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ahejlsbergahejlsberg
authoredSep 13, 2022
Discriminant of type never should never be matched (#50755)
* Discriminant of type 'never' should never be matched * Add tests
·
v5.8.2v4.9-beta
1 parent e37ea53 commit 60963d7

8 files changed

+1101
-1
lines changed
 

‎src/compiler/checker.ts

+1-1
Original file line numberDiff line numberDiff line change
@@ -25130,7 +25130,7 @@ namespace ts {
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const narrowedPropType = narrowType(propType);
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return filterType(type, t => {
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const discriminantType = getTypeOfPropertyOrIndexSignature(t, propName);
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return !(narrowedPropType.flags & TypeFlags.Never) && areTypesComparable(narrowedPropType, discriminantType);
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return !(discriminantType.flags & TypeFlags.Never) && !(narrowedPropType.flags & TypeFlags.Never) && areTypesComparable(narrowedPropType, discriminantType);
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});
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}
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‎tests/baselines/reference/neverAsDiscriminantType(strict=false).js

+143
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@@ -0,0 +1,143 @@
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//// [neverAsDiscriminantType.ts]
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type Foo1 = { kind: 'a', a: number } | { kind: 'b' } | { kind: never };
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function f1(foo: Foo1) {
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if (foo.kind === 'a') {
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foo.a;
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}
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}
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type Foo2 = { kind?: 'a', a: number } | { kind?: 'b' } | { kind?: never };
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function f2(foo: Foo2) {
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if (foo.kind === 'a') {
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foo.a;
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}
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}
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// Repro from #50716
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export interface GatewayPayloadStructure<O extends GatewayOpcode, T extends keyof GatewayEvents, D> {
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op: O
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d: D
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t?: T
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s?: number
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}
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export type GatewayPayload = {
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[O in GatewayOpcode]: O extends GatewayOpcode.DISPATCH
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? {
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[T in keyof GatewayEvents]: GatewayPayloadStructure<GatewayOpcode.DISPATCH, T, GatewayEvents[T]>
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}[keyof GatewayEvents]
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: GatewayPayloadStructure<O, never, O extends keyof GatewayParams ? GatewayParams[O] : never>
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}[GatewayOpcode]
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export interface GatewayParams {
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[GatewayOpcode.HELLO]: { b: 1 }
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}
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export enum GatewayOpcode {
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DISPATCH = 0,
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HEARTBEAT = 1,
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IDENTIFY = 2,
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PRESENCE_UPDATE = 3,
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VOICE_STATE_UPDATE = 4,
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RESUME = 6,
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RECONNECT = 7,
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REQUEST_GUILD_MEMBERS = 8,
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INVALID_SESSION = 9,
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HELLO = 10,
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HEARTBEAT_ACK = 11,
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}
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export interface GatewayEvents {
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MESSAGE_CREATE: { a: 1 }
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MESSAGE_UPDATE: { a: 2 }
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MESSAGE_DELETE: { a: 3 }
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}
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function assertMessage(event: { a: 1 }) { }
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export async function adaptSession(input: GatewayPayload) {
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if (input.t === 'MESSAGE_CREATE') {
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assertMessage(input.d)
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}
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}
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//// [neverAsDiscriminantType.js]
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"use strict";
