Allow export declarations in ambient namespaces

src/compiler/checker.ts

@@ -19372,7 +19372,9 @@ namespace ts {
                     forEach(node.exportClause.elements, checkExportSpecifier);
 
                     const inAmbientExternalModule = node.parent.kind === SyntaxKind.ModuleBlock && isAmbientModule(node.parent.parent);
-                    if (node.parent.kind !== SyntaxKind.SourceFile && !inAmbientExternalModule) {
+                    const inAmbientNamespaceDeclaration = !inAmbientExternalModule && node.parent.kind === SyntaxKind.ModuleBlock &&
+                        !node.moduleSpecifier && isInAmbientContext(node);
+                    if (node.parent.kind !== SyntaxKind.SourceFile && !inAmbientExternalModule && !inAmbientNamespaceDeclaration) {
                         error(node, Diagnostics.Export_declarations_are_not_permitted_in_a_namespace);
                     }
                 }

tests/baselines/reference/exportDeclarationsInAmbientNamespaces.js

@@ -0,0 +1,13 @@
+//// [exportDeclarationsInAmbientNamespaces.ts]
+
+declare namespace Q {
+    function _try(method: Function, ...args: any[]): any;
+    export { _try as try };
+}
+
+Q.try(() => { });
+
+
+
+//// [exportDeclarationsInAmbientNamespaces.js]
+Q["try"](function () { });

tests/baselines/reference/exportDeclarationsInAmbientNamespaces.symbols

@@ -0,0 +1,22 @@
+=== tests/cases/compiler/exportDeclarationsInAmbientNamespaces.ts ===
+
+declare namespace Q {
+>Q : Symbol(Q, Decl(exportDeclarationsInAmbientNamespaces.ts, 0, 0))
+
+    function _try(method: Function, ...args: any[]): any;
+>_try : Symbol(_try, Decl(exportDeclarationsInAmbientNamespaces.ts, 1, 21))
+>method : Symbol(method, Decl(exportDeclarationsInAmbientNamespaces.ts, 2, 18))
+>Function : Symbol(Function, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>args : Symbol(args, Decl(exportDeclarationsInAmbientNamespaces.ts, 2, 35))
+
+    export { _try as try };
+>_try : Symbol(try, Decl(exportDeclarationsInAmbientNamespaces.ts, 3, 12))
+>try : Symbol(try, Decl(exportDeclarationsInAmbientNamespaces.ts, 3, 12))
+}
+
+Q.try(() => { });
+>Q.try : Symbol(Q.try, Decl(exportDeclarationsInAmbientNamespaces.ts, 3, 12))
+>Q : Symbol(Q, Decl(exportDeclarationsInAmbientNamespaces.ts, 0, 0))
+>try : Symbol(Q.try, Decl(exportDeclarationsInAmbientNamespaces.ts, 3, 12))
+
+

tests/baselines/reference/exportDeclarationsInAmbientNamespaces.types

@@ -0,0 +1,24 @@
+=== tests/cases/compiler/exportDeclarationsInAmbientNamespaces.ts ===
+
+declare namespace Q {
+>Q : typeof Q
+
+    function _try(method: Function, ...args: any[]): any;
+>_try : (method: Function, ...args: any[]) => any
+>method : Function
+>Function : Function
+>args : any[]
+
+    export { _try as try };
+>_try : (method: Function, ...args: any[]) => any
+>try : (method: Function, ...args: any[]) => any
+}
+
+Q.try(() => { });
+>Q.try(() => { }) : any
+>Q.try : (method: Function, ...args: any[]) => any
+>Q : typeof Q
+>try : (method: Function, ...args: any[]) => any
+>() => { } : () => void
+
+

tests/baselines/reference/exportDeclarationsInAmbientNamespaces2.errors.txt

@@ -0,0 +1,16 @@
+tests/cases/compiler/exportDeclarationsInAmbientNamespaces2.ts(7,23): error TS1194: Export declarations are not permitted in a namespace.
+
+
+==== tests/cases/compiler/exportDeclarationsInAmbientNamespaces2.ts (1 errors) ====
+
+    declare module "mod" {
+        export var x: number;
+    }
+
+    declare namespace N {
+        export { x } from "mod"; // Error
+                          ~~~~~
+!!! error TS1194: Export declarations are not permitted in a namespace.
+    }
+
+

tests/baselines/reference/exportDeclarationsInAmbientNamespaces2.js

@@ -0,0 +1,13 @@
+//// [exportDeclarationsInAmbientNamespaces2.ts]
+
+declare module "mod" {
+    export var x: number;
+}
+
+declare namespace N {
+    export { x } from "mod"; // Error
+}
+
+
+
+//// [exportDeclarationsInAmbientNamespaces2.js]

tests/cases/compiler/exportDeclarationsInAmbientNamespaces.ts

@@ -0,0 +1,8 @@
+
+declare namespace Q {
+    function _try(method: Function, ...args: any[]): any;
+    export { _try as try };
+}
+
+Q.try(() => { });
+

tests/cases/compiler/exportDeclarationsInAmbientNamespaces2.ts

@@ -0,0 +1,9 @@
+
+declare module "mod" {
+    export var x: number;
+}
+
+declare namespace N {
+    export { x } from "mod"; // Error
+}
+