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Add __spreadArrays helper
1 parent 7423c69 commit 528601f

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4 files changed

+50
-20
lines changed

4 files changed

+50
-20
lines changed

‎src/compiler/checker.ts

+3-2
Original file line numberDiff line numberDiff line change
@@ -18671,8 +18671,8 @@ namespace ts {
1867118671
}
1867218672

1867318673
function checkSpreadExpression(node: SpreadElement, checkMode?: CheckMode): Type {
18674-
if (languageVersion < ScriptTarget.ES2015 && compilerOptions.downlevelIteration) {
18675-
checkExternalEmitHelpers(node, ExternalEmitHelpers.SpreadIncludes);
18674+
if (languageVersion < ScriptTarget.ES2015) {
18675+
checkExternalEmitHelpers(node, compilerOptions.downlevelIteration ? ExternalEmitHelpers.SpreadIncludes : ExternalEmitHelpers.SpreadArrays);
1867618676
}
1867718677

1867818678
const arrayOrIterableType = checkExpression(node.expression, checkMode);
@@ -30611,6 +30611,7 @@ namespace ts {
3061130611
case ExternalEmitHelpers.Values: return "__values";
3061230612
case ExternalEmitHelpers.Read: return "__read";
3061330613
case ExternalEmitHelpers.Spread: return "__spread";
30614+
case ExternalEmitHelpers.SpreadArrays: return "__spreadArrays";
3061430615
case ExternalEmitHelpers.Await: return "__await";
3061530616
case ExternalEmitHelpers.AsyncGenerator: return "__asyncGenerator";
3061630617
case ExternalEmitHelpers.AsyncDelegator: return "__asyncDelegator";

‎src/compiler/factory.ts

+24
Original file line numberDiff line numberDiff line change
@@ -3693,6 +3693,30 @@ namespace ts {
36933693
);
36943694
}
36953695

3696+
export const spreadArraysHelper: UnscopedEmitHelper = {
3697+
name: "typescript:spreadArrays",
3698+
scoped: false,
3699+
text: `
3700+
var __spreadArrays = (this && this.__spreadArrays) || function () {
3701+
for (var ar = [], i = 0; i < arguments.length; i++)
3702+
for (var j = 0; j < arguments[i].length; j++)
3703+
ar.push(arguments[i][j]);
3704+
return ar;
3705+
};`
3706+
};
3707+
3708+
export function createSpreadArraysHelper(context: TransformationContext, argumentList: ReadonlyArray<Expression>, location?: TextRange) {
3709+
context.requestEmitHelper(spreadArraysHelper);
3710+
return setTextRange(
3711+
createCall(
3712+
getHelperName("__spreadArrays"),
3713+
/*typeArguments*/ undefined,
3714+
argumentList
3715+
),
3716+
location
3717+
);
3718+
}
3719+
36963720
// Utilities
36973721

36983722
export function createForOfBindingStatement(node: ForInitializer, boundValue: Expression): Statement {

‎src/compiler/transformers/es2015.ts

+16-12
Original file line numberDiff line numberDiff line change
@@ -3522,7 +3522,7 @@ namespace ts {
35223522
function visitArrayLiteralExpression(node: ArrayLiteralExpression): Expression {
35233523
if (some(node.elements, isSpreadElement)) {
35243524
// We are here because we contain a SpreadElementExpression.
3525-
return transformAndSpreadElements(node.elements, /*needsUniqueCopy*/ true, !!node.multiLine, /*hasTrailingComma*/ !!node.elements.hasTrailingComma);
3525+
return transformAndSpreadElements(node.elements, !!node.multiLine, /*hasTrailingComma*/ !!node.elements.hasTrailingComma);
35263526
}
35273527
return visitEachChild(node, visitor, context);
35283528
}
@@ -3737,7 +3737,7 @@ namespace ts {
37373737
resultingCall = createFunctionApply(
37383738
visitNode(target, callExpressionVisitor, isExpression),
37393739
node.expression.kind === SyntaxKind.SuperKeyword ? thisArg : visitNode(thisArg, visitor, isExpression),
3740-
transformAndSpreadElements(node.arguments, /*needsUniqueCopy*/ false, /*multiLine*/ false, /*hasTrailingComma*/ false)
3740+
transformAndSpreadElements(node.arguments, /*multiLine*/ false, /*hasTrailingComma*/ false)
37413741
);
37423742
}
37433743
else {
@@ -3793,7 +3793,7 @@ namespace ts {
37933793
createFunctionApply(
37943794
visitNode(target, visitor, isExpression),
37953795
thisArg,
3796-
transformAndSpreadElements(createNodeArray([createVoidZero(), ...node.arguments!]), /*needsUniqueCopy*/ false, /*multiLine*/ false, /*hasTrailingComma*/ false)
3796+
transformAndSpreadElements(createNodeArray([createVoidZero(), ...node.arguments!]), /*multiLine*/ false, /*hasTrailingComma*/ false)
37973797
),
37983798
/*typeArguments*/ undefined,
37993799
[]
@@ -3806,15 +3806,17 @@ namespace ts {
38063806
* Transforms an array of Expression nodes that contains a SpreadExpression.
38073807
*
38083808
* @param elements The array of Expression nodes.
3809-
* @param needsUniqueCopy A value indicating whether to ensure that the result is a fresh array.
38103809
* @param multiLine A value indicating whether the result should be emitted on multiple lines.
38113810
*/
3812-
function transformAndSpreadElements(elements: NodeArray<Expression>, needsUniqueCopy: boolean, multiLine: boolean, hasTrailingComma: boolean): Expression {
3811+
function transformAndSpreadElements(elements: NodeArray<Expression>, multiLine: boolean, hasTrailingComma: boolean): Expression {
38133812
// [source]
38143813
// [a, ...b, c]
38153814
//
3815+
// [output (downlevelIteration)]
3816+
// __spread([a], b, [c])
3817+
//
38163818
// [output]
3817-
// [a].concat(b, [c])
3819+
// __spreadArrays([a], b, [c])
38183820