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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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var __generator = (this && this.__generator) || function (thisArg, body) {
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var _ = { label: 0, sent: function() { if (t[0] & 1) throw t[1]; return t[1]; }, trys: [], ops: [] }, f, y, t, g;
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return g = { next: verb(0), "throw": verb(1), "return": verb(2) }, typeof Symbol === "function" && (g[Symbol.iterator] = function() { return this; }), g;
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function verb(n) { return function (v) { return step([n, v]); }; }
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function step(op) {
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if (f) throw new TypeError("Generator is already executing.");
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while (_) try {
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if (f = 1, y && (t = op[0] & 2 ? y["return"] : op[0] ? y["throw"] || ((t = y["return"]) && t.call(y), 0) : y.next) && !(t = t.call(y, op[1])).done) return t;
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if (y = 0, t) op = [op[0] & 2, t.value];
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switch (op[0]) {
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case 0: case 1: t = op; break;
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case 4: _.label++; return { value: op[1], done: false };
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case 5: _.label++; y = op[1]; op = [0]; continue;
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case 7: op = _.ops.pop(); _.trys.pop(); continue;
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default:
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if (!(t = _.trys, t = t.length > 0 && t[t.length - 1]) && (op[0] === 6 || op[0] === 2)) { _ = 0; continue; }
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if (op[0] === 3 && (!t || (op[1] > t[0] && op[1] < t[3]))) { _.label = op[1]; break; }
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if (op[0] === 6 && _.label < t[1]) { _.label = t[1]; t = op; break; }
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if (t && _.label < t[2]) { _.label = t[2]; _.ops.push(op); break; }
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if (t[2]) _.ops.pop();
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_.trys.pop(); continue;
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}
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op = body.call(thisArg, _);
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} catch (e) { op = [6, e]; y = 0; } finally { f = t = 0; }
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if (op[0] & 5) throw op[1]; return { value: op[0] ? op[1] : void 0, done: true };
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}
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};
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exports.__esModule = true;
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exports.adaptSession = exports.GatewayOpcode = void 0;
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function f1(foo) {
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if (foo.kind === 'a') {
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foo.a;
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}
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}
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function f2(foo) {
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if (foo.kind === 'a') {
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foo.a;
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}
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}
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var GatewayOpcode;
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(function (GatewayOpcode) {
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GatewayOpcode[GatewayOpcode["DISPATCH"] = 0] = "DISPATCH";
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GatewayOpcode[GatewayOpcode["HEARTBEAT"] = 1] = "HEARTBEAT";
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GatewayOpcode[GatewayOpcode["IDENTIFY"] = 2] = "IDENTIFY";
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GatewayOpcode[GatewayOpcode["PRESENCE_UPDATE"] = 3] = "PRESENCE_UPDATE";
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GatewayOpcode[GatewayOpcode["VOICE_STATE_UPDATE"] = 4] = "VOICE_STATE_UPDATE";
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GatewayOpcode[GatewayOpcode["RESUME"] = 6] = "RESUME";
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GatewayOpcode[GatewayOpcode["RECONNECT"] = 7] = "RECONNECT";
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GatewayOpcode[GatewayOpcode["REQUEST_GUILD_MEMBERS"] = 8] = "REQUEST_GUILD_MEMBERS";
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GatewayOpcode[GatewayOpcode["INVALID_SESSION"] = 9] = "INVALID_SESSION";
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GatewayOpcode[GatewayOpcode["HELLO"] = 10] = "HELLO";
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GatewayOpcode[GatewayOpcode["HEARTBEAT_ACK"] = 11] = "HEARTBEAT_ACK";
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})(GatewayOpcode = exports.GatewayOpcode || (exports.GatewayOpcode = {}));
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function assertMessage(event) { }
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function adaptSession(input) {
134+
return __awaiter(this, void 0, void 0, function () {
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return __generator(this, function (_a) {
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if (input.t === 'MESSAGE_CREATE') {
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assertMessage(input.d);
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}
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return [2 /*return*/];
