From cbce76ed13a56cc5726d4f8691f8b161f8993824 Mon Sep 17 00:00:00 2001
From: Wesley Wigham <wwigham@gmail.com>
Date: Tue, 3 Apr 2018 12:27:16 -0700
Subject: [PATCH] Consider jscontainer aliases as referencible even if they
 have other local meanings (#23119)

---
 src/compiler/checker.ts                       |  4 +++-
 .../exportDefaultMarksIdentifierAsUsed.js     | 20 +++++++++++++++++++
 ...exportDefaultMarksIdentifierAsUsed.symbols | 16 +++++++++++++++
 .../exportDefaultMarksIdentifierAsUsed.types  | 19 ++++++++++++++++++
 .../exportDefaultMarksIdentifierAsUsed.ts     | 12 +++++++++++
 5 files changed, 70 insertions(+), 1 deletion(-)
 create mode 100644 tests/baselines/reference/exportDefaultMarksIdentifierAsUsed.js
 create mode 100644 tests/baselines/reference/exportDefaultMarksIdentifierAsUsed.symbols
 create mode 100644 tests/baselines/reference/exportDefaultMarksIdentifierAsUsed.types
 create mode 100644 tests/cases/compiler/exportDefaultMarksIdentifierAsUsed.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 651736e5f64..18f0846b713 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -1933,9 +1933,11 @@ namespace ts {
 
         /**
          * Indicates that a symbol is an alias that does not merge with a local declaration.
+         * OR Is a JSContainer which may merge an alias with a local declaration
          */
         function isNonLocalAlias(symbol: Symbol, excludes = SymbolFlags.Value | SymbolFlags.Type | SymbolFlags.Namespace) {
-            return symbol && (symbol.flags & (SymbolFlags.Alias | excludes)) === SymbolFlags.Alias;
+            if (!symbol) return false;
+            return (symbol.flags & (SymbolFlags.Alias | excludes)) === SymbolFlags.Alias || (symbol.flags & SymbolFlags.Alias && symbol.flags & SymbolFlags.JSContainer);
         }
 
         function resolveSymbol(symbol: Symbol, dontResolveAlias?: boolean): Symbol {
diff --git a/tests/baselines/reference/exportDefaultMarksIdentifierAsUsed.js b/tests/baselines/reference/exportDefaultMarksIdentifierAsUsed.js
new file mode 100644
index 00000000000..5772dcfa15f
--- /dev/null
+++ b/tests/baselines/reference/exportDefaultMarksIdentifierAsUsed.js
@@ -0,0 +1,20 @@
+//// [tests/cases/compiler/exportDefaultMarksIdentifierAsUsed.ts] ////
+
+//// [a.js]
+const Obj = {};
+export default Obj;
+//// [b.js]
+import Obj from './a';
+
+Obj.fn = function() {};
+
+//// [a.js]
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+const Obj = {};
+exports.default = Obj;
+//// [b.js]
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+const a_1 = require("./a");
+a_1.default.fn = function () { };
diff --git a/tests/baselines/reference/exportDefaultMarksIdentifierAsUsed.symbols b/tests/baselines/reference/exportDefaultMarksIdentifierAsUsed.symbols
new file mode 100644
index 00000000000..ffb9643c6bb
--- /dev/null
+++ b/tests/baselines/reference/exportDefaultMarksIdentifierAsUsed.symbols
@@ -0,0 +1,16 @@
+=== tests/cases/compiler/a.js ===
+const Obj = {};
+>Obj : Symbol(Obj, Decl(a.js, 0, 5))
+
+export default Obj;
+>Obj : Symbol(Obj, Decl(a.js, 0, 5))
+
+=== tests/cases/compiler/b.js ===
+import Obj from './a';
+>Obj : Symbol(Obj, Decl(b.js, 0, 6), Decl(b.js, 0, 22))
+
+Obj.fn = function() {};
+>Obj.fn : Symbol(Obj.fn, Decl(b.js, 0, 22))
+>Obj : Symbol(Obj, Decl(b.js, 0, 6), Decl(b.js, 0, 22))
+>fn : Symbol(Obj.fn, Decl(b.js, 0, 22))
+
diff --git a/tests/baselines/reference/exportDefaultMarksIdentifierAsUsed.types b/tests/baselines/reference/exportDefaultMarksIdentifierAsUsed.types
new file mode 100644
index 00000000000..73ab0a11b21
--- /dev/null
+++ b/tests/baselines/reference/exportDefaultMarksIdentifierAsUsed.types
@@ -0,0 +1,19 @@
+=== tests/cases/compiler/a.js ===
+const Obj = {};
+>Obj : { [x: string]: any; }
+>{} : { [x: string]: any; }
+
+export default Obj;
+>Obj : { [x: string]: any; }
+
+=== tests/cases/compiler/b.js ===
+import Obj from './a';
+>Obj : typeof Obj
+
+Obj.fn = function() {};
+>Obj.fn = function() {} : () => void
+>Obj.fn : () => void
+>Obj : typeof Obj
+>fn : () => void
+>function() {} : () => void
+
diff --git a/tests/cases/compiler/exportDefaultMarksIdentifierAsUsed.ts b/tests/cases/compiler/exportDefaultMarksIdentifierAsUsed.ts
new file mode 100644
index 00000000000..f11e61ccbb7
--- /dev/null
+++ b/tests/cases/compiler/exportDefaultMarksIdentifierAsUsed.ts
@@ -0,0 +1,12 @@
+// @target: es2017
+// @module: commonjs
+// @strict: true
+// @allowJs: true
+// @outDir: /dist
+// @filename: a.js
+const Obj = {};
+export default Obj;
+// @filename: b.js
+import Obj from './a';
+
+Obj.fn = function() {};
\ No newline at end of file