From dafe7c8958bee8cfae4e9b7b264336fa7f1178eb Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Wed, 14 Jan 2015 17:02:31 -0800
Subject: [PATCH 1/3] Added tests.

---
 .../optionalBindingParameters1.errors.txt     | 14 +++++++++++++
 .../reference/optionalBindingParameters1.js   | 16 +++++++++++++++
 .../optionalBindingParameters2.errors.txt     | 18 +++++++++++++++++
 .../reference/optionalBindingParameters2.js   | 16 +++++++++++++++
 ...alBindingParametersInOverloads1.errors.txt | 15 ++++++++++++++
 .../optionalBindingParametersInOverloads1.js  | 20 +++++++++++++++++++
 ...alBindingParametersInOverloads2.errors.txt | 19 ++++++++++++++++++
 .../optionalBindingParametersInOverloads2.js  | 20 +++++++++++++++++++
 .../optionalBindingParameters1.ts             |  8 ++++++++
 .../optionalBindingParameters2.ts             |  8 ++++++++
 .../optionalBindingParametersInOverloads1.ts  |  9 +++++++++
 .../optionalBindingParametersInOverloads2.ts  |  9 +++++++++
 12 files changed, 172 insertions(+)
 create mode 100644 tests/baselines/reference/optionalBindingParameters1.errors.txt
 create mode 100644 tests/baselines/reference/optionalBindingParameters1.js
 create mode 100644 tests/baselines/reference/optionalBindingParameters2.errors.txt
 create mode 100644 tests/baselines/reference/optionalBindingParameters2.js
 create mode 100644 tests/baselines/reference/optionalBindingParametersInOverloads1.errors.txt
 create mode 100644 tests/baselines/reference/optionalBindingParametersInOverloads1.js
 create mode 100644 tests/baselines/reference/optionalBindingParametersInOverloads2.errors.txt
 create mode 100644 tests/baselines/reference/optionalBindingParametersInOverloads2.js
 create mode 100644 tests/cases/conformance/es6/destructuring/optionalBindingParameters1.ts
 create mode 100644 tests/cases/conformance/es6/destructuring/optionalBindingParameters2.ts
 create mode 100644 tests/cases/conformance/es6/destructuring/optionalBindingParametersInOverloads1.ts
 create mode 100644 tests/cases/conformance/es6/destructuring/optionalBindingParametersInOverloads2.ts

