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Malte UblandClaude Opus 5.5
fc407d0751
`.join(sep)` over a checked-dynamic separator fenced with SC2020. JS substitutes the default comma only for the undefined VALUE; every other value goes through ToString, which prints "null" for null, the digits for a number or boolean, and throws the catchable TypeError for a symbol. Evaluate the separator once into a hidden local, test it against the undefined dyn kind, and answer either the comma literal or dyn.toStringCoerce of the value. Unlike the statically typed arms (string, and a union with an undefined arm), a dynamic separator cannot be resolved statically, so this is the runtime test the dynamic tier exists for. Fixes the 2 pi sites (@anthropic-ai/sdk's node.mjs, pi's interactive-mode.ts). Evidence: tests/corpus/array-join-dynamic-separator.ts, run under Node and natively in the plain and sanitized differential lanes, plus its order-parity baseline. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
33 lines
1.0 KiB
TypeScript
33 lines
1.0 KiB
TypeScript
// Array.prototype.join over a checked-dynamic separator: only the
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// undefined VALUE means the default comma; every other value is ToString
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// (null prints "null", numbers and booleans their text), and the
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// separator expression evaluates once.
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function joinWith(sep: any): string {
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return ["a", "b", "c"].join(sep);
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}
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console.log(joinWith(undefined));
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console.log(joinWith(null));
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console.log(joinWith("-"));
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console.log(joinWith(0));
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console.log(joinWith(false));
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console.log(joinWith(""));
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const held: any = "+";
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console.log(["x", "y"].join(held), ["x", "y"].join(undefined));
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const numbers = [1, 2, 3];
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console.log(numbers.join(held), numbers.join(null as any));
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let reads = 0;
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function separator(): any {
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reads += 1;
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return "/";
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}
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console.log(["p", "q"].join(separator()), reads);
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// A dynamic separator that turns out to be undefined keeps the default.
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function maybe(flagValue: boolean): any {
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return flagValue ? "-" : undefined;
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}
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console.log(["m", "n"].join(maybe(true)), ["m", "n"].join(maybe(false)));
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