Allow Symbol indexer in ES6

Author: JsonFreeman

src/compiler/checker.ts

@@ -10472,25 +10472,33 @@ module ts {
                     return grammarErrorOnNode(node, Diagnostics.An_index_signature_must_have_exactly_one_parameter);
                 }
             }
-            else if (parameter.dotDotDotToken) {
+            if (parameter.dotDotDotToken) {
                 return grammarErrorOnNode(parameter.dotDotDotToken, Diagnostics.An_index_signature_cannot_have_a_rest_parameter);
             }
-            else if (parameter.flags & NodeFlags.Modifier) {
+            if (parameter.flags & NodeFlags.Modifier) {
                 return grammarErrorOnNode(parameter.name, Diagnostics.An_index_signature_parameter_cannot_have_an_accessibility_modifier);
             }
-            else if (parameter.questionToken) {
+            if (parameter.questionToken) {
                 return grammarErrorOnNode(parameter.questionToken, Diagnostics.An_index_signature_parameter_cannot_have_a_question_mark);
             }
-            else if (parameter.initializer) {
+            if (parameter.initializer) {
                 return grammarErrorOnNode(parameter.name, Diagnostics.An_index_signature_parameter_cannot_have_an_initializer);
             }
-            else if (!parameter.type) {
+            if (!parameter.type) {
                 return grammarErrorOnNode(parameter.name, Diagnostics.An_index_signature_parameter_must_have_a_type_annotation);
             }
-            else if (parameter.type.kind !== SyntaxKind.StringKeyword && parameter.type.kind !== SyntaxKind.NumberKeyword) {
-                return grammarErrorOnNode(parameter.name, Diagnostics.An_index_signature_parameter_type_must_be_string_or_number);
+            if (parameter.type.kind !== SyntaxKind.StringKeyword && parameter.type.kind !== SyntaxKind.NumberKeyword) {
+                if (isESSymbolTypeNode(parameter.type)) {
+                    if (languageVersion < ScriptTarget.ES6) {
+                        return grammarErrorOnNode(parameter.type, Diagnostics.Symbol_indexers_are_only_available_when_targeting_ECMAScript_6_and_higher);
+                    }
+                    // No error for parameter type
+                }
+                else {
+                    return grammarErrorOnNode(parameter.name, Diagnostics.An_index_signature_parameter_type_must_be_string_number_or_Symbol);
+                }
             }
-            else if (!node.type) {
+            if (!node.type) {
                 return grammarErrorOnNode(node, Diagnostics.An_index_signature_must_have_a_type_annotation);
             }
         }

src/compiler/diagnosticInformationMap.generated.ts

@@ -19,7 +19,7 @@ module ts {
         An_index_signature_parameter_cannot_have_an_initializer: { code: 1020, category: DiagnosticCategory.Error, key: "An index signature parameter cannot have an initializer." },
         An_index_signature_must_have_a_type_annotation: { code: 1021, category: DiagnosticCategory.Error, key: "An index signature must have a type annotation." },
         An_index_signature_parameter_must_have_a_type_annotation: { code: 1022, category: DiagnosticCategory.Error, key: "An index signature parameter must have a type annotation." },
-        An_index_signature_parameter_type_must_be_string_or_number: { code: 1023, category: DiagnosticCategory.Error, key: "An index signature parameter type must be 'string' or 'number'." },
+        An_index_signature_parameter_type_must_be_string_number_or_Symbol: { code: 1023, category: DiagnosticCategory.Error, key: "An index signature parameter type must be 'string', 'number', or 'Symbol'." },
         A_class_or_interface_declaration_can_only_have_one_extends_clause: { code: 1024, category: DiagnosticCategory.Error, key: "A class or interface declaration can only have one 'extends' clause." },
         An_extends_clause_must_precede_an_implements_clause: { code: 1025, category: DiagnosticCategory.Error, key: "An 'extends' clause must precede an 'implements' clause." },
         A_class_can_only_extend_a_single_class: { code: 1026, category: DiagnosticCategory.Error, key: "A class can only extend a single class." },
@@ -147,6 +147,7 @@ module ts {
         Merge_conflict_marker_encountered: { code: 1185, category: DiagnosticCategory.Error, key: "Merge conflict marker encountered." },
         A_rest_element_cannot_have_an_initializer: { code: 1186, category: DiagnosticCategory.Error, key: "A rest element cannot have an initializer." },
         A_parameter_property_may_not_be_a_binding_pattern: { code: 1187, category: DiagnosticCategory.Error, key: "A parameter property may not be a binding pattern." },
+        Symbol_indexers_are_only_available_when_targeting_ECMAScript_6_and_higher: { code: 1188, category: DiagnosticCategory.Error, key: "'Symbol' indexers are only available when targeting ECMAScript 6 and higher.", isEarly: true },
         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." },

