From c2b11702b3aee7abd1159c06369a4864689d30be Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <293473+sandersn@users.noreply.github.com>
Date: Fri, 18 Oct 2019 09:51:21 -0700
Subject: [PATCH 1/2] Fix crash in expando assignment to alias

This PR disallows expando assignments

Fixes #34493, but disallows the prototype assignment nonetheless.
---
 src/compiler/binder.ts                        |  5 ++-
 .../importAliasModuleExports.errors.txt       | 20 ++++++++++
 .../importAliasModuleExports.symbols          | 30 ++++++++++++++
 .../reference/importAliasModuleExports.types  | 40 +++++++++++++++++++
 .../salsa/importAliasModuleExports.ts         | 15 +++++++
 5 files changed, 108 insertions(+), 2 deletions(-)
 create mode 100644 tests/baselines/reference/importAliasModuleExports.errors.txt
 create mode 100644 tests/baselines/reference/importAliasModuleExports.symbols
 create mode 100644 tests/baselines/reference/importAliasModuleExports.types
 create mode 100644 tests/cases/conformance/salsa/importAliasModuleExports.ts

diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index e3fcc4624cf57..7a2117f772b72 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -2691,7 +2691,8 @@ namespace ts {
             const flags = exportAssignmentIsAlias(node)
                 ? SymbolFlags.Alias // An export= with an EntityNameExpression or a ClassExpression exports all meanings of that identifier or class
                 : SymbolFlags.Property | SymbolFlags.ExportValue | SymbolFlags.ValueModule;
-            declareSymbol(file.symbol.exports!, file.symbol, node, flags | SymbolFlags.Assignment, SymbolFlags.None);
+            const symbol = declareSymbol(file.symbol.exports!, file.symbol, node, flags | SymbolFlags.Assignment, SymbolFlags.None);
+            setValueDeclaration(symbol, node);
         }
 
