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3692 lines (3286 loc) · 172 KB
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/// <reference path="../factory.ts" />
/// <reference path="../visitor.ts" />
/*@internal*/
namespace ts {
const enum ES2015SubstitutionFlags {
/** Enables substitutions for captured `this` */
CapturedThis = 1 << 0,
/** Enables substitutions for block-scoped bindings. */
BlockScopedBindings = 1 << 1,
}
/**
* If loop contains block scoped binding captured in some function then loop body is converted to a function.
* Lexical bindings declared in loop initializer will be passed into the loop body function as parameters,
* however if this binding is modified inside the body - this new value should be propagated back to the original binding.
* This is done by declaring new variable (out parameter holder) outside of the loop for every binding that is reassigned inside the body.
* On every iteration this variable is initialized with value of corresponding binding.
* At every point where control flow leaves the loop either explicitly (break/continue) or implicitly (at the end of loop body)
* we copy the value inside the loop to the out parameter holder.
*
* for (let x;;) {
* let a = 1;
* let b = () => a;
* x++
* if (...) break;
* ...
* }
*
* will be converted to
*
* var out_x;
* var loop = function(x) {
* var a = 1;
* var b = function() { return a; }
* x++;
* if (...) return out_x = x, "break";
* ...
* out_x = x;
* }
* for (var x;;) {
* out_x = x;
* var state = loop(x);
* x = out_x;
* if (state === "break") break;
* }
*
* NOTE: values to out parameters are not copies if loop is abrupted with 'return' - in this case this will end the entire enclosing function
* so nobody can observe this new value.
*/
interface LoopOutParameter {
originalName: Identifier;
outParamName: Identifier;
}
const enum CopyDirection {
ToOriginal,
ToOutParameter
}
const enum Jump {
Break = 1 << 1,
Continue = 1 << 2,
Return = 1 << 3
}
interface ConvertedLoopState {
/*
* set of labels that occurred inside the converted loop
* used to determine if labeled jump can be emitted as is or it should be dispatched to calling code
*/
labels?: Map<string>;
/*
* collection of labeled jumps that transfer control outside the converted loop.
* maps store association 'label -> labelMarker' where
* - label - value of label as it appear in code
* - label marker - return value that should be interpreted by calling code as 'jump to <label>'
*/
labeledNonLocalBreaks?: Map<string>;
labeledNonLocalContinues?: Map<string>;
/*
* set of non-labeled jumps that transfer control outside the converted loop
* used to emit dispatching logic in the caller of converted loop
*/
nonLocalJumps?: Jump;
/*
* set of non-labeled jumps that should be interpreted as local
* i.e. if converted loop contains normal loop or switch statement then inside this loop break should be treated as local jump
*/
allowedNonLabeledJumps?: Jump;
/*
* alias for 'arguments' object from the calling code stack frame
* i.e.
* for (let x;;) <statement that captures x in closure and uses 'arguments'>
* should be converted to
* var loop = function(x) { <code where 'arguments' is replaced with 'arguments_1'> }
* var arguments_1 = arguments
* for (var x;;) loop(x);
* otherwise semantics of the code will be different since 'arguments' inside converted loop body
* will refer to function that holds converted loop.
* This value is set on demand.
*/
argumentsName?: Identifier;
/*
* alias for 'this' from the calling code stack frame in case if this was used inside the converted loop
*/
thisName?: Identifier;
/*
* set to true if node contains lexical 'this' so we can mark function that wraps convered loop body as 'CapturedThis' for subsequent substitution.
*/
containsLexicalThis?: boolean;
/*
* list of non-block scoped variable declarations that appear inside converted loop
* such variable declarations should be moved outside the loop body
* for (let x;;) {
* var y = 1;
* ...
* }
* should be converted to
* var loop = function(x) {
* y = 1;
* ...
* }
* var y;
* for (var x;;) loop(x);
*/
hoistedLocalVariables?: Identifier[];
/**
* List of loop out parameters - detailed descripion can be found in the comment to LoopOutParameter
*/
loopOutParameters?: LoopOutParameter[];
}
const enum SuperCaptureResult {
/**
* A capture may have been added for calls to 'super', but
* the caller should emit subsequent statements normally.
*/
NoReplacement,
/**
* A call to 'super()' got replaced with a capturing statement like:
*
* var _this = _super.call(...) || this;
*
* Callers should skip the current statement.
*/
ReplaceSuperCapture,
/**
* A call to 'super()' got replaced with a capturing statement like:
*
* return _super.call(...) || this;
*
* Callers should skip the current statement and avoid any returns of '_this'.
