From 87ee72b25a10588ca5573c377e3fb24eeca5a096 Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Fri, 3 Jun 2016 17:31:28 -0700
Subject: [PATCH] Add regression test

---
 .../reference/classStaticPropertyTypeGuard.js | 32 +++++++++++++++++++
 .../classStaticPropertyTypeGuard.symbols      | 29 +++++++++++++++++
 .../classStaticPropertyTypeGuard.types        | 31 ++++++++++++++++++
 .../compiler/classStaticPropertyTypeGuard.ts  | 15 +++++++++
 4 files changed, 107 insertions(+)
 create mode 100644 tests/baselines/reference/classStaticPropertyTypeGuard.js
 create mode 100644 tests/baselines/reference/classStaticPropertyTypeGuard.symbols
 create mode 100644 tests/baselines/reference/classStaticPropertyTypeGuard.types
 create mode 100644 tests/cases/compiler/classStaticPropertyTypeGuard.ts

diff --git a/tests/baselines/reference/classStaticPropertyTypeGuard.js b/tests/baselines/reference/classStaticPropertyTypeGuard.js
new file mode 100644
index 00000000000..872f78db4c4
--- /dev/null
+++ b/tests/baselines/reference/classStaticPropertyTypeGuard.js
@@ -0,0 +1,32 @@
+//// [classStaticPropertyTypeGuard.ts]
+
+// Repro from #8923
+
+class A {
+    private static _a: string | undefined;
+
+    public get a(): string {
+        if (A._a) {
+            return A._a; // is possibly null or undefined.
+        }
+        return A._a = 'helloworld';
+    }
+}
+
+//// [classStaticPropertyTypeGuard.js]
+// Repro from #8923
+var A = (function () {
+    function A() {
+    }
+    Object.defineProperty(A.prototype, "a", {
+        get: function () {
+            if (A._a) {
+                return A._a; // is possibly null or undefined.
+            }
+            return A._a = 'helloworld';
+        },
+        enumerable: true,
+        configurable: true
+    });
+    return A;
+}());
diff --git a/tests/baselines/reference/classStaticPropertyTypeGuard.symbols b/tests/baselines/reference/classStaticPropertyTypeGuard.symbols
new file mode 100644
index 00000000000..c4d2acd50b0
--- /dev/null
+++ b/tests/baselines/reference/classStaticPropertyTypeGuard.symbols
@@ -0,0 +1,29 @@
+=== tests/cases/compiler/classStaticPropertyTypeGuard.ts ===
+
+// Repro from #8923
+
+class A {
+>A : Symbol(A, Decl(classStaticPropertyTypeGuard.ts, 0, 0))
+
+    private static _a: string | undefined;
+>_a : Symbol(A._a, Decl(classStaticPropertyTypeGuard.ts, 3, 9))
+
+    public get a(): string {
+>a : Symbol(A.a, Decl(classStaticPropertyTypeGuard.ts, 4, 42))
+
+        if (A._a) {
+>A._a : Symbol(A._a, Decl(classStaticPropertyTypeGuard.ts, 3, 9))
+>A : Symbol(A, Decl(classStaticPropertyTypeGuard.ts, 0, 0))
+>_a : Symbol(A._a, Decl(classStaticPropertyTypeGuard.ts, 3, 9))
+
+            return A._a; // is possibly null or undefined.
+>A._a : Symbol(A._a, Decl(classStaticPropertyTypeGuard.ts, 3, 9))
+>A : Symbol(A, Decl(classStaticPropertyTypeGuard.ts, 0, 0))
+>_a : Symbol(A._a, Decl(classStaticPropertyTypeGuard.ts, 3, 9))
+        }
+        return A._a = 'helloworld';
+>A._a : Symbol(A._a, Decl(classStaticPropertyTypeGuard.ts, 3, 9))
+>A : Symbol(A, Decl(classStaticPropertyTypeGuard.ts, 0, 0))
+>_a : Symbol(A._a, Decl(classStaticPropertyTypeGuard.ts, 3, 9))
+    }
+}
diff --git a/tests/baselines/reference/classStaticPropertyTypeGuard.types b/tests/baselines/reference/classStaticPropertyTypeGuard.types
new file mode 100644
index 00000000000..f89854c919d
--- /dev/null
+++ b/tests/baselines/reference/classStaticPropertyTypeGuard.types
@@ -0,0 +1,31 @@
+=== tests/cases/compiler/classStaticPropertyTypeGuard.ts ===
+
+// Repro from #8923
+
+class A {
+>A : A
+
+    private static _a: string | undefined;
+>_a : string | undefined
+
+    public get a(): string {
+>a : string
+
+        if (A._a) {
+>A._a : string | undefined
+>A : typeof A
+>_a : string | undefined
+
+            return A._a; // is possibly null or undefined.
+>A._a : string
+>A : typeof A
+>_a : string
+        }
+        return A._a = 'helloworld';
+>A._a = 'helloworld' : string
+>A._a : string | undefined
+>A : typeof A
+>_a : string | undefined
+>'helloworld' : string
+    }
+}
diff --git a/tests/cases/compiler/classStaticPropertyTypeGuard.ts b/tests/cases/compiler/classStaticPropertyTypeGuard.ts
new file mode 100644
index 00000000000..93655cfb092
--- /dev/null
+++ b/tests/cases/compiler/classStaticPropertyTypeGuard.ts
@@ -0,0 +1,15 @@
+// @strictNullChecks: true
+// @target: ES5
+
+// Repro from #8923
+
+class A {
+    private static _a: string | undefined;
+
+    public get a(): string {
+        if (A._a) {
+            return A._a; // is possibly null or undefined.
+        }
+        return A._a = 'helloworld';
+    }
+}
\ No newline at end of file