Support interpreting non-literal computed properties in classes as implicit index signatures (#59860)

Author: weswigham

src/compiler/checker.ts

@@ -1167,6 +1167,7 @@ export const notImplementedResolver: EmitResolver = {
     getDeclarationStatementsForSourceFile: notImplemented,
     isImportRequiredByAugmentation: notImplemented,
     isDefinitelyReferenceToGlobalSymbolObject: notImplemented,
+    createLateBoundIndexSignatures: notImplemented,
 };
 
 const enum PipelinePhase {

src/compiler/emitter.ts

@@ -12,6 +12,7 @@ import {
     canHaveModifiers,
     canProduceDiagnostics,
     ClassDeclaration,
+    ClassElement,
     compact,
     concatenate,
     ConditionalTypeNode,
@@ -1652,7 +1653,8 @@ export function transformDeclarations(context: TransformationContext): Transform
                         /*initializer*/ undefined,
                     ),
                 ] : undefined;
-                const memberNodes = concatenate(concatenate(privateIdentifier, parameterProperties), visitNodes(input.members, visitDeclarationSubtree, isClassElement));
+                const lateIndexes = resolver.createLateBoundIndexSignatures(input, enclosingDeclaration, declarationEmitNodeBuilderFlags, declarationEmitInternalNodeBuilderFlags, symbolTracker);
+                const memberNodes = concatenate(concatenate(concatenate<ClassElement>(privateIdentifier, lateIndexes), parameterProperties), visitNodes(input.members, visitDeclarationSubtree, isClassElement));
                 const members = factory.createNodeArray(memberNodes);
 
                 const extendsClause = getEffectiveBaseTypeNode(input);

src/compiler/transformers/declarations.ts

@@ -5048,7 +5048,7 @@ export interface TypeChecker {
     /** @internal */ getTypeOfPropertyOfType(type: Type, propertyName: string): Type | undefined;
     getIndexInfoOfType(type: Type, kind: IndexKind): IndexInfo | undefined;
     getIndexInfosOfType(type: Type): readonly IndexInfo[];
-    getIndexInfosOfIndexSymbol: (indexSymbol: Symbol) => IndexInfo[];
+    getIndexInfosOfIndexSymbol: (indexSymbol: Symbol, siblingSymbols?: Symbol[] | undefined) => IndexInfo[];
     getSignaturesOfType(type: Type, kind: SignatureKind): readonly Signature[];
     getIndexTypeOfType(type: Type, kind: IndexKind): Type | undefined;
     /** @internal */ getIndexType(type: Type): Type;
@@ -5867,6 +5867,7 @@ export interface EmitResolver {
     getDeclarationStatementsForSourceFile(node: SourceFile, flags: NodeBuilderFlags, internalFlags: InternalNodeBuilderFlags, tracker: SymbolTracker): Statement[] | undefined;
     isImportRequiredByAugmentation(decl: ImportDeclaration): boolean;
     isDefinitelyReferenceToGlobalSymbolObject(node: Node): boolean;
+    createLateBoundIndexSignatures(cls: ClassLikeDeclaration, enclosingDeclaration: Node, flags: NodeBuilderFlags, internalFlags: InternalNodeBuilderFlags, tracker: SymbolTracker): IndexSignatureDeclaration[] | undefined;
 }
 
 // dprint-ignore

src/compiler/types.ts

@@ -24,8 +24,8 @@ module M {
 >         : ^^^
     }
     (new C)[Symbol.iterator];
->(new C)[Symbol.iterator] : any
->                         : ^^^
+>(new C)[Symbol.iterator] : () => void
+>                         : ^^^^^^^^^^
 >(new C) : C
 >        : ^
 >new C : C
@@ -41,8 +41,8 @@ module M {
 }
 
 (new M.C)[Symbol.iterator];
->(new M.C)[Symbol.iterator] : any
->                           : ^^^
+>(new M.C)[Symbol.iterator] : () => void
+>                           : ^^^^^^^^^^
 >(new M.C) : M.C
 >          : ^^^
 >new M.C : M.C

tests/baselines/reference/ES5SymbolProperty2.types

@@ -19,7 +19,8 @@ class C {
 }
 
 (new C)[Symbol.iterator]
->(new C)[Symbol.iterator] : error
+>(new C)[Symbol.iterator] : () => void
+>                         : ^^^^^^^^^^
 >(new C) : C
 >        : ^
 >new C : C

tests/baselines/reference/ES5SymbolProperty3.types

@@ -23,7 +23,8 @@ class C {
 }
 
 (new C)[Symbol.iterator]
->(new C)[Symbol.iterator] : error
+>(new C)[Symbol.iterator] : () => void
+>                         : ^^^^^^^^^^
 >(new C) : C
 >        : ^
 >new C : C

tests/baselines/reference/ES5SymbolProperty4.types

@@ -0,0 +1,13 @@
+ES5SymbolProperty5.ts(7,26): error TS2554: Expected 0 arguments, but got 1.
+
+
+==== ES5SymbolProperty5.ts (1 errors) ====
+    var Symbol: { iterator: symbol };
+    
+    class C {
+        [Symbol.iterator]() { }
+    }
+    
+    (new C)[Symbol.iterator](0) // Should error
+                             ~
+!!! error TS2554: Expected 0 arguments, but got 1.

tests/baselines/reference/ES5SymbolProperty5.errors.txt

@@ -23,8 +23,10 @@ class C {
 }
 
 (new C)[Symbol.iterator](0) // Should error
->(new C)[Symbol.iterator](0) : error
->(new C)[Symbol.iterator] : error
+>(new C)[Symbol.iterator](0) : void
+>                            : ^^^^
+>(new C)[Symbol.iterator] : () => void
+>                         : ^^^^^^^^^^
 >(new C) : C
 >        : ^
 >new C : C

tests/baselines/reference/ES5SymbolProperty5.types

@@ -17,8 +17,8 @@ class C {
 }
 
 (new C)[Symbol.iterator]
->(new C)[Symbol.iterator] : any
->                         : ^^^
+>(new C)[Symbol.iterator] : () => void
+>                         : ^^^^^^^^^^
 >(new C) : C
 >        : ^
 >new C : C