From 18e1ac030613bd15a55156bd95e16b5002e99ffd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stephan=20Ginth=C3=B6r?=
 <26004708+Lazarus535@users.noreply.github.com>
Date: Mon, 22 Jan 2018 09:52:58 +0100
Subject: [PATCH 1/4] Fixes #17080

Changes are in src/compiler.checker.ts only
The second arguments to the function "removeOptionalityFromDeclaredType" has been changed from "getRootDeclaration(declaration)" to "declaration".
---
 pull_request_template.md                      |   9 +-
 src/compiler/checker.ts                       |   2 +-
 ...rInDestructuringWithInitializer.errors.txt |  62 ++++++
 ...ParameterInDestructuringWithInitializer.js |  80 +++++++
 ...eterInDestructuringWithInitializer.symbols | 154 ++++++++++++++
 ...ameterInDestructuringWithInitializer.types | 198 ++++++++++++++++++
 ...ParameterInDestructuringWithInitializer.ts |  39 ++++
 7 files changed, 539 insertions(+), 5 deletions(-)
 create mode 100644 tests/baselines/reference/optionalParameterInDestructuringWithInitializer.errors.txt
 create mode 100644 tests/baselines/reference/optionalParameterInDestructuringWithInitializer.js
 create mode 100644 tests/baselines/reference/optionalParameterInDestructuringWithInitializer.symbols
 create mode 100644 tests/baselines/reference/optionalParameterInDestructuringWithInitializer.types
 create mode 100644 tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts

diff --git a/pull_request_template.md b/pull_request_template.md
index 2c49c84641b..faa484054be 100644
--- a/pull_request_template.md
+++ b/pull_request_template.md
@@ -2,15 +2,16 @@
 Thank you for submitting a pull request!
 
 Here's a checklist you might find useful.
-[ ] There is an associated issue that is labelled
+[X] There is an associated issue that is labelled
   'Bug' or 'help wanted' or is in the Community milestone
-[ ] Code is up-to-date with the `master` branch
-[ ] You've successfully run `jake runtests` locally
+[X] Code is up-to-date with the `master` branch
+[X] You've successfully run `jake runtests` locally
 [ ] You've signed the CLA
-[ ] There are new or updated unit tests validating the change
+[X] There are new or updated unit tests validating the change
 
 Refer to CONTRIBUTING.MD for more details.
   https://github.com/Microsoft/TypeScript/blob/master/CONTRIBUTING.md
 -->
 
