Avoid a crash with @typedef in a script file.

Scripts (as opposed to modules) do not have a symbol object. If a script
contains a `@typdef` defined on a namespace called `exports`, TypeScript
crashes because it attempts to create an exported symbol on the
(non-existent) symbol of the SourceFile.

This change avoids the crash by explicitly checking if the source file
has a symbol object, i.e. whether it is a module.

src/compiler/binder.ts

@@ -564,7 +564,7 @@ namespace ts {
                 //       and this case is specially handled. Module augmentations should only be merged with original module definition
                 //       and should never be merged directly with other augmentation, and the latter case would be possible if automatic merge is allowed.
                 if (isJSDocTypeAlias(node)) Debug.assert(isInJSFile(node)); // We shouldn't add symbols for JSDoc nodes if not in a JS file.
-                if ((!isAmbientModule(node) && (hasExportModifier || container.flags & NodeFlags.ExportContext)) || isJSDocTypeAlias(node)) {
+                if ((!isAmbientModule(node) && (hasExportModifier || container.flags & NodeFlags.ExportContext)) || (isJSDocTypeAlias(node) && container.symbol)) {
                     if (!container.locals || (hasModifier(node, ModifierFlags.Default) && !getDeclarationName(node))) {
                         return declareSymbol(container.symbol.exports!, container.symbol, node, symbolFlags, symbolExcludes); // No local symbol for an unnamed default!
                     }

tests/baselines/reference/checkJsdocTypedefOnlySourceFile.js

@@ -0,0 +1,18 @@
+//// [0.js]
+// @ts-check
+
+var exports = {};
+
+/**
+ * @typedef {string}
+ */
+exports.SomeName;
+
+
+//// [0.js]
+// @ts-check
+var exports = {};
+/**
+ * @typedef {string}
+ */
+exports.SomeName;

tests/baselines/reference/checkJsdocTypedefOnlySourceFile.symbols

@@ -0,0 +1,12 @@
+=== tests/cases/conformance/jsdoc/0.js ===
+// @ts-check
+
+var exports = {};
+>exports : Symbol(exports, Decl(0.js, 2, 3))
+
+/**
+ * @typedef {string}
+ */
+exports.SomeName;
+>exports : Symbol(exports, Decl(0.js, 2, 3))
+

tests/baselines/reference/checkJsdocTypedefOnlySourceFile.types

@@ -0,0 +1,15 @@
+=== tests/cases/conformance/jsdoc/0.js ===
+// @ts-check
+
+var exports = {};
+>exports : {}
+>{} : {}
+
+/**
+ * @typedef {string}
+ */
+exports.SomeName;
+>exports.SomeName : any
+>exports : {}
+>SomeName : any
+

tests/cases/conformance/jsdoc/checkJsdocTypedefOnlySourceFile.ts

@@ -0,0 +1,12 @@
+// @allowJS: true
+// @suppressOutputPathCheck: true
+
+// @filename: 0.js
+// @ts-check
+
+var exports = {};
+
+/**
+ * @typedef {string}
+ */
+exports.SomeName;