ToUnit for IValueQuantity<T> should return IValueQuantity<T> (#1224)

Author: tmilnthorp

CodeGen/Generators/UnitsNetGen/QuantityGenerator.cs

@@ -1093,6 +1093,18 @@ IQuantity IQuantity.ToUnit(Enum unit)
         /// <inheritdoc />
         IQuantity<{_unitEnumName}> IQuantity<{_unitEnumName}>.ToUnit(UnitSystem unitSystem) => ToUnit(unitSystem);
 
+        /// <inheritdoc />
+        IValueQuantity<{_quantity.ValueType}> IValueQuantity<{_quantity.ValueType}>.ToUnit(Enum unit)
+        {{
+            if (unit is not {_unitEnumName} typedUnit)
+                throw new ArgumentException($""The given unit is of type {{unit.GetType()}}. Only {{typeof({_unitEnumName})}} is supported."", nameof(unit));
+
+            return ToUnit(typedUnit);
+        }}
+
+        /// <inheritdoc />
+        IValueQuantity<{_quantity.ValueType}> IValueQuantity<{_quantity.ValueType}>.ToUnit(UnitSystem unitSystem) => ToUnit(unitSystem);
+
         #endregion
 ");
         }