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parser.ts
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/**
* @fileoverview A TypeScript parser for the AssemblyScript subset.
*
* Takes the tokens produced by the `Tokenizer` and builds an abstract
* syntax tree composed of `Node`s wrapped in a `Source` out of it.
*
* @license Apache-2.0
*/
import {
CommonFlags,
LIBRARY_PREFIX,
PATH_DELIMITER
} from "./common";
import {
Tokenizer,
Token,
CommentHandler,
IdentifierHandling,
isIllegalVariableIdentifier
} from "./tokenizer";
import {
Range,
DiagnosticCode,
DiagnosticEmitter,
DiagnosticMessage
} from "./diagnostics";
import {
CharCode,
normalizePath
} from "./util";
import {
Node,
NodeKind,
Source,
SourceKind,
TypeNode,
TypeName,
NamedTypeNode,
FunctionTypeNode,
ArrowKind,
Expression,
AssertionKind,
CallExpression,
ClassExpression,
FunctionExpression,
IdentifierExpression,
StringLiteralExpression,
Statement,
BlockStatement,
BreakStatement,
ClassDeclaration,
ContinueStatement,
DeclarationStatement,
DecoratorNode,
DoStatement,
EnumDeclaration,
EnumValueDeclaration,
ExportImportStatement,
ExportMember,
ExportStatement,
ExpressionStatement,
ForOfStatement,
FunctionDeclaration,
IfStatement,
ImportDeclaration,
ImportStatement,
IndexSignatureNode,
NamespaceDeclaration,
ParameterNode,
ParameterKind,
ReturnStatement,
SwitchCase,
SwitchStatement,
ThrowStatement,
TryStatement,
TypeDeclaration,
TypeParameterNode,
VariableStatement,
VariableDeclaration,
VoidStatement,
WhileStatement,
ModuleDeclaration,
mangleInternalPath
} from "./ast";
/** Represents a dependee. */
class Dependee {
constructor(
public source: Source,
public reportNode: Node
) {}
}
/** Parser interface. */
export class Parser extends DiagnosticEmitter {
/** Source file names to be requested next. */
backlog: string[] = new Array();
/** Source file names already seen, that is processed or backlogged. */
seenlog: Set<string> = new Set();
/** Source file names already completely processed. */
donelog: Set<string> = new Set();
/** Optional handler to intercept comments while tokenizing. */
onComment: CommentHandler | null = null;
/** Current file being parsed. */
currentSource: Source | null = null;
/** Map of dependees being depended upon by a source, by path. */
dependees: Map<string, Dependee> = new Map();
/** An array of parsed sources. */
sources: Source[];
/** Current overridden module name. */
currentModuleName: string | null = null;
/** Constructs a new parser. */
constructor(
diagnostics: DiagnosticMessage[] | null = null,
sources: Source[] = []
) {
super(diagnostics);
this.sources = sources;
}
/** Parses a file and adds its definitions to the program. */
parseFile(
/** Source text of the file, or `null` to indicate not found. */
text: string | null,
/** Normalized path of the file. */
path: string,
/** Whether this is an entry file. */
isEntry: bool
): void {
// the frontend gives us paths with file extensions
let normalizedPath = normalizePath(path);
let internalPath = mangleInternalPath(normalizedPath);
// check if already processed
if (this.donelog.has(internalPath)) return;
this.donelog.add(internalPath); // do not parse again
this.seenlog.add(internalPath); // do not request again
// check if this is an error
if (text == null) {
let dependees = this.dependees;
let dependee: Dependee | null = null;
if (dependees.has(internalPath)) dependee = assert(dependees.get(internalPath));
this.error(
DiagnosticCode.File_0_not_found,
dependee
? dependee.reportNode.range
: null,
path
);
return;
}
// create the source element
let source = new Source(
isEntry
? SourceKind.UserEntry
: path.startsWith(LIBRARY_PREFIX)
? path.indexOf(PATH_DELIMITER, LIBRARY_PREFIX.length) < 0
? SourceKind.LibraryEntry
: SourceKind.Library
: SourceKind.User,
normalizedPath,
text
);
this.sources.push(source);
this.currentSource = source;
