Index signatures for symbols and template literal strings (#44512)

* Switch index signature storage to 'indexInfos: IndexInfo[]' property

* Accept new baselines

* Remove another usage of IndexKind enum

* Update getIndexedAccessType and resolveMappedTypeMembers

* Accept new baselines

* Update grammar checking for index signatures

* Accept new baselines

* Consider all index signatures in mapped types and union types

* Accept new baselines

* Update getIndexType

* Accept new baselines

* Intersect multiple applicable index signatures

* Use getApplicableIndexInfo instead of hardwired string/number handling

* Update index signature relationship checking

* Report type for which index signature is missing

* Report type for which index signature is missing

* Accept new baselines

* Make 'number' index signatures consistently apply to numeric strings

* Accept new baselines

* Update fourslash test

* Revise index constraint checking

* Accept new baselines

* Update error messages

* Accept new baselines

* Update type inference from index signatures

* Update isKnownProperty

* Update contextual typing based on index signatures

* Accept new baselines

* Support union types in index signature declarations

* Accept new baselines

* Check duplicate index signatures / remove redundant template literals from unions with string

* Accept new baselines

* Include key type in diagnostic / check symbol-named properties

* Accept new baselines

* Minor fix

* Add tests

* Accept new baselines

* Add optimized findApplicableIndexInfoForName

* Accept new baselines

* Another place we don't need to obtain literal type for property name

* Accept new baselines

* Don't create literal types that are going to be discarded

* Individual maps for string, number, bigint, and enum literal types

* Remove ineffective optimizations

* Accept new baselines

* Permit intersections as key types in index signatures

* Index expression in element access is template literal context

* Add tests

* Accept new baselines

* Symbol index signatures from object literals with computed symbol properties

* Accept new baselines

* Add more tests

* Accept new baselines

* Implement Go To Definition for all applicable index signatures

* Add fourslash test

* Accept new API baselines

Author: ahejlsberg

src/compiler/checker.ts

@@ -75,10 +75,6 @@
         "category": "Error",
         "code": 1022
     },
-    "An index signature parameter type must be either 'string' or 'number'.": {
-        "category": "Error",
-        "code": 1023
-    },
     "'readonly' modifier can only appear on a property declaration or index signature.": {
         "category": "Error",
         "code": 1024
@@ -891,6 +887,10 @@
         "category": "Error",
         "code": 1267
     },
+    "An index signature parameter type must be 'string', 'number', 'symbol', or a template literal type.": {
+        "category": "Error",
+        "code": 1268
+    },
 
     "'with' statements are not allowed in an async function block.": {
         "category": "Error",
@@ -996,11 +996,7 @@
         "category": "Error",
         "code": 1335
     },
-    "An index signature parameter type cannot be a type alias. Consider writing '[{0}: {1}]: {2}' instead.": {
-        "category": "Error",
-        "code": 1336
-    },
-    "An index signature parameter type cannot be a union type. Consider using a mapped object type instead.": {
+    "An index signature parameter type cannot be a literal type or generic type. Consider using a mapped object type instead.": {
         "category": "Error",
         "code": 1337
     },
@@ -1518,11 +1514,11 @@
         "category": "Error",
         "code": 2328
     },
-    "Index signature is missing in type '{0}'.": {
+    "Index signature for type '{0}' is missing in type '{1}'.": {
         "category": "Error",
         "code": 2329
     },
-    "Index signatures are incompatible.": {
+    "'{0}' and '{1}' index signatures are incompatible.": {
         "category": "Error",
         "code": 2330
     },
@@ -1698,14 +1694,10 @@
         "category": "Error",
         "code": 2373
     },
-    "Duplicate string index signature.": {
+    "Duplicate index signature for type '{0}'.": {
         "category": "Error",
         "code": 2374
     },
-    "Duplicate number index signature.": {
-        "category": "Error",
-        "code": 2375
-    },
     "A 'super' call must be the first statement in the constructor when a class contains initialized properties, parameter properties, or private identifiers.": {
         "category": "Error",
         "code": 2376
@@ -1842,15 +1834,11 @@
         "category": "Error",
         "code": 2410
     },
-    "Property '{0}' of type '{1}' is not assignable to string index type '{2}'.": {
+    "Property '{0}' of type '{1}' is not assignable to '{2}' index type '{3}'.": {
         "category": "Error",
         "code": 2411
     },
-    "Property '{0}' of type '{1}' is not assignable to numeric index type '{2}'.": {
-        "category": "Error",
-        "code": 2412
-    },
-    "Numeric index type '{0}' is not assignable to string index type '{1}'.": {
+    "'{0}' index type '{1}' is not assignable to '{2}' index type '{3}'.": {
         "category": "Error",
         "code": 2413
     },
@@ -2690,6 +2678,10 @@
         "category": "Error",
         "code": 2633
     },
+    "'{0}' index signatures are incompatible.": {
+        "category": "Error",
+        "code": 2634
+    },
 
