Weird compiler warning for functions without return type annotation

Consider the following QML function

function foo() {
    return 1 + 1
} 

qmlcachegen in verbose mode prints

Warning: Main.qml:10:9: function without return type annotation returns double of double [compiler]
        return 1 + 1
        ^^^^^^

First of all "returns double of double" reads very weird. Presumably this should be "returns double".

But even beyond that the warning could be improved, maybe even with a suggestion

Warning: Main.qml:9: function with return value but no return type annotation
    function foo(): double {
                  ^^^^^^^^

Tested with 6.7 and current dev