this.currentModuleName = null;
// tokenize and parse
let tn = new Tokenizer(source, this.diagnostics);
tn.onComment = this.onComment;
let statements = source.statements;
while (!tn.skip(Token.EndOfFile)) {
let statement = this.parseTopLevelStatement(tn, null);
if (statement) {
statements.push(statement);
} else {
this.skipStatement(tn);
}
}
}
/** Parses a top-level statement. */
parseTopLevelStatement(
tn: Tokenizer,
namespace: NamespaceDeclaration | null = null
): Statement | null {
let flags = namespace ? namespace.flags & CommonFlags.Ambient : CommonFlags.None;
let startPos = -1;
// check decorators
let decorators: DecoratorNode[] | null = null;
while (tn.skip(Token.At)) {
if (startPos < 0) startPos = tn.tokenPos;
let decorator = this.parseDecorator(tn);
if (!decorator) {
this.skipStatement(tn);
continue;
}
if (!decorators) decorators = [decorator];
else decorators.push(decorator);
}
// check modifiers
let exportStart = 0;
let exportEnd = 0;
let defaultStart = 0;
let defaultEnd = 0;
if (tn.skip(Token.Export)) {
if (startPos < 0) startPos = tn.tokenPos;
flags |= CommonFlags.Export;
exportStart = tn.tokenPos;
exportEnd = tn.pos;
if (tn.skip(Token.Default)) {
defaultStart = tn.tokenPos;
defaultEnd = tn.pos;
}
}
let declareStart = 0;
let declareEnd = 0;
let contextIsAmbient = namespace != null && namespace.is(CommonFlags.Ambient);
if (tn.skip(Token.Declare)) {
if (contextIsAmbient) {
this.error(
DiagnosticCode.A_declare_modifier_cannot_be_used_in_an_already_ambient_context,
tn.range()
); // recoverable
} else {
if (startPos < 0) startPos = tn.tokenPos;
declareStart = startPos;
declareEnd = tn.pos;
flags |= CommonFlags.Declare | CommonFlags.Ambient;
}
} else if (contextIsAmbient) {
flags |= CommonFlags.Ambient;
}
// parse the statement
let statement: Statement | null = null;
// handle declarations
let first = tn.peek();
if (startPos < 0) startPos = tn.nextTokenPos;
switch (first) {
case Token.Const: {
tn.next();
flags |= CommonFlags.Const;
if (tn.skip(Token.Enum)) {
statement = this.parseEnum(tn, flags, decorators, startPos);
} else {
statement = this.parseVariable(tn, flags, decorators, startPos);
}
decorators = null;
break;
}
case Token.Let: flags |= CommonFlags.Let;
case Token.Var: {
tn.next();
statement = this.parseVariable(tn, flags, decorators, startPos);
decorators = null;
break;
}
case Token.Enum: {
tn.next();
statement = this.parseEnum(tn, flags, decorators, startPos);
decorators = null;
break;
}
case Token.Function: {
tn.next();
statement = this.parseFunction(tn, flags, decorators, startPos);
decorators = null;
break;
}
case Token.Abstract: {
let state = tn.mark();
tn.next();
let abstractStart = tn.tokenPos;
let abstractEnd = tn.pos;
if (tn.peekOnNewLine()) {
tn.reset(state);
statement = this.parseStatement(tn, true);
break;
}
let next = tn.peek();
if (next != Token.Class) {
if (next == Token.Interface) {
this.error(
DiagnosticCode._abstract_modifier_can_only_appear_on_a_class_method_or_property_declaration,
tn.range(abstractStart, abstractEnd)
);
}
tn.reset(state);
statement = this.parseStatement(tn, true);
break;
} else {
tn.discard(state);
}
flags |= CommonFlags.Abstract;
// fall through
}
case Token.Class:
case Token.Interface: {
tn.next();
statement = this.parseClassOrInterface(tn, flags, decorators, startPos);
decorators = null;
break;
}
case Token.Namespace: {
let state = tn.mark();
tn.next();
if (tn.peek(IdentifierHandling.Prefer) == Token.Identifier) {
tn.discard(state);
statement = this.parseNamespace(tn, flags, decorators, startPos);
decorators = null;
} else {
tn.reset(state);
statement = this.parseStatement(tn, true);
}
break;
}
case Token.Import: {
tn.next();
flags |= CommonFlags.Import;
if (flags & CommonFlags.Export) {
statement = this.parseExportImport(tn, startPos);
} else {
statement = this.parseImport(tn);
}
break;
}
case Token.Type: { // also identifier