     "Cannot augment module '{0}' with value exports because it resolves to a non-module entity.": {
         "category": "Error",

src/compiler/diagnosticMessages.json

@@ -8,7 +8,6 @@ namespace ts {
         resolveStructuredTypeMembers: (type: ObjectType) => ResolvedType,
         getTypeOfSymbol: (sym: Symbol) => Type,
         getResolvedSymbol: (node: Node) => Symbol,
-        getIndexTypeOfStructuredType: (type: Type, kind: IndexKind) => Type | undefined,
         getConstraintOfTypeParameter: (typeParameter: TypeParameter) => Type | undefined,
         getFirstIdentifier: (node: EntityNameOrEntityNameExpression) => Identifier,
         getTypeArguments: (type: TypeReference) => readonly Type[]) {
@@ -140,13 +139,11 @@ namespace ts {
             }
 
             function visitObjectType(type: ObjectType): void {
-                const stringIndexType = getIndexTypeOfStructuredType(type, IndexKind.String);
-                visitType(stringIndexType);
-                const numberIndexType = getIndexTypeOfStructuredType(type, IndexKind.Number);
-                visitType(numberIndexType);
-
-                // The two checks above *should* have already resolved the type (if needed), so this should be cached
                 const resolved = resolveStructuredTypeMembers(type);
+                for (const info of resolved.indexInfos) {
+                    visitType(info.keyType);
+                    visitType(info.type);
+                }
                 for (const signature of resolved.callSignatures) {
                     visitSignature(signature);
                 }

src/compiler/symbolWalker.ts

@@ -4088,6 +4088,7 @@ namespace ts {
         getPrivateIdentifierPropertyOfType(leftType: Type, name: string, location: Node): Symbol | undefined;
         /* @internal */ getTypeOfPropertyOfType(type: Type, propertyName: string): Type | undefined;
         getIndexInfoOfType(type: Type, kind: IndexKind): IndexInfo | undefined;
+        getIndexInfosOfType(type: Type): readonly IndexInfo[];
         getSignaturesOfType(type: Type, kind: SignatureKind): readonly Signature[];
         getIndexTypeOfType(type: Type, kind: IndexKind): Type | undefined;
         getBaseTypes(type: InterfaceType): BaseType[];
@@ -4117,8 +4118,8 @@ namespace ts {
         signatureToSignatureDeclaration(signature: Signature, kind: SyntaxKind, enclosingDeclaration: Node | undefined, flags: NodeBuilderFlags | undefined): SignatureDeclaration & {typeArguments?: NodeArray<TypeNode>} | undefined;
         /* @internal */ signatureToSignatureDeclaration(signature: Signature, kind: SyntaxKind, enclosingDeclaration: Node | undefined, flags: NodeBuilderFlags | undefined, tracker?: SymbolTracker): SignatureDeclaration & {typeArguments?: NodeArray<TypeNode>} | undefined; // eslint-disable-line @typescript-eslint/unified-signatures
         /** Note that the resulting nodes cannot be checked. */
-        indexInfoToIndexSignatureDeclaration(indexInfo: IndexInfo, kind: IndexKind, enclosingDeclaration: Node | undefined, flags: NodeBuilderFlags | undefined): IndexSignatureDeclaration | undefined;
-        /* @internal */ indexInfoToIndexSignatureDeclaration(indexInfo: IndexInfo, kind: IndexKind, enclosingDeclaration: Node | undefined, flags: NodeBuilderFlags | undefined, tracker?: SymbolTracker): IndexSignatureDeclaration | undefined; // eslint-disable-line @typescript-eslint/unified-signatures
+        indexInfoToIndexSignatureDeclaration(indexInfo: IndexInfo, enclosingDeclaration: Node | undefined, flags: NodeBuilderFlags | undefined): IndexSignatureDeclaration | undefined;
+        /* @internal */ indexInfoToIndexSignatureDeclaration(indexInfo: IndexInfo, enclosingDeclaration: Node | undefined, flags: NodeBuilderFlags | undefined, tracker?: SymbolTracker): IndexSignatureDeclaration | undefined; // eslint-disable-line @typescript-eslint/unified-signatures
         /** Note that the resulting nodes cannot be checked. */
         symbolToEntityName(symbol: Symbol, meaning: SymbolFlags, enclosingDeclaration: Node | undefined, flags: NodeBuilderFlags | undefined): EntityName | undefined;
         /** Note that the resulting nodes cannot be checked. */
@@ -4132,6 +4133,7 @@ namespace ts {
 
