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Chris Tateandejc3
009a01d074
An unannotated `const xs = []` (or `let`) inside a function, which TypeScript types by the elements written before each read, takes the array type its settled reads have: records pushed in a loop give a record array, numbers a number[], strings a string[]. Reads inside closures, which the checker leaves unsettled, do not count. When settled reads disagree or the binding is reassigned, the binding is a dynamic array, as the same binding already is at module scope. Before, such a binding was always number[] and pushes of other values were refused. Fixes #1623 Co-authored-by: ejc3 <1694850+ejc3@users.noreply.github.com>
25 lines
806 B
TypeScript
25 lines
806 B
TypeScript
// Derived values of an evolving-`any` closure array, at file scope and in
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// a function body: slice and concat preserve the handle-element array
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// (JS's IsArray decides concat's spread over the VALUE, not the evolved
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// checker spelling), and the function-scope filter result adopts the
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// handle-element type through the local declaration.
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const fns = [];
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fns.push(() => 1);
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fns.push(() => 2);
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fns.push(() => 3);
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const tail = fns.slice(1);
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console.log(tail.length);
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tail.forEach(fn => console.log(fn()));
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const both = fns.concat(tail);
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console.log(both.length);
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console.log(both.map(fn => fn()));
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function pick(limit: number) {
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const cbs = [];
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cbs.push(() => limit);
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cbs.push(() => limit * 2);
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const kept = cbs.filter(fn => fn() > limit);
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return kept.map(fn => fn());
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}
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console.log(pick(4));
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