let state = tn.mark();
tn.next();
if (tn.peek(IdentifierHandling.Prefer) == Token.Identifier) {
tn.discard(state);
statement = this.parseTypeDeclaration(tn, flags, decorators, startPos);
decorators = null;
} else {
tn.reset(state);
statement = this.parseStatement(tn, true);
}
break;
}
case Token.Module: { // also identifier
let state = tn.mark();
tn.next();
if (tn.peek() == Token.StringLiteral && !tn.peekOnNewLine()) {
tn.discard(state);
statement = this.parseModuleDeclaration(tn, flags);
} else {
tn.reset(state);
statement = this.parseStatement(tn, true);
}
break;
}
default: {
// handle plain exports
if (flags & CommonFlags.Export) {
if (defaultEnd && tn.skipIdentifier(IdentifierHandling.Prefer)) {
if (declareEnd) {
this.error(
DiagnosticCode.An_export_assignment_cannot_have_modifiers,
tn.range(declareStart, declareEnd)
);
}
statement = this.parseExportDefaultAlias(tn, startPos, defaultStart, defaultEnd);
defaultStart = defaultEnd = 0; // consume
} else {
statement = this.parseExport(tn, startPos, (flags & CommonFlags.Declare) != 0);
}
// handle non-declaration statements
} else {
if (exportEnd) {
this.error(
DiagnosticCode._0_modifier_cannot_be_used_here,
tn.range(exportStart, exportEnd), "export"
); // recoverable
}
if (declareEnd) {
this.error(
DiagnosticCode._0_modifier_cannot_be_used_here,
tn.range(declareStart, declareEnd), "declare"
); // recoverable
}
if (namespace) {
this.error(
DiagnosticCode.Namespace_can_only_have_declarations,
tn.range(startPos)
);
} else {
statement = this.parseStatement(tn, true);
}
}
break;
}
}
// check for decorators that weren't consumed
if (decorators) {
for (let i = 0, k = decorators.length; i < k; ++i) {
this.error(
DiagnosticCode.Decorators_are_not_valid_here,
decorators[i].range
);
}
}
// check if this an `export default` declaration
if (defaultEnd && statement != null) {
switch (statement.kind) {
case NodeKind.EnumDeclaration:
case NodeKind.FunctionDeclaration:
case NodeKind.ClassDeclaration:
case NodeKind.InterfaceDeclaration:
case NodeKind.NamespaceDeclaration: {
return Node.createExportDefaultStatement(<DeclarationStatement>statement, tn.range(startPos, tn.pos));
}
default: {
this.error(
DiagnosticCode._0_modifier_cannot_be_used_here,
tn.range(defaultStart, defaultEnd), "default"
);
}
}
}
return statement;
}
/** Obtains the next file to parse. */
nextFile(): string | null {
let backlog = this.backlog;
return backlog.length ? assert(backlog.shift()) : null;
}
/** Obtains the path of the dependee of the given imported file. */
getDependee(dependent: string): string | null {
let dependees = this.dependees;
if (dependees.has(dependent)) {
let dependee = assert(dependees.get(dependent));
return dependee.source.internalPath;
}
return null;
}
/** Finishes parsing. */
finish(): void {
if (this.backlog.length) throw new Error("backlog is not empty");
this.backlog = [];
this.seenlog.clear();
this.donelog.clear();
this.dependees.clear();
}
// types
/** Parses a type name. */
parseTypeName(
tn: Tokenizer
): TypeName | null {
// at: Identifier ('.' Identifier)*
let first = Node.createSimpleTypeName(tn.readIdentifier(), tn.range());
let current = first;
while (tn.skip(Token.Dot)) {
if (tn.skip(Token.Identifier)) {
let next = Node.createSimpleTypeName(tn.readIdentifier(), tn.range());
current.next = next;
current = next;
} else {
this.error(
DiagnosticCode.Identifier_expected,
tn.range(tn.pos)
);
return null;
}
}
return first;
}
/** Parses a type. */
parseType(
tn: Tokenizer,
acceptParenthesized: bool = true,
suppressErrors: bool = false
): TypeNode | null {
// before: Type
// NOTE: this parses our limited subset
let token = tn.next();
let startPos = tn.tokenPos;
let type: TypeNode;
// '(' ...
if (token == Token.OpenParen) {
// '(' FunctionSignature ')'
let isInnerParenthesized = tn.skip(Token.OpenParen);
// FunctionSignature?
