correctly merge const enum only and instantiated modules

src/compiler/binder.ts

@@ -322,13 +322,14 @@ module ts {
                 }
                 else {
                     bindDeclaration(node, SymbolFlags.ValueModule, SymbolFlags.ValueModuleExcludes, /*isBlockScopeContainer*/ true);
-                    if (state === ModuleInstanceState.ConstEnumOnly) {
-                        // mark value module as module that contains only enums
-                        node.symbol.constEnumOnlyModule = true;
+                    let currentModuleIsConstEnumOnly = state === ModuleInstanceState.ConstEnumOnly;
+                    if (node.symbol.constEnumOnlyModule === undefined) {
+                        // non-merged case - use the current state
+                        node.symbol.constEnumOnlyModule = currentModuleIsConstEnumOnly;
                     }
-                    else if (node.symbol.constEnumOnlyModule) {
-                        // const only value module was merged with instantiated module - reset flag
-                        node.symbol.constEnumOnlyModule = false;
+                    else {
+                        // merged case: module is const enum only if all its pieces are non-instantiated or const enum
+                        node.symbol.constEnumOnlyModule = node.symbol.constEnumOnlyModule && currentModuleIsConstEnumOnly;
                     }
                 }
             }

tests/baselines/reference/constEnumOnlyModuleMerging.js

@@ -0,0 +1,26 @@
+//// [constEnumOnlyModuleMerging.ts]
+module Outer {
+    export var x = 1;
+}
+
+module Outer {
+    export const enum A { X }
+}
+
+module B {
+    import O = Outer;
+    var x = O.A.X;
+    var y = O.x;
+}
+
+//// [constEnumOnlyModuleMerging.js]
+var Outer;
+(function (Outer) {
+    Outer.x = 1;
+})(Outer || (Outer = {}));
+var B;
+(function (B) {
+    var O = Outer;
+    var x = 0 /* X */;
+    var y = O.x;
+})(B || (B = {}));

tests/baselines/reference/constEnumOnlyModuleMerging.types

@@ -0,0 +1,37 @@
+=== tests/cases/compiler/constEnumOnlyModuleMerging.ts ===
+module Outer {
+>Outer : typeof Outer
+
+    export var x = 1;
+>x : number
+}
+
+module Outer {
+>Outer : typeof Outer
+
+    export const enum A { X }
+>A : A
+>X : A
+}
+
+module B {
+>B : typeof B
+
+    import O = Outer;
+>O : typeof O
+>Outer : typeof O
+
+    var x = O.A.X;
+>x : O.A
+>O.A.X : O.A
+>O.A : typeof O.A
+>O : typeof O
+>A : typeof O.A
+>X : O.A
+
+    var y = O.x;
+>y : number
+>O.x : number
+>O : typeof O
+>x : number
+}

tests/cases/compiler/constEnumOnlyModuleMerging.ts

@@ -0,0 +1,13 @@
+module Outer {
+    export var x = 1;
+}
+
+module Outer {
+    export const enum A { X }
+}
+
+module B {
+    import O = Outer;
+    var x = O.A.X;
+    var y = O.x;
+}