dmd/compiler/test/fail_compilation/test14238.d

/* REQUIRED_ARGS: -preview=dip1000
   TEST_OUTPUT:
---
fail_compilation/test14238.d(22): Error: scope parameter `fn` may not be returned
fail_compilation/test14238.d(25): Error: function `test14238.bar` is `@nogc` yet allocates closure for `bar()` with the GC
fail_compilation/test14238.d(27):        function `baz` closes over variable `x`
fail_compilation/test14238.d(26):        `x` declared here
---
*/
// https://issues.dlang.org/show_bug.cgi?id=14238

@safe:

alias Fn = ref int delegate() return @nogc;

ref int call(return scope Fn fn) @nogc
{
    return fn(); // Ok
}

ref int foo2(scope Fn fn) {
    return fn(); // Error
}

ref int bar() @nogc {
    int x;
    ref int baz() {
            return x;
    }

    if (x == 0)
        return call(&baz);
    else
        return (&baz)();
}