         getSymbolsInScope(location: Node, meaning: SymbolFlags): Symbol[];
         getSymbolAtLocation(node: Node): Symbol | undefined;
+        /* @internal */ getIndexInfosAtLocation(node: Node): readonly IndexInfo[] | undefined;
         getSymbolsOfParameterPropertyDeclaration(parameter: ParameterDeclaration, parameterName: string): Symbol[];
         /**
          * The function returns the value (local variable) symbol of an identifier in the short-hand property assignment.
@@ -4244,7 +4246,7 @@ namespace ts {
         /* @internal */ createPromiseType(type: Type): Type;
 
         /* @internal */ isTypeAssignableTo(source: Type, target: Type): boolean;
-        /* @internal */ createAnonymousType(symbol: Symbol | undefined, members: SymbolTable, callSignatures: Signature[], constructSignatures: Signature[], stringIndexInfo: IndexInfo | undefined, numberIndexInfo: IndexInfo | undefined): Type;
+        /* @internal */ createAnonymousType(symbol: Symbol | undefined, members: SymbolTable, callSignatures: Signature[], constructSignatures: Signature[], indexInfos: IndexInfo[]): Type;
         /* @internal */ createSignature(
             declaration: SignatureDeclaration | undefined,
             typeParameters: readonly TypeParameter[] | undefined,
@@ -4256,7 +4258,7 @@ namespace ts {
             flags: SignatureFlags
         ): Signature;
         /* @internal */ createSymbol(flags: SymbolFlags, name: __String): TransientSymbol;
-        /* @internal */ createIndexInfo(type: Type, isReadonly: boolean, declaration?: SignatureDeclaration): IndexInfo;
+        /* @internal */ createIndexInfo(keyType: Type, type: Type, isReadonly: boolean, declaration?: SignatureDeclaration): IndexInfo;
         /* @internal */ isSymbolAccessible(symbol: Symbol, enclosingDeclaration: Node | undefined, meaning: SymbolFlags, shouldComputeAliasToMarkVisible: boolean): SymbolAccessibilityResult;
         /* @internal */ tryFindAmbientModule(moduleName: string): Symbol | undefined;
         /* @internal */ tryFindAmbientModuleWithoutAugmentations(moduleName: string): Symbol | undefined;
@@ -5272,8 +5274,7 @@ namespace ts {
         /* @internal */ properties?: Symbol[];             // Properties
         /* @internal */ callSignatures?: readonly Signature[];      // Call signatures of type
         /* @internal */ constructSignatures?: readonly Signature[]; // Construct signatures of type
-        /* @internal */ stringIndexInfo?: IndexInfo;      // String indexing info
-        /* @internal */ numberIndexInfo?: IndexInfo;      // Numeric indexing info
+        /* @internal */ indexInfos?: readonly IndexInfo[];  // Index signatures
         /* @internal */ objectTypeWithoutAbstractConstructSignatures?: ObjectType;
     }
 
@@ -5298,8 +5299,7 @@ namespace ts {
         declaredProperties: Symbol[];                   // Declared members
         declaredCallSignatures: Signature[];            // Declared call signatures
         declaredConstructSignatures: Signature[];       // Declared construct signatures
-        declaredStringIndexInfo?: IndexInfo; // Declared string indexing info
-        declaredNumberIndexInfo?: IndexInfo; // Declared numeric indexing info
+        declaredIndexInfos: IndexInfo[];                // Declared index signatures
     }
 
     /**
@@ -5457,6 +5457,7 @@ namespace ts {
         properties: Symbol[];             // Properties
         callSignatures: readonly Signature[];      // Call signatures of type
         constructSignatures: readonly Signature[]; // Construct signatures of type
+        indexInfos: readonly IndexInfo[];  // Index signatures
     }
 
