Disallow optional destructured parameters in implementation signatures.

Author: DanielRosenwasser

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);

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}'." },

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",

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.
 
     }
 

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.
 
     }