src/compiler/diagnosticMessages.json

@@ -67,7 +67,7 @@
         "category": "Error",
         "code": 1022
     },
-    "An index signature parameter type must be 'string' or 'number'.": {
+    "An index signature parameter type must be 'string', 'number', or 'Symbol'.": {
         "category": "Error",
         "code": 1023
     },
@@ -579,6 +579,11 @@
         "category": "Error",
         "code": 1187
     },
+    "'Symbol' indexers are only available when targeting ECMAScript 6 and higher.": {
+        "category": "Error",
+        "code": 1188,
+        "isEarly": true
+    },
 
     "Duplicate identifier '{0}'.": {
         "category": "Error",

src/compiler/utilities.ts

@@ -835,6 +835,13 @@ module ts {
         return SyntaxKind.FirstTriviaToken <= token && token <= SyntaxKind.LastTriviaToken;
     }
 
+    export function isESSymbolTypeNode(node: Node): boolean {
+        return node.kind === SyntaxKind.TypeReference &&
+            (<TypeReferenceNode>node).typeArguments === undefined &&
+            (<TypeReferenceNode>node).typeName.kind === SyntaxKind.Identifier &&
+            (<Identifier>(<TypeReferenceNode>node).typeName).text === "Symbol";
+    }
+
     export function isModifier(token: SyntaxKind): boolean {
         switch (token) {
             case SyntaxKind.PublicKeyword:

tests/baselines/reference/arraySigChecking.errors.txt

@@ -1,4 +1,4 @@
-tests/cases/compiler/arraySigChecking.ts(11,17): error TS1023: An index signature parameter type must be 'string' or 'number'.
+tests/cases/compiler/arraySigChecking.ts(11,17): error TS1023: An index signature parameter type must be 'string', 'number', or 'Symbol'.
 tests/cases/compiler/arraySigChecking.ts(18,5): error TS2322: Type 'void[]' is not assignable to type 'string[]'.
   Type 'void' is not assignable to type 'string'.
 tests/cases/compiler/arraySigChecking.ts(22,1): error TS2322: Type 'number[][]' is not assignable to type 'number[][][]'.
@@ -20,7 +20,7 @@ tests/cases/compiler/arraySigChecking.ts(22,1): error TS2322: Type 'number[][]'
 
         var foo: { [index: any]; }; // expect an error here
                     ~~~~~
-!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
+!!! error TS1023: An index signature parameter type must be 'string', 'number', or 'Symbol'.
     }
 
     interface myInt {

tests/baselines/reference/genericTypeReferenceWithoutTypeArgument.d.errors.txt

@@ -2,7 +2,7 @@ tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenc
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.d.ts(10,21): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.d.ts(11,22): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.d.ts(11,26): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
-tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.d.ts(12,19): error TS1023: An index signature parameter type must be 'string' or 'number'.
+tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.d.ts(12,19): error TS1023: An index signature parameter type must be 'string', 'number', or 'Symbol'.
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.d.ts(12,22): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.d.ts(12,26): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.d.ts(14,23): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
@@ -36,7 +36,7 @@ tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenc
 !!! error TS2314: Generic type 'C<T>' requires 1 type argument(s).
     declare var d: { [x: C]: C };
                       ~
-!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
+!!! error TS1023: An index signature parameter type must be 'string', 'number', or 'Symbol'.
                          ~
 !!! error TS2314: Generic type 'C<T>' requires 1 type argument(s).
                              ~

