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Perryvwtomblind
Perryvw
and
tomblind
authored
Async await (#1093)
* Initial lualib promise class implementation * First promise tests * More promise tests * Promise class implementation * Implemented Promise.all * Promise.any * Promise.race * Promise.allSettled * fix prettier * Add promise example usage test * Added missing lualib dependencies for PromiseConstructor functions * Immediately call then/catch/finally callbacks on promises that are already resolved * Transform all references to Promise to __TS__Promise * PR feedback * Removed incorrect asyncs * Add test for direct chaining * Add test for finally and correct wrong behavior it caught * Added test throwing in parallel and chained then onFulfilleds * Fixed pull request link in ArrayIsArray lualib comment * Initial async await * Disallow await in top-level scope * Add await rejection test * Give await the correct lualib dependencies * use coroutine.status instead of lastData * Better top level await check * Add tests for async lambdas and throws in async functions * Moved toplevel await check to transformAwaitExpression and removed superfluous try/catch * fix for vararg access in async functions (#1096) Co-authored-by: Tom <tomblind@users.noreply.github.com> Co-authored-by: Tom <26638278+tomblind@users.noreply.github.com> Co-authored-by: Tom <tomblind@users.noreply.github.com>
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‎src/LuaLib.ts‎

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@@ -28,6 +28,7 @@ export enum LuaLibFeature {
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ArrayFlat = "ArrayFlat",
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ArrayFlatMap = "ArrayFlatMap",
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ArraySetLength = "ArraySetLength",
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Await = "Await",
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Class = "Class",
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ClassExtends = "ClassExtends",
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CloneDescriptor = "CloneDescriptor",
@@ -101,6 +102,7 @@ const luaLibDependencies: Partial<Record<LuaLibFeature, LuaLibFeature[]>> = {
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ArrayConcat: [LuaLibFeature.ArrayIsArray],
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ArrayFlat: [LuaLibFeature.ArrayConcat, LuaLibFeature.ArrayIsArray],
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ArrayFlatMap: [LuaLibFeature.ArrayConcat, LuaLibFeature.ArrayIsArray],
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Await: [LuaLibFeature.InstanceOf, LuaLibFeature.New],
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Decorate: [LuaLibFeature.ObjectGetOwnPropertyDescriptor, LuaLibFeature.SetDescriptor, LuaLibFeature.ObjectAssign],
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DelegatedYield: [LuaLibFeature.StringAccess],
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Delete: [LuaLibFeature.ObjectGetOwnPropertyDescriptors],

‎src/lualib/Await.ts‎

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@@ -0,0 +1,52 @@
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// The following is a translation of the TypeScript async awaiter which uses generators and yields.
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// For Lua we use coroutines instead.
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//
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// Source:
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//
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// var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
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// function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
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// return new (P || (P = Promise))(function (resolve, reject) {
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// function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
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// function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
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// function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
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// step((generator = generator.apply(thisArg, _arguments || [])).next());
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// });
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// };
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//
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// eslint-disable-next-line @typescript-eslint/promise-function-async
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function __TS__AsyncAwaiter(this: void, generator: (this: void) => void) {
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return new Promise((resolve, reject) => {
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const asyncCoroutine = coroutine.create(generator);
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// eslint-disable-next-line @typescript-eslint/promise-function-async
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function adopt(value: unknown) {
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return value instanceof __TS__Promise ? value : Promise.resolve(value);
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}
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function fulfilled(value) {
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const [success, resultOrError] = coroutine.resume(asyncCoroutine, value);
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if (success) {
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step(resultOrError);
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} else {
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reject(resultOrError);
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}
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}
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function step(result: unknown) {
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if (coroutine.status(asyncCoroutine) === "dead") {
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resolve(result);
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} else {
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adopt(result).then(fulfilled, reason => reject(reason));
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}
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}
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const [success, resultOrError] = coroutine.resume(asyncCoroutine);
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if (success) {
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step(resultOrError);
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} else {
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reject(resultOrError);
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}
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});
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}
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function __TS__Await(this: void, thing: unknown) {
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return coroutine.yield(thing);
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}

‎src/transformation/utils/diagnostics.ts‎

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@@ -147,3 +147,7 @@ export const annotationDeprecated = createWarningDiagnosticFactory(
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export const notAllowedOptionalAssignment = createErrorDiagnosticFactory(
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"The left-hand side of an assignment expression may not be an optional property access."
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);
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export const awaitMustBeInAsyncFunction = createErrorDiagnosticFactory(
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"Await can only be used inside async functions."
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);