*/
ReplaceWithReturn,
}
type LoopConverter = (node: IterationStatement, outermostLabeledStatement: LabeledStatement, convertedLoopBodyStatements: Statement[]) => Statement;
// Facts we track as we traverse the tree
const enum HierarchyFacts {
None = 0,
//
// Ancestor facts
//
Function = 1 << 0, // Enclosed in a non-arrow function
ArrowFunction = 1 << 1, // Enclosed in an arrow function
AsyncFunctionBody = 1 << 2, // Enclosed in an async function body
NonStaticClassElement = 1 << 3, // Enclosed in a non-static, non-async class element
CapturesThis = 1 << 4, // Enclosed in a function that captures the lexical 'this' (used in substitution)
ExportedVariableStatement = 1 << 5, // Enclosed in an exported variable statement in the current scope
TopLevel = 1 << 6, // Enclosing block-scoped container is a top-level container
Block = 1 << 7, // Enclosing block-scoped container is a Block
IterationStatement = 1 << 8, // Enclosed in an IterationStatement
IterationStatementBlock = 1 << 9, // Enclosing Block is enclosed in an IterationStatement
ForStatement = 1 << 10, // Enclosing block-scoped container is a ForStatement
ForInOrForOfStatement = 1 << 11, // Enclosing block-scoped container is a ForInStatement or ForOfStatement
ConstructorWithCapturedSuper = 1 << 12, // Enclosed in a constructor that captures 'this' for use with 'super'
ComputedPropertyName = 1 << 13, // Enclosed in a computed property name
// NOTE: do not add more ancestor flags without also updating AncestorFactsMask below.
//
// Ancestor masks
//
AncestorFactsMask = (ComputedPropertyName << 1) - 1,
// We are always in *some* kind of block scope, but only specific block-scope containers are
// top-level or Blocks.
BlockScopeIncludes = None,
BlockScopeExcludes = TopLevel | Block | IterationStatement | IterationStatementBlock | ForStatement | ForInOrForOfStatement,
// A source file is a top-level block scope.
SourceFileIncludes = TopLevel,
SourceFileExcludes = BlockScopeExcludes & ~TopLevel,
// Functions, methods, and accessors are both new lexical scopes and new block scopes.
FunctionIncludes = Function | TopLevel,
FunctionExcludes = BlockScopeExcludes & ~TopLevel | ArrowFunction | AsyncFunctionBody | CapturesThis | NonStaticClassElement | ConstructorWithCapturedSuper | ComputedPropertyName,
AsyncFunctionBodyIncludes = FunctionIncludes | AsyncFunctionBody,
AsyncFunctionBodyExcludes = FunctionExcludes & ~NonStaticClassElement,
// Arrow functions are lexically scoped to their container, but are new block scopes.
ArrowFunctionIncludes = ArrowFunction | TopLevel,
ArrowFunctionExcludes = BlockScopeExcludes & ~TopLevel | ConstructorWithCapturedSuper | ComputedPropertyName,
// Constructors are both new lexical scopes and new block scopes. Constructors are also
// always considered non-static members of a class.
ConstructorIncludes = FunctionIncludes | NonStaticClassElement,
ConstructorExcludes = FunctionExcludes & ~NonStaticClassElement,
// 'do' and 'while' statements are not block scopes. We track that the subtree is contained
// within an IterationStatement to indicate whether the embedded statement is an
// IterationStatementBlock.
DoOrWhileStatementIncludes = IterationStatement,
DoOrWhileStatementExcludes = None,
// 'for' statements are new block scopes and have special handling for 'let' declarations.
ForStatementIncludes = IterationStatement | ForStatement,
ForStatementExcludes = BlockScopeExcludes & ~ForStatement,
// 'for-in' and 'for-of' statements are new block scopes and have special handling for
// 'let' declarations.
ForInOrForOfStatementIncludes = IterationStatement | ForInOrForOfStatement,
ForInOrForOfStatementExcludes = BlockScopeExcludes & ~ForInOrForOfStatement,
// Blocks (other than function bodies) are new block scopes.
BlockIncludes = Block,
BlockExcludes = BlockScopeExcludes & ~Block,
IterationStatementBlockIncludes = IterationStatementBlock,
IterationStatementBlockExcludes = BlockScopeExcludes,
// Computed property names track subtree flags differently than their containing members.