tests/baselines/reference/genericTypeReferenceWithoutTypeArgument.errors.txt

@@ -2,7 +2,7 @@ tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenc
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.ts(10,13): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.ts(11,14): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.ts(11,18): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
-tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.ts(12,11): error TS1023: An index signature parameter type must be 'string' or 'number'.
+tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.ts(12,11): error TS1023: An index signature parameter type must be 'string', 'number', or 'Symbol'.
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.ts(12,14): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.ts(12,18): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument.ts(14,13): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
@@ -46,7 +46,7 @@ tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenc
 !!! error TS2314: Generic type 'C<T>' requires 1 type argument(s).
     var d: { [x: C]: C };
               ~
-!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
+!!! error TS1023: An index signature parameter type must be 'string', 'number', or 'Symbol'.
                  ~
 !!! error TS2314: Generic type 'C<T>' requires 1 type argument(s).
                      ~

tests/baselines/reference/genericTypeReferenceWithoutTypeArgument2.errors.txt

@@ -2,7 +2,7 @@ tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenc
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(10,13): error TS2314: Generic type 'I<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(11,14): error TS2314: Generic type 'I<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(11,18): error TS2314: Generic type 'I<T>' requires 1 type argument(s).
-tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(12,11): error TS1023: An index signature parameter type must be 'string' or 'number'.
+tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(12,11): error TS1023: An index signature parameter type must be 'string', 'number', or 'Symbol'.
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(12,14): error TS2314: Generic type 'I<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(12,18): error TS2314: Generic type 'I<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument2.ts(14,13): error TS2314: Generic type 'I<T>' requires 1 type argument(s).
@@ -46,7 +46,7 @@ tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenc
 !!! error TS2314: Generic type 'I<T>' requires 1 type argument(s).
     var d: { [x: I]: I };
               ~
-!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
+!!! error TS1023: An index signature parameter type must be 'string', 'number', or 'Symbol'.
                  ~
 !!! error TS2314: Generic type 'I<T>' requires 1 type argument(s).
                      ~

tests/baselines/reference/genericTypeReferenceWithoutTypeArgument3.errors.txt

@@ -2,7 +2,7 @@ tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenc
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument3.ts(10,21): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument3.ts(11,22): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument3.ts(11,26): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
-tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument3.ts(12,19): error TS1023: An index signature parameter type must be 'string' or 'number'.
+tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument3.ts(12,19): error TS1023: An index signature parameter type must be 'string', 'number', or 'Symbol'.
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument3.ts(12,22): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument3.ts(12,26): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
 tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenceWithoutTypeArgument3.ts(14,23): error TS2314: Generic type 'C<T>' requires 1 type argument(s).
@@ -36,7 +36,7 @@ tests/cases/conformance/types/specifyingTypes/typeReferences/genericTypeReferenc
 !!! error TS2314: Generic type 'C<T>' requires 1 type argument(s).
     declare var d: { [x: C]: C };
                       ~
-!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
+!!! error TS1023: An index signature parameter type must be 'string', 'number', or 'Symbol'.
                          ~
 !!! error TS2314: Generic type 'C<T>' requires 1 type argument(s).
                              ~

tests/baselines/reference/indexTypeCheck.errors.txt

@@ -4,7 +4,7 @@ tests/cases/compiler/indexTypeCheck.ts(17,2): error TS2413: Numeric index type '
 tests/cases/compiler/indexTypeCheck.ts(22,2): error TS2413: Numeric index type 'Orange' is not assignable to string index type 'Yellow'.
 tests/cases/compiler/indexTypeCheck.ts(27,2): error TS2413: Numeric index type 'number' is not assignable to string index type 'string'.
 tests/cases/compiler/indexTypeCheck.ts(32,3): error TS1096: An index signature must have exactly one parameter.
-tests/cases/compiler/indexTypeCheck.ts(36,3): error TS1023: An index signature parameter type must be 'string' or 'number'.
+tests/cases/compiler/indexTypeCheck.ts(36,3): error TS1023: An index signature parameter type must be 'string', 'number', or 'Symbol'.
 tests/cases/compiler/indexTypeCheck.ts(51,1): error TS2342: An index expression argument must be of type 'string', 'number', or 'any'.
 
 
@@ -58,7 +58,7 @@ tests/cases/compiler/indexTypeCheck.ts(51,1): error TS2342: An index expression
     interface Magenta {
     	[p:Purple]; // error
     	 ~
-!!! error TS1023: An index signature parameter type must be 'string' or 'number'.
+!!! error TS1023: An index signature parameter type must be 'string', 'number', or 'Symbol'.
     }
 
     var yellow: Yellow;