 Fixes #
+#17080
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 405fd11f138..74c60bcdb62 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -13046,7 +13046,7 @@ namespace ts {
                 node.parent.kind === SyntaxKind.NonNullExpression ||
                 declaration.kind === SyntaxKind.VariableDeclaration && (<VariableDeclaration>declaration).exclamationToken ||
                 declaration.flags & NodeFlags.Ambient;
-            const initialType = assumeInitialized ? (isParameter ? removeOptionalityFromDeclaredType(type, getRootDeclaration(declaration) as VariableLikeDeclaration) : type) :
+            const initialType = assumeInitialized ? (isParameter ? removeOptionalityFromDeclaredType(type, declaration as VariableLikeDeclaration) : type) :
                 type === autoType || type === autoArrayType ? undefinedType :
                     getOptionalType(type);
             const flowType = getFlowTypeOfReference(node, type, initialType, flowContainer, !assumeInitialized);
diff --git a/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.errors.txt b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.errors.txt
new file mode 100644
index 00000000000..14bc3ea8e6c
--- /dev/null
+++ b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.errors.txt
@@ -0,0 +1,62 @@
+tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts(6,8): error TS2345: Argument of type 'number | undefined' is not assignable to parameter of type 'number'.
+  Type 'undefined' is not assignable to type 'number'.
+tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts(16,7): error TS2345: Argument of type 'number | undefined' is not assignable to parameter of type 'number'.
+  Type 'undefined' is not assignable to type 'number'.
+tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts(21,7): error TS2345: Argument of type 'number | undefined' is not assignable to parameter of type 'number'.
+  Type 'undefined' is not assignable to type 'number'.
+tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts(31,8): error TS2345: Argument of type 'number | undefined' is not assignable to parameter of type 'number'.
+  Type 'undefined' is not assignable to type 'number'.
+
+
+==== tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts (4 errors) ====
+    // https://github.com/Microsoft/TypeScript/issues/17080
+    function f(a:number,b:number) {
+    }
+    
+    function func1( {a, b}: {a: number, b?: number} = {a: 1, b: 2} ) {
+      f(a, b)
+           ~
+!!! error TS2345: Argument of type 'number | undefined' is not assignable to parameter of type 'number'.
+!!! error TS2345:   Type 'undefined' is not assignable to type 'number'.
+      // error
+    }
+    
+    function func2( {a, b = 3}: {a: number, b?:number} = {a: 1,b: 2} ) {
+      f(a, b)
+      // no error
+    }
+    
+    function func3( {a, b}: {a: number, b?: number} = {a: 1} ) {
+      f(a,b)
+          ~
+!!! error TS2345: Argument of type 'number | undefined' is not assignable to parameter of type 'number'.
+!!! error TS2345:   Type 'undefined' is not assignable to type 'number'.
+      // error
+    }
+    
+    function func4( {a: {b, c}, d}: {a: {b: number,c?: number},d: number} = {a: {b: 1,c: 2},d: 3} ) {
+      f(b,c)
+          ~
+!!! error TS2345: Argument of type 'number | undefined' is not assignable to parameter of type 'number'.
+!!! error TS2345:   Type 'undefined' is not assignable to type 'number'.
+      // error
+    }
+    
+    function func5({a: {b, c = 4}, d}: {a: {b: number,c?: number},d: number} = {a: {b: 1,c: 2},d: 3} ) {
+      f(b, c)
+      // no error
+    }
+    
+    function func6( {a: {b, c} = {b: 4, c: 5}, d}: {a: {b: number, c?: number}, d: number} = {a: {b: 1,c: 2}, d: 3} ) {
+      f(b, c)
+           ~
+!!! error TS2345: Argument of type 'number | undefined' is not assignable to parameter of type 'number'.
+!!! error TS2345:   Type 'undefined' is not assignable to type 'number'.
+      // error
+    }
+    
+    function func7( {a: {b, c = 6} = {b: 4, c: 5}, d}: {a: {b: number, c?: number}, d: number} = {a: {b: 1, c: 2}, d: 3} ) {
+      f(b, c)
+      // no error
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.js b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.js
new file mode 100644
index 00000000000..8c297088f14
--- /dev/null
+++ b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.js
@@ -0,0 +1,80 @@
+//// [optionalParameterInDestructuringWithInitializer.ts]
+// https://github.com/Microsoft/TypeScript/issues/17080
+function f(a:number,b:number) {
+}
+
+function func1( {a, b}: {a: number, b?: number} = {a: 1, b: 2} ) {
+  f(a, b)
+  // error
+}
+
+function func2( {a, b = 3}: {a: number, b?:number} = {a: 1,b: 2} ) {
+  f(a, b)
+  // no error
+}
+
+function func3( {a, b}: {a: number, b?: number} = {a: 1} ) {
+  f(a,b)
+  // error
+}
+
+function func4( {a: {b, c}, d}: {a: {b: number,c?: number},d: number} = {a: {b: 1,c: 2},d: 3} ) {
+  f(b,c)
+  // error
+}
+
+function func5({a: {b, c = 4}, d}: {a: {b: number,c?: number},d: number} = {a: {b: 1,c: 2},d: 3} ) {
+  f(b, c)
+  // no error
+}
+
+function func6( {a: {b, c} = {b: 4, c: 5}, d}: {a: {b: number, c?: number}, d: number} = {a: {b: 1,c: 2}, d: 3} ) {
+  f(b, c)
+  // error
+}
+
+function func7( {a: {b, c = 6} = {b: 4, c: 5}, d}: {a: {b: number, c?: number}, d: number} = {a: {b: 1, c: 2}, d: 3} ) {
+  f(b, c)
+  // no error
+}
+
+
+//// [optionalParameterInDestructuringWithInitializer.js]
+// https://github.com/Microsoft/TypeScript/issues/17080
+function f(a, b) {
+}
+function func1(_a) {
+    var _b = _a === void 0 ? { a: 1, b: 2 } : _a, a = _b.a, b = _b.b;
+    f(a, b);
+    // error
+}
+function func2(_a) {
+    var _b = _a === void 0 ? { a: 1, b: 2 } : _a, a = _b.a, _c = _b.b, b = _c === void 0 ? 3 : _c;
+    f(a, b);
+    // no error
+}
+function func3(_a) {
+    var _b = _a === void 0 ? { a: 1 } : _a, a = _b.a, b = _b.b;
+    f(a, b);
+    // error
+}
+function func4(_a) {
+    var _b = _a === void 0 ? { a: { b: 1, c: 2 }, d: 3 } : _a, _c = _b.a, b = _c.b, c = _c.c, d = _b.d;
+    f(b, c);
+    // error
+}
+function func5(_a) {
+    var _b = _a === void 0 ? { a: { b: 1, c: 2 }, d: 3 } : _a, _c = _b.a, b = _c.b, _d = _c.c, c = _d === void 0 ? 4 : _d, d = _b.d;
+    f(b, c);
+    // no error
+}
+function func6(_a) {
+    var _b = _a === void 0 ? { a: { b: 1, c: 2 }, d: 3 } : _a, _c = _b.a, _d = _c === void 0 ? { b: 4, c: 5 } : _c, b = _d.b, c = _d.c, d = _b.d;
+    f(b, c);
+    // error
+}
+function func7(_a) {
+    var _b = _a === void 0 ? { a: { b: 1, c: 2 }, d: 3 } : _a, _c = _b.a, _d = _c === void 0 ? { b: 4, c: 5 } : _c, b = _d.b, _e = _d.c, c = _e === void 0 ? 6 : _e, d = _b.d;
+    f(b, c);
+    // no error
+}
diff --git a/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.symbols b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.symbols
new file mode 100644
index 00000000000..fc068a0babb
--- /dev/null
+++ b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.symbols
@@ -0,0 +1,154 @@