ComputedPropertyNameIncludes = ComputedPropertyName,
ComputedPropertyNameExcludes = None,
//
// Subtree facts
//
NewTarget = 1 << 14, // Contains a 'new.target' meta-property
NewTargetInComputedPropertyName = 1 << 15, // Contains a 'new.target' meta-property in a computed property name.
//
// Subtree masks
//
SubtreeFactsMask = ~AncestorFactsMask,
PropagateNewTargetMask = NewTarget | NewTargetInComputedPropertyName,
}
export function transformES2015(context: TransformationContext) {
const {
startLexicalEnvironment,
resumeLexicalEnvironment,
endLexicalEnvironment,
hoistVariableDeclaration,
} = context;
const resolver = context.getEmitResolver();
const previousOnSubstituteNode = context.onSubstituteNode;
const previousOnEmitNode = context.onEmitNode;
context.onEmitNode = onEmitNode;
context.onSubstituteNode = onSubstituteNode;
let currentSourceFile: SourceFile;
let currentText: string;
let hierarchyFacts: HierarchyFacts;
/**
* Used to track if we are emitting body of the converted loop
*/
let convertedLoopState: ConvertedLoopState;
/**
* Keeps track of whether substitutions have been enabled for specific cases.
* They are persisted between each SourceFile transformation and should not
* be reset.
*/
let enabledSubstitutions: ES2015SubstitutionFlags;
return transformSourceFile;
function transformSourceFile(node: SourceFile) {
if (isDeclarationFile(node)) {
return node;
}
currentSourceFile = node;
currentText = node.text;
const visited = visitSourceFile(node);
addEmitHelpers(visited, context.readEmitHelpers());
currentSourceFile = undefined;
currentText = undefined;
hierarchyFacts = HierarchyFacts.None;
return visited;
}
/**
* Sets the `HierarchyFacts` for this node prior to visiting this node's subtree, returning the facts set prior to modification.
* @param excludeFacts The existing `HierarchyFacts` to reset before visiting the subtree.
* @param includeFacts The new `HierarchyFacts` to set before visiting the subtree.
**/
function enterSubtree(excludeFacts: HierarchyFacts, includeFacts: HierarchyFacts) {
const ancestorFacts = hierarchyFacts;
hierarchyFacts = (hierarchyFacts & ~excludeFacts | includeFacts) & HierarchyFacts.AncestorFactsMask;
return ancestorFacts;
}
/**
* Restores the `HierarchyFacts` for this node's ancestor after visiting this node's
* subtree, propagating specific facts from the subtree.
* @param ancestorFacts The `HierarchyFacts` of the ancestor to restore after visiting the subtree.
* @param excludeFacts The existing `HierarchyFacts` of the subtree that should not be propagated.
* @param includeFacts The new `HierarchyFacts` of the subtree that should be propagated.
**/
function exitSubtree(ancestorFacts: HierarchyFacts, excludeFacts: HierarchyFacts, includeFacts: HierarchyFacts) {
hierarchyFacts = (hierarchyFacts & ~excludeFacts | includeFacts) & HierarchyFacts.SubtreeFactsMask | ancestorFacts;
}
function isReturnVoidStatementInConstructorWithCapturedSuper(node: Node): boolean {
return hierarchyFacts & HierarchyFacts.ConstructorWithCapturedSuper
&& node.kind === SyntaxKind.ReturnStatement
&& !(<ReturnStatement>node).expression;
}
function shouldVisitNode(node: Node): boolean {
return (node.transformFlags & TransformFlags.ContainsES2015) !== 0
|| convertedLoopState !== undefined
|| (hierarchyFacts & HierarchyFacts.ConstructorWithCapturedSuper && isStatement(node))
|| (isIterationStatement(node, /*lookInLabeledStatements*/ false) && shouldConvertIterationStatementBody(node));
}
function visitor(node: Node): VisitResult<Node> {
if (shouldVisitNode(node)) {
return visitJavaScript(node);
}
else {
return node;
}
}
function functionBodyVisitor(node: Block): Block {
if (shouldVisitNode(node)) {
return visitBlock(node, /*isFunctionBody*/ true);
}
return node;
}
function callExpressionVisitor(node: Node): VisitResult<Node> {
if (node.kind === SyntaxKind.SuperKeyword) {
return visitSuperKeyword(/*isExpressionOfCall*/ true);
}
return visitor(node);
}
function visitJavaScript(node: Node): VisitResult<Node> {
switch (node.kind) {
case SyntaxKind.StaticKeyword:
