E2420 Interface '%s' used in '%s' is not yet completely defined (Delphi)
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Interface used in is not yet completely defined. Forward declared interfaces must be declared in the same type section that they are used in. As an example the following code will not compile because of the above error message:
program Project3; {$APPTYPE CONSOLE} type TInterface = interface; TFoo = class type TBar = class(TObject, TInterface) procedure Bar; end; end; TInterface = interface procedure Intf; end; procedure TFoo.TBar.Bar; begin end; begin end.