From 0106d19785ecb834a40d2458601d9da7ec3dab02 Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <293473+sandersn@users.noreply.github.com>
Date: Thu, 25 Oct 2018 09:06:48 -0700
Subject: [PATCH 1/2] Do not merge commonsjs exports onto an alias

getCommonJSExportEquals merges export assignments and export property
assignments. Something like this, which has no equivalent structure in
TS:

```js
module.exports = function() { }
module.exports.expando = 1
```

However, it is sometimes called with an alias, when its
parent, resolveExternalModuleSymbol, is called with dontResolveAlias:
true, and when the initialiser of the export assignment is an alias:

```js
function alias() { }
module.exports = alias
module.exports.expando = 1
```

In this case, (1) the actual value `alias` will have already merged in a
previous call to getCommonJSExportEquals and
(2) getTypeOfSymbol will follow the alias symbol to get the right type.
So getCommonJSExportEquals should do nothing in this case.

This bug manifests in the code for dynamic imports, which calls
getTypeOfSymbol on the incorrectly merged alias, which now has enough
value flags--Function, for example--to take the wrong branch and
subsequently crash.
---
 src/compiler/checker.ts                       |  2 +-
 .../moduleExportAliasImported.symbols         | 19 +++++++++++++++
 .../reference/moduleExportAliasImported.types | 23 +++++++++++++++++++
 .../salsa/moduleExportAliasImported.ts        | 12 ++++++++++
 4 files changed, 55 insertions(+), 1 deletion(-)
 create mode 100644 tests/baselines/reference/moduleExportAliasImported.symbols
 create mode 100644 tests/baselines/reference/moduleExportAliasImported.types
 create mode 100644 tests/cases/conformance/salsa/moduleExportAliasImported.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index fd786799b8b4c..8862960558ea4 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -2362,7 +2362,7 @@ namespace ts {
         }
 
         function getCommonJsExportEquals(exported: Symbol | undefined, moduleSymbol: Symbol): Symbol | undefined {
-            if (!exported || exported === unknownSymbol || exported === moduleSymbol || moduleSymbol.exports!.size === 1) {
+            if (!exported || exported === unknownSymbol || exported === moduleSymbol || moduleSymbol.exports!.size === 1 || exported.flags & SymbolFlags.Alias) {
                 return exported;
             }
             const merged = cloneSymbol(exported);
diff --git a/tests/baselines/reference/moduleExportAliasImported.symbols b/tests/baselines/reference/moduleExportAliasImported.symbols
new file mode 100644
index 0000000000000..9649cc0a3b64c
--- /dev/null
+++ b/tests/baselines/reference/moduleExportAliasImported.symbols
@@ -0,0 +1,19 @@
+=== tests/cases/conformance/salsa/bug28014.js ===
+exports.version = 1
+>exports.version : Symbol(version)
+>exports : Symbol(version, Decl(bug28014.js, 0, 0))
+>version : Symbol(version, Decl(bug28014.js, 0, 0))
+
+function alias() { }
+>alias : Symbol(alias, Decl(bug28014.js, 0, 19))
+
+module.exports = alias
+>module.exports : Symbol("tests/cases/conformance/salsa/bug28014", Decl(bug28014.js, 0, 0))
+>module : Symbol(export=, Decl(bug28014.js, 1, 20))
+>exports : Symbol(export=, Decl(bug28014.js, 1, 20))
+>alias : Symbol(alias, Decl(bug28014.js, 0, 19))
+
+=== tests/cases/conformance/salsa/importer.js ===
+import('./bug28014')
+>'./bug28014' : Symbol("tests/cases/conformance/salsa/bug28014", Decl(bug28014.js, 0, 0))
+
diff --git a/tests/baselines/reference/moduleExportAliasImported.types b/tests/baselines/reference/moduleExportAliasImported.types
new file mode 100644
index 0000000000000..9691acfab2254
--- /dev/null
+++ b/tests/baselines/reference/moduleExportAliasImported.types
@@ -0,0 +1,23 @@
+=== tests/cases/conformance/salsa/bug28014.js ===
+exports.version = 1
+>exports.version = 1 : 1
+>exports.version : number
+>exports : typeof alias
+>version : number
+>1 : 1
+
+function alias() { }
+>alias : typeof alias
+
+module.exports = alias
+>module.exports = alias : typeof alias
+>module.exports : typeof alias
+>module : { "tests/cases/conformance/salsa/bug28014": typeof alias; }
+>exports : typeof alias
+>alias : typeof alias
+
+=== tests/cases/conformance/salsa/importer.js ===
+import('./bug28014')
+>import('./bug28014') : Promise<() => void>
+>'./bug28014' : "./bug28014"
+
diff --git a/tests/cases/conformance/salsa/moduleExportAliasImported.ts b/tests/cases/conformance/salsa/moduleExportAliasImported.ts
new file mode 100644
index 0000000000000..95c029813828d
--- /dev/null
+++ b/tests/cases/conformance/salsa/moduleExportAliasImported.ts
@@ -0,0 +1,12 @@
+// @allowJs: true
+// @noEmit: true
+// @checkJs: true
+// @target: esnext
+// @module: esnext
+// @Filename: bug28014.js
+exports.version = 1
+function alias() { }
+module.exports = alias
+
+// @Filename: importer.js
+import('./bug28014')

From 56cbb183e8a8a012a591994c8dce9158901f49b2 Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <293473+sandersn@users.noreply.github.com>
Date: Thu, 25 Oct 2018 10:06:43 -0700
Subject: [PATCH 2/2] Update baselines

---
 .../reference/errorForConflictingExportEqualsValue.types        | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/baselines/reference/errorForConflictingExportEqualsValue.types b/tests/baselines/reference/errorForConflictingExportEqualsValue.types
index b99151691203f..5d2b63f2e9ae0 100644
--- a/tests/baselines/reference/errorForConflictingExportEqualsValue.types
+++ b/tests/baselines/reference/errorForConflictingExportEqualsValue.types
@@ -6,6 +6,6 @@ export = x;
 >x : any
 
 import("./a");
->import("./a") : Promise<typeof import("/a").x>
+>import("./a") : Promise<any>
 >"./a" : "./a"