let signature = this.tryParseFunctionType(tn);
if (signature) {
if (isInnerParenthesized) {
if (!tn.skip(Token.CloseParen)) {
if (!suppressErrors) {
this.error(
DiagnosticCode._0_expected,
tn.range(), ")"
);
}
return null;
}
}
type = signature;
} else if (isInnerParenthesized || this.tryParseSignatureIsSignature) {
if (!suppressErrors) {
this.error(
DiagnosticCode.Unexpected_token,
tn.range()
);
}
return null;
// Type (',' Type)* ')'
} else if (acceptParenthesized) {
let innerType = this.parseType(tn, false, suppressErrors);
if (!innerType) return null;
if (!tn.skip(Token.CloseParen)) {
if (!suppressErrors) {
this.error(
DiagnosticCode._0_expected,
tn.range(tn.pos), ")"
);
}
return null;
}
type = innerType;
type.range.start = startPos;
type.range.end = tn.pos;
} else {
if (!suppressErrors) {
this.error(
DiagnosticCode.Unexpected_token,
tn.range()
);
}
return null;
}
// 'void'
} else if (token == Token.Void) {
type = Node.createNamedType(
Node.createSimpleTypeName("void", tn.range()), [], false, tn.range(startPos, tn.pos)
);
// 'this'
} else if (token == Token.This) {
type = Node.createNamedType(
Node.createSimpleTypeName("this", tn.range()), [], false, tn.range(startPos, tn.pos)
);
// 'true'
} else if (token == Token.True || token == Token.False) {
type = Node.createNamedType(
Node.createSimpleTypeName("bool", tn.range()), [], false, tn.range(startPos, tn.pos)
);
// 'null'
} else if (token == Token.Null) {
type = Node.createNamedType(
Node.createSimpleTypeName("null", tn.range()), [], false, tn.range(startPos, tn.pos)
);
// StringLiteral
} else if (token == Token.StringLiteral) {
tn.readString();
type = Node.createNamedType(
Node.createSimpleTypeName("string", tn.range()), [], false, tn.range(startPos, tn.pos)
);
// Identifier
} else if (token == Token.Identifier) {
let name = this.parseTypeName(tn);
if (!name) return null;
let parameters: TypeNode[] | null = null;
// Name<T>
if (tn.skip(Token.LessThan)) {
do {
let parameter = this.parseType(tn, true, suppressErrors);
if (!parameter) return null;
if (!parameters) parameters = [ parameter ];
else parameters.push(parameter);
} while (tn.skip(Token.Comma));
if (!tn.skip(Token.GreaterThan)) {
if (!suppressErrors) {
this.error(
DiagnosticCode._0_expected,
tn.range(tn.pos), ">"
);
}
return null;
}
}
if (!parameters) parameters = [];
type = Node.createNamedType(name, parameters, false, tn.range(startPos, tn.pos));
} else {
if (!suppressErrors) {
this.error(
DiagnosticCode.Type_expected,
tn.range()
);
}
return null;
}
// ... | type
while (tn.skip(Token.Bar)) {
let nextType = this.parseType(tn, true, false);
if (!nextType) return null;
let typeIsNull = type.kind == NodeKind.NamedType && (<NamedTypeNode>type).isNull;
let nextTypeIsNull = nextType.kind == NodeKind.NamedType && (<NamedTypeNode>nextType).isNull;
if (!typeIsNull && !nextTypeIsNull) {
if (!suppressErrors) {
this.error(
DiagnosticCode.Not_implemented_0, nextType.range, "union types"
);
}
return null;
} else if (nextTypeIsNull) {
type.isNullable = true;
type.range.end = nextType.range.end;
} else if (typeIsNull) {
nextType.range.start = type.range.start;
nextType.isNullable = true;
type = nextType;
} else {
// `null | null` still `null`
type.range.end = nextType.range.end;
}
}
// ... [][]
while (tn.skip(Token.OpenBracket)) {
let bracketStart = tn.tokenPos;
if (!tn.skip(Token.CloseBracket)) {
if (!suppressErrors) {