     /* @internal */
@@ -5693,6 +5694,7 @@ namespace ts {
     }
 
     export interface IndexInfo {
+        keyType: Type;
         type: Type;
         isReadonly: boolean;
         declaration?: IndexSignatureDeclaration;

src/compiler/types.ts

@@ -2,7 +2,7 @@
 namespace ts.codefix {
     const fixIdAddMissingTypeof = "fixConvertToMappedObjectType";
     const fixId = fixIdAddMissingTypeof;
-    const errorCodes = [Diagnostics.An_index_signature_parameter_type_cannot_be_a_union_type_Consider_using_a_mapped_object_type_instead.code];
+    const errorCodes = [Diagnostics.An_index_signature_parameter_type_cannot_be_a_literal_type_or_generic_type_Consider_using_a_mapped_object_type_instead.code];
 
     type FixableDeclaration = InterfaceDeclaration | TypeAliasDeclaration;
 

src/services/codefixes/convertToMappedObjectType.ts

@@ -70,7 +70,7 @@ namespace ts.codefix {
         function createMissingIndexSignatureDeclaration(type: InterfaceType, kind: IndexKind): void {
             const indexInfoOfKind = checker.getIndexInfoOfType(type, kind);
             if (indexInfoOfKind) {
-                insertInterfaceMemberNode(sourceFile, classDeclaration, checker.indexInfoToIndexSignatureDeclaration(indexInfoOfKind, kind, classDeclaration, /*flags*/ undefined, getNoopSymbolTrackerWithResolver(context))!);
+                insertInterfaceMemberNode(sourceFile, classDeclaration, checker.indexInfoToIndexSignatureDeclaration(indexInfoOfKind, classDeclaration, /*flags*/ undefined, getNoopSymbolTrackerWithResolver(context))!);
             }
         }
 

src/services/codefixes/fixClassIncorrectlyImplementsInterface.ts

@@ -57,9 +57,8 @@ namespace ts.codefix {
             Diagnostics.Type_0_is_not_assignable_to_type_1.code,
             Diagnostics.Type_0_is_not_assignable_to_type_1_Two_different_types_with_this_name_exist_but_they_are_unrelated.code,
             Diagnostics.Type_predicate_0_is_not_assignable_to_1.code,
-            Diagnostics.Property_0_of_type_1_is_not_assignable_to_string_index_type_2.code,
-            Diagnostics.Property_0_of_type_1_is_not_assignable_to_numeric_index_type_2.code,
-            Diagnostics.Numeric_index_type_0_is_not_assignable_to_string_index_type_1.code,
+            Diagnostics.Property_0_of_type_1_is_not_assignable_to_2_index_type_3.code,
+            Diagnostics._0_index_type_1_is_not_assignable_to_2_index_type_3.code,
             Diagnostics.Property_0_in_type_1_is_not_assignable_to_the_same_property_in_base_type_2.code,
             Diagnostics.Property_0_in_type_1_is_not_assignable_to_type_2.code,
             Diagnostics.Property_0_of_JSX_spread_attribute_is_not_assignable_to_target_property.code,

src/services/codefixes/fixInvalidImportSyntax.ts

@@ -955,13 +955,15 @@ namespace ts.codefix {
                 }
                 calls.push(...checker.getSignaturesOfType(anon, SignatureKind.Call));
                 constructs.push(...checker.getSignaturesOfType(anon, SignatureKind.Construct));
-                if (anon.stringIndexInfo) {
-                    stringIndices.push(anon.stringIndexInfo.type);
-                    stringIndexReadonly = stringIndexReadonly || anon.stringIndexInfo.isReadonly;
+                const stringIndexInfo = checker.getIndexInfoOfType(anon, IndexKind.String);
+                if (stringIndexInfo) {
+                    stringIndices.push(stringIndexInfo.type);
+                    stringIndexReadonly = stringIndexReadonly || stringIndexInfo.isReadonly;
                 }
-                if (anon.numberIndexInfo) {
-                    numberIndices.push(anon.numberIndexInfo.type);
-                    numberIndexReadonly = numberIndexReadonly || anon.numberIndexInfo.isReadonly;
+                const numberIndexInfo = checker.getIndexInfoOfType(anon, IndexKind.Number);
+                if (numberIndexInfo) {
+                    numberIndices.push(numberIndexInfo.type);
+                    numberIndexReadonly = numberIndexReadonly || numberIndexInfo.isReadonly;
                 }
             }
             const members = mapEntries(props, (name, types) => {
@@ -970,13 +972,15 @@ namespace ts.codefix {
                 s.type = checker.getUnionType(types);
                 return [name, s];
             });
+            const indexInfos = [];
+            if (stringIndices.length) indexInfos.push(checker.createIndexInfo(checker.getStringType(), checker.getUnionType(stringIndices), stringIndexReadonly));
+            if (numberIndices.length) indexInfos.push(checker.createIndexInfo(checker.getNumberType(), checker.getUnionType(numberIndices), numberIndexReadonly));
             return checker.createAnonymousType(
                 anons[0].symbol,
                 members as UnderscoreEscapedMap<TransientSymbol>,
                 calls,
                 constructs,
-                stringIndices.length ? checker.createIndexInfo(checker.getUnionType(stringIndices), stringIndexReadonly) : undefined,
-                numberIndices.length ? checker.createIndexInfo(checker.getUnionType(numberIndices), numberIndexReadonly) : undefined);
+                indexInfos);
         }
 
