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GeezerVison is showing github.com — Support spread operator in call expressions by ahejlsberg · Pull Request #1931 · microsoft/TypeScript Conversation
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This PR adds support for the spread ( function drawText(x: number, y: number, ...strings: string[]) { // draw text } drawText(10, 20, "hello"); drawText(10, 20, "hello", "world"); var a = ["one", "two"]; drawText(10, 20, ...a); drawText(10, 20, "zero", ...a, "three"); The function calls are emitted unchanged for ES6, but when the target is ES3 or ES5, the calls are rewritten as follows: drawText(10, 20, "hello"); drawText(10, 20, "hello", "world"); var a = ["one", "two"]; drawText.apply(void 0, [10, 20].concat(a)); drawText.apply(void 0, [10, 20, "zero"].concat(a, ["three"])); Type checking requires spread elements to match up with a rest parameter. Thus, in a typed function call it is not possible to use a spread element for non-rest parameters. For example: var pos = [10, 20]; drawText(...pos, "hello", "world"); // Error (<any>drawText)(...pos, "hello", "world"); // But ok in untyped call A temporary variable may be injected to ensure the interface Context { drawText(x: number, y: number, ...strings: string[]); } declare function getContext(): Context; var text = ["hello", "world"]; getContext().drawText(10, 20, ...text); This generates the code: var text = ["hello", "world"]; (_a = getContext()).drawText.apply(_a, [10, 20].concat(text)); var _a;
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There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. This class C/D can be pull out into its own test cases
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Anders Hejlsberg (ahejlsberg)
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Support spread operator in call expressions
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