this.error(
DiagnosticCode._0_expected,
tn.range(), "]"
);
}
return null;
}
let bracketRange = tn.range(bracketStart, tn.pos);
// ...[] | null
let nullable = false;
if (tn.skip(Token.Bar)) {
if (tn.skip(Token.Null)) {
nullable = true;
} else {
if (!suppressErrors) {
this.error(
DiagnosticCode.Not_implemented_0,
tn.range(), "union types"
);
}
return null;
}
}
type = Node.createNamedType(
Node.createSimpleTypeName("Array", bracketRange),
[ type ],
nullable,
tn.range(startPos, tn.pos)
);
if (nullable) break;
}
return type;
}
// Indicates whether tryParseSignature determined that it is handling a Signature
private tryParseSignatureIsSignature: bool = false;
/** Parses a function type, as used in type declarations. */
tryParseFunctionType(
tn: Tokenizer
): FunctionTypeNode | null {
// at '(': ('...'? Identifier '?'? ':' Type (',' '...'? Identifier '?'? ':' Type)* )? ')' '=>' Type
let state = tn.mark();
let startPos = tn.tokenPos;
let parameters: ParameterNode[] | null = null;
let thisType: NamedTypeNode | null = null;
let isSignature: bool = false;
let firstParamNameNoType: IdentifierExpression | null = null;
let firstParamKind: ParameterKind = ParameterKind.Default;
if (tn.skip(Token.CloseParen)) {
isSignature = true;
tn.discard(state);
parameters = [];
} else {
isSignature = false; // not yet known
do {
let paramStart = -1;
let kind = ParameterKind.Default;
if (tn.skip(Token.Dot_Dot_Dot)) {
paramStart = tn.tokenPos;
isSignature = true;
tn.discard(state);
kind = ParameterKind.Rest;
}
if (tn.skip(Token.This)) {
if (paramStart < 0) paramStart = tn.tokenPos;
if (tn.skip(Token.Colon)) {
isSignature = true;
tn.discard(state);
let type = this.parseType(tn, false);
if (!type) return null;
if (type.kind != NodeKind.NamedType) {
this.error(
DiagnosticCode.Identifier_expected,
type.range
);
this.tryParseSignatureIsSignature = true;
return null;
}
thisType = <NamedTypeNode>type;
} else {
tn.reset(state);
this.tryParseSignatureIsSignature = false;
return null;
}
} else if (tn.skipIdentifier()) {
if (paramStart < 0) paramStart = tn.tokenPos;
let name = Node.createIdentifierExpression(tn.readIdentifier(), tn.range(tn.tokenPos, tn.pos));
if (tn.skip(Token.Question)) {
isSignature = true;
tn.discard(state);
if (kind == ParameterKind.Rest) {
this.error(
DiagnosticCode.A_rest_parameter_cannot_be_optional,
tn.range()
); // recoverable
} else {
kind = ParameterKind.Optional;
}
}
if (tn.skip(Token.Colon)) {
isSignature = true;
tn.discard(state);
let type = this.parseType(tn); // not suppressing errors because known
if (!type) {
this.tryParseSignatureIsSignature = isSignature;
return null;
}
let param = Node.createParameter(kind, name, type, null, tn.range(paramStart, tn.pos));
if (!parameters) parameters = [ param ];
else parameters.push(param);
} else {
if (!isSignature) {
if (tn.peek() == Token.Comma) {
isSignature = true;
tn.discard(state);
}
}
if (isSignature) {
let param = Node.createParameter(kind, name, Node.createOmittedType(tn.range(tn.pos)), null, tn.range(paramStart, tn.pos));
if (!parameters) parameters = [ param ];
else parameters.push(param);
this.error(
DiagnosticCode.Type_expected,
param.type.range
); // recoverable
} else if (!parameters) {
// on '(' Identifier ^',' we don't yet know whether this is a
// parenthesized or a function type, hence we have to delay the
// respective diagnostic until we know for sure.
