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https://github.com/vercel-labs/scriptc.git
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Malte Ubl
8f5ec2d94f
SC6001 only looked at call arguments and typed initializers, and only at strict field subsets: a target that adds optional properties, the empty record type, `r as T`, a later `v = r` into a typed binding, and records stored as elements of a typed array literal copied silently. The scan now reports a copy whenever the property sets differ, covers those sites, and reports a class instance that reaches a plain record type which does not keep its identity (the remaining boundary: interfaces of only generic methods). Every corpus program still reports no divergence.
40 lines
1.1 KiB
TypeScript
40 lines
1.1 KiB
TypeScript
// Record width copies beyond parameters and typed initializers: each site
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// stores a record in a narrower or differently shaped record type, and the
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// program then writes through or compares the copy.
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interface Labeled {
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label: string;
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}
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interface Tagged {
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label: string;
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tag: string;
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}
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interface Noted {
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label: string;
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note?: string;
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}
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const tagged: Tagged = { label: "first", tag: "t" };
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// A target that adds an optional property is a different shape: a copy.
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function annotate(target: Noted): void {
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target.label = "noted";
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}
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annotate(tagged);
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// The empty record type keeps no property, and no identity either.
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const anything: {} = tagged;
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console.log(anything === tagged);
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// An assertion to a narrower record type copies as well.
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const asserted = tagged as Labeled;
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asserted.label = "asserted";
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// So does a later assignment to a binding declared with that type.
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let later: Labeled = { label: "later" };
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later = tagged;
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later.label = "assigned";
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// Array elements are stored as copies of the element type.
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const list: Labeled[] = [tagged];
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for (const item of list) item.label = "element";
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console.log(tagged.label);
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