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Support spread operator in call expressions #1931

Merged
merged 3 commits into from Feb 10, 2015
Merged

Support spread operator in call expressions #1931

merged 3 commits into from Feb 10, 2015

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ahejlsberg
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This PR adds support for the spread (...) operator in call expressions with down-level code generation for ES3/5. For example:

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 this argument is only evaluated once. For example:

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;

yuit
yuit reviewed Feb 5, 2015
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tests/cases/conformance/expressions/functionCalls/callWithSpreadES6.ts

(<Function>xa[1].foo)(...[1, 2, "abc"]);

class C {
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This class C/D can be pull out into its own test cases

ahejlsberg added a commit that referenced this pull request Feb 10, 2015
@ahejlsberg
Merge pull request #1931 from Microsoft/spreadCall
4b92e42 
Support spread operator in call expressions
@ahejlsberg ahejlsberg merged commit 4b92e42 into master Feb 10, 2015
@ahejlsberg ahejlsberg deleted the spreadCall branch February 10, 2015 17:25
@DickvdBrink DickvdBrink mentioned this pull request Mar 8, 2015
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@saschanaz saschanaz mentioned this pull request Mar 16, 2015
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@nycdotnet nycdotnet mentioned this pull request Apr 16, 2015
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@tinganho tinganho mentioned this pull request May 7, 2015
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@basarat basarat mentioned this pull request Feb 28, 2016
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@microsoft microsoft locked and limited conversation to collaborators Jun 18, 2018
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5 participants
@ahejlsberg @robertpenner @yuit @JsonFreeman @msftclas