+=== tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts ===
+// https://github.com/Microsoft/TypeScript/issues/17080
+function f(a:number,b:number) {
+>f : Symbol(f, Decl(optionalParameterInDestructuringWithInitializer.ts, 0, 0))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 1, 11))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 1, 20))
+}
+
+function func1( {a, b}: {a: number, b?: number} = {a: 1, b: 2} ) {
+>func1 : Symbol(func1, Decl(optionalParameterInDestructuringWithInitializer.ts, 2, 1))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 4, 17))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 4, 19))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 4, 25))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 4, 35))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 4, 51))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 4, 56))
+
+  f(a, b)
+>f : Symbol(f, Decl(optionalParameterInDestructuringWithInitializer.ts, 0, 0))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 4, 17))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 4, 19))
+
+  // error
+}
+
+function func2( {a, b = 3}: {a: number, b?:number} = {a: 1,b: 2} ) {
+>func2 : Symbol(func2, Decl(optionalParameterInDestructuringWithInitializer.ts, 7, 1))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 9, 17))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 9, 19))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 9, 29))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 9, 39))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 9, 54))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 9, 59))
+
+  f(a, b)
+>f : Symbol(f, Decl(optionalParameterInDestructuringWithInitializer.ts, 0, 0))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 9, 17))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 9, 19))
+
+  // no error
+}
+
+function func3( {a, b}: {a: number, b?: number} = {a: 1} ) {
+>func3 : Symbol(func3, Decl(optionalParameterInDestructuringWithInitializer.ts, 12, 1))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 14, 17))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 14, 19))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 14, 25))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 14, 35))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 14, 51))
+
+  f(a,b)
+>f : Symbol(f, Decl(optionalParameterInDestructuringWithInitializer.ts, 0, 0))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 14, 17))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 14, 19))
+
+  // error
+}
+
+function func4( {a: {b, c}, d}: {a: {b: number,c?: number},d: number} = {a: {b: 1,c: 2},d: 3} ) {
+>func4 : Symbol(func4, Decl(optionalParameterInDestructuringWithInitializer.ts, 17, 1))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 19, 33))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 19, 21))
+>c : Symbol(c, Decl(optionalParameterInDestructuringWithInitializer.ts, 19, 23))
+>d : Symbol(d, Decl(optionalParameterInDestructuringWithInitializer.ts, 19, 27))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 19, 33))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 19, 37))
+>c : Symbol(c, Decl(optionalParameterInDestructuringWithInitializer.ts, 19, 47))
+>d : Symbol(d, Decl(optionalParameterInDestructuringWithInitializer.ts, 19, 59))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 19, 73))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 19, 77))
+>c : Symbol(c, Decl(optionalParameterInDestructuringWithInitializer.ts, 19, 82))
+>d : Symbol(d, Decl(optionalParameterInDestructuringWithInitializer.ts, 19, 88))
+
+  f(b,c)
+>f : Symbol(f, Decl(optionalParameterInDestructuringWithInitializer.ts, 0, 0))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 19, 21))
+>c : Symbol(c, Decl(optionalParameterInDestructuringWithInitializer.ts, 19, 23))
+
+  // error
+}
+
+function func5({a: {b, c = 4}, d}: {a: {b: number,c?: number},d: number} = {a: {b: 1,c: 2},d: 3} ) {
+>func5 : Symbol(func5, Decl(optionalParameterInDestructuringWithInitializer.ts, 22, 1))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 24, 36))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 24, 20))
+>c : Symbol(c, Decl(optionalParameterInDestructuringWithInitializer.ts, 24, 22))
+>d : Symbol(d, Decl(optionalParameterInDestructuringWithInitializer.ts, 24, 30))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 24, 36))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 24, 40))
+>c : Symbol(c, Decl(optionalParameterInDestructuringWithInitializer.ts, 24, 50))
+>d : Symbol(d, Decl(optionalParameterInDestructuringWithInitializer.ts, 24, 62))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 24, 76))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 24, 80))
+>c : Symbol(c, Decl(optionalParameterInDestructuringWithInitializer.ts, 24, 85))
+>d : Symbol(d, Decl(optionalParameterInDestructuringWithInitializer.ts, 24, 91))
+
+  f(b, c)
+>f : Symbol(f, Decl(optionalParameterInDestructuringWithInitializer.ts, 0, 0))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 24, 20))
+>c : Symbol(c, Decl(optionalParameterInDestructuringWithInitializer.ts, 24, 22))
+
+  // no error
+}
+
+function func6( {a: {b, c} = {b: 4, c: 5}, d}: {a: {b: number, c?: number}, d: number} = {a: {b: 1,c: 2}, d: 3} ) {
+>func6 : Symbol(func6, Decl(optionalParameterInDestructuringWithInitializer.ts, 27, 1))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 29, 48))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 29, 21))
+>c : Symbol(c, Decl(optionalParameterInDestructuringWithInitializer.ts, 29, 23))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 29, 30))
+>c : Symbol(c, Decl(optionalParameterInDestructuringWithInitializer.ts, 29, 35))
+>d : Symbol(d, Decl(optionalParameterInDestructuringWithInitializer.ts, 29, 42))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 29, 48))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 29, 52))
+>c : Symbol(c, Decl(optionalParameterInDestructuringWithInitializer.ts, 29, 62))
+>d : Symbol(d, Decl(optionalParameterInDestructuringWithInitializer.ts, 29, 75))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 29, 90))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 29, 94))
+>c : Symbol(c, Decl(optionalParameterInDestructuringWithInitializer.ts, 29, 99))
+>d : Symbol(d, Decl(optionalParameterInDestructuringWithInitializer.ts, 29, 105))
+
+  f(b, c)
+>f : Symbol(f, Decl(optionalParameterInDestructuringWithInitializer.ts, 0, 0))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 29, 21))
+>c : Symbol(c, Decl(optionalParameterInDestructuringWithInitializer.ts, 29, 23))
+
+  // error
+}
+
+function func7( {a: {b, c = 6} = {b: 4, c: 5}, d}: {a: {b: number, c?: number}, d: number} = {a: {b: 1, c: 2}, d: 3} ) {
+>func7 : Symbol(func7, Decl(optionalParameterInDestructuringWithInitializer.ts, 32, 1))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 34, 52))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 34, 21))