diff --git a/tests/baselines/reference/optionalBindingParameters1.errors.txt b/tests/baselines/reference/optionalBindingParameters1.errors.txt
new file mode 100644
index 00000000000..dbc0f9a44e9
--- /dev/null
+++ b/tests/baselines/reference/optionalBindingParameters1.errors.txt
@@ -0,0 +1,14 @@
+tests/cases/conformance/es6/destructuring/optionalBindingParameters1.ts(8,5): error TS2345: Argument of type '[boolean, number, string]' is not assignable to parameter of type '[string, number, boolean]'.
+
+
+==== tests/cases/conformance/es6/destructuring/optionalBindingParameters1.ts (1 errors) ====
+    
+    function foo([x,y,z]?: [string, number, boolean]) {
+    
+    }
+    
+    foo(["", 0, false]);
+    
+    foo([false, 0, ""]);
+        ~~~~~~~~~~~~~~
+!!! error TS2345: Argument of type '[boolean, number, string]' is not assignable to parameter of type '[string, number, boolean]'.
\ No newline at end of file
diff --git a/tests/baselines/reference/optionalBindingParameters1.js b/tests/baselines/reference/optionalBindingParameters1.js
new file mode 100644
index 00000000000..536cb1e567a
--- /dev/null
+++ b/tests/baselines/reference/optionalBindingParameters1.js
@@ -0,0 +1,16 @@
+//// [optionalBindingParameters1.ts]
+
+function foo([x,y,z]?: [string, number, boolean]) {
+
+}
+
+foo(["", 0, false]);
+
+foo([false, 0, ""]);
+
+//// [optionalBindingParameters1.js]
+function foo(_a) {
+    var x = _a[0], y = _a[1], z = _a[2];
+}
+foo(["", 0, false]);
+foo([false, 0, ""]);
diff --git a/tests/baselines/reference/optionalBindingParameters2.errors.txt b/tests/baselines/reference/optionalBindingParameters2.errors.txt
new file mode 100644
index 00000000000..b906bc6a231
--- /dev/null
+++ b/tests/baselines/reference/optionalBindingParameters2.errors.txt
@@ -0,0 +1,18 @@
+tests/cases/conformance/es6/destructuring/optionalBindingParameters2.ts(8,5): error TS2345: Argument of type '{ x: boolean; y: number; z: string; }' is not assignable to parameter of type '{ x: string; y: number; z: boolean; }'.
+  Types of property 'x' are incompatible.
+    Type 'boolean' is not assignable to type 'string'.
+
+
+==== tests/cases/conformance/es6/destructuring/optionalBindingParameters2.ts (1 errors) ====
+    
+    function foo({ x, y, z }?: { x: string; y: number; z: boolean }) {
+    
+    }
+    
+    foo({ x: "", y: 0, z: false });
+    
+    foo({ x: false, y: 0, z: "" });
+        ~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2345: Argument of type '{ x: boolean; y: number; z: string; }' is not assignable to parameter of type '{ x: string; y: number; z: boolean; }'.
+!!! error TS2345:   Types of property 'x' are incompatible.
+!!! error TS2345:     Type 'boolean' is not assignable to type 'string'.
\ No newline at end of file
diff --git a/tests/baselines/reference/optionalBindingParameters2.js b/tests/baselines/reference/optionalBindingParameters2.js
new file mode 100644
index 00000000000..04e1138561a
--- /dev/null
+++ b/tests/baselines/reference/optionalBindingParameters2.js
@@ -0,0 +1,16 @@
+//// [optionalBindingParameters2.ts]
+
+function foo({ x, y, z }?: { x: string; y: number; z: boolean }) {
+
+}
+
+foo({ x: "", y: 0, z: false });
+
+foo({ x: false, y: 0, z: "" });
+
+//// [optionalBindingParameters2.js]
+function foo(_a) {
+    var x = _a.x, y = _a.y, z = _a.z;
+}
+foo({ x: "", y: 0, z: false });
+foo({ x: false, y: 0, z: "" });
diff --git a/tests/baselines/reference/optionalBindingParametersInOverloads1.errors.txt b/tests/baselines/reference/optionalBindingParametersInOverloads1.errors.txt
new file mode 100644
index 00000000000..5999ec514b0
--- /dev/null
+++ b/tests/baselines/reference/optionalBindingParametersInOverloads1.errors.txt
@@ -0,0 +1,15 @@
+tests/cases/conformance/es6/destructuring/optionalBindingParametersInOverloads1.ts(9,5): error TS2345: Argument of type '[boolean, number, string]' is not assignable to parameter of type '[string, number, boolean]'.
+
+
+==== tests/cases/conformance/es6/destructuring/optionalBindingParametersInOverloads1.ts (1 errors) ====
+    
+    function foo([x, y, z] ?: [string, number, boolean]);
+    function foo(...rest: any[]) {
+    
+    }
+    
+    foo(["", 0, false]);
+    
+    foo([false, 0, ""]);
+        ~~~~~~~~~~~~~~
+!!! error TS2345: Argument of type '[boolean, number, string]' is not assignable to parameter of type '[string, number, boolean]'.
\ No newline at end of file
diff --git a/tests/baselines/reference/optionalBindingParametersInOverloads1.js b/tests/baselines/reference/optionalBindingParametersInOverloads1.js
new file mode 100644
index 00000000000..3658efa72c6
--- /dev/null
