Disallow return expressions in a generator

Author: JsonFreeman

src/compiler/checker.ts

@@ -9720,6 +9720,9 @@ module ts {
                     if (func.kind === SyntaxKind.SetAccessor) {
                         error(node.expression, Diagnostics.Setters_cannot_return_a_value);
                     }
+                    else if (func.asteriskToken) {
+                        error(node.expression, Diagnostics.A_return_statement_cannot_specify_a_value_in_a_generator_function);
+                    }
                     else {
                         if (func.kind === SyntaxKind.Constructor) {
                             if (!isTypeAssignableTo(exprType, returnType)) {

src/compiler/diagnosticInformationMap.generated.ts

@@ -366,6 +366,7 @@ module ts {
         An_interface_can_only_extend_an_identifier_Slashqualified_name_with_optional_type_arguments: { code: 2499, category: DiagnosticCategory.Error, key: "An interface can only extend an identifier/qualified-name with optional type arguments." },
         A_class_can_only_implement_an_identifier_Slashqualified_name_with_optional_type_arguments: { code: 2500, category: DiagnosticCategory.Error, key: "A class can only implement an identifier/qualified-name with optional type arguments." },
         A_rest_element_cannot_contain_a_binding_pattern: { code: 2501, category: DiagnosticCategory.Error, key: "A rest element cannot contain a binding pattern." },
+        A_return_statement_cannot_specify_a_value_in_a_generator_function: { code: 2502, category: DiagnosticCategory.Error, key: "A return statement cannot specify a value in a generator function." },
         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

@@ -1453,6 +1453,10 @@
         "category": "Error",
         "code": 2501
     },
+    "A return statement cannot specify a value in a generator function.": {
+        "category": "Error",
+        "code": 2502
+    },
 
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",