+>c : Symbol(c, Decl(optionalParameterInDestructuringWithInitializer.ts, 34, 23))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 34, 34))
+>c : Symbol(c, Decl(optionalParameterInDestructuringWithInitializer.ts, 34, 39))
+>d : Symbol(d, Decl(optionalParameterInDestructuringWithInitializer.ts, 34, 46))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 34, 52))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 34, 56))
+>c : Symbol(c, Decl(optionalParameterInDestructuringWithInitializer.ts, 34, 66))
+>d : Symbol(d, Decl(optionalParameterInDestructuringWithInitializer.ts, 34, 79))
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 34, 94))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 34, 98))
+>c : Symbol(c, Decl(optionalParameterInDestructuringWithInitializer.ts, 34, 103))
+>d : Symbol(d, Decl(optionalParameterInDestructuringWithInitializer.ts, 34, 110))
+
+  f(b, c)
+>f : Symbol(f, Decl(optionalParameterInDestructuringWithInitializer.ts, 0, 0))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 34, 21))
+>c : Symbol(c, Decl(optionalParameterInDestructuringWithInitializer.ts, 34, 23))
+
+  // no error
+}
+
diff --git a/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.types b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.types
new file mode 100644
index 00000000000..8def19dde20
--- /dev/null
+++ b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.types
@@ -0,0 +1,198 @@
+=== tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts ===
+// https://github.com/Microsoft/TypeScript/issues/17080
+function f(a:number,b:number) {
+>f : (a: number, b: number) => void
+>a : number
+>b : number
+}
+
+function func1( {a, b}: {a: number, b?: number} = {a: 1, b: 2} ) {
+>func1 : ({ a, b }?: { a: number; b?: number | undefined; }) => void
+>a : number
+>b : number | undefined
+>a : number
+>b : number | undefined
+>{a: 1, b: 2} : { a: number; b: number; }
+>a : number
+>1 : 1
+>b : number
+>2 : 2
+
+  f(a, b)
+>f(a, b) : void
+>f : (a: number, b: number) => void
+>a : number
+>b : number | undefined
+
+  // error
+}
+
+function func2( {a, b = 3}: {a: number, b?:number} = {a: 1,b: 2} ) {
+>func2 : ({ a, b }?: { a: number; b?: number | undefined; }) => void
+>a : number
+>b : number
+>3 : 3
+>a : number
+>b : number | undefined
+>{a: 1,b: 2} : { a: number; b: number; }
+>a : number
+>1 : 1
+>b : number
+>2 : 2
+
+  f(a, b)
+>f(a, b) : void
+>f : (a: number, b: number) => void
+>a : number
+>b : number
+
+  // no error
+}
+
+function func3( {a, b}: {a: number, b?: number} = {a: 1} ) {
+>func3 : ({ a, b }?: { a: number; b?: number | undefined; }) => void
+>a : number
+>b : number | undefined
+>a : number
+>b : number | undefined
+>{a: 1} : { a: number; }
+>a : number
+>1 : 1
+
+  f(a,b)
+>f(a,b) : void
+>f : (a: number, b: number) => void
+>a : number
+>b : number | undefined
+
+  // error
+}
+
+function func4( {a: {b, c}, d}: {a: {b: number,c?: number},d: number} = {a: {b: 1,c: 2},d: 3} ) {
+>func4 : ({ a: { b, c }, d }?: { a: { b: number; c?: number | undefined; }; d: number; }) => void
+>a : any
+>b : number
+>c : number | undefined
+>d : number
+>a : { b: number; c?: number | undefined; }
+>b : number
+>c : number | undefined
+>d : number
+>{a: {b: 1,c: 2},d: 3} : { a: { b: number; c: number; }; d: number; }
+>a : { b: number; c: number; }
+>{b: 1,c: 2} : { b: number; c: number; }
+>b : number
+>1 : 1
+>c : number
+>2 : 2
+>d : number
+>3 : 3
+
+  f(b,c)
+>f(b,c) : void
+>f : (a: number, b: number) => void
+>b : number
+>c : number | undefined
+
+  // error
+}
+
+function func5({a: {b, c = 4}, d}: {a: {b: number,c?: number},d: number} = {a: {b: 1,c: 2},d: 3} ) {
+>func5 : ({ a: { b, c }, d }?: { a: { b: number; c?: number | undefined; }; d: number; }) => void
+>a : any
+>b : number
+>c : number
+>4 : 4
+>d : number
+>a : { b: number; c?: number | undefined; }
+>b : number
+>c : number | undefined
+>d : number
+>{a: {b: 1,c: 2},d: 3} : { a: { b: number; c: number; }; d: number; }
+>a : { b: number; c: number; }
+>{b: 1,c: 2} : { b: number; c: number; }
+>b : number
+>1 : 1
+>c : number
+>2 : 2
+>d : number
+>3 : 3
+
+  f(b, c)
+>f(b, c) : void
+>f : (a: number, b: number) => void
+>b : number
+>c : number
+
+  // no error
+}
+
+function func6( {a: {b, c} = {b: 4, c: 5}, d}: {a: {b: number, c?: number}, d: number} = {a: {b: 1,c: 2}, d: 3} ) {
+>func6 : ({ a: { b, c }, d }?: { a: { b: number; c?: number | undefined; }; d: number; }) => void
+>a : any
+>b : number
+>c : number | undefined
+>{b: 4, c: 5} : { b: number; c: number; }
+>b : number
+>4 : 4
+>c : number
+>5 : 5
+>d : number
+>a : { b: number; c?: number | undefined; }
+>b : number
+>c : number | undefined
+>d : number
+>{a: {b: 1,c: 2}, d: 3} : { a: { b: number; c: number; }; d: number; }
+>a : { b: number; c: number; }
+>{b: 1,c: 2} : { b: number; c: number; }
+>b : number
+>1 : 1
+>c : number
+>2 : 2
+>d : number
+>3 : 3
+
+  f(b, c)
+>f(b, c) : void
+>f : (a: number, b: number) => void
+>b : number
+>c : number | undefined
+
+  // error
+}
+
+function func7( {a: {b, c = 6} = {b: 4, c: 5}, d}: {a: {b: number, c?: number}, d: number} = {a: {b: 1, c: 2}, d: 3} ) {
+>func7 : ({ a: { b, c }, d }?: { a: { b: number; c?: number | undefined; }; d: number; }) => void
+>a : any
+>b : number
+>c : number
+>6 : 6
+>{b: 4, c: 5} : { b: number; c?: number; }
+>b : number
+>4 : 4
+>c : number
+>5 : 5
+>d : number
+>a : { b: number; c?: number | undefined; }
+>b : number
+>c : number | undefined
+>d : number
+>{a: {b: 1, c: 2}, d: 3} : { a: { b: number; c: number; }; d: number; }
+>a : { b: number; c: number; }
+>{b: 1, c: 2} : { b: number; c: number; }
+>b : number
+>1 : 1
+>c : number
+>2 : 2
+>d : number
+>3 : 3
+
+  f(b, c)
+>f(b, c) : void
+>f : (a: number, b: number) => void
+>b : number
+>c : number
+
+  // no error
+}
+
diff --git a/tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts b/tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts
new file mode 100644
index 00000000000..3666ee2d954
--- /dev/null
+++ b/tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts
@@ -0,0 +1,39 @@
+// @strictNullChecks: true
+// https://github.com/Microsoft/TypeScript/issues/17080
+function f(a:number,b:number) {
+}
+
+function func1( {a, b}: {a: number, b?: number} = {a: 1, b: 2} ) {
+  f(a, b)
+  // error
+}
+
+function func2( {a, b = 3}: {a: number, b?:number} = {a: 1,b: 2} ) {
+  f(a, b)
+  // no error
+}
+
+function func3( {a, b}: {a: number, b?: number} = {a: 1} ) {
+  f(a,b)
+  // error
+}
+
+function func4( {a: {b, c}, d}: {a: {b: number,c?: number},d: number} = {a: {b: 1,c: 2},d: 3} ) {
+  f(b,c)
+  // error
+}
+
+function func5({a: {b, c = 4}, d}: {a: {b: number,c?: number},d: number} = {a: {b: 1,c: 2},d: 3} ) {
+  f(b, c)
+  // no error
+}
+
+function func6( {a: {b, c} = {b: 4, c: 5}, d}: {a: {b: number, c?: number}, d: number} = {a: {b: 1,c: 2}, d: 3} ) {
+  f(b, c)
+  // error
+}
+
+function func7( {a: {b, c = 6} = {b: 4, c: 5}, d}: {a: {b: number, c?: number}, d: number} = {a: {b: 1, c: 2}, d: 3} ) {
+  f(b, c)
+  // no error
+}