return undefined; // elide static keyword
case SyntaxKind.ClassDeclaration:
return visitClassDeclaration(<ClassDeclaration>node);
case SyntaxKind.ClassExpression:
return visitClassExpression(<ClassExpression>node);
case SyntaxKind.Parameter:
return visitParameter(<ParameterDeclaration>node);
case SyntaxKind.FunctionDeclaration:
return visitFunctionDeclaration(<FunctionDeclaration>node);
case SyntaxKind.ArrowFunction:
return visitArrowFunction(<ArrowFunction>node);
case SyntaxKind.FunctionExpression:
return visitFunctionExpression(<FunctionExpression>node);
case SyntaxKind.VariableDeclaration:
return visitVariableDeclaration(<VariableDeclaration>node);
case SyntaxKind.Identifier:
return visitIdentifier(<Identifier>node);
case SyntaxKind.VariableDeclarationList:
return visitVariableDeclarationList(<VariableDeclarationList>node);
case SyntaxKind.SwitchStatement:
return visitSwitchStatement(<SwitchStatement>node);
case SyntaxKind.CaseBlock:
return visitCaseBlock(<CaseBlock>node);
case SyntaxKind.Block:
return visitBlock(<Block>node, /*isFunctionBody*/ false);
case SyntaxKind.BreakStatement:
case SyntaxKind.ContinueStatement:
return visitBreakOrContinueStatement(<BreakOrContinueStatement>node);
case SyntaxKind.LabeledStatement:
return visitLabeledStatement(<LabeledStatement>node);
case SyntaxKind.DoStatement:
case SyntaxKind.WhileStatement:
return visitDoOrWhileStatement(<DoStatement | WhileStatement>node, /*outermostLabeledStatement*/ undefined);
case SyntaxKind.ForStatement:
return visitForStatement(<ForStatement>node, /*outermostLabeledStatement*/ undefined);
case SyntaxKind.ForInStatement:
return visitForInStatement(<ForInStatement>node, /*outermostLabeledStatement*/ undefined);
case SyntaxKind.ForOfStatement:
return visitForOfStatement(<ForOfStatement>node, /*outermostLabeledStatement*/ undefined);
case SyntaxKind.ExpressionStatement:
return visitExpressionStatement(<ExpressionStatement>node);
case SyntaxKind.ObjectLiteralExpression:
return visitObjectLiteralExpression(<ObjectLiteralExpression>node);
case SyntaxKind.CatchClause:
return visitCatchClause(<CatchClause>node);
case SyntaxKind.ShorthandPropertyAssignment:
return visitShorthandPropertyAssignment(<ShorthandPropertyAssignment>node);
case SyntaxKind.ComputedPropertyName:
return visitComputedPropertyName(<ComputedPropertyName>node);
case SyntaxKind.ArrayLiteralExpression:
return visitArrayLiteralExpression(<ArrayLiteralExpression>node);
case SyntaxKind.CallExpression:
return visitCallExpression(<CallExpression>node);
case SyntaxKind.NewExpression:
return visitNewExpression(<NewExpression>node);
case SyntaxKind.ParenthesizedExpression:
return visitParenthesizedExpression(<ParenthesizedExpression>node, /*needsDestructuringValue*/ true);
case SyntaxKind.BinaryExpression:
return visitBinaryExpression(<BinaryExpression>node, /*needsDestructuringValue*/ true);
case SyntaxKind.NoSubstitutionTemplateLiteral:
case SyntaxKind.TemplateHead:
case SyntaxKind.TemplateMiddle:
case SyntaxKind.TemplateTail:
return visitTemplateLiteral(<LiteralExpression>node);
case SyntaxKind.TaggedTemplateExpression:
return visitTaggedTemplateExpression(<TaggedTemplateExpression>node);
case SyntaxKind.TemplateExpression:
return visitTemplateExpression(<TemplateExpression>node);
case SyntaxKind.YieldExpression:
return visitYieldExpression(<YieldExpression>node);
case SyntaxKind.SpreadElement:
return visitSpreadElement(<SpreadElement>node);
case SyntaxKind.SuperKeyword:
return visitSuperKeyword(/*isExpressionOfCall*/ false);
case SyntaxKind.ThisKeyword:
return visitThisKeyword(node);
case SyntaxKind.MetaProperty:
return visitMetaProperty(<MetaProperty>node);
case SyntaxKind.MethodDeclaration:
return visitMethodDeclaration(<MethodDeclaration>node);
case SyntaxKind.GetAccessor:
case SyntaxKind.SetAccessor:
return visitAccessorDeclaration(<AccessorDeclaration>node);
case SyntaxKind.VariableStatement:
return visitVariableStatement(<VariableStatement>node);
case SyntaxKind.ReturnStatement:
return visitReturnStatement(<ReturnStatement>node);
