Basic support for generators as iterators

src/compiler/diagnosticInformationMap.generated.ts

@@ -120,7 +120,7 @@ module ts {
         Unterminated_template_literal: { code: 1160, category: DiagnosticCategory.Error, key: "Unterminated template literal." },
         Unterminated_regular_expression_literal: { code: 1161, category: DiagnosticCategory.Error, key: "Unterminated regular expression literal." },
         An_object_member_cannot_be_declared_optional: { code: 1162, category: DiagnosticCategory.Error, key: "An object member cannot be declared optional." },
-        yield_expression_must_be_contained_within_a_generator_declaration: { code: 1163, category: DiagnosticCategory.Error, key: "'yield' expression must be contained_within a generator declaration." },
+        A_yield_expression_is_only_allowed_in_a_generator_body: { code: 1163, category: DiagnosticCategory.Error, key: "A 'yield' expression is only allowed in a generator body." },
         Computed_property_names_are_not_allowed_in_enums: { code: 1164, category: DiagnosticCategory.Error, key: "Computed property names are not allowed in enums." },
         A_computed_property_name_in_an_ambient_context_must_directly_refer_to_a_built_in_symbol: { code: 1165, category: DiagnosticCategory.Error, key: "A computed property name in an ambient context must directly refer to a built-in symbol." },
         A_computed_property_name_in_a_class_property_declaration_must_directly_refer_to_a_built_in_symbol: { code: 1166, category: DiagnosticCategory.Error, key: "A computed property name in a class property declaration must directly refer to a built-in symbol." },
@@ -174,6 +174,9 @@ module ts {
         Type_expected_0_is_a_reserved_word_in_strict_mode: { code: 1215, category: DiagnosticCategory.Error, key: "Type expected. '{0}' is a reserved word in strict mode" },
         Type_expected_0_is_a_reserved_word_in_strict_mode_Class_definitions_are_automatically_in_strict_mode: { code: 1216, category: DiagnosticCategory.Error, key: "Type expected. '{0}' is a reserved word in strict mode. Class definitions are automatically in strict mode." },
         Export_assignment_is_not_supported_when_module_flag_is_system: { code: 1218, category: DiagnosticCategory.Error, key: "Export assignment is not supported when '--module' flag is 'system'." },
+        Generators_are_only_available_when_targeting_ECMAScript_6_or_higher: { code: 1219, category: DiagnosticCategory.Error, key: "Generators are only available when targeting ECMAScript 6 or higher." },
+        Generators_are_not_allowed_in_an_ambient_context: { code: 1220, category: DiagnosticCategory.Error, key: "Generators are not allowed in an ambient context." },
+        An_overload_signature_cannot_be_declared_as_a_generator: { code: 1221, category: DiagnosticCategory.Error, key: "An overload signature cannot be declared as a generator." },
         Duplicate_identifier_0: { code: 2300, category: DiagnosticCategory.Error, key: "Duplicate identifier '{0}'." },
         Initializer_of_instance_member_variable_0_cannot_reference_identifier_1_declared_in_the_constructor: { code: 2301, category: DiagnosticCategory.Error, key: "Initializer of instance member variable '{0}' cannot reference identifier '{1}' declared in the constructor." },
         Static_members_cannot_reference_class_type_parameters: { code: 2302, category: DiagnosticCategory.Error, key: "Static members cannot reference class type parameters." },
@@ -365,6 +368,8 @@ module ts {
         A_rest_element_cannot_contain_a_binding_pattern: { code: 2501, category: DiagnosticCategory.Error, key: "A rest element cannot contain a binding pattern." },
         _0_is_referenced_directly_or_indirectly_in_its_own_type_annotation: { code: 2502, category: DiagnosticCategory.Error, key: "'{0}' is referenced directly or indirectly in its own type annotation." },
         Cannot_find_namespace_0: { code: 2503, category: DiagnosticCategory.Error, key: "Cannot find namespace '{0}'." },
