Merge pull request #6563 from Microsoft/reExportUndefined

handle undefined entry as export specifier

src/compiler/checker.ts

@@ -14476,7 +14476,7 @@ namespace ts {
                 // find immediate value referenced by exported name (SymbolFlags.Alias is set so we don't chase down aliases)
                 const symbol = resolveName(exportedName, exportedName.text, SymbolFlags.Value | SymbolFlags.Type | SymbolFlags.Namespace | SymbolFlags.Alias,
                     /*nameNotFoundMessage*/ undefined, /*nameArg*/ undefined);
-                if (symbol && isGlobalSourceFile(getDeclarationContainer(symbol.declarations[0]))) {
+                if (symbol && (symbol === undefinedSymbol || isGlobalSourceFile(getDeclarationContainer(symbol.declarations[0])))) {
                     error(exportedName, Diagnostics.Cannot_re_export_name_that_is_not_defined_in_the_module);
                 }
                 else {

tests/baselines/reference/reExportUndefined1.errors.txt

@@ -0,0 +1,8 @@
+tests/cases/compiler/a.ts(2,10): error TS2661: Cannot re-export name that is not defined in the module.
+
+
+==== tests/cases/compiler/a.ts (1 errors) ====
+    
+    export { undefined };
+             ~~~~~~~~~
+!!! error TS2661: Cannot re-export name that is not defined in the module.

tests/baselines/reference/reExportUndefined1.js

@@ -0,0 +1,6 @@
+//// [a.ts]
+
+export { undefined };
+
+//// [a.js]
+"use strict";

tests/baselines/reference/reExportUndefined2.js

@@ -0,0 +1,20 @@
+//// [tests/cases/compiler/reExportUndefined2.ts] ////
+
+//// [a.ts]
+
+var undefined;
+export { undefined };
+
+//// [b.ts]
+import { undefined } from "./a";
+declare function use(a: number);
+use(undefined);
+
+//// [a.js]
+"use strict";
+var undefined;
+exports.undefined = undefined;
+//// [b.js]
+"use strict";
+var a_1 = require("./a");
+use(a_1.undefined);

tests/baselines/reference/reExportUndefined2.symbols

@@ -0,0 +1,20 @@
+=== tests/cases/compiler/a.ts ===
+
+var undefined;
+>undefined : Symbol(undefined, Decl(a.ts, 1, 3))
+
+export { undefined };
+>undefined : Symbol(undefined, Decl(a.ts, 2, 8))
+
+=== tests/cases/compiler/b.ts ===
+import { undefined } from "./a";
+>undefined : Symbol(undefined, Decl(b.ts, 0, 8))
+
+declare function use(a: number);
+>use : Symbol(use, Decl(b.ts, 0, 32))
+>a : Symbol(a, Decl(b.ts, 1, 21))
+
+use(undefined);
+>use : Symbol(use, Decl(b.ts, 0, 32))
+>undefined : Symbol(undefined, Decl(b.ts, 0, 8))
+

tests/baselines/reference/reExportUndefined2.types

@@ -0,0 +1,21 @@
+=== tests/cases/compiler/a.ts ===
+
+var undefined;
+>undefined : any
+
+export { undefined };
+>undefined : any
+
+=== tests/cases/compiler/b.ts ===
+import { undefined } from "./a";
+>undefined : any
+
+declare function use(a: number);
+>use : (a: number) => any
+>a : number
+
+use(undefined);
+>use(undefined) : any
+>use : (a: number) => any
+>undefined : any
+

tests/cases/compiler/reExportUndefined1.ts

@@ -0,0 +1,4 @@
+// @module: commonjs
+
+// @filename: a.ts
+export { undefined };

tests/cases/compiler/reExportUndefined2.ts

@@ -0,0 +1,10 @@
+// @module: commonjs
+
+// @filename: a.ts
+var undefined;
+export { undefined };
+
+// @filename: b.ts
+import { undefined } from "./a";
+declare function use(a: number);
+use(undefined);