default:
return visitEachChild(node, visitor, context);
}
}
function visitSourceFile(node: SourceFile): SourceFile {
const ancestorFacts = enterSubtree(HierarchyFacts.SourceFileExcludes, HierarchyFacts.SourceFileIncludes);
const statements: Statement[] = [];
startLexicalEnvironment();
const statementOffset = addPrologueDirectives(statements, node.statements, /*ensureUseStrict*/ false, visitor);
addCaptureThisForNodeIfNeeded(statements, node);
addRange(statements, visitNodes(node.statements, visitor, isStatement, statementOffset));
addRange(statements, endLexicalEnvironment());
exitSubtree(ancestorFacts, HierarchyFacts.None, HierarchyFacts.None);
return updateSourceFileNode(
node,
setTextRange(createNodeArray(statements), node.statements)
);
}
function visitSwitchStatement(node: SwitchStatement): SwitchStatement {
if (convertedLoopState !== undefined) {
const savedAllowedNonLabeledJumps = convertedLoopState.allowedNonLabeledJumps;
// for switch statement allow only non-labeled break
convertedLoopState.allowedNonLabeledJumps |= Jump.Break;
const result = visitEachChild(node, visitor, context);
convertedLoopState.allowedNonLabeledJumps = savedAllowedNonLabeledJumps;
return result;
}
return visitEachChild(node, visitor, context);
}
function visitCaseBlock(node: CaseBlock): CaseBlock {
const ancestorFacts = enterSubtree(HierarchyFacts.BlockScopeExcludes, HierarchyFacts.BlockScopeIncludes);
const updated = visitEachChild(node, visitor, context);
exitSubtree(ancestorFacts, HierarchyFacts.None, HierarchyFacts.None);
return updated;
}
function returnCapturedThis(node: Node): ReturnStatement {
return setOriginalNode(createReturn(createIdentifier("_this")), node);
}
function visitReturnStatement(node: ReturnStatement): Statement {
if (convertedLoopState) {
convertedLoopState.nonLocalJumps |= Jump.Return;
if (isReturnVoidStatementInConstructorWithCapturedSuper(node)) {
node = returnCapturedThis(node);
}
return createReturn(
createObjectLiteral(
[
createPropertyAssignment(
createIdentifier("value"),
node.expression
? visitNode(node.expression, visitor, isExpression)
: createVoidZero()
)
]
)
);
}
else if (isReturnVoidStatementInConstructorWithCapturedSuper(node)) {
return returnCapturedThis(node);
}
return visitEachChild(node, visitor, context);
}
function visitThisKeyword(node: Node): Node {
if (convertedLoopState) {
if (hierarchyFacts & HierarchyFacts.ArrowFunction) {
// if the enclosing function is an ArrowFunction then we use the captured 'this' keyword.
convertedLoopState.containsLexicalThis = true;
return node;
}
return convertedLoopState.thisName || (convertedLoopState.thisName = createUniqueName("this"));
}
return node;
}
function visitIdentifier(node: Identifier): Identifier {
if (!convertedLoopState) {
return node;
}
if (isGeneratedIdentifier(node)) {
return node;
}
if (node.text !== "arguments" || !resolver.isArgumentsLocalBinding(node)) {
return node;
}
return convertedLoopState.argumentsName || (convertedLoopState.argumentsName = createUniqueName("arguments"));
}
function visitBreakOrContinueStatement(node: BreakOrContinueStatement): Statement {
if (convertedLoopState) {
// check if we can emit break/continue as is
// it is possible if either
// - break/continue is labeled and label is located inside the converted loop
// - break/continue is non-labeled and located in non-converted loop/switch statement
const jump = node.kind === SyntaxKind.BreakStatement ? Jump.Break : Jump.Continue;
const canUseBreakOrContinue =
(node.label && convertedLoopState.labels && convertedLoopState.labels.get(node.label.text)) ||
(!node.label && (convertedLoopState.allowedNonLabeledJumps & jump));
if (!canUseBreakOrContinue) {
let labelMarker: string;
if (!node.label) {
if (node.kind === SyntaxKind.BreakStatement) {
convertedLoopState.nonLocalJumps |= Jump.Break;
labelMarker = "break";
}
else {
convertedLoopState.nonLocalJumps |= Jump.Continue;
// note: return value is emitted only to simplify debugging, call to converted loop body does not do any dispatching on it.
