* ⚗️ Add test to verify code fix works when implementing a mapped type with indirect keyof

Signed-off-by: Babak K. Shandiz <babak.k.shandiz@gmail.com>

* 🔨 Add property as implementation for symbols that has no declaration

Signed-off-by: Babak K. Shandiz <babak.k.shandiz@gmail.com>

diff --git a/src/services/codefixes/helpers.ts b/src/services/codefixes/helpers.ts
index 94b64e57..a4c11fd5 100644
--- a/src/services/codefixes/helpers.ts
+++ b/src/services/codefixes/helpers.ts
@@ -60,21 +60,19 @@ namespace ts.codefix {
         isAmbient = false,
     ): void {
         const declarations = symbol.getDeclarations();
-        if (!(declarations && declarations.length)) {
-            return undefined;
-        }
+        const declaration = declarations ? declarations[0] : undefined;
         const checker = context.program.getTypeChecker();
         const scriptTarget = getEmitScriptTarget(context.program.getCompilerOptions());
-        const declaration = declarations[0];
+        const kind = declaration?.kind ?? SyntaxKind.PropertySignature;
         const name = getSynthesizedDeepClone(getNameOfDeclaration(declaration), /*includeTrivia*/ false) as PropertyName;
-        const visibilityModifier = createVisibilityModifier(getEffectiveModifierFlags(declaration));
+        const visibilityModifier = createVisibilityModifier(declaration ? getEffectiveModifierFlags(declaration) : ModifierFlags.None);
         const modifiers = visibilityModifier ? factory.createNodeArray([visibilityModifier]) : undefined;
         const type = checker.getWidenedType(checker.getTypeOfSymbolAtLocation(symbol, enclosingDeclaration));
         const optional = !!(symbol.flags & SymbolFlags.Optional);
         const ambient = !!(enclosingDeclaration.flags & NodeFlags.Ambient) || isAmbient;
         const quotePreference = getQuotePreference(sourceFile, preferences);

-        switch (declaration.kind) {
+        switch (kind) {
             case SyntaxKind.PropertySignature:
             case SyntaxKind.PropertyDeclaration:
                 const flags = quotePreference === QuotePreference.Single ? NodeBuilderFlags.UseSingleQuotesForStringLiteralType : undefined;
@@ -88,13 +86,16 @@ namespace ts.codefix {
                 }
                 addClassElement(factory.createPropertyDeclaration(
                     modifiers,
-                    name,
+                    declaration ? name : symbol.getName(),
                     optional && (preserveOptional & PreserveOptionalFlags.Property) ? factory.createToken(SyntaxKind.QuestionToken) : undefined,
                     typeNode,
                     /*initializer*/ undefined));
                 break;
             case SyntaxKind.GetAccessor:
             case SyntaxKind.SetAccessor: {
+                if (!declarations) {
+                    break;
+                }
                 let typeNode = checker.typeToTypeNode(type, enclosingDeclaration, /*flags*/ undefined, getNoopSymbolTrackerWithResolver(context));
                 const allAccessors = getAllAccessorDeclarations(declarations, declaration as AccessorDeclaration);
                 const orderedAccessors = allAccessors.secondAccessor
@@ -138,6 +139,10 @@ namespace ts.codefix {
                 // If there is more than one overload but no implementation signature
                 // (eg: an abstract method or interface declaration), there is a 1-1
                 // correspondence of declarations and signatures.
+                if (!declarations) {
+                    break;
+                }
+
                 const signatures = checker.getSignaturesOfType(type, SignatureKind.Call);
                 if (!some(signatures)) {
                     break;

* 🔨 Improve code readability

Signed-off-by: Babak K. Shandiz <babak.k.shandiz@gmail.com>

diff --git a/src/services/codefixes/helpers.ts b/src/services/codefixes/helpers.ts
index 2f5c8703ab..aea0206a8a 100644
--- a/src/services/codefixes/helpers.ts
+++ b/src/services/codefixes/helpers.ts
@@ -60,7 +60,7 @@ namespace ts.codefix {
         isAmbient = false,
     ): void {
         const declarations = symbol.getDeclarations();
-        const declaration = declarations ? declarations[0] : undefined;
+        const declaration = declarations?.[0];
         const checker = context.program.getTypeChecker();
         const scriptTarget = getEmitScriptTarget(context.program.getCompilerOptions());
         const kind = declaration?.kind ?? SyntaxKind.PropertySignature;
@@ -93,9 +93,7 @@ namespace ts.codefix {
                 break;
             case SyntaxKind.GetAccessor:
             case SyntaxKind.SetAccessor: {
-                if (!declarations) {
-                    break;
-                }
+                Debug.assertIsDefined(declarations);
                 let typeNode = checker.typeToTypeNode(type, enclosingDeclaration, /*flags*/ undefined, getNoopSymbolTrackerWithResolver(context));
                 const allAccessors = getAllAccessorDeclarations(declarations, declaration as AccessorDeclaration);
                 const orderedAccessors = allAccessors.secondAccessor
@@ -139,10 +137,7 @@ namespace ts.codefix {
                 // If there is more than one overload but no implementation signature
                 // (eg: an abstract method or interface declaration), there is a 1-1
                 // correspondence of declarations and signatures.
-                if (!declarations) {
-                    break;
-                }
-
+                Debug.assertIsDefined(declarations);
                 const signatures = type.isUnion() ? flatMap(type.types, t => t.getCallSignatures()) : type.getCallSignatures();
                 if (!some(signatures)) {
                     break;

* 📜 Add comment regarding mapped type children's  missing declaration

Signed-off-by: Babak K. Shandiz <babak.k.shandiz@gmail.com>

Signed-off-by: Babak K. Shandiz <babak.k.shandiz@gmail.com>
Co-authored-by: Andrew Branch <andrew@wheream.io>