Fix missing index increment (#1606)

Perryvw · web-flow · commit 030bb2a80a51 · 2024-12-25T16:17:14.000+01:00
diff --git a/src/transformation/utils/typescript/types.ts b/src/transformation/utils/typescript/types.ts
@@ -56,17 +56,27 @@ export function isNumberType(context: TransformationContext, type: ts.Type): boo
 
 function isExplicitArrayType(context: TransformationContext, type: ts.Type): boolean {
     if (context.checker.isArrayType(type) || context.checker.isTupleType(type)) return true;
+
+    if (type.isUnionOrIntersection()) {
+        if (type.types.some(t => isExplicitArrayType(context, t))) {
+            return true;
+        }
+    }
+
+    const baseTypes = type.getBaseTypes();
+    if (baseTypes) {
+        if (baseTypes.some(t => isExplicitArrayType(context, t))) {
+            return true;
+        }
+    }
+
     if (type.symbol) {
         const baseConstraint = context.checker.getBaseConstraintOfType(type);
         if (baseConstraint && baseConstraint !== type) {
             return isExplicitArrayType(context, baseConstraint);
         }
     }
 
-    if (type.isUnionOrIntersection()) {
-        return type.types.some(t => isExplicitArrayType(context, t));
-    }
-
     return false;
 }
 
diff --git a/test/unit/builtins/array.spec.ts b/test/unit/builtins/array.spec.ts
@@ -884,3 +884,17 @@ describe("copying array methods", () => {
         });
     });
 });
+
+// https://github.com/TypeScriptToLua/TypeScriptToLua/issues/1605
+test("array indexing in optional chain (#1605)", () => {
+    util.testModule`
+        interface Foo extends Array<number> {}
+        const b: {arr?: Foo} = {arr:[1,2]};
+        export const t = b.arr?.[1];
+
+        const c: Foo | undefined = b.arr;
+        export const u = c?.[1];
+    `
+        .setOptions({ strict: true }) // crucial to reproducing for some reason
+        .expectToMatchJsResult();
+});
