TypeScriptToLua
diff --git a/‎src/transformation/utils/diagnostics.ts‎
Lines changed: 2 additions & 0 deletions b/‎src/transformation/utils/diagnostics.ts‎
Lines changed: 2 additions & 0 deletions
diff --git a/‎src/transformation/visitors/access.ts‎
Lines changed: 5 additions & 1 deletion b/‎src/transformation/visitors/access.ts‎
Lines changed: 5 additions & 1 deletion
diff --git a/‎test/unit/optionalChaining.spec.ts‎
Lines changed: 9 additions & 0 deletions b/‎test/unit/optionalChaining.spec.ts‎
Lines changed: 9 additions & 0 deletions
@@ -177,3 +177,5 @@ export const annotationDeprecated = createWarningDiagnosticFactory(
         `'@${kind}' is deprecated and will be removed in a future update. Please update your code before upgrading to the next release, otherwise your project will no longer compile. ` +
         `See https://typescripttolua.github.io/docs/advanced/compiler-annotations#${kind.toLowerCase()} for more information.`
 );
+
+export const optionalChainingNotSupported = createErrorDiagnosticFactory("Optional chaining is not supported yet.");
@@ -3,7 +3,7 @@ import * as lua from "../../LuaAST";
 import { transformBuiltinPropertyAccessExpression } from "../builtins";
 import { FunctionVisitor, TransformationContext } from "../context";
 import { AnnotationKind, getTypeAnnotations } from "../utils/annotations";
-import { invalidMultiReturnAccess } from "../utils/diagnostics";
+import { invalidMultiReturnAccess, optionalChainingNotSupported } from "../utils/diagnostics";
 import { addToNumericExpression } from "../utils/lua-ast";
 import { LuaLibFeature, transformLuaLibFunction } from "../utils/lualib";
 import { isArrayType, isNumberType, isStringType } from "../utils/typescript";
@@ -63,6 +63,10 @@ export const transformPropertyAccessExpression: FunctionVisitor<ts.PropertyAcces
     expression,
     context
 ) => {
+    if (ts.isOptionalChain(expression)) {
+        context.diagnostics.push(optionalChainingNotSupported(expression));
+    }
+
     const constEnumValue = tryGetConstEnumValue(context, expression);
     if (constEnumValue) {
         return constEnumValue;
 
@@ -0,0 +1,9 @@
+import { optionalChainingNotSupported } from "../../src/transformation/utils/diagnostics";
+import * as util from "../util";
+
+test("Diagnostic optional chaining is not supported yet", () => {
+    util.testFunction`
+        let func = (value: number) => value != 0 ? {value} : undefined;
+        return func(1)?.value;
+    `.expectToHaveDiagnostics([optionalChainingNotSupported.code]);
+});