+++ b/tests/baselines/reference/optionalBindingParametersInOverloads1.js
@@ -0,0 +1,20 @@
+//// [optionalBindingParametersInOverloads1.ts]
+
+function foo([x, y, z] ?: [string, number, boolean]);
+function foo(...rest: any[]) {
+
+}
+
+foo(["", 0, false]);
+
+foo([false, 0, ""]);
+
+//// [optionalBindingParametersInOverloads1.js]
+function foo() {
+    var rest = [];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        rest[_i - 0] = arguments[_i];
+    }
+}
+foo(["", 0, false]);
+foo([false, 0, ""]);
diff --git a/tests/baselines/reference/optionalBindingParametersInOverloads2.errors.txt b/tests/baselines/reference/optionalBindingParametersInOverloads2.errors.txt
new file mode 100644
index 00000000000..765fd5e3de6
--- /dev/null
+++ b/tests/baselines/reference/optionalBindingParametersInOverloads2.errors.txt
@@ -0,0 +1,19 @@
+tests/cases/conformance/es6/destructuring/optionalBindingParametersInOverloads2.ts(9,5): error TS2345: Argument of type '{ x: boolean; y: number; z: string; }' is not assignable to parameter of type '{ x: string; y: number; z: boolean; }'.
+  Types of property 'x' are incompatible.
+    Type 'boolean' is not assignable to type 'string'.
+
+
+==== tests/cases/conformance/es6/destructuring/optionalBindingParametersInOverloads2.ts (1 errors) ====
+    
+    function foo({ x, y, z }?: { x: string; y: number; z: boolean });
+    function foo(...rest: any[]) {
+    
+    }
+    
+    foo({ x: "", y: 0, z: false });
+    
+    foo({ x: false, y: 0, z: "" });
+        ~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2345: Argument of type '{ x: boolean; y: number; z: string; }' is not assignable to parameter of type '{ x: string; y: number; z: boolean; }'.
+!!! error TS2345:   Types of property 'x' are incompatible.
+!!! error TS2345:     Type 'boolean' is not assignable to type 'string'.
\ No newline at end of file
diff --git a/tests/baselines/reference/optionalBindingParametersInOverloads2.js b/tests/baselines/reference/optionalBindingParametersInOverloads2.js
new file mode 100644
index 00000000000..1ddfdae4f07
--- /dev/null
+++ b/tests/baselines/reference/optionalBindingParametersInOverloads2.js
@@ -0,0 +1,20 @@
+//// [optionalBindingParametersInOverloads2.ts]
+
+function foo({ x, y, z }?: { x: string; y: number; z: boolean });
+function foo(...rest: any[]) {
+
+}
+
+foo({ x: "", y: 0, z: false });
+
+foo({ x: false, y: 0, z: "" });
+
+//// [optionalBindingParametersInOverloads2.js]
+function foo() {
+    var rest = [];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        rest[_i - 0] = arguments[_i];
+    }
+}
+foo({ x: "", y: 0, z: false });
+foo({ x: false, y: 0, z: "" });
diff --git a/tests/cases/conformance/es6/destructuring/optionalBindingParameters1.ts b/tests/cases/conformance/es6/destructuring/optionalBindingParameters1.ts
new file mode 100644
index 00000000000..5bdcb49e5d9
--- /dev/null
+++ b/tests/cases/conformance/es6/destructuring/optionalBindingParameters1.ts
@@ -0,0 +1,8 @@
+
+function foo([x,y,z]?: [string, number, boolean]) {
+
+}
+
+foo(["", 0, false]);
+
+foo([false, 0, ""]);
\ No newline at end of file
diff --git a/tests/cases/conformance/es6/destructuring/optionalBindingParameters2.ts b/tests/cases/conformance/es6/destructuring/optionalBindingParameters2.ts
new file mode 100644
index 00000000000..12338aeb445
--- /dev/null
+++ b/tests/cases/conformance/es6/destructuring/optionalBindingParameters2.ts
@@ -0,0 +1,8 @@
+
+function foo({ x, y, z }?: { x: string; y: number; z: boolean }) {
+
+}
+
+foo({ x: "", y: 0, z: false });
+
+foo({ x: false, y: 0, z: "" });
\ No newline at end of file
diff --git a/tests/cases/conformance/es6/destructuring/optionalBindingParametersInOverloads1.ts b/tests/cases/conformance/es6/destructuring/optionalBindingParametersInOverloads1.ts
new file mode 100644
index 00000000000..82aa49d346a
--- /dev/null
+++ b/tests/cases/conformance/es6/destructuring/optionalBindingParametersInOverloads1.ts
@@ -0,0 +1,9 @@
+
+function foo([x, y, z] ?: [string, number, boolean]);
+function foo(...rest: any[]) {
+
+}
+
+foo(["", 0, false]);
+
+foo([false, 0, ""]);
\ No newline at end of file
diff --git a/tests/cases/conformance/es6/destructuring/optionalBindingParametersInOverloads2.ts b/tests/cases/conformance/es6/destructuring/optionalBindingParametersInOverloads2.ts
new file mode 100644
index 00000000000..bbe763b3008
--- /dev/null
+++ b/tests/cases/conformance/es6/destructuring/optionalBindingParametersInOverloads2.ts
@@ -0,0 +1,9 @@
+
+function foo({ x, y, z }?: { x: string; y: number; z: boolean });
+function foo(...rest: any[]) {
+
+}
+
+foo({ x: "", y: 0, z: false });
+
+foo({ x: false, y: 0, z: "" });
\ No newline at end of file

