I now see my mistake.
Let me think out loud,...
Current through diode must be equal current through resistor, because (almost) no current flows into opamp inverting input.
As both opamp inputs are equal voltage ("virtual ground"?), because of the negative feedback, voltage at inverting input must be equal Vin.
Did I say something not correct?
Yes, you were right
Let me think out loud,...
Current through diode must be equal current through resistor, because (almost) no current flows into opamp inverting input.
As both opamp inputs are equal voltage ("virtual ground"?), because of the negative feedback, voltage at inverting input must be equal Vin.
Did I say something not correct?
Yes, you were right