labelMarker = "continue";
}
}
else {
if (node.kind === SyntaxKind.BreakStatement) {
labelMarker = `break-${node.label.text}`;
setLabeledJump(convertedLoopState, /*isBreak*/ true, node.label.text, labelMarker);
}
else {
labelMarker = `continue-${node.label.text}`;
setLabeledJump(convertedLoopState, /*isBreak*/ false, node.label.text, labelMarker);
}
}
let returnExpression: Expression = createLiteral(labelMarker);
if (convertedLoopState.loopOutParameters.length) {
const outParams = convertedLoopState.loopOutParameters;
let expr: Expression;
for (let i = 0; i < outParams.length; i++) {
const copyExpr = copyOutParameter(outParams[i], CopyDirection.ToOutParameter);
if (i === 0) {
expr = copyExpr;
}
else {
expr = createBinary(expr, SyntaxKind.CommaToken, copyExpr);
}
}
returnExpression = createBinary(expr, SyntaxKind.CommaToken, returnExpression);
}
return createReturn(returnExpression);
}
}
return visitEachChild(node, visitor, context);
}
/**
* Visits a ClassDeclaration and transforms it into a variable statement.
*
* @param node A ClassDeclaration node.
*/
function visitClassDeclaration(node: ClassDeclaration): VisitResult<Statement> {
// [source]
// class C { }
//
// [output]
// var C = (function () {
// function C() {
// }
// return C;
// }());
const variable = createVariableDeclaration(
getLocalName(node, /*allowComments*/ true),
/*type*/ undefined,
transformClassLikeDeclarationToExpression(node)
);
setOriginalNode(variable, node);
const statements: Statement[] = [];
const statement = createVariableStatement(/*modifiers*/ undefined, createVariableDeclarationList([variable]));
setOriginalNode(statement, node);
setTextRange(statement, node);
startOnNewLine(statement);
statements.push(statement);
// Add an `export default` statement for default exports (for `--target es5 --module es6`)
if (hasModifier(node, ModifierFlags.Export)) {
const exportStatement = hasModifier(node, ModifierFlags.Default)
? createExportDefault(getLocalName(node))
: createExternalModuleExport(getLocalName(node));
setOriginalNode(exportStatement, statement);
statements.push(exportStatement);
}
const emitFlags = getEmitFlags(node);
if ((emitFlags & EmitFlags.HasEndOfDeclarationMarker) === 0) {
// Add a DeclarationMarker as a marker for the end of the declaration
statements.push(createEndOfDeclarationMarker(node));
setEmitFlags(statement, emitFlags | EmitFlags.HasEndOfDeclarationMarker);
}
return singleOrMany(statements);
}
/**
* Visits a ClassExpression and transforms it into an expression.
*
* @param node A ClassExpression node.
*/
function visitClassExpression(node: ClassExpression): Expression {
// [source]
// C = class { }
//
// [output]
// C = (function () {
// function class_1() {
// }
// return class_1;
// }())
return transformClassLikeDeclarationToExpression(node);
}
/**
* Transforms a ClassExpression or ClassDeclaration into an expression.
*
* @param node A ClassExpression or ClassDeclaration node.
*/
function transformClassLikeDeclarationToExpression(node: ClassExpression | ClassDeclaration): Expression {
// [source]
// class C extends D {
// constructor() {}
// method() {}
// get prop() {}
// set prop(v) {}
// }
//
// [output]
// (function (_super) {
// __extends(C, _super);
// function C() {
// }
// C.prototype.method = function () {}
// Object.defineProperty(C.prototype, "prop", {
// get: function() {},
// set: function() {},
// enumerable: true,
// configurable: true
// });
// return C;
// }(D))
if (node.name) {
enableSubstitutionsForBlockScopedBindings();
}
const extendsClauseElement = getClassExtendsHeritageClauseElement(node);
const classFunction = createFunctionExpression(
/*modifiers*/ undefined,
/*asteriskToken*/ undefined,
/*name*/ undefined,
/*typeParameters*/ undefined,
extendsClauseElement ? [createParameter(/*decorators*/ undefined, /*modifiers*/ undefined, /*dotDotDotToken*/ undefined, "_super")] : [],
/*type*/ undefined,
transformClassBody(node, extendsClauseElement)
);
// To preserve the behavior of the old emitter, we explicitly indent
// the body of the function here if it was requested in an earlier
// transformation.
