[Webkit-unassigned] [Bug 160992] New: Wrong error message for a program that calls a function with arguments that do a getByVal off of undefined

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=160992

            Bug ID: 160992
           Summary: Wrong error message for a program that calls a
                    function with arguments that do a getByVal off of
                    undefined
    Classification: Unclassified
           Product: WebKit
           Version: WebKit Local Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: sbarati at apple.com
                CC: benjamin at webkit.org, fpizlo at apple.com,
                    ggaren at apple.com, gskachkov at gmail.com,
                    jfbastien at apple.com, joepeck at webkit.org,
                    keith_miller at apple.com, mark.lam at apple.com,
                    msaboff at apple.com, oliver at apple.com,
                    sukolsak at gmail.com, ticaiolima at gmail.com,
                    utatane.tea at gmail.com

We print the wrong error message in this program:
```
function foo() {
    let additions = [
        [10, 20],
        //[{}, Symbol()]
        [{}, {}]
    ];
    let addedAdditions = [];
    let allItems = [];

    let map = new Map;
    map.set('foo', 'bar');
    map.set(20, {});
    //let item;
    for (let item of map) {
        if (item[0] === 20) {
            map.delete(20);
            map.set(30, 40);
        }
        print(JSON.stringify(item));
        let addition = additions.pop();
        addedAdditions.push(addition);
        allItems.push(item);
        print(addition);

        map.set(addition[0], addition[1]);

    }

}
foo();
```
We print:
Exception: TypeError: undefined is not an object (evaluating 'map.set')

even though it's "addition[0]" where the undefined load is happening.

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