From 5a87a94c59a7ea137113a873b163c98e7322fa81 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stephan=20Ginth=C3=B6r?=
 <26004708+Lazarus535@users.noreply.github.com>
Date: Mon, 22 Jan 2018 13:40:57 +0100
Subject: [PATCH 2/4] Fixes #17080
 https://github.com/Microsoft/TypeScript/issues/17080 Added testcases from the
 Github bugreport (all working as intended now). Signed CLA.

---
 pull_request_template.md                      |  2 +-
 ...rInDestructuringWithInitializer.errors.txt | 38 ++++++++++-
 ...ParameterInDestructuringWithInitializer.js | 44 +++++++++++++
 ...eterInDestructuringWithInitializer.symbols | 55 ++++++++++++++++
 ...ameterInDestructuringWithInitializer.types | 66 +++++++++++++++++++
 ...ParameterInDestructuringWithInitializer.ts | 26 ++++++++
 6 files changed, 229 insertions(+), 2 deletions(-)

diff --git a/pull_request_template.md b/pull_request_template.md
index faa484054be..4243c2f671f 100644
--- a/pull_request_template.md
+++ b/pull_request_template.md
@@ -6,7 +6,7 @@ Here's a checklist you might find useful.
   'Bug' or 'help wanted' or is in the Community milestone
 [X] Code is up-to-date with the `master` branch
 [X] You've successfully run `jake runtests` locally
-[ ] You've signed the CLA
+[X] You've signed the CLA
 [X] There are new or updated unit tests validating the change
 
 Refer to CONTRIBUTING.MD for more details.
diff --git a/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.errors.txt b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.errors.txt
index 14bc3ea8e6c..8965d7172e8 100644
--- a/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.errors.txt
+++ b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.errors.txt
@@ -6,9 +6,13 @@ tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts(21,7): e
   Type 'undefined' is not assignable to type 'number'.
 tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts(31,8): error TS2345: Argument of type 'number | undefined' is not assignable to parameter of type 'number'.
   Type 'undefined' is not assignable to type 'number'.
+tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts(45,10): error TS2345: Argument of type 'number | undefined' is not assignable to parameter of type 'number'.
+  Type 'undefined' is not assignable to type 'number'.
+tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts(55,11): error TS2345: Argument of type 'number | null' is not assignable to parameter of type 'number | undefined'.
+  Type 'null' is not assignable to type 'number | undefined'.
 
 
-==== tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts (4 errors) ====
+==== tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts (6 errors) ====
     // https://github.com/Microsoft/TypeScript/issues/17080
     function f(a:number,b:number) {
     }
@@ -59,4 +63,36 @@ tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts(31,8): e
       f(b, c)
       // no error
     }
+    
+    interface Foo {
+      readonly bar?: number;
+    }
+    
+    function performFoo({ bar }: Foo = {}) {
+      useBar(bar);
+             ~~~
+!!! error TS2345: Argument of type 'number | undefined' is not assignable to parameter of type 'number'.
+!!! error TS2345:   Type 'undefined' is not assignable to type 'number'.
+    }
+    
+    function useBar(bar: number) {
+      f(bar, 1)
+    }
+    
+    performFoo();
+    
+    function performFoo2({ bar = null }: Foo = {}) {
+      useBar2(bar);
+              ~~~
+!!! error TS2345: Argument of type 'number | null' is not assignable to parameter of type 'number | undefined'.
+!!! error TS2345:   Type 'null' is not assignable to type 'number | undefined'.
+    }
+    
+    function useBar2(bar: number | undefined) {
+      if (bar) {
+        f(bar, 1)
+      }
+    }
+    
+    performFoo2();
     
\ No newline at end of file
diff --git a/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.js b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.js
index 8c297088f14..cb929d89112 100644
--- a/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.js
+++ b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.js
@@ -37,6 +37,32 @@ function func7( {a: {b, c = 6} = {b: 4, c: 5}, d}: {a: {b: number, c?: number},
   f(b, c)
   // no error
 }
+
+interface Foo {
+  readonly bar?: number;
+}
+
+function performFoo({ bar }: Foo = {}) {
+  useBar(bar);
+}
+
+function useBar(bar: number) {
+  f(bar, 1)
+}
+
+performFoo();
+
+function performFoo2({ bar = null }: Foo = {}) {
+  useBar2(bar);
+}
+
+function useBar2(bar: number | undefined) {
+  if (bar) {
+    f(bar, 1)
+  }
+}
+
+performFoo2();
 
 
 //// [optionalParameterInDestructuringWithInitializer.js]
@@ -78,3 +104,21 @@ function func7(_a) {
     f(b, c);
     // no error
 }
+function performFoo(_a) {
+    var bar = (_a === void 0 ? {} : _a).bar;
+    useBar(bar);
+}
+function useBar(bar) {
+    f(bar, 1);
+}
+performFoo();
+function performFoo2(_a) {
+    var _b = (_a === void 0 ? {} : _a).bar, bar = _b === void 0 ? null : _b;
+    useBar2(bar);
+}
+function useBar2(bar) {
+    if (bar) {
+        f(bar, 1);
+    }
+}
+performFoo2();
diff --git a/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.symbols b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.symbols
index fc068a0babb..399956476c8 100644
--- a/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.symbols
+++ b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.symbols
@@ -152,3 +152,58 @@ function func7( {a: {b, c = 6} = {b: 4, c: 5}, d}: {a: {b: number, c?: number},
   // no error
 }
 