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});
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});
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}
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exports.adaptSession = adaptSession;

‎tests/baselines/reference/neverAsDiscriminantType(strict=false).symbols

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@@ -0,0 +1,197 @@
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=== tests/cases/compiler/neverAsDiscriminantType.ts ===
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type Foo1 = { kind: 'a', a: number } | { kind: 'b' } | { kind: never };
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>Foo1 : Symbol(Foo1, Decl(neverAsDiscriminantType.ts, 0, 0))
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>kind : Symbol(kind, Decl(neverAsDiscriminantType.ts, 0, 13))
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>a : Symbol(a, Decl(neverAsDiscriminantType.ts, 0, 24))
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>kind : Symbol(kind, Decl(neverAsDiscriminantType.ts, 0, 40))
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>kind : Symbol(kind, Decl(neverAsDiscriminantType.ts, 0, 56))
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function f1(foo: Foo1) {
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>f1 : Symbol(f1, Decl(neverAsDiscriminantType.ts, 0, 71))
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>foo : Symbol(foo, Decl(neverAsDiscriminantType.ts, 2, 12))
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>Foo1 : Symbol(Foo1, Decl(neverAsDiscriminantType.ts, 0, 0))
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if (foo.kind === 'a') {
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>foo.kind : Symbol(kind, Decl(neverAsDiscriminantType.ts, 0, 13), Decl(neverAsDiscriminantType.ts, 0, 40), Decl(neverAsDiscriminantType.ts, 0, 56))
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>foo : Symbol(foo, Decl(neverAsDiscriminantType.ts, 2, 12))
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>kind : Symbol(kind, Decl(neverAsDiscriminantType.ts, 0, 13), Decl(neverAsDiscriminantType.ts, 0, 40), Decl(neverAsDiscriminantType.ts, 0, 56))
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foo.a;
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>foo.a : Symbol(a, Decl(neverAsDiscriminantType.ts, 0, 24))
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>foo : Symbol(foo, Decl(neverAsDiscriminantType.ts, 2, 12))
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>a : Symbol(a, Decl(neverAsDiscriminantType.ts, 0, 24))
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}
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}
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type Foo2 = { kind?: 'a', a: number } | { kind?: 'b' } | { kind?: never };
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>Foo2 : Symbol(Foo2, Decl(neverAsDiscriminantType.ts, 6, 1))
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>kind : Symbol(kind, Decl(neverAsDiscriminantType.ts, 8, 13))
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>a : Symbol(a, Decl(neverAsDiscriminantType.ts, 8, 25))
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>kind : Symbol(kind, Decl(neverAsDiscriminantType.ts, 8, 41))
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>kind : Symbol(kind, Decl(neverAsDiscriminantType.ts, 8, 58))
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function f2(foo: Foo2) {
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>f2 : Symbol(f2, Decl(neverAsDiscriminantType.ts, 8, 74))
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>foo : Symbol(foo, Decl(neverAsDiscriminantType.ts, 10, 12))
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>Foo2 : Symbol(Foo2, Decl(neverAsDiscriminantType.ts, 6, 1))
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if (foo.kind === 'a') {
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>foo.kind : Symbol(kind, Decl(neverAsDiscriminantType.ts, 8, 13), Decl(neverAsDiscriminantType.ts, 8, 41), Decl(neverAsDiscriminantType.ts, 8, 58))
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>foo : Symbol(foo, Decl(neverAsDiscriminantType.ts, 10, 12))
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>kind : Symbol(kind, Decl(neverAsDiscriminantType.ts, 8, 13), Decl(neverAsDiscriminantType.ts, 8, 41), Decl(neverAsDiscriminantType.ts, 8, 58))
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foo.a;
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>foo.a : Symbol(a, Decl(neverAsDiscriminantType.ts, 8, 25))
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>foo : Symbol(foo, Decl(neverAsDiscriminantType.ts, 10, 12))
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>a : Symbol(a, Decl(neverAsDiscriminantType.ts, 8, 25))
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}
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}
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// Repro from #50716
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export interface GatewayPayloadStructure<O extends GatewayOpcode, T extends keyof GatewayEvents, D> {
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>GatewayPayloadStructure : Symbol(GatewayPayloadStructure, Decl(neverAsDiscriminantType.ts, 14, 1))
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>O : Symbol(O, Decl(neverAsDiscriminantType.ts, 18, 41))
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>GatewayOpcode : Symbol(GatewayOpcode, Decl(neverAsDiscriminantType.ts, 35, 1))
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>T : Symbol(T, Decl(neverAsDiscriminantType.ts, 18, 65))
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>GatewayEvents : Symbol(GatewayEvents, Decl(neverAsDiscriminantType.ts, 49, 1))
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>D : Symbol(D, Decl(neverAsDiscriminantType.ts, 18, 96))
