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esnext.ts
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/*@internal*/
namespace ts {
export function transformESNext(context: TransformationContext) {
const {
hoistVariableDeclaration,
} = context;
return chainBundle(transformSourceFile);
function transformSourceFile(node: SourceFile) {
if (node.isDeclarationFile) {
return node;
}
return visitEachChild(node, visitor, context);
}
function visitor(node: Node): VisitResult<Node> {
if ((node.transformFlags & TransformFlags.ContainsESNext) === 0) {
return node;
}
switch (node.kind) {
case SyntaxKind.PropertyAccessExpression:
case SyntaxKind.ElementAccessExpression:
case SyntaxKind.CallExpression:
if (node.flags & NodeFlags.OptionalChain) {
const updated = visitOptionalExpression(node as OptionalChain, /*captureThisArg*/ false);
Debug.assertNotNode(updated, isSyntheticReference);
return updated;
}
return visitEachChild(node, visitor, context);
case SyntaxKind.BinaryExpression:
if ((<BinaryExpression>node).operatorToken.kind === SyntaxKind.QuestionQuestionToken) {
return transformNullishCoalescingExpression(<BinaryExpression>node);
}
return visitEachChild(node, visitor, context);
default:
return visitEachChild(node, visitor, context);
}
}
function flattenChain(chain: OptionalChain) {
const links: OptionalChain[] = [chain];
while (!chain.questionDotToken && !isTaggedTemplateExpression(chain)) {
chain = cast(chain.expression, isOptionalChain);
links.unshift(chain);
}
return { expression: chain.expression, chain: links };
}
function visitNonOptionalParenthesizedExpression(node: ParenthesizedExpression, captureThisArg: boolean): Expression {
const expression = visitNonOptionalExpression(node.expression, captureThisArg);
if (isSyntheticReference(expression)) {
// `(a.b)` -> { expression `((_a = a).b)`, thisArg: `_a` }
// `(a[b])` -> { expression `((_a = a)[b])`, thisArg: `_a` }
return createSyntheticReferenceExpression(updateParen(node, expression.expression), expression.thisArg);
}
return updateParen(node, expression);
}
function visitNonOptionalPropertyAccessExpression(node: PropertyAccessExpression, captureThisArg: boolean): Expression {
if (isOptionalChain(node)) {
// If `node` is an optional chain, then it is the outermost chain of an optional expression.
return visitOptionalExpression(node, captureThisArg);
}
let expression = visitNode(node.expression, visitor, isExpression);
Debug.assertNotNode(expression, isSyntheticReference);
let thisArg: Expression | undefined;
if (captureThisArg) {
// `a.b` -> { expression: `(_a = a).b`, thisArg: `_a` }
thisArg = createTempVariable(hoistVariableDeclaration);
expression = createParen(createAssignment(thisArg, expression));
}
expression = updatePropertyAccess(node, expression, visitNode(node.name, visitor, isIdentifier));
return thisArg ? createSyntheticReferenceExpression(expression, thisArg) : expression;
}
function visitNonOptionalElementAccessExpression(node: ElementAccessExpression, captureThisArg: boolean): Expression {
if (isOptionalChain(node)) {
// If `node` is an optional chain, then it is the outermost chain of an optional expression.
return visitOptionalExpression(node, captureThisArg);
}
let expression = visitNode(node.expression, visitor, isExpression);
Debug.assertNotNode(expression, isSyntheticReference);
let thisArg: Expression | undefined;
if (captureThisArg) {
// `a[b]` -> { expression: `(_a = a)[b]`, thisArg: `_a` }
thisArg = createTempVariable(hoistVariableDeclaration);
expression = createParen(createAssignment(thisArg, expression));
}
expression = updateElementAccess(node, expression, visitNode(node.argumentExpression, visitor, isExpression));
return thisArg ? createSyntheticReferenceExpression(expression, thisArg) : expression;
}
function visitNonOptionalCallExpression(node: CallExpression, captureThisArg: boolean): Expression {
if (isOptionalChain(node)) {
// If `node` is an optional chain, then it is the outermost chain of an optional expression.
