From c5e680c8be31b0b7651e3ccb078d421e34a76e57 Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <nathansa@microsoft.com>
Date: Wed, 29 Jun 2016 09:12:50 -0700
Subject: [PATCH 1/2] Destructuring assignment removes undefined from type when
 default value is given

---
 src/compiler/checker.ts                         |  6 ++++++
 .../destructuringAssignmentWithDefault.js       | 11 +++++++++++
 .../destructuringAssignmentWithDefault.symbols  | 12 ++++++++++++
 .../destructuringAssignmentWithDefault.types    | 17 +++++++++++++++++
 .../destructuringAssignmentWithDefault.ts       |  4 ++++
 5 files changed, 50 insertions(+)
 create mode 100644 tests/baselines/reference/destructuringAssignmentWithDefault.js
 create mode 100644 tests/baselines/reference/destructuringAssignmentWithDefault.symbols
 create mode 100644 tests/baselines/reference/destructuringAssignmentWithDefault.types
 create mode 100644 tests/cases/compiler/destructuringAssignmentWithDefault.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 06591a7ab3d44..9ec2ec3309b57 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -12544,6 +12544,12 @@ namespace ts {
             if (exprOrAssignment.kind === SyntaxKind.ShorthandPropertyAssignment) {
                 const prop = <ShorthandPropertyAssignment>exprOrAssignment;
                 if (prop.objectAssignmentInitializer) {
+                    // In strict null checking mode, if a default value of a non-undefined type is specified, remove
+                    // undefined from the final type.
+                    if (strictNullChecks &&
+                        !(getCombinedTypeFlags(checkExpressionCached(prop.objectAssignmentInitializer)) & TypeFlags.Undefined)) {
+                        sourceType = getTypeWithFacts(sourceType, TypeFacts.NEUndefined);
+                    }
                     checkBinaryLikeExpression(prop.name, prop.equalsToken, prop.objectAssignmentInitializer, contextualMapper);
                 }
                 target = (<ShorthandPropertyAssignment>exprOrAssignment).name;
diff --git a/tests/baselines/reference/destructuringAssignmentWithDefault.js b/tests/baselines/reference/destructuringAssignmentWithDefault.js
new file mode 100644
index 0000000000000..ce3837e1162d9
--- /dev/null
+++ b/tests/baselines/reference/destructuringAssignmentWithDefault.js
@@ -0,0 +1,11 @@
+//// [destructuringAssignmentWithDefault.ts]
+const a: { x?: number } = { };
+let x = 0;
+({x = 1} = a);
+
+
+//// [destructuringAssignmentWithDefault.js]
+var a = {};
+var x = 0;
+(_a = a.x, x = _a === void 0 ? 1 : _a, a);
+var _a;
diff --git a/tests/baselines/reference/destructuringAssignmentWithDefault.symbols b/tests/baselines/reference/destructuringAssignmentWithDefault.symbols
new file mode 100644
index 0000000000000..b011834c4f09f
--- /dev/null
+++ b/tests/baselines/reference/destructuringAssignmentWithDefault.symbols
@@ -0,0 +1,12 @@
+=== tests/cases/compiler/destructuringAssignmentWithDefault.ts ===
+const a: { x?: number } = { };
+>a : Symbol(a, Decl(destructuringAssignmentWithDefault.ts, 0, 5))
+>x : Symbol(x, Decl(destructuringAssignmentWithDefault.ts, 0, 10))
+
+let x = 0;
+>x : Symbol(x, Decl(destructuringAssignmentWithDefault.ts, 1, 3))
+
+({x = 1} = a);
+>x : Symbol(x, Decl(destructuringAssignmentWithDefault.ts, 2, 2))
+>a : Symbol(a, Decl(destructuringAssignmentWithDefault.ts, 0, 5))
+
diff --git a/tests/baselines/reference/destructuringAssignmentWithDefault.types b/tests/baselines/reference/destructuringAssignmentWithDefault.types
new file mode 100644
index 0000000000000..1dc1fe2353343
--- /dev/null
+++ b/tests/baselines/reference/destructuringAssignmentWithDefault.types
@@ -0,0 +1,17 @@
+=== tests/cases/compiler/destructuringAssignmentWithDefault.ts ===
+const a: { x?: number } = { };
+>a : { x?: number | undefined; }
+>x : number | undefined
+>{ } : {}
+
+let x = 0;
+>x : number
+>0 : number
+
+({x = 1} = a);
+>({x = 1} = a) : { x?: number | undefined; }
+>{x = 1} = a : { x?: number | undefined; }
+>{x = 1} : { x?: number; }
+>x : number
+>a : { x?: number | undefined; }
+
diff --git a/tests/cases/compiler/destructuringAssignmentWithDefault.ts b/tests/cases/compiler/destructuringAssignmentWithDefault.ts
new file mode 100644
index 0000000000000..45ade402eb846
--- /dev/null
+++ b/tests/cases/compiler/destructuringAssignmentWithDefault.ts
@@ -0,0 +1,4 @@
+// @strictNullChecks: true
+const a: { x?: number } = { };
+let x = 0;
+({x = 1} = a);

From 5f6e25c8d2994694cefc907e50d7ba19f1e07722 Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <nathansa@microsoft.com>
Date: Wed, 29 Jun 2016 18:47:10 -0700
Subject: [PATCH 2/2] Use checkExpression, not checkExpressionCached

---
 src/compiler/checker.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 9ec2ec3309b57..0aad4f6196057 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -12547,7 +12547,7 @@ namespace ts {
                     // In strict null checking mode, if a default value of a non-undefined type is specified, remove
                     // undefined from the final type.
                     if (strictNullChecks &&
-                        !(getCombinedTypeFlags(checkExpressionCached(prop.objectAssignmentInitializer)) & TypeFlags.Undefined)) {
+                        !(getCombinedTypeFlags(checkExpression(prop.objectAssignmentInitializer)) & TypeFlags.Undefined)) {
                         sourceType = getTypeWithFacts(sourceType, TypeFacts.NEUndefined);
                     }
                     checkBinaryLikeExpression(prop.name, prop.equalsToken, prop.objectAssignmentInitializer, contextualMapper);