         function inferTypes(usage: Usage): Type[] {
@@ -1015,8 +1019,8 @@ namespace ts.codefix {
             }
             const callSignatures: Signature[] = usage.calls ? [getSignatureFromCalls(usage.calls)] : [];
             const constructSignatures: Signature[] = usage.constructs ? [getSignatureFromCalls(usage.constructs)] : [];
-            const stringIndexInfo = usage.stringIndex && checker.createIndexInfo(combineFromUsage(usage.stringIndex), /*isReadonly*/ false);
-            return checker.createAnonymousType(/*symbol*/ undefined, members, callSignatures, constructSignatures, stringIndexInfo, /*numberIndexInfo*/ undefined);
+            const indexInfos = usage.stringIndex ? [checker.createIndexInfo(checker.getStringType(), combineFromUsage(usage.stringIndex), /*isReadonly*/ false)] : [];
+            return checker.createAnonymousType(/*symbol*/ undefined, members, callSignatures, constructSignatures, indexInfos);
         }
 
         function inferNamedTypesFromProperties(usage: Usage): Type[] {
@@ -1121,7 +1125,7 @@ namespace ts.codefix {
         }
 
         function getFunctionFromCalls(calls: CallUsage[]) {
-            return checker.createAnonymousType(/*symbol*/ undefined, createSymbolTable(), [getSignatureFromCalls(calls)], emptyArray, /*stringIndexInfo*/ undefined, /*numberIndexInfo*/ undefined);
+            return checker.createAnonymousType(/*symbol*/ undefined, createSymbolTable(), [getSignatureFromCalls(calls)], emptyArray, emptyArray);
         }
 
         function getSignatureFromCalls(calls: CallUsage[]): Signature {

src/services/codefixes/inferFromUsage.ts

@@ -76,7 +76,7 @@ namespace ts.codefix {
         const member = checker.createSymbol(SymbolFlags.Property, label.escapedText);
         member.type = checker.getTypeAtLocation(expression);
         const members = createSymbolTable([member]);
-        return checker.createAnonymousType(/*symbol*/ undefined, members, [], [], /*stringIndexInfo*/ undefined, /*numberIndexInfo*/ undefined);
+        return checker.createAnonymousType(/*symbol*/ undefined, members, [], [], []);
     }
 
     function getFixInfo(checker: TypeChecker, declaration: FunctionLikeDeclaration, expectType: Type, isFunctionType: boolean): Info | undefined {
@@ -152,8 +152,7 @@ namespace ts.codefix {
                     createSymbolTable(),
                     [newSig],
                     [],
-                    /*stringIndexInfo*/ undefined,
-                    /*numberIndexInfo*/ undefined);
+                    []);
             }
             else {
                 exprType = checker.getAnyType();

src/services/codefixes/returnValueCorrect.ts

@@ -212,12 +212,7 @@ namespace ts.GoToDefinition {
 
     // At 'x.foo', see if the type of 'x' has an index signature, and if so find its declarations.
     function getDefinitionInfoForIndexSignatures(node: Node, checker: TypeChecker): DefinitionInfo[] | undefined {
-        if (!isPropertyAccessExpression(node.parent) || node.parent.name !== node) return;
-        const type = checker.getTypeAtLocation(node.parent.expression);
-        return mapDefined(type.isUnionOrIntersection() ? type.types : [type], nonUnionType => {
-            const info = checker.getIndexInfoOfType(nonUnionType, IndexKind.String);
-            return info && info.declaration && createDefinitionFromSignatureDeclaration(checker, info.declaration);
-        });
+        return mapDefined(checker.getIndexInfosAtLocation(node), info => info.declaration && createDefinitionFromSignatureDeclaration(checker, info.declaration));
     }
 
     function getSymbol(node: Node, checker: TypeChecker): Symbol | undefined {