From 75a1a8a493675f4e0744ebddb52d0e50fd185001 Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Wed, 14 Jan 2015 17:25:37 -0800
Subject: [PATCH 2/3] Disallow optional destructured parameters in
 implementation signatures.

---
 src/compiler/checker.ts                                   | 3 +++
 src/compiler/diagnosticInformationMap.generated.ts        | 1 +
 src/compiler/diagnosticMessages.json                      | 8 ++++++--
 .../reference/optionalBindingParameters1.errors.txt       | 5 ++++-
 .../reference/optionalBindingParameters2.errors.txt       | 5 ++++-
 5 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 8e23fb2050d..781718f7299 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -7212,6 +7212,9 @@ module ts {
                     error(node, Diagnostics.A_parameter_property_is_only_allowed_in_a_constructor_implementation);
                 }
             }
+            if (node.questionToken && isBindingPattern(node.name) && func.body) {
+                error(node, Diagnostics.A_binding_pattern_parameter_may_not_be_optional_in_an_implementation_signature);
+            }
             if (node.dotDotDotToken) {
                 if (!isArrayType(getTypeOfSymbol(node.symbol))) {
                     error(node, Diagnostics.A_rest_parameter_must_be_of_an_array_type);
diff --git a/src/compiler/diagnosticInformationMap.generated.ts b/src/compiler/diagnosticInformationMap.generated.ts
index 2a342fa17d2..5f404d51c23 100644
--- a/src/compiler/diagnosticInformationMap.generated.ts
+++ b/src/compiler/diagnosticInformationMap.generated.ts
@@ -297,6 +297,7 @@ module ts {
         Type_0_has_no_property_1: { code: 2460, category: DiagnosticCategory.Error, key: "Type '{0}' has no property '{1}'." },
         Type_0_is_not_an_array_type: { code: 2461, category: DiagnosticCategory.Error, key: "Type '{0}' is not an array type." },
         A_rest_element_must_be_last_in_an_array_destructuring_pattern: { code: 2462, category: DiagnosticCategory.Error, key: "A rest element must be last in an array destructuring pattern" },
+        A_binding_pattern_parameter_may_not_be_optional_in_an_implementation_signature: { code: 2463, category: DiagnosticCategory.Error, key: "A binding pattern parameter may not be optional in an implementation signature." },
         Import_declaration_0_is_using_private_name_1: { code: 4000, category: DiagnosticCategory.Error, key: "Import declaration '{0}' is using private name '{1}'." },
         Type_parameter_0_of_exported_class_has_or_is_using_private_name_1: { code: 4002, category: DiagnosticCategory.Error, key: "Type parameter '{0}' of exported class has or is using private name '{1}'." },
         Type_parameter_0_of_exported_interface_has_or_is_using_private_name_1: { code: 4004, category: DiagnosticCategory.Error, key: "Type parameter '{0}' of exported interface has or is using private name '{1}'." },
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index efb2bfe7e94..aa0af6ff743 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -224,7 +224,7 @@
     "A 'declare' modifier cannot be used with an import declaration.": {
         "category": "Error",
         "code": 1079,
-        "isEarly":  true
+        "isEarly": true
     },
     "Invalid 'reference' directive syntax.": {
         "category": "Error",
@@ -659,7 +659,7 @@
     "An implementation cannot be declared in ambient contexts.": {
         "category": "Error",
         "code": 1184,
-        "isEarly":  true
+        "isEarly": true
     },
     "Modifiers cannot appear here.": {
         "category": "Error",
@@ -1282,6 +1282,10 @@
         "category": "Error",
         "code": 2462
     },
+    "A binding pattern parameter may not be optional in an implementation signature.": {
+        "category": "Error",
+        "code":  2463
+    },
 
