCheck(DirName: String): Boolean;
  

• Scripted Constants: The function must return a string and take one string parameter, even if no parameter is provided in the scripted constant. I assume this is your use case. If you do not need any parameter, just declare it, but do not use it:

  function GetRoot(Param: String): string;
  begin
    Result := ROOTPage.Values[0];
  end;