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op: O
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>op : Symbol(GatewayPayloadStructure.op, Decl(neverAsDiscriminantType.ts, 18, 101))
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>O : Symbol(O, Decl(neverAsDiscriminantType.ts, 18, 41))
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d: D
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>d : Symbol(GatewayPayloadStructure.d, Decl(neverAsDiscriminantType.ts, 19, 9))
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>D : Symbol(D, Decl(neverAsDiscriminantType.ts, 18, 96))
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t?: T
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>t : Symbol(GatewayPayloadStructure.t, Decl(neverAsDiscriminantType.ts, 20, 8))
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>T : Symbol(T, Decl(neverAsDiscriminantType.ts, 18, 65))
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s?: number
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>s : Symbol(GatewayPayloadStructure.s, Decl(neverAsDiscriminantType.ts, 21, 9))
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}
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export type GatewayPayload = {
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>GatewayPayload : Symbol(GatewayPayload, Decl(neverAsDiscriminantType.ts, 23, 1))
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[O in GatewayOpcode]: O extends GatewayOpcode.DISPATCH
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>O : Symbol(O, Decl(neverAsDiscriminantType.ts, 26, 5))
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>GatewayOpcode : Symbol(GatewayOpcode, Decl(neverAsDiscriminantType.ts, 35, 1))
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>O : Symbol(O, Decl(neverAsDiscriminantType.ts, 26, 5))
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>GatewayOpcode : Symbol(GatewayOpcode, Decl(neverAsDiscriminantType.ts, 35, 1))
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>DISPATCH : Symbol(GatewayOpcode.DISPATCH, Decl(neverAsDiscriminantType.ts, 37, 27))
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? {
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[T in keyof GatewayEvents]: GatewayPayloadStructure<GatewayOpcode.DISPATCH, T, GatewayEvents[T]>
88+
>T : Symbol(T, Decl(neverAsDiscriminantType.ts, 28, 9))
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>GatewayEvents : Symbol(GatewayEvents, Decl(neverAsDiscriminantType.ts, 49, 1))
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>GatewayPayloadStructure : Symbol(GatewayPayloadStructure, Decl(neverAsDiscriminantType.ts, 14, 1))
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>GatewayOpcode : Symbol(GatewayOpcode, Decl(neverAsDiscriminantType.ts, 35, 1))
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>DISPATCH : Symbol(GatewayOpcode.DISPATCH, Decl(neverAsDiscriminantType.ts, 37, 27))
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>T : Symbol(T, Decl(neverAsDiscriminantType.ts, 28, 9))
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>GatewayEvents : Symbol(GatewayEvents, Decl(neverAsDiscriminantType.ts, 49, 1))
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>T : Symbol(T, Decl(neverAsDiscriminantType.ts, 28, 9))
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}[keyof GatewayEvents]
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>GatewayEvents : Symbol(GatewayEvents, Decl(neverAsDiscriminantType.ts, 49, 1))
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: GatewayPayloadStructure<O, never, O extends keyof GatewayParams ? GatewayParams[O] : never>
101+
>GatewayPayloadStructure : Symbol(GatewayPayloadStructure, Decl(neverAsDiscriminantType.ts, 14, 1))
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>O : Symbol(O, Decl(neverAsDiscriminantType.ts, 26, 5))
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>O : Symbol(O, Decl(neverAsDiscriminantType.ts, 26, 5))
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>GatewayParams : Symbol(GatewayParams, Decl(neverAsDiscriminantType.ts, 31, 16))
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>GatewayParams : Symbol(GatewayParams, Decl(neverAsDiscriminantType.ts, 31, 16))
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>O : Symbol(O, Decl(neverAsDiscriminantType.ts, 26, 5))
107+
108+
}[GatewayOpcode]
109+
>GatewayOpcode : Symbol(GatewayOpcode, Decl(neverAsDiscriminantType.ts, 35, 1))
110+
111+
export interface GatewayParams {
112+
>GatewayParams : Symbol(GatewayParams, Decl(neverAsDiscriminantType.ts, 31, 16))
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114+
[GatewayOpcode.HELLO]: { b: 1 }
115+
>[GatewayOpcode.HELLO] : Symbol(GatewayParams[GatewayOpcode.HELLO], Decl(neverAsDiscriminantType.ts, 33, 32))
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>GatewayOpcode.HELLO : Symbol(GatewayOpcode.HELLO, Decl(neverAsDiscriminantType.ts, 46, 24))
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>GatewayOpcode : Symbol(GatewayOpcode, Decl(neverAsDiscriminantType.ts, 35, 1))
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>HELLO : Symbol(GatewayOpcode.HELLO, Decl(neverAsDiscriminantType.ts, 46, 24))
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>b : Symbol(b, Decl(neverAsDiscriminantType.ts, 34, 28))
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}
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export enum GatewayOpcode {
123+
>GatewayOpcode : Symbol(GatewayOpcode, Decl(neverAsDiscriminantType.ts, 35, 1))
124+
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DISPATCH = 0,
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>DISPATCH : Symbol(GatewayOpcode.DISPATCH, Decl(neverAsDiscriminantType.ts, 37, 27))
127+
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HEARTBEAT = 1,
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>HEARTBEAT : Symbol(GatewayOpcode.HEARTBEAT, Decl(neverAsDiscriminantType.ts, 38, 17))
