```==================== .D.TS ====================

declare function foo(): number;
// inferred type is number
declare function bar(): number | undefined;
// inferred type is number | undefined
declare function baz();
// We can't infer return type if there are multiple return statements with different types
declare function qux(): string;
declare function quux(): string;
// Inferred type is string
declare function returnFunctionOrNothing(): (() => number) | undefined;


==================== Errors ====================
  x TS9007: Function must have an explicit return type annotation with --isolatedDeclarations.
    ,-[$DIR/tests/oxc_fixture/infer-return-type.ts:14:1]
 13 | 
 14 | function baz() {
    :          ^^^
 15 |  if (a) {
    `----


```