+interface Foo {
+>Foo : Symbol(Foo, Decl(optionalParameterInDestructuringWithInitializer.ts, 37, 1))
+
+  readonly bar?: number;
+>bar : Symbol(Foo.bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 39, 15))
+}
+
+function performFoo({ bar }: Foo = {}) {
+>performFoo : Symbol(performFoo, Decl(optionalParameterInDestructuringWithInitializer.ts, 41, 1))
+>bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 43, 21))
+>Foo : Symbol(Foo, Decl(optionalParameterInDestructuringWithInitializer.ts, 37, 1))
+
+  useBar(bar);
+>useBar : Symbol(useBar, Decl(optionalParameterInDestructuringWithInitializer.ts, 45, 1))
+>bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 43, 21))
+}
+
+function useBar(bar: number) {
+>useBar : Symbol(useBar, Decl(optionalParameterInDestructuringWithInitializer.ts, 45, 1))
+>bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 47, 16))
+
+  f(bar, 1)
+>f : Symbol(f, Decl(optionalParameterInDestructuringWithInitializer.ts, 0, 0))
+>bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 47, 16))
+}
+
+performFoo();
+>performFoo : Symbol(performFoo, Decl(optionalParameterInDestructuringWithInitializer.ts, 41, 1))
+
+function performFoo2({ bar = null }: Foo = {}) {
+>performFoo2 : Symbol(performFoo2, Decl(optionalParameterInDestructuringWithInitializer.ts, 51, 13))
+>bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 53, 22))
+>Foo : Symbol(Foo, Decl(optionalParameterInDestructuringWithInitializer.ts, 37, 1))
+
+  useBar2(bar);
+>useBar2 : Symbol(useBar2, Decl(optionalParameterInDestructuringWithInitializer.ts, 55, 1))
+>bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 53, 22))
+}
+
+function useBar2(bar: number | undefined) {
+>useBar2 : Symbol(useBar2, Decl(optionalParameterInDestructuringWithInitializer.ts, 55, 1))
+>bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 57, 17))
+
+  if (bar) {
+>bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 57, 17))
+
+    f(bar, 1)
+>f : Symbol(f, Decl(optionalParameterInDestructuringWithInitializer.ts, 0, 0))
+>bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 57, 17))
+  }
+}
+
+performFoo2();
+>performFoo2 : Symbol(performFoo2, Decl(optionalParameterInDestructuringWithInitializer.ts, 51, 13))
+
diff --git a/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.types b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.types
index 8def19dde20..1d1618e12e3 100644
--- a/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.types
+++ b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.types
@@ -196,3 +196,69 @@ function func7( {a: {b, c = 6} = {b: 4, c: 5}, d}: {a: {b: number, c?: number},
   // no error
 }
 
+interface Foo {
+>Foo : Foo
+
+  readonly bar?: number;
+>bar : number | undefined
+}
+
+function performFoo({ bar }: Foo = {}) {
+>performFoo : ({ bar }?: Foo) => void
+>bar : number | undefined
+>Foo : Foo
+>{} : {}
+
+  useBar(bar);
+>useBar(bar) : void
+>useBar : (bar: number) => void
+>bar : number | undefined
+}
+
+function useBar(bar: number) {
+>useBar : (bar: number) => void
+>bar : number
+
+  f(bar, 1)
+>f(bar, 1) : void
+>f : (a: number, b: number) => void
+>bar : number
+>1 : 1
+}
+
+performFoo();
+>performFoo() : void
+>performFoo : ({ bar }?: Foo) => void
+
+function performFoo2({ bar = null }: Foo = {}) {
+>performFoo2 : ({ bar }?: Foo) => void
+>bar : number | null
+>null : null
+>Foo : Foo
+>{} : {}
+
+  useBar2(bar);
+>useBar2(bar) : void
+>useBar2 : (bar: number | undefined) => void
+>bar : number | null
+}
+
+function useBar2(bar: number | undefined) {
+>useBar2 : (bar: number | undefined) => void
+>bar : number | undefined
+
+  if (bar) {
+>bar : number | undefined
+
+    f(bar, 1)
+>f(bar, 1) : void
+>f : (a: number, b: number) => void
+>bar : number
+>1 : 1
+  }
+}
+
+performFoo2();
+>performFoo2() : void
+>performFoo2 : ({ bar }?: Foo) => void
+
diff --git a/tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts b/tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts
index 3666ee2d954..1f1847a19a7 100644
--- a/tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts
+++ b/tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts
@@ -37,3 +37,29 @@ function func7( {a: {b, c = 6} = {b: 4, c: 5}, d}: {a: {b: number, c?: number},
   f(b, c)
   // no error
 }
+
+interface Foo {
+  readonly bar?: number;
+}
+
+function performFoo({ bar }: Foo = {}) {
+  useBar(bar);
+}
+
+function useBar(bar: number) {
+  f(bar, 1)
+}
+
+performFoo();
+
+function performFoo2({ bar = null }: Foo = {}) {
+  useBar2(bar);
+}
+
+function useBar2(bar: number | undefined) {
+  if (bar) {
+    f(bar, 1)
+  }
+}
+
+performFoo2();

From d11341820e3aa3d99c918700a113f2819d8c381e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stephan=20Ginth=C3=B6r?=
 <26004708+Lazarus535@users.noreply.github.com>
Date: Mon, 22 Jan 2018 21:45:37 +0100
Subject: [PATCH 3/4] Fixes #17080