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IDENTIFY = 2,
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>IDENTIFY : Symbol(GatewayOpcode.IDENTIFY, Decl(neverAsDiscriminantType.ts, 39, 18))
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PRESENCE_UPDATE = 3,
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>PRESENCE_UPDATE : Symbol(GatewayOpcode.PRESENCE_UPDATE, Decl(neverAsDiscriminantType.ts, 40, 17))
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VOICE_STATE_UPDATE = 4,
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>VOICE_STATE_UPDATE : Symbol(GatewayOpcode.VOICE_STATE_UPDATE, Decl(neverAsDiscriminantType.ts, 41, 24))
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RESUME = 6,
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>RESUME : Symbol(GatewayOpcode.RESUME, Decl(neverAsDiscriminantType.ts, 42, 27))
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RECONNECT = 7,
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>RECONNECT : Symbol(GatewayOpcode.RECONNECT, Decl(neverAsDiscriminantType.ts, 43, 15))
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REQUEST_GUILD_MEMBERS = 8,
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>REQUEST_GUILD_MEMBERS : Symbol(GatewayOpcode.REQUEST_GUILD_MEMBERS, Decl(neverAsDiscriminantType.ts, 44, 18))
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INVALID_SESSION = 9,
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>INVALID_SESSION : Symbol(GatewayOpcode.INVALID_SESSION, Decl(neverAsDiscriminantType.ts, 45, 30))
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HELLO = 10,
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>HELLO : Symbol(GatewayOpcode.HELLO, Decl(neverAsDiscriminantType.ts, 46, 24))
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HEARTBEAT_ACK = 11,
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>HEARTBEAT_ACK : Symbol(GatewayOpcode.HEARTBEAT_ACK, Decl(neverAsDiscriminantType.ts, 47, 15))
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}
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export interface GatewayEvents {
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>GatewayEvents : Symbol(GatewayEvents, Decl(neverAsDiscriminantType.ts, 49, 1))
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MESSAGE_CREATE: { a: 1 }
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>MESSAGE_CREATE : Symbol(GatewayEvents.MESSAGE_CREATE, Decl(neverAsDiscriminantType.ts, 51, 32))
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>a : Symbol(a, Decl(neverAsDiscriminantType.ts, 52, 21))
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MESSAGE_UPDATE: { a: 2 }
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>MESSAGE_UPDATE : Symbol(GatewayEvents.MESSAGE_UPDATE, Decl(neverAsDiscriminantType.ts, 52, 28))
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>a : Symbol(a, Decl(neverAsDiscriminantType.ts, 53, 21))
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MESSAGE_DELETE: { a: 3 }
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>MESSAGE_DELETE : Symbol(GatewayEvents.MESSAGE_DELETE, Decl(neverAsDiscriminantType.ts, 53, 28))
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>a : Symbol(a, Decl(neverAsDiscriminantType.ts, 54, 21))
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}
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function assertMessage(event: { a: 1 }) { }
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>assertMessage : Symbol(assertMessage, Decl(neverAsDiscriminantType.ts, 55, 1))
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>event : Symbol(event, Decl(neverAsDiscriminantType.ts, 57, 23))
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>a : Symbol(a, Decl(neverAsDiscriminantType.ts, 57, 31))
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export async function adaptSession(input: GatewayPayload) {
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>adaptSession : Symbol(adaptSession, Decl(neverAsDiscriminantType.ts, 57, 43))
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>input : Symbol(input, Decl(neverAsDiscriminantType.ts, 59, 35))
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>GatewayPayload : Symbol(GatewayPayload, Decl(neverAsDiscriminantType.ts, 23, 1))
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if (input.t === 'MESSAGE_CREATE') {
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>input.t : Symbol(GatewayPayloadStructure.t, Decl(neverAsDiscriminantType.ts, 20, 8), Decl(neverAsDiscriminantType.ts, 20, 8), Decl(neverAsDiscriminantType.ts, 20, 8), Decl(neverAsDiscriminantType.ts, 20, 8), Decl(neverAsDiscriminantType.ts, 20, 8) ... and 8 more)
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>input : Symbol(input, Decl(neverAsDiscriminantType.ts, 59, 35))
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>t : Symbol(GatewayPayloadStructure.t, Decl(neverAsDiscriminantType.ts, 20, 8), Decl(neverAsDiscriminantType.ts, 20, 8), Decl(neverAsDiscriminantType.ts, 20, 8), Decl(neverAsDiscriminantType.ts, 20, 8), Decl(neverAsDiscriminantType.ts, 20, 8) ... and 8 more)
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assertMessage(input.d)
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>assertMessage : Symbol(assertMessage, Decl(neverAsDiscriminantType.ts, 55, 1))
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>input.d : Symbol(GatewayPayloadStructure.d, Decl(neverAsDiscriminantType.ts, 19, 9))
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>input : Symbol(input, Decl(neverAsDiscriminantType.ts, 59, 35))
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>d : Symbol(GatewayPayloadStructure.d, Decl(neverAsDiscriminantType.ts, 19, 9))
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}
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}
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