Better error message

Author: ahejlsberg

src/compiler/checker.ts

@@ -4698,7 +4698,7 @@ namespace ts {
                 for (let prop of getPropertiesOfObjectType(source)) {
                     if (!isKnownProperty(target, prop.name)) {
                         if (reportErrors) {
-                            reportError(Diagnostics.Property_0_does_not_exist_on_type_1, symbolToString(prop), typeToString(target));
+                            reportError(Diagnostics.Object_literal_may_only_specify_known_properties_and_0_does_not_exist_in_type_1, symbolToString(prop), typeToString(target));
                         }
                         return true;
                     }

src/compiler/diagnosticInformationMap.generated.ts

@@ -254,6 +254,7 @@ namespace ts {
         Only_a_void_function_can_be_called_with_the_new_keyword: { code: 2350, category: DiagnosticCategory.Error, key: "Only a void function can be called with the 'new' keyword." },
         Cannot_use_new_with_an_expression_whose_type_lacks_a_call_or_construct_signature: { code: 2351, category: DiagnosticCategory.Error, key: "Cannot use 'new' with an expression whose type lacks a call or construct signature." },
         Neither_type_0_nor_type_1_is_assignable_to_the_other: { code: 2352, category: DiagnosticCategory.Error, key: "Neither type '{0}' nor type '{1}' is assignable to the other." },
+        Object_literal_may_only_specify_known_properties_and_0_does_not_exist_in_type_1: { code: 2353, category: DiagnosticCategory.Error, key: "Object literal may only specify known properties and '{0}' does not exist in type '{1}'." },
         No_best_common_type_exists_among_return_expressions: { code: 2354, category: DiagnosticCategory.Error, key: "No best common type exists among return expressions." },
         A_function_whose_declared_type_is_neither_void_nor_any_must_return_a_value_or_consist_of_a_single_throw_statement: { code: 2355, category: DiagnosticCategory.Error, key: "A function whose declared type is neither 'void' nor 'any' must return a value or consist of a single 'throw' statement." },
         An_arithmetic_operand_must_be_of_type_any_number_or_an_enum_type: { code: 2356, category: DiagnosticCategory.Error, key: "An arithmetic operand must be of type 'any', 'number' or an enum type." },

src/compiler/diagnosticMessages.json

@@ -1005,6 +1005,10 @@
         "category": "Error",
         "code": 2352
     },
+    "Object literal may only specify known properties and '{0}' does not exist in type '{1}'.": {
+        "category": "Error",
+        "code": 2353
+    },
     "No best common type exists among return expressions.": {
         "category": "Error",
         "code": 2354