+        No_best_common_type_exists_among_yield_expressions: { code: 2504, category: DiagnosticCategory.Error, key: "No best common type exists among yield expressions." },
+        A_generator_cannot_have_a_void_type_annotation: { code: 2505, category: DiagnosticCategory.Error, key: "A generator cannot have a 'void' type annotation." },
         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}'." },
@@ -522,6 +527,7 @@ module ts {
         _0_implicitly_has_type_any_because_it_is_does_not_have_a_type_annotation_and_is_referenced_directly_or_indirectly_in_its_own_initializer: { code: 7022, category: DiagnosticCategory.Error, key: "'{0}' implicitly has type 'any' because it is does not have a type annotation and is referenced directly or indirectly in its own initializer." },
         _0_implicitly_has_return_type_any_because_it_does_not_have_a_return_type_annotation_and_is_referenced_directly_or_indirectly_in_one_of_its_return_expressions: { code: 7023, category: DiagnosticCategory.Error, key: "'{0}' implicitly has return type 'any' because it does not have a return type annotation and is referenced directly or indirectly in one of its return expressions." },
         Function_implicitly_has_return_type_any_because_it_does_not_have_a_return_type_annotation_and_is_referenced_directly_or_indirectly_in_one_of_its_return_expressions: { code: 7024, category: DiagnosticCategory.Error, key: "Function implicitly has return type 'any' because it does not have a return type annotation and is referenced directly or indirectly in one of its return expressions." },
+        Generator_implicitly_has_type_0_because_it_does_not_yield_any_values_Consider_supplying_a_return_type: { code: 7025, category: DiagnosticCategory.Error, key: "Generator implicitly has type '{0}' because it does not yield any values. Consider supplying a return type." },
         You_cannot_rename_this_element: { code: 8000, category: DiagnosticCategory.Error, key: "You cannot rename this element." },
         You_cannot_rename_elements_that_are_defined_in_the_standard_TypeScript_library: { code: 8001, category: DiagnosticCategory.Error, key: "You cannot rename elements that are defined in the standard TypeScript library." },
         import_can_only_be_used_in_a_ts_file: { code: 8002, category: DiagnosticCategory.Error, key: "'import ... =' can only be used in a .ts file." },
@@ -540,8 +546,6 @@ module ts {
         enum_declarations_can_only_be_used_in_a_ts_file: { code: 8015, category: DiagnosticCategory.Error, key: "'enum declarations' can only be used in a .ts file." },
         type_assertion_expressions_can_only_be_used_in_a_ts_file: { code: 8016, category: DiagnosticCategory.Error, key: "'type assertion expressions' can only be used in a .ts file." },
         decorators_can_only_be_used_in_a_ts_file: { code: 8017, category: DiagnosticCategory.Error, key: "'decorators' can only be used in a .ts file." },
-        yield_expressions_are_not_currently_supported: { code: 9000, category: DiagnosticCategory.Error, key: "'yield' expressions are not currently supported." },
-        Generators_are_not_currently_supported: { code: 9001, category: DiagnosticCategory.Error, key: "Generators are not currently supported." },
         Only_identifiers_Slashqualified_names_with_optional_type_arguments_are_currently_supported_in_a_class_extends_clauses: { code: 9002, category: DiagnosticCategory.Error, key: "Only identifiers/qualified-names with optional type arguments are currently supported in a class 'extends' clauses." },
         class_expressions_are_not_currently_supported: { code: 9003, category: DiagnosticCategory.Error, key: "'class' expressions are not currently supported." },
         class_declarations_are_only_supported_directly_inside_a_module_or_as_a_top_level_declaration: { code: 9004, category: DiagnosticCategory.Error, key: "'class' declarations are only supported directly inside a module or as a top level declaration." },