if (getEmitFlags(node) & EmitFlags.Indented) {
setEmitFlags(classFunction, EmitFlags.Indented);
}
// "inner" and "outer" below are added purely to preserve source map locations from
// the old emitter
const inner = createPartiallyEmittedExpression(classFunction);
inner.end = node.end;
setEmitFlags(inner, EmitFlags.NoComments);
const outer = createPartiallyEmittedExpression(inner);
outer.end = skipTrivia(currentText, node.pos);
setEmitFlags(outer, EmitFlags.NoComments);
return createParen(
createCall(
outer,
/*typeArguments*/ undefined,
extendsClauseElement
? [visitNode(extendsClauseElement.expression, visitor, isExpression)]
: []
)
);
}
/**
* Transforms a ClassExpression or ClassDeclaration into a function body.
*
* @param node A ClassExpression or ClassDeclaration node.
* @param extendsClauseElement The expression for the class `extends` clause.
*/
function transformClassBody(node: ClassExpression | ClassDeclaration, extendsClauseElement: ExpressionWithTypeArguments): Block {
const statements: Statement[] = [];
startLexicalEnvironment();
addExtendsHelperIfNeeded(statements, node, extendsClauseElement);
addConstructor(statements, node, extendsClauseElement);
addClassMembers(statements, node);
// Create a synthetic text range for the return statement.
const closingBraceLocation = createTokenRange(skipTrivia(currentText, node.members.end), SyntaxKind.CloseBraceToken);
const localName = getLocalName(node);
// The following partially-emitted expression exists purely to align our sourcemap
// emit with the original emitter.
const outer = createPartiallyEmittedExpression(localName);
outer.end = closingBraceLocation.end;
setEmitFlags(outer, EmitFlags.NoComments);
const statement = createReturn(outer);
statement.pos = closingBraceLocation.pos;
setEmitFlags(statement, EmitFlags.NoComments | EmitFlags.NoTokenSourceMaps);
statements.push(statement);
addRange(statements, endLexicalEnvironment());
const block = createBlock(setTextRange(createNodeArray(statements), /*location*/ node.members), /*multiLine*/ true);
setEmitFlags(block, EmitFlags.NoComments);
return block;
}
/**
* Adds a call to the `__extends` helper if needed for a class.
*
* @param statements The statements of the class body function.
* @param node The ClassExpression or ClassDeclaration node.
* @param extendsClauseElement The expression for the class `extends` clause.
*/
function addExtendsHelperIfNeeded(statements: Statement[], node: ClassExpression | ClassDeclaration, extendsClauseElement: ExpressionWithTypeArguments): void {
if (extendsClauseElement) {
statements.push(
setTextRange(
createStatement(
createExtendsHelper(context, getLocalName(node))
),
/*location*/ extendsClauseElement
)
);
}
}
/**
* Adds the constructor of the class to a class body function.
*
* @param statements The statements of the class body function.
* @param node The ClassExpression or ClassDeclaration node.
* @param extendsClauseElement The expression for the class `extends` clause.
*/
function addConstructor(statements: Statement[], node: ClassExpression | ClassDeclaration, extendsClauseElement: ExpressionWithTypeArguments): void {
const savedConvertedLoopState = convertedLoopState;
convertedLoopState = undefined;
const ancestorFacts = enterSubtree(HierarchyFacts.ConstructorExcludes, HierarchyFacts.ConstructorIncludes);
const constructor = getFirstConstructorWithBody(node);
const hasSynthesizedSuper = hasSynthesizedDefaultSuperCall(constructor, extendsClauseElement !== undefined);
const constructorFunction = createFunctionDeclaration(
/*decorators*/ undefined,
/*modifiers*/ undefined,
/*asteriskToken*/ undefined,
getDeclarationName(node),
/*typeParameters*/ undefined,
transformConstructorParameters(constructor, hasSynthesizedSuper),
/*type*/ undefined,
transformConstructorBody(constructor, node, extendsClauseElement, hasSynthesizedSuper)
);
setTextRange(constructorFunction, constructor || node);
if (extendsClauseElement) {
setEmitFlags(constructorFunction, EmitFlags.CapturesThis);
}
statements.push(constructorFunction);
exitSubtree(ancestorFacts, HierarchyFacts.PropagateNewTargetMask, HierarchyFacts.None);
convertedLoopState = savedConvertedLoopState;
}
/**
* Transforms the parameters of the constructor declaration of a class.
*
* @param constructor The constructor for the class.
* @param hasSynthesizedSuper A value indicating whether the constructor starts with a
* synthesized `super` call.