         function bindThisPropertyAssignment(node: BindablePropertyAssignmentExpression | PropertyAccessExpression | LiteralLikeElementAccessExpression) {
@@ -2870,7 +2871,7 @@ namespace ts {
                     }
                 });
             }
-            if (containerIsClass && namespaceSymbol) {
+            if (containerIsClass && namespaceSymbol && namespaceSymbol.valueDeclaration) {
                 addDeclarationToSymbol(namespaceSymbol, namespaceSymbol.valueDeclaration, SymbolFlags.Class);
             }
             return namespaceSymbol;
diff --git a/tests/baselines/reference/importAliasModuleExports.errors.txt b/tests/baselines/reference/importAliasModuleExports.errors.txt
new file mode 100644
index 0000000000000..ea3dd9ef0e018
--- /dev/null
+++ b/tests/baselines/reference/importAliasModuleExports.errors.txt
@@ -0,0 +1,20 @@
+tests/cases/conformance/salsa/main.js(2,13): error TS2339: Property 'foo' does not exist on type 'Alias'.
+tests/cases/conformance/salsa/main.js(4,9): error TS2339: Property 'foo' does not exist on type 'Alias'.
+
+
+==== tests/cases/conformance/salsa/mod1.js (0 errors) ====
+    class Alias {
+        bar() { return 1 }
+    }
+    module.exports = Alias;
+    
+==== tests/cases/conformance/salsa/main.js (2 errors) ====
+    import A from './mod1'
+    A.prototype.foo = 0
+                ~~~
+!!! error TS2339: Property 'foo' does not exist on type 'Alias'.
+    new A().bar
+    new A().foo
+            ~~~
+!!! error TS2339: Property 'foo' does not exist on type 'Alias'.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/importAliasModuleExports.symbols b/tests/baselines/reference/importAliasModuleExports.symbols
new file mode 100644
index 0000000000000..4ab081d608f8f
--- /dev/null
+++ b/tests/baselines/reference/importAliasModuleExports.symbols
@@ -0,0 +1,30 @@
+=== tests/cases/conformance/salsa/mod1.js ===
+class Alias {
+>Alias : Symbol(Alias, Decl(mod1.js, 0, 0))
+
+    bar() { return 1 }
+>bar : Symbol(Alias.bar, Decl(mod1.js, 0, 13))
+}
+module.exports = Alias;
+>module.exports : Symbol("tests/cases/conformance/salsa/mod1", Decl(mod1.js, 0, 0))
+>module : Symbol(export=, Decl(mod1.js, 2, 1))
+>exports : Symbol(export=, Decl(mod1.js, 2, 1))
+>Alias : Symbol(Alias, Decl(mod1.js, 0, 0))
+
+=== tests/cases/conformance/salsa/main.js ===
+import A from './mod1'
+>A : Symbol(A, Decl(main.js, 0, 6))
+
+A.prototype.foo = 0
+>A.prototype : Symbol(A.prototype)
+>A : Symbol(A, Decl(main.js, 0, 6))
+>prototype : Symbol(A.prototype)
+
+new A().bar
+>new A().bar : Symbol(A.bar, Decl(mod1.js, 0, 13))
+>A : Symbol(A, Decl(main.js, 0, 6))
+>bar : Symbol(A.bar, Decl(mod1.js, 0, 13))
+
+new A().foo
+>A : Symbol(A, Decl(main.js, 0, 6))
+
diff --git a/tests/baselines/reference/importAliasModuleExports.types b/tests/baselines/reference/importAliasModuleExports.types
new file mode 100644
index 0000000000000..1303ba6e8c4b4
--- /dev/null
+++ b/tests/baselines/reference/importAliasModuleExports.types
@@ -0,0 +1,40 @@
+=== tests/cases/conformance/salsa/mod1.js ===
+class Alias {
+>Alias : Alias
+
+    bar() { return 1 }
+>bar : () => number
+>1 : 1
+}
+module.exports = Alias;
+>module.exports = Alias : typeof Alias
+>module.exports : typeof Alias
+>module : { "tests/cases/conformance/salsa/mod1": typeof Alias; }
+>exports : typeof Alias
+>Alias : typeof Alias
+
+=== tests/cases/conformance/salsa/main.js ===
+import A from './mod1'
+>A : typeof A
+
+A.prototype.foo = 0
+>A.prototype.foo = 0 : 0
+>A.prototype.foo : any
+>A.prototype : A
+>A : typeof A
+>prototype : A
+>foo : any
+>0 : 0
+
+new A().bar
+>new A().bar : () => number
+>new A() : A
+>A : typeof A
+>bar : () => number
+
+new A().foo
+>new A().foo : any
+>new A() : A
+>A : typeof A
+>foo : any
+
diff --git a/tests/cases/conformance/salsa/importAliasModuleExports.ts b/tests/cases/conformance/salsa/importAliasModuleExports.ts
new file mode 100644
index 0000000000000..5e850206676a2
--- /dev/null
+++ b/tests/cases/conformance/salsa/importAliasModuleExports.ts
@@ -0,0 +1,15 @@
+// @allowJs: true
+// @checkJs: true
+// @noEmit: true
+// @esModuleInterop: true
+// @filename: mod1.js
+class Alias {
+    bar() { return 1 }
+}
+module.exports = Alias;
+
+// @filename: main.js
+import A from './mod1'
+A.prototype.foo = 0
+new A().bar
+new A().foo

From f70a8b63f55202f6bac2650c16085b55cbf10235 Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <293473+sandersn@users.noreply.github.com>
Date: Fri, 18 Oct 2019 10:35:50 -0700
Subject: [PATCH 2/2] Revert mistaken changes

---
 src/compiler/binder.ts | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index 7a2117f772b72..0b0ef4825b385 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -2691,8 +2691,7 @@ namespace ts {
             const flags = exportAssignmentIsAlias(node)
                 ? SymbolFlags.Alias // An export= with an EntityNameExpression or a ClassExpression exports all meanings of that identifier or class
                 : SymbolFlags.Property | SymbolFlags.ExportValue | SymbolFlags.ValueModule;
-            const symbol = declareSymbol(file.symbol.exports!, file.symbol, node, flags | SymbolFlags.Assignment, SymbolFlags.None);
-            setValueDeclaration(symbol, node);
+            declareSymbol(file.symbol.exports!, file.symbol, node, flags | SymbolFlags.Assignment, SymbolFlags.None);
         }
 
         function bindThisPropertyAssignment(node: BindablePropertyAssignmentExpression | PropertyAccessExpression | LiteralLikeElementAccessExpression) {