firstParamNameNoType = name;
firstParamKind = kind;
}
}
} else {
if (isSignature) {
if (tn.peek() == Token.CloseParen) break; // allow trailing comma
this.error(
DiagnosticCode.Identifier_expected,
tn.range()
);
} else {
tn.reset(state);
}
this.tryParseSignatureIsSignature = isSignature;
return null;
}
} while (tn.skip(Token.Comma));
if (!tn.skip(Token.CloseParen)) {
if (isSignature) {
this.error(
DiagnosticCode._0_expected,
tn.range(), ")"
);
} else {
tn.reset(state);
}
this.tryParseSignatureIsSignature = isSignature;
return null;
}
}
let returnType: TypeNode | null;
if (tn.skip(Token.Equals_GreaterThan)) {
if (!isSignature) {
isSignature = true;
tn.discard(state);
if (firstParamNameNoType) { // now we know
let param = Node.createParameter(
firstParamKind,
firstParamNameNoType,
Node.createOmittedType(firstParamNameNoType.range.atEnd),
null,
firstParamNameNoType.range
);
if (!parameters) parameters = [ param ];
else parameters.push(param);
this.error(
DiagnosticCode.Type_expected,
param.type.range
); // recoverable
}
}
returnType = this.parseType(tn);
if (!returnType) {
this.tryParseSignatureIsSignature = isSignature;
return null;
}
} else {
if (isSignature) {
this.error(
DiagnosticCode._0_expected,
tn.range(), "=>"
);
} else {
tn.reset(state);
}
this.tryParseSignatureIsSignature = isSignature;
return null;
}
this.tryParseSignatureIsSignature = true;
if (!parameters) parameters = [];
return Node.createFunctionType(
parameters,
returnType,
thisType,
false,
tn.range(startPos, tn.pos)
);
}
// statements
parseDecorator(
tn: Tokenizer
): DecoratorNode | null {
// at '@': Identifier ('.' Identifier)* '(' Arguments
let startPos = tn.tokenPos;
if (tn.skipIdentifier()) {
let name = tn.readIdentifier();
let expression: Expression = Node.createIdentifierExpression(name, tn.range(startPos, tn.pos));
while (tn.skip(Token.Dot)) {
if (tn.skipIdentifier(IdentifierHandling.Prefer)) {
name = tn.readIdentifier();
expression = Node.createPropertyAccessExpression(
expression,
Node.createIdentifierExpression(name, tn.range()),
tn.range(startPos, tn.pos)
);
} else {
this.error(
DiagnosticCode.Identifier_expected,
tn.range()
);
return null;
}
}
let args: Expression[] | null;
if (tn.skip(Token.OpenParen)) {
args = this.parseArguments(tn);
if (args) {
return Node.createDecorator(expression, args, tn.range(startPos, tn.pos));
}
} else {
return Node.createDecorator(expression, null, tn.range(startPos, tn.pos));
}
} else {
this.error(
DiagnosticCode.Identifier_expected,
tn.range()
);
}
return null;
}
parseVariable(
tn: Tokenizer,
flags: CommonFlags,
decorators: DecoratorNode[] | null,
startPos: i32,
isFor: bool = false
): VariableStatement | null {
// at ('const' | 'let' | 'var'): VariableDeclaration (',' VariableDeclaration)* ';'?
let declarations = new Array<VariableDeclaration>();
do {
let declaration = this.parseVariableDeclaration(tn, flags, decorators, isFor);
if (!declaration) return null;
declaration.overriddenModuleName = this.currentModuleName;
declarations.push(declaration);
} while (tn.skip(Token.Comma));
let ret = Node.createVariableStatement(decorators, declarations, tn.range(startPos, tn.pos));
if (!tn.skip(Token.Semicolon) && !isFor) this.checkASI(tn);
return ret;
}
parseVariableDeclaration(
tn: Tokenizer,
parentFlags: CommonFlags,
parentDecorators: DecoratorNode[] | null,
isFor: bool = false
): VariableDeclaration | null {
// before: Identifier (':' Type)? ('=' Expression)?
if (!tn.skipIdentifier()) {
this.error(
DiagnosticCode.Identifier_expected,
tn.range()
);
return null;
}
let identifier = Node.createIdentifierExpression(tn.readIdentifier(), tn.range());
if (isIllegalVariableIdentifier(identifier.text)) {
this.error(
DiagnosticCode.Identifier_expected,
identifier.range
);
}
let flags = parentFlags;
if (tn.skip(Token.Exclamation)) {
flags |= CommonFlags.DefinitelyAssigned;
}
let type: TypeNode | null = null;
if (tn.skip(Token.Colon)) {
type = this.parseType(tn, true);
}
let initializer: Expression | null = null;
if (tn.skip(Token.Equals)) {
if (flags & CommonFlags.Ambient) {
this.error(
DiagnosticCode.Initializers_are_not_allowed_in_ambient_contexts,
tn.range()
); // recoverable
}
initializer = this.parseExpression(tn, Precedence.Comma + 1);
if (!initializer) return null;
if (flags & CommonFlags.DefinitelyAssigned) {
this.error(
DiagnosticCode.Declarations_with_initializers_cannot_also_have_definite_assignment_assertions,
initializer.range
);
}
} else if (!isFor) {
if (flags & CommonFlags.Const) {