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Chris Tate
723975d01c
The constructor copies the array it is passed into the instance, and other reads of the field give a new array over the elements, while under Node.js the field holds that array itself. The contract check now proves the two agree, and reports SC7009 where it cannot: - The arrays fields hold are never written. A whole-program graph of the places arrays are held (locals, parameters, results, class and record fields, and the elements of arrays, Maps and Sets by where those are held) follows every array a field read may give, and reports a write to one, or one that reaches a dynamic value, a call through a function value or a library call other than printing and JSON.stringify without a replacer. Functions that return their argument give each caller its own argument back. The report names the field read. - The array passed to the constructor is one nothing else keeps: a new array (a literal, a copy, or the result of a function that returns only such arrays or its argument), a local array at its last use (after calls that only read it or write it in place, or in a loop that then assigns the local a new array), a parameter whose every caller passes such an array, an array a field already holds, or a const array that is never written, which is then followed like a field's. The review fixes from before stay: `new` evaluates its arguments into locals unless they are all locals and constants, so that the allocation reads the length after every argument has run; the constructor uses the array parameter only to store it; and the dynamic view of an instance reads the field as an array of its elements.