38193821
// Map spans of spread expressions into their expressions and spans of other
38203822
// expressions into an array literal.
@@ -3840,14 +3842,16 @@ namespace ts {
38403842
}
38413843
else {
38423844
if (segments.length === 1) {
3843-
const firstElement = elements[0];
3844-
return needsUniqueCopy && isSpreadElement(firstElement) && firstElement.expression.kind !== SyntaxKind.ArrayLiteralExpression
3845-
? createArraySlice(segments[0])
3846-
: segments[0];
3845+
const firstSegment = segments[0];
3846+
if (isCallExpression(firstSegment)
3847+
&& isIdentifier(firstSegment.expression)
3848+
&& (getEmitFlags(firstSegment.expression) & EmitFlags.HelperName)
3849+
&& firstSegment.expression.escapedText === "___spreadArrays") {
3850+
return segments[0];
3851+
}
38473852
}
38483853

3849-
// Rewrite using the pattern <segment0>.concat(<segment1>, <segment2>, ...)
3850-
return createArrayConcat(segments.shift()!, segments);
3854+
return createSpreadArraysHelper(context, segments);
38513855
}
38523856
}
38533857

‎src/compiler/types.ts

+7-6
Original file line numberDiff line numberDiff line change
@@ -5307,12 +5307,13 @@ namespace ts {
53075307
Values = 1 << 8, // __values (used by ES2015 for..of and yield* transformations)
53085308
Read = 1 << 9, // __read (used by ES2015 iterator destructuring transformation)
53095309
Spread = 1 << 10, // __spread (used by ES2015 array spread and argument list spread transformations)
5310-
Await = 1 << 11, // __await (used by ES2017 async generator transformation)
5311-
AsyncGenerator = 1 << 12, // __asyncGenerator (used by ES2017 async generator transformation)
5312-
AsyncDelegator = 1 << 13, // __asyncDelegator (used by ES2017 async generator yield* transformation)
5313-
AsyncValues = 1 << 14, // __asyncValues (used by ES2017 for..await..of transformation)
5314-
ExportStar = 1 << 15, // __exportStar (used by CommonJS/AMD/UMD module transformation)
5315-
MakeTemplateObject = 1 << 16, // __makeTemplateObject (used for constructing template string array objects)
5310+
SpreadArrays = 1 << 11, // __spreadArrays (used by ES2015 array spread and argument list spread transformations)
5311+
Await = 1 << 12, // __await (used by ES2017 async generator transformation)
5312+
AsyncGenerator = 1 << 13, // __asyncGenerator (used by ES2017 async generator transformation)
5313+
AsyncDelegator = 1 << 14, // __asyncDelegator (used by ES2017 async generator yield* transformation)
5314+
AsyncValues = 1 << 15, // __asyncValues (used by ES2017 for..await..of transformation)
5315+
ExportStar = 1 << 16, // __exportStar (used by CommonJS/AMD/UMD module transformation)
5316+
MakeTemplateObject = 1 << 17, // __makeTemplateObject (used for constructing template string array objects)
53165317
FirstEmitHelper = Extends,
53175318
LastEmitHelper = MakeTemplateObject,
53185319

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