src/compiler/diagnosticMessages.json

@@ -467,7 +467,7 @@
         "category": "Error",
         "code": 1162
     },
-    "'yield' expression must be contained_within a generator declaration.": {
+    "A 'yield' expression is only allowed in a generator body.": {
         "category": "Error",
         "code": 1163
     },
@@ -682,8 +682,21 @@
     "Export assignment is not supported when '--module' flag is 'system'.": {
         "category": "Error",
         "code": 1218
+    },    
+    "Generators are only available when targeting ECMAScript 6 or higher.": {
+        "category": "Error",
+        "code": 1219
+    },
+    "Generators are not allowed in an ambient context.": {
+        "category": "Error",
+        "code": 1220
+    },
+    "An overload signature cannot be declared as a generator.": {
+        "category": "Error",
+        "code": 1221
     },
 
+
     "Duplicate identifier '{0}'.": {
         "category": "Error",
         "code": 2300
@@ -1439,15 +1452,23 @@
     "A rest element cannot contain a binding pattern.": {
         "category": "Error",
         "code": 2501
-    },
+    },
     "'{0}' is referenced directly or indirectly in its own type annotation.": {
         "category": "Error",
         "code": 2502
-    },
+    },
     "Cannot find namespace '{0}'.": {
         "category": "Error",
         "code": 2503
+    },
+    "No best common type exists among yield expressions.": {
+        "category": "Error",
+        "code": 2504
     },
+    "A generator cannot have a 'void' type annotation.": {
+        "category": "Error",
+        "code": 2505
+    },
 
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",
@@ -2080,6 +2101,10 @@
         "category": "Error",
         "code": 7024
     },
+    "Generator implicitly has type '{0}' because it does not yield any values. Consider supplying a return type.": {
+        "category": "Error",
+        "code": 7025
+    },
     "You cannot rename this element.": {
         "category": "Error",
         "code": 8000
@@ -2153,14 +2178,6 @@
         "code": 8017
     },
 
-    "'yield' expressions are not currently supported.": {
-        "category": "Error",
-        "code": 9000
-    },
-    "Generators are not currently supported.": {
-        "category": "Error",
-        "code": 9001
-    },
     "Only identifiers/qualified-names with optional type arguments are currently supported in a class 'extends' clauses.": {
         "category": "Error",
         "code": 9002

src/compiler/parser.ts

@@ -4010,7 +4010,20 @@ module ts {
             property.name = name;
             property.questionToken = questionToken;
             property.type = parseTypeAnnotation();
-            property.initializer = allowInAnd(parseNonParameterInitializer);
+
+            // For initializers, we always want to allow 'in' expressions. For instance properties specifically,
+            // since they are evaluated inside the constructor, we do *not* want to parse yield expressions,
+            // so we specifically turn the yield context off. The grammar would look something like this:
+            //
+            //    MemberVariableDeclaration[Yield]:
+            //        AccessibilityModifier_opt   PropertyName   TypeAnnotation_opt   Initialiser_opt[In];
+            //        AccessibilityModifier_opt  static_opt  PropertyName   TypeAnnotation_opt   Initialiser_opt[In, ?Yield];
+            //
+            // The checker may still error in the static case to explicitly disallow the yield expression.
+            property.initializer = modifiers && modifiers.flags & NodeFlags.Static
+                ? allowInAnd(parseNonParameterInitializer)
+                : doOutsideOfContext(ParserContextFlags.Yield | ParserContextFlags.DisallowIn, parseNonParameterInitializer);
+
             parseSemicolon();
             return finishNode(property);
         }

src/compiler/types.ts

@@ -660,7 +660,7 @@ module ts {
 
     export interface YieldExpression extends Expression {
         asteriskToken?: Node;
-        expression: Expression;
+        expression?: Expression;
     }
 
     export interface BinaryExpression extends Expression {
@@ -1543,6 +1543,13 @@ module ts {
         numberIndexType: Type;             // Numeric index type
     }
 
+    /* @internal */
+    // Just a place to cache element types of iterables and iterators
+    export interface IterableOrIteratorType extends ObjectType, UnionType {
+        iterableElementType?: Type;
+        iteratorElementType?: Type;
+    }
+
     // Type parameters (TypeFlags.TypeParameter)
     export interface TypeParameter extends Type {
         constraint: Type;        // Constraint