Memoization of closures

[lars-reimann]

Describe the bug

Our code generation for calls with a closure as argument is wrong. We don't check whether the enclosed values changed, but just return the memoized result regardless.

To Reproduce

package bug

pipeline bug {
    val table = Table({
        "a": [1, 2]
    });
    val threshold = table.numberOfRows - 2; // Change this, observe result

    val result = table.filterRows((row) ->
        row.getValue("a") as Int > threshold
    );
}

Expected behavior

If an enclosed value changes, we should recalculate instead of looking up the result in the memoization table.

A quick fix would be that we don't memoize calls that have a lambda as an argument that references values outside of it.

Long term, we should just add those values as hidden arguments to the call, however. If the partial evaluator can already evaluate the reference, there's no need to add it as a hidden argument. We still need to add them to keep the order the same. Together with the generated Python code of the lambda, we must get something unique.

Screenshots (optional)

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Additional Context (optional)

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