Fix crashes when the global JSX namespace is an alias

src/compiler/checker.ts

@@ -25142,7 +25142,7 @@ namespace ts {
                 const resolvedNamespace = resolveName(location, namespaceName, SymbolFlags.Namespace, /*diagnosticMessage*/ undefined, namespaceName, /*isUse*/ false);
                 if (resolvedNamespace) {
                     const candidate = resolveSymbol(getSymbol(getExportsOfSymbol(resolveSymbol(resolvedNamespace)), JsxNames.JSX, SymbolFlags.Namespace));
-                    if (candidate) {
+                    if (candidate && candidate !== unknownSymbol) {
                         if (links) {
                             links.jsxNamespace = candidate;
                         }
@@ -25154,7 +25154,11 @@ namespace ts {
                 }
             }
             // JSX global fallback
-            return getGlobalSymbol(JsxNames.JSX, SymbolFlags.Namespace, /*diagnosticMessage*/ undefined)!; // TODO: GH#18217
+            const s = resolveSymbol(getGlobalSymbol(JsxNames.JSX, SymbolFlags.Namespace, /*diagnosticMessage*/ undefined));
+            if (s === unknownSymbol) {
+                return undefined!; // TODO: GH#18217
+            }
+            return s!; // TODO: GH#18217
         }
 
         /**

tests/baselines/reference/jsxNamespaceGlobalReexport.js

@@ -0,0 +1,114 @@
+//// [tests/cases/compiler/jsxNamespaceGlobalReexport.tsx] ////
+
+//// [index.d.ts]
+type Defaultize<Props, Defaults> =
+	// Distribute over unions
+	Props extends any // Make any properties included in Default optional
+		? Partial<Pick<Props, Extract<keyof Props, keyof Defaults>>> &
+				// Include the remaining properties from Props
+				Pick<Props, Exclude<keyof Props, keyof Defaults>>
+		: never;
+export namespace JSXInternal {
+    interface HTMLAttributes<T = {}> { }
+    interface SVGAttributes<T = {}> { }
+    type LibraryManagedAttributes<Component, Props> = Component extends {
+        defaultProps: infer Defaults;
+    }
+        ? Defaultize<Props, Defaults>
+        : Props;
+
+    interface IntrinsicAttributes {
+        key?: any;
+    }
+
+    interface Element extends VNode<any> { }
+
+    interface ElementClass extends Component<any, any> { }
+
+    interface ElementAttributesProperty {
+        props: any;
+    }
+
+    interface ElementChildrenAttribute {
+        children: any;
+    }
+
+    interface IntrinsicElements {
+        div: HTMLAttributes;
+    }
+}
+export const Fragment: unique symbol;
+export type ComponentType<T = {}> = {};
+export type ComponentChild = {};
+export type ComponentChildren = {};
+export type VNode<T = {}> = {};
+export type Attributes = {};
+export type Component<T = {}, U = {}> = {};
+//// [index.d.ts]
+export { Fragment } from '..';
+import {
+    ComponentType,
+    ComponentChild,
+    ComponentChildren,
+    VNode,
+    Attributes
+} from '..';
+import { JSXInternal } from '..';
+
+export function jsx(
+    type: string,
+    props: JSXInternal.HTMLAttributes &
+        JSXInternal.SVGAttributes &
+        Record<string, any> & { children?: ComponentChild },
+    key?: string
+): VNode<any>;
+export function jsx<P>(
+    type: ComponentType<P>,
+    props: Attributes & P & { children?: ComponentChild },
+    key?: string
+): VNode<any>;
+
+export function jsxs(
+    type: string,
+    props: JSXInternal.HTMLAttributes &
+        JSXInternal.SVGAttributes &
+        Record<string, any> & { children?: ComponentChild[] },
+    key?: string
+): VNode<any>;
+export function jsxs<P>(
+    type: ComponentType<P>,
+    props: Attributes & P & { children?: ComponentChild[] },
+    key?: string
+): VNode<any>;
+
+export function jsxDEV(
+    type: string,
+    props: JSXInternal.HTMLAttributes &
+        JSXInternal.SVGAttributes &
+        Record<string, any> & { children?: ComponentChildren },
+    key?: string
+): VNode<any>;
+export function jsxDEV<P>(
+    type: ComponentType<P>,
+    props: Attributes & P & { children?: ComponentChildren },
+    key?: string
+): VNode<any>;
+// This shouldn't be preferred over
+//export namespace jsxDEV {
+//    export import JSX = JSXInternal;
+//}
+// but it sort-of should work and it shouldn't crash.
+declare global {
+    // @ts-ignore
+    export import JSX = JSXInternal;
+}
+//// [index.tsx]
+export const Comp = () => <div></div>;
+
+//// [index.js]
+"use strict";
+exports.__esModule = true;
+exports.Comp = void 0;
+var jsx_runtime_1 = require("preact/jsx-runtime");
+var Comp = function () { return jsx_runtime_1.jsx("div", {}, void 0); };
+exports.Comp = Comp;