microsoft · vladima · Nov 10, 2016 · Nov 10, 2016
diff --git a/src/compiler/program.ts b/src/compiler/program.ts
@@ -1140,9 +1140,14 @@ namespace ts {
            if (options.importHelpers
                && (options.isolatedModules || isExternalModuleFile)
                && !file.isDeclarationFile) {
-                const externalHelpersModuleReference = <StringLiteral>createNode(SyntaxKind.StringLiteral);
+                // synthesize 'import "tslib"' declaration
+                const externalHelpersModuleReference = <StringLiteral>createSynthesizedNode(SyntaxKind.StringLiteral);
                externalHelpersModuleReference.text = externalHelpersModuleNameText;
-                externalHelpersModuleReference.parent = file;
+                const importDecl = createSynthesizedNode(SyntaxKind.ImportDeclaration);
+
+                importDecl.parent = file;
+                externalHelpersModuleReference.parent = importDecl;
+
                imports = [externalHelpersModuleReference];
            }


diff --git a/src/harness/unittests/tsserverProjectSystem.ts b/src/harness/unittests/tsserverProjectSystem.ts
@@ -2576,4 +2576,21 @@ namespace ts.projectSystem {
            assert.isTrue(diags.length === 0);
        });
    });
+
+    describe("import helpers", () => {
+        it("should not crash in tsserver", () => {
+            const f1 = {
+                path: "/a/app.ts",
+                content: "export async function foo() { return 100; }"
+            };
+            const tslib = {
+                path: "/a/node_modules/tslib/index.d.ts",
+                content: ""
+            };
+            const host = createServerHost([f1, tslib]);
+            const service = createProjectService(host);
+            service.openExternalProject({ projectFileName: "p", rootFiles: [toExternalFile(f1.path)], options: { importHelpers: true } });
+            service.checkNumberOfProjects({ externalProjects: 1 });
+        });
+    });
 }