return visitOptionalExpression(node, captureThisArg);
}
return visitEachChild(node, visitor, context);
}
function visitNonOptionalExpression(node: Expression, captureThisArg: boolean): Expression {
switch (node.kind) {
case SyntaxKind.ParenthesizedExpression: return visitNonOptionalParenthesizedExpression(node as ParenthesizedExpression, captureThisArg);
case SyntaxKind.PropertyAccessExpression: return visitNonOptionalPropertyAccessExpression(node as PropertyAccessExpression, captureThisArg);
case SyntaxKind.ElementAccessExpression: return visitNonOptionalElementAccessExpression(node as ElementAccessExpression, captureThisArg);
case SyntaxKind.CallExpression: return visitNonOptionalCallExpression(node as CallExpression, captureThisArg);
default: return visitNode(node, visitor, isExpression);
}
}
function visitOptionalExpression(node: OptionalChain, captureThisArg: boolean): Expression {
const { expression, chain } = flattenChain(node);
const left = visitNonOptionalExpression(expression, isCallChain(chain[0]));
const temp = createTempVariable(hoistVariableDeclaration);
const leftThisArg = isSyntheticReference(left) ? left.thisArg : undefined;
const leftExpression = isSyntheticReference(left) ? left.expression : left;
let rightExpression: Expression = temp;
let thisArg: Expression | undefined;
for (let i = 0; i < chain.length; i++) {
const segment = chain[i];
switch (segment.kind) {
case SyntaxKind.PropertyAccessExpression:
if (i === chain.length - 1 && captureThisArg) {
thisArg = createTempVariable(hoistVariableDeclaration);
rightExpression = createParen(createAssignment(thisArg, rightExpression));
}
rightExpression = createPropertyAccess(
rightExpression,
visitNode(segment.name, visitor, isIdentifier)
);
break;
case SyntaxKind.ElementAccessExpression:
if (i === chain.length - 1 && captureThisArg) {
thisArg = createTempVariable(hoistVariableDeclaration);
rightExpression = createParen(createAssignment(thisArg, rightExpression));
}
rightExpression = createElementAccess(
rightExpression,
visitNode(segment.argumentExpression, visitor, isExpression)
);
break;
case SyntaxKind.CallExpression:
if (i === 0 && leftThisArg) {
rightExpression = createFunctionCall(
rightExpression,
leftThisArg,
visitNodes(segment.arguments, visitor, isExpression)
);
}
else {
rightExpression = createCall(
rightExpression,
/*typeArguments*/ undefined,
visitNodes(segment.arguments, visitor, isExpression)
);
}
break;
}
setOriginalNode(rightExpression, segment);
}
const target = createConditional(
createLogicalOr(
createStrictEquality(createAssignment(temp, leftExpression), createNull()),
createStrictEquality(temp, createVoidZero())
),
createVoidZero(),
rightExpression
);
return thisArg ? createSyntheticReferenceExpression(target, thisArg) : target;
}
function createNotNullCondition(node: Expression) {
return createBinary(
createBinary(
node,
createToken(SyntaxKind.ExclamationEqualsEqualsToken),
createNull()
),
createToken(SyntaxKind.AmpersandAmpersandToken),
createBinary(
node,
createToken(SyntaxKind.ExclamationEqualsEqualsToken),
createVoidZero()
)
);
}
function transformNullishCoalescingExpression(node: BinaryExpression) {
const expressions: Expression[] = [];
let left = visitNode(node.left, visitor, isExpression);
if (!isIdentifier(left)) {
const temp = createTempVariable(hoistVariableDeclaration);
expressions.push(createAssignment(temp, left));
left = temp;
}
expressions.push(
createParen(
createConditional(
createNotNullCondition(left),
left,
visitNode(node.right, visitor, isExpression)))
);
return inlineExpressions(expressions);
}
}
}