‎src/transformation/visitors/async-await.ts‎

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import * as ts from "typescript";
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import * as lua from "../../LuaAST";
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import { FunctionVisitor, TransformationContext } from "../context";
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import { awaitMustBeInAsyncFunction } from "../utils/diagnostics";
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import { importLuaLibFeature, LuaLibFeature, transformLuaLibFunction } from "../utils/lualib";
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import { findFirstNodeAbove } from "../utils/typescript";
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export const transformAwaitExpression: FunctionVisitor<ts.AwaitExpression> = (node, context) => {
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// Check if await is inside an async function, it is not allowed at top level or in non-async functions
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const containingFunction = findFirstNodeAbove(node, ts.isFunctionLike);
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if (
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containingFunction === undefined ||
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!containingFunction.modifiers?.some(m => m.kind === ts.SyntaxKind.AsyncKeyword)
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) {
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context.diagnostics.push(awaitMustBeInAsyncFunction(node));
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}
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const expression = context.transformExpression(node.expression);
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return transformLuaLibFunction(context, LuaLibFeature.Await, node, expression);
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};
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export function isAsyncFunction(declaration: ts.FunctionLikeDeclaration): boolean {
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return declaration.modifiers?.some(m => m.kind === ts.SyntaxKind.AsyncKeyword) ?? false;
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}
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export function wrapInAsyncAwaiter(context: TransformationContext, statements: lua.Statement[]): lua.Statement[] {
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importLuaLibFeature(context, LuaLibFeature.Await);
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return [
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lua.createReturnStatement([
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lua.createCallExpression(lua.createIdentifier("__TS__AsyncAwaiter"), [
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lua.createFunctionExpression(lua.createBlock(statements)),
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]),
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]),
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];
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}

‎src/transformation/visitors/function.ts‎

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@@ -13,6 +13,7 @@ import {
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} from "../utils/lua-ast";
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import { LuaLibFeature, transformLuaLibFunction } from "../utils/lualib";
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import { peekScope, performHoisting, popScope, pushScope, Scope, ScopeType } from "../utils/scope";
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import { isAsyncFunction, wrapInAsyncAwaiter } from "./async-await";
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import { transformIdentifier } from "./identifier";
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import { transformExpressionBodyToReturnStatement } from "./return";
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import { transformBindingPattern } from "./variable-declaration";
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): [lua.Statement[], Scope] {
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const scope = pushScope(context, ScopeType.Function);
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scope.node = node;
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const bodyStatements = transformFunctionBodyContent(context, body);
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let bodyStatements = transformFunctionBodyContent(context, body);
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if (node && isAsyncFunction(node)) {
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bodyStatements = wrapInAsyncAwaiter(context, bodyStatements);
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}
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const headerStatements = transformFunctionBodyHeader(context, scope, parameters, spreadIdentifier);
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popScope(context);
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return [[...headerStatements, ...bodyStatements], scope];
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spreadIdentifier,
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node
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);
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const functionExpression = lua.createFunctionExpression(
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lua.createBlock(transformedBody),
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paramNames,

‎src/transformation/visitors/index.ts‎

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@@ -41,6 +41,7 @@ import { typescriptVisitors } from "./typescript";
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import { transformPostfixUnaryExpression, transformPrefixUnaryExpression } from "./unary-expression";
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import { transformVariableStatement } from "./variable-declaration";
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import { jsxVisitors } from "./jsx/jsx";
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import { transformAwaitExpression } from "./async-await";
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const transformEmptyStatement: FunctionVisitor<ts.EmptyStatement> = () => undefined;
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const transformParenthesizedExpression: FunctionVisitor<ts.ParenthesizedExpression> = (node, context) =>
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...typescriptVisitors,
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...jsxVisitors,
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[ts.SyntaxKind.ArrowFunction]: transformFunctionLikeDeclaration,
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[ts.SyntaxKind.AwaitExpression]: transformAwaitExpression,
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[ts.SyntaxKind.BinaryExpression]: transformBinaryExpression,
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[ts.SyntaxKind.Block]: transformBlock,
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[ts.SyntaxKind.BreakStatement]: transformBreakStatement,

‎src/transformation/visitors/sourceFile.ts‎

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@@ -23,6 +23,7 @@ export const transformSourceFileNode: FunctionVisitor<ts.SourceFile> = (node, co
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}
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} else {
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pushScope(context, ScopeType.File);
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statements = performHoisting(context, context.transformStatements(node.statements));
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popScope(context);
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‎src/transformation/visitors/spread.ts‎

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@@ -37,6 +37,11 @@ export function isOptimizedVarArgSpread(context: TransformationContext, symbol:
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return false;
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}
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// Scope cannot be an async function
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if (scope.node.modifiers?.some(m => m.kind === ts.SyntaxKind.AsyncKeyword)) {
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return false;
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}
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// Identifier must be a vararg in the local function scope's parameters
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const isSpreadParameter = (p: ts.ParameterDeclaration) =>
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p.dotDotDotToken && ts.isIdentifier(p.name) && context.checker.getSymbolAtLocation(p.name) === symbol;

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