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",
diff --git a/tests/baselines/reference/optionalBindingParameters1.errors.txt b/tests/baselines/reference/optionalBindingParameters1.errors.txt
index dbc0f9a44e9..51cc9d7817f 100644
--- a/tests/baselines/reference/optionalBindingParameters1.errors.txt
+++ b/tests/baselines/reference/optionalBindingParameters1.errors.txt
@@ -1,9 +1,12 @@
+tests/cases/conformance/es6/destructuring/optionalBindingParameters1.ts(2,14): error TS2463: A binding pattern parameter may not be optional in an implementation signature.
 tests/cases/conformance/es6/destructuring/optionalBindingParameters1.ts(8,5): error TS2345: Argument of type '[boolean, number, string]' is not assignable to parameter of type '[string, number, boolean]'.
 
 
-==== tests/cases/conformance/es6/destructuring/optionalBindingParameters1.ts (1 errors) ====
+==== tests/cases/conformance/es6/destructuring/optionalBindingParameters1.ts (2 errors) ====
     
     function foo([x,y,z]?: [string, number, boolean]) {
+                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2463: A binding pattern parameter may not be optional in an implementation signature.
     
     }
     
diff --git a/tests/baselines/reference/optionalBindingParameters2.errors.txt b/tests/baselines/reference/optionalBindingParameters2.errors.txt
index b906bc6a231..56a0a339cc7 100644
--- a/tests/baselines/reference/optionalBindingParameters2.errors.txt
+++ b/tests/baselines/reference/optionalBindingParameters2.errors.txt
@@ -1,11 +1,14 @@
+tests/cases/conformance/es6/destructuring/optionalBindingParameters2.ts(2,14): error TS2463: A binding pattern parameter may not be optional in an implementation signature.
 tests/cases/conformance/es6/destructuring/optionalBindingParameters2.ts(8,5): error TS2345: Argument of type '{ x: boolean; y: number; z: string; }' is not assignable to parameter of type '{ x: string; y: number; z: boolean; }'.
   Types of property 'x' are incompatible.
     Type 'boolean' is not assignable to type 'string'.
 
 
-==== tests/cases/conformance/es6/destructuring/optionalBindingParameters2.ts (1 errors) ====
+==== tests/cases/conformance/es6/destructuring/optionalBindingParameters2.ts (2 errors) ====
     
     function foo({ x, y, z }?: { x: string; y: number; z: boolean }) {
+                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2463: A binding pattern parameter may not be optional in an implementation signature.
     
     }
     

From 2a11222050ddbc0e9902476d9b1d3eb3885970fb Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Thu, 15 Jan 2015 16:29:50 -0800
Subject: [PATCH 3/3] 'may not' -> 'cannot'

