undefined identifier doesn't make sense

[Enjoys Math]

Here's Gui.d:

module Gui;
private import gtk.MainWindow;

private import ProjectFile;

// @@TODO: remove
private import gtk.Label;

class Gui : MainWindow
{
private:
        ProjectFile* proj;

public:
        this() {
                super("Our Audio Synth App");
                
                proj = ProjectFile.loadLastProjectOrNew();
                
		setDefaultSize(600, 400);	// @@TODO: default size should be 
loaded from last user-defined
                maximize();             // Maximize window if available
                
                add(new Label("epic lulz"));
                showAll();
        }

        ~this() {

                // @@ TODO
                // If AppSettings dir DNE
                        // Create AppSettings dir

                // Save AppSettings file

        }
}


Here's ProjectFile.d:

module ProjectFile;

private import std.stdio;

struct ProjectFile
{
private:
        struct GuiSettings
        {
                // Main window settings
                uint winPosX, winPosY;
                uint winWidth, winHeight;
        }

public:
        GuiSettings gui;
        

        static ProjectFile* loadLastProjectOrNew()
        {
                // if LastProject.txt exits
                   // open LastProject.txt and read the first line
                   // try opening the file with that path & name
				// if success convert the data into a Project file object and 
return it
                // create new ProjectFile using default constructor and return
                
                auto lastProjectDotTxt = new File("LastProject.txt");
                
                return new ProjectFile;
        }
}

The error is:

Building Debug\TheApp.exe...
Gui.d(19): Error: undefined identifier 'loadLastProjectOrNew'

Doesn't make any sense.