Fixed the two requested changes.
1) Deleting the file "pull_request_template.md"
2) Declaring functions in tests, instead of defining
---
 pull_request_template.md                      | 17 -------
 ...rInDestructuringWithInitializer.errors.txt | 16 +++----
 ...ParameterInDestructuringWithInitializer.js | 24 ++--------
 ...eterInDestructuringWithInitializer.symbols | 44 +++++++------------
 ...ameterInDestructuringWithInitializer.types | 26 ++---------
 ...ParameterInDestructuringWithInitializer.ts | 14 ++----
 6 files changed, 32 insertions(+), 109 deletions(-)
 delete mode 100644 pull_request_template.md

diff --git a/pull_request_template.md b/pull_request_template.md
deleted file mode 100644
index 4243c2f671f..00000000000
--- a/pull_request_template.md
+++ /dev/null
@@ -1,17 +0,0 @@
-<!--
-Thank you for submitting a pull request!
-
-Here's a checklist you might find useful.
-[X] There is an associated issue that is labelled
-  'Bug' or 'help wanted' or is in the Community milestone
-[X] Code is up-to-date with the `master` branch
-[X] You've successfully run `jake runtests` locally
-[X] You've signed the CLA
-[X] There are new or updated unit tests validating the change
-
-Refer to CONTRIBUTING.MD for more details.
-  https://github.com/Microsoft/TypeScript/blob/master/CONTRIBUTING.md
--->
-
-Fixes #
-#17080
diff --git a/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.errors.txt b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.errors.txt
index 8965d7172e8..b2fea589cb1 100644
--- a/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.errors.txt
+++ b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.errors.txt
@@ -8,14 +8,14 @@ tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts(31,8): e
   Type 'undefined' is not assignable to type 'number'.
 tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts(45,10): error TS2345: Argument of type 'number | undefined' is not assignable to parameter of type 'number'.
   Type 'undefined' is not assignable to type 'number'.
-tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts(55,11): error TS2345: Argument of type 'number | null' is not assignable to parameter of type 'number | undefined'.
+tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts(53,11): error TS2345: Argument of type 'number | null' is not assignable to parameter of type 'number | undefined'.
   Type 'null' is not assignable to type 'number | undefined'.
 
 
 ==== tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts (6 errors) ====
     // https://github.com/Microsoft/TypeScript/issues/17080
-    function f(a:number,b:number) {
-    }
+    
+    declare function f(a:number,b:number): void;
     
     function func1( {a, b}: {a: number, b?: number} = {a: 1, b: 2} ) {
       f(a, b)
@@ -75,9 +75,7 @@ tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts(55,11):
 !!! error TS2345:   Type 'undefined' is not assignable to type 'number'.
     }
     
-    function useBar(bar: number) {
-      f(bar, 1)
-    }
+    declare function useBar(bar: number): void;
     
     performFoo();
     
@@ -88,11 +86,7 @@ tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts(55,11):
 !!! error TS2345:   Type 'null' is not assignable to type 'number | undefined'.
     }
     
-    function useBar2(bar: number | undefined) {
-      if (bar) {
-        f(bar, 1)
-      }
-    }
+    declare function useBar2(bar: number | undefined): void;
     
     performFoo2();
     
\ No newline at end of file
diff --git a/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.js b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.js
index cb929d89112..642f00a4f50 100644
--- a/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.js
+++ b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.js
@@ -1,7 +1,7 @@
 //// [optionalParameterInDestructuringWithInitializer.ts]
 // https://github.com/Microsoft/TypeScript/issues/17080
-function f(a:number,b:number) {
-}
+
+declare function f(a:number,b:number): void;
 
 function func1( {a, b}: {a: number, b?: number} = {a: 1, b: 2} ) {
   f(a, b)
@@ -46,9 +46,7 @@ function performFoo({ bar }: Foo = {}) {
   useBar(bar);
 }
 
-function useBar(bar: number) {
-  f(bar, 1)
-}
+declare function useBar(bar: number): void;
 
 performFoo();
 
@@ -56,19 +54,13 @@ function performFoo2({ bar = null }: Foo = {}) {
   useBar2(bar);
 }
 
-function useBar2(bar: number | undefined) {
-  if (bar) {
-    f(bar, 1)
-  }
-}
+declare function useBar2(bar: number | undefined): void;
 
 performFoo2();
 
 
 //// [optionalParameterInDestructuringWithInitializer.js]
 // https://github.com/Microsoft/TypeScript/issues/17080
-function f(a, b) {
-}
 function func1(_a) {
     var _b = _a === void 0 ? { a: 1, b: 2 } : _a, a = _b.a, b = _b.b;
     f(a, b);
@@ -108,17 +100,9 @@ function performFoo(_a) {
     var bar = (_a === void 0 ? {} : _a).bar;
     useBar(bar);
 }
-function useBar(bar) {
-    f(bar, 1);
-}
 performFoo();
 function performFoo2(_a) {
     var _b = (_a === void 0 ? {} : _a).bar, bar = _b === void 0 ? null : _b;
     useBar2(bar);
 }
-function useBar2(bar) {
-    if (bar) {
-        f(bar, 1);
-    }
-}
 performFoo2();
diff --git a/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.symbols b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.symbols
index 399956476c8..6d4cf484d92 100644
--- a/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.symbols
+++ b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.symbols
@@ -1,13 +1,13 @@
 === tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts ===
 // https://github.com/Microsoft/TypeScript/issues/17080
-function f(a:number,b:number) {
+
+declare function f(a:number,b:number): void;
 >f : Symbol(f, Decl(optionalParameterInDestructuringWithInitializer.ts, 0, 0))
->a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 1, 11))
->b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 1, 20))
-}
+>a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 2, 19))
+>b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 2, 28))
 
 function func1( {a, b}: {a: number, b?: number} = {a: 1, b: 2} ) {
->func1 : Symbol(func1, Decl(optionalParameterInDestructuringWithInitializer.ts, 2, 1))
+>func1 : Symbol(func1, Decl(optionalParameterInDestructuringWithInitializer.ts, 2, 44))
 >a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 4, 17))
 >b : Symbol(b, Decl(optionalParameterInDestructuringWithInitializer.ts, 4, 19))
 >a : Symbol(a, Decl(optionalParameterInDestructuringWithInitializer.ts, 4, 25))
@@ -169,41 +169,27 @@ function performFoo({ bar }: Foo = {}) {
 >bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 43, 21))
 }
 