---
 src/compiler/checker.ts                                       | 2 +-
 src/compiler/diagnosticInformationMap.generated.ts            | 2 +-
 src/compiler/diagnosticMessages.json                          | 2 +-
 .../baselines/reference/optionalBindingParameters1.errors.txt | 4 ++--
 .../baselines/reference/optionalBindingParameters2.errors.txt | 4 ++--
 5 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 781718f7299..e3fbff9dc4e 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -7213,7 +7213,7 @@ module ts {
                 }
             }
             if (node.questionToken && isBindingPattern(node.name) && func.body) {
-                error(node, Diagnostics.A_binding_pattern_parameter_may_not_be_optional_in_an_implementation_signature);
+                error(node, Diagnostics.A_binding_pattern_parameter_cannot_be_optional_in_an_implementation_signature);
             }
             if (node.dotDotDotToken) {
                 if (!isArrayType(getTypeOfSymbol(node.symbol))) {
diff --git a/src/compiler/diagnosticInformationMap.generated.ts b/src/compiler/diagnosticInformationMap.generated.ts
index 5f404d51c23..a04338de49a 100644
--- a/src/compiler/diagnosticInformationMap.generated.ts
+++ b/src/compiler/diagnosticInformationMap.generated.ts
@@ -297,7 +297,7 @@ module ts {
         Type_0_has_no_property_1: { code: 2460, category: DiagnosticCategory.Error, key: "Type '{0}' has no property '{1}'." },
         Type_0_is_not_an_array_type: { code: 2461, category: DiagnosticCategory.Error, key: "Type '{0}' is not an array type." },
         A_rest_element_must_be_last_in_an_array_destructuring_pattern: { code: 2462, category: DiagnosticCategory.Error, key: "A rest element must be last in an array destructuring pattern" },
-        A_binding_pattern_parameter_may_not_be_optional_in_an_implementation_signature: { code: 2463, category: DiagnosticCategory.Error, key: "A binding pattern parameter may not be optional in an implementation signature." },
+        A_binding_pattern_parameter_cannot_be_optional_in_an_implementation_signature: { code: 2463, category: DiagnosticCategory.Error, key: "A binding pattern parameter cannot be optional in an implementation signature." },
         Import_declaration_0_is_using_private_name_1: { code: 4000, category: DiagnosticCategory.Error, key: "Import declaration '{0}' is using private name '{1}'." },
         Type_parameter_0_of_exported_class_has_or_is_using_private_name_1: { code: 4002, category: DiagnosticCategory.Error, key: "Type parameter '{0}' of exported class has or is using private name '{1}'." },
         Type_parameter_0_of_exported_interface_has_or_is_using_private_name_1: { code: 4004, category: DiagnosticCategory.Error, key: "Type parameter '{0}' of exported interface has or is using private name '{1}'." },
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index aa0af6ff743..43f671713e9 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -1282,7 +1282,7 @@
         "category": "Error",
         "code": 2462
     },
-    "A binding pattern parameter may not be optional in an implementation signature.": {
+    "A binding pattern parameter cannot be optional in an implementation signature.": {
         "category": "Error",
         "code":  2463
     },
diff --git a/tests/baselines/reference/optionalBindingParameters1.errors.txt b/tests/baselines/reference/optionalBindingParameters1.errors.txt
index 51cc9d7817f..a2961fb9651 100644
--- a/tests/baselines/reference/optionalBindingParameters1.errors.txt
+++ b/tests/baselines/reference/optionalBindingParameters1.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/conformance/es6/destructuring/optionalBindingParameters1.ts(2,14): error TS2463: A binding pattern parameter may not be optional in an implementation signature.
+tests/cases/conformance/es6/destructuring/optionalBindingParameters1.ts(2,14): error TS2463: A binding pattern parameter cannot be optional in an implementation signature.
 tests/cases/conformance/es6/destructuring/optionalBindingParameters1.ts(8,5): error TS2345: Argument of type '[boolean, number, string]' is not assignable to parameter of type '[string, number, boolean]'.
 
 
@@ -6,7 +6,7 @@ tests/cases/conformance/es6/destructuring/optionalBindingParameters1.ts(8,5): er
     
     function foo([x,y,z]?: [string, number, boolean]) {
                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2463: A binding pattern parameter may not be optional in an implementation signature.
+!!! error TS2463: A binding pattern parameter cannot be optional in an implementation signature.
     
     }
     
diff --git a/tests/baselines/reference/optionalBindingParameters2.errors.txt b/tests/baselines/reference/optionalBindingParameters2.errors.txt
index 56a0a339cc7..e67687722d0 100644
--- a/tests/baselines/reference/optionalBindingParameters2.errors.txt
+++ b/tests/baselines/reference/optionalBindingParameters2.errors.txt
@@ -1,4 +1,4 @@
-tests/cases/conformance/es6/destructuring/optionalBindingParameters2.ts(2,14): error TS2463: A binding pattern parameter may not be optional in an implementation signature.
+tests/cases/conformance/es6/destructuring/optionalBindingParameters2.ts(2,14): error TS2463: A binding pattern parameter cannot be optional in an implementation signature.
 tests/cases/conformance/es6/destructuring/optionalBindingParameters2.ts(8,5): error TS2345: Argument of type '{ x: boolean; y: number; z: string; }' is not assignable to parameter of type '{ x: string; y: number; z: boolean; }'.
   Types of property 'x' are incompatible.
     Type 'boolean' is not assignable to type 'string'.
@@ -8,7 +8,7 @@ tests/cases/conformance/es6/destructuring/optionalBindingParameters2.ts(8,5): er
     
     function foo({ x, y, z }?: { x: string; y: number; z: boolean }) {
                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2463: A binding pattern parameter may not be optional in an implementation signature.
+!!! error TS2463: A binding pattern parameter cannot be optional in an implementation signature.
     
     }