*/
function transformConstructorParameters(constructor: ConstructorDeclaration, hasSynthesizedSuper: boolean) {
// If the TypeScript transformer needed to synthesize a constructor for property
// initializers, it would have also added a synthetic `...args` parameter and
// `super` call.
// If this is the case, we do not include the synthetic `...args` parameter and
// will instead use the `arguments` object in ES5/3.
return visitParameterList(constructor && !hasSynthesizedSuper && constructor.parameters, visitor, context)
|| <ParameterDeclaration[]>[];
}
/**
* Transforms the body of a constructor declaration of a class.
*
* @param constructor The constructor for the class.
* @param node The node which contains the constructor.
* @param extendsClauseElement The expression for the class `extends` clause.
* @param hasSynthesizedSuper A value indicating whether the constructor starts with a
* synthesized `super` call.
*/
function transformConstructorBody(constructor: ConstructorDeclaration | undefined, node: ClassDeclaration | ClassExpression, extendsClauseElement: ExpressionWithTypeArguments, hasSynthesizedSuper: boolean) {
const statements: Statement[] = [];
resumeLexicalEnvironment();
let statementOffset = -1;
if (hasSynthesizedSuper) {
// If a super call has already been synthesized,
// we're going to assume that we should just transform everything after that.
// The assumption is that no prior step in the pipeline has added any prologue directives.
statementOffset = 0;
}
else if (constructor) {
// Otherwise, try to emit all potential prologue directives first.
statementOffset = addPrologueDirectives(statements, constructor.body.statements, /*ensureUseStrict*/ false, visitor);
}
if (constructor) {
addDefaultValueAssignmentsIfNeeded(statements, constructor);
addRestParameterIfNeeded(statements, constructor, hasSynthesizedSuper);
Debug.assert(statementOffset >= 0, "statementOffset not initialized correctly!");
}
// determine whether the class is known syntactically to be a derived class (e.g. a
// class that extends a value that is not syntactically known to be `null`).
const isDerivedClass = extendsClauseElement && skipOuterExpressions(extendsClauseElement.expression).kind !== SyntaxKind.NullKeyword;
const superCaptureStatus = declareOrCaptureOrReturnThisForConstructorIfNeeded(statements, constructor, isDerivedClass, hasSynthesizedSuper, statementOffset);
// The last statement expression was replaced. Skip it.
if (superCaptureStatus === SuperCaptureResult.ReplaceSuperCapture || superCaptureStatus === SuperCaptureResult.ReplaceWithReturn) {
statementOffset++;
}
if (constructor) {
if (superCaptureStatus === SuperCaptureResult.ReplaceSuperCapture) {
hierarchyFacts |= HierarchyFacts.ConstructorWithCapturedSuper;
}
addRange(statements, visitNodes(constructor.body.statements, visitor, isStatement, /*start*/ statementOffset));
}
// Return `_this` unless we're sure enough that it would be pointless to add a return statement.
// If there's a constructor that we can tell returns in enough places, then we *do not* want to add a return.
if (isDerivedClass
&& superCaptureStatus !== SuperCaptureResult.ReplaceWithReturn
&& !(constructor && isSufficientlyCoveredByReturnStatements(constructor.body))) {
statements.push(
createReturn(
createIdentifier("_this")
)
);
}
addRange(statements, endLexicalEnvironment());
if (constructor) {
prependCaptureNewTargetIfNeeded(statements, constructor, /*copyOnWrite*/ false);
}
const block = createBlock(
setTextRange(
createNodeArray(
statements
),
/*location*/ constructor ? constructor.body.statements : node.members
),
/*multiLine*/ true
);
setTextRange(block, constructor ? constructor.body : node);
if (!constructor) {
setEmitFlags(block, EmitFlags.NoComments);
}
return block;
}
/**
* We want to try to avoid emitting a return statement in certain cases if a user already returned something.
* It would generate obviously dead code, so we'll try to make things a little bit prettier
* by doing a minimal check on whether some common patterns always explicitly return.
*/
function isSufficientlyCoveredByReturnStatements(statement: Statement): boolean {
// A return statement is considered covered.
if (statement.kind === SyntaxKind.ReturnStatement) {
return true;
}
// An if-statement with two covered branches is covered.
else if (statement.kind === SyntaxKind.IfStatement) {
const ifStatement = statement as IfStatement;
if (ifStatement.elseStatement) {
return isSufficientlyCoveredByReturnStatements(ifStatement.thenStatement) &&
isSufficientlyCoveredByReturnStatements(ifStatement.elseStatement);
}