-function useBar(bar: number) {
+declare function useBar(bar: number): void;
 >useBar : Symbol(useBar, Decl(optionalParameterInDestructuringWithInitializer.ts, 45, 1))
->bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 47, 16))
-
-  f(bar, 1)
->f : Symbol(f, Decl(optionalParameterInDestructuringWithInitializer.ts, 0, 0))
->bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 47, 16))
-}
+>bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 47, 24))
 
 performFoo();
 >performFoo : Symbol(performFoo, Decl(optionalParameterInDestructuringWithInitializer.ts, 41, 1))
 
 function performFoo2({ bar = null }: Foo = {}) {
->performFoo2 : Symbol(performFoo2, Decl(optionalParameterInDestructuringWithInitializer.ts, 51, 13))
->bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 53, 22))
+>performFoo2 : Symbol(performFoo2, Decl(optionalParameterInDestructuringWithInitializer.ts, 49, 13))
+>bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 51, 22))
 >Foo : Symbol(Foo, Decl(optionalParameterInDestructuringWithInitializer.ts, 37, 1))
 
   useBar2(bar);
->useBar2 : Symbol(useBar2, Decl(optionalParameterInDestructuringWithInitializer.ts, 55, 1))
->bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 53, 22))
+>useBar2 : Symbol(useBar2, Decl(optionalParameterInDestructuringWithInitializer.ts, 53, 1))
+>bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 51, 22))
 }
 
-function useBar2(bar: number | undefined) {
->useBar2 : Symbol(useBar2, Decl(optionalParameterInDestructuringWithInitializer.ts, 55, 1))
->bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 57, 17))
-
-  if (bar) {
->bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 57, 17))
-
-    f(bar, 1)
->f : Symbol(f, Decl(optionalParameterInDestructuringWithInitializer.ts, 0, 0))
->bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 57, 17))
-  }
-}
+declare function useBar2(bar: number | undefined): void;
+>useBar2 : Symbol(useBar2, Decl(optionalParameterInDestructuringWithInitializer.ts, 53, 1))
+>bar : Symbol(bar, Decl(optionalParameterInDestructuringWithInitializer.ts, 55, 25))
 
 performFoo2();
->performFoo2 : Symbol(performFoo2, Decl(optionalParameterInDestructuringWithInitializer.ts, 51, 13))
+>performFoo2 : Symbol(performFoo2, Decl(optionalParameterInDestructuringWithInitializer.ts, 49, 13))
 
diff --git a/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.types b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.types
index 1d1618e12e3..26110e71051 100644
--- a/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.types
+++ b/tests/baselines/reference/optionalParameterInDestructuringWithInitializer.types
@@ -1,10 +1,10 @@
 === tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts ===
 // https://github.com/Microsoft/TypeScript/issues/17080
-function f(a:number,b:number) {
+
+declare function f(a:number,b:number): void;
 >f : (a: number, b: number) => void
 >a : number
 >b : number
-}
 
 function func1( {a, b}: {a: number, b?: number} = {a: 1, b: 2} ) {
 >func1 : ({ a, b }?: { a: number; b?: number | undefined; }) => void
@@ -215,17 +215,10 @@ function performFoo({ bar }: Foo = {}) {
 >bar : number | undefined
 }
 
-function useBar(bar: number) {
+declare function useBar(bar: number): void;
 >useBar : (bar: number) => void
 >bar : number
 
-  f(bar, 1)
->f(bar, 1) : void
->f : (a: number, b: number) => void
->bar : number
->1 : 1
-}
-
 performFoo();
 >performFoo() : void
 >performFoo : ({ bar }?: Foo) => void
@@ -243,21 +236,10 @@ function performFoo2({ bar = null }: Foo = {}) {
 >bar : number | null
 }
 
-function useBar2(bar: number | undefined) {
+declare function useBar2(bar: number | undefined): void;
 >useBar2 : (bar: number | undefined) => void
 >bar : number | undefined
 
-  if (bar) {
->bar : number | undefined
-
-    f(bar, 1)
->f(bar, 1) : void
->f : (a: number, b: number) => void
->bar : number
->1 : 1
-  }
-}
-
 performFoo2();
 >performFoo2() : void
 >performFoo2 : ({ bar }?: Foo) => void
diff --git a/tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts b/tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts
index 1f1847a19a7..d3ebd99efa1 100644
--- a/tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts
+++ b/tests/cases/compiler/optionalParameterInDestructuringWithInitializer.ts
@@ -1,7 +1,7 @@
 // @strictNullChecks: true
 // https://github.com/Microsoft/TypeScript/issues/17080
-function f(a:number,b:number) {
-}
+
+declare function f(a:number,b:number): void;
 
 function func1( {a, b}: {a: number, b?: number} = {a: 1, b: 2} ) {
   f(a, b)
@@ -46,9 +46,7 @@ function performFoo({ bar }: Foo = {}) {
   useBar(bar);
 }
 
-function useBar(bar: number) {
-  f(bar, 1)
-}
+declare function useBar(bar: number): void;
 
 performFoo();
 
@@ -56,10 +54,6 @@ function performFoo2({ bar = null }: Foo = {}) {
   useBar2(bar);
 }
 
-function useBar2(bar: number | undefined) {
-  if (bar) {
-    f(bar, 1)
-  }
-}
+declare function useBar2(bar: number | undefined): void;
 
 performFoo2();

From 7b449a5e6230b5ec9445902a87148a698719baa7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Stephan=20Ginth=C3=B6r?=
 <26004708+Lazarus535@users.noreply.github.com>
Date: Mon, 22 Jan 2018 22:09:35 +0100
Subject: [PATCH 4/4] Fixes #17080

Readded untouched pull_request_template.md
---
 pull_request_template.md | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)
 create mode 100644 pull_request_template.md

diff --git a/pull_request_template.md b/pull_request_template.md
new file mode 100644
index 00000000000..2c49c84641b
--- /dev/null
+++ b/pull_request_template.md
@@ -0,0 +1,16 @@
+<!--
+Thank you for submitting a pull request!
+
+Here's a checklist you might find useful.
+[ ] There is an associated issue that is labelled
+  'Bug' or 'help wanted' or is in the Community milestone
+[ ] Code is up-to-date with the `master` branch
+[ ] You've successfully run `jake runtests` locally
+[ ] You've signed the CLA
+[ ] There are new or updated unit tests validating the change
+
+Refer to CONTRIBUTING.MD for more details.
+  https://github.com/Microsoft/TypeScript/blob/master/CONTRIBUTING.md
+-->
+
+Fixes #