struct Data {
mut:
    counter int
}

fn (mut d Data) operation(fail bool) !int {
    if fail {
        return error('')
    }
    return 10
}

fn (mut d Data) run_operation(fail bool) !int {
    return d.operation(fail) or {
        defer {
            d.counter++
        }
        err
    }
}

fn test_defer_with_or_expr() {
    mut d := Data{}
    d.run_operation(true) or {}
    assert d.counter == 1

    d.run_operation(false) or {}
    assert d.counter == 1

    d.run_operation(true) or {}
    assert d.counter == 2
}

fn some() !int {
    return 5
}

fn test_if_expr_with_defer() {
    mut abc := 0
    x := if v := some() {
        defer { assert abc == 9090 }
        defer { abc = 9090 }
        v
    } else {
        2004
    }
    assert x == 5
}

fn test_scoped_defer() {
    mut res := 0

    defer {
        res++
        assert res == 5
    }
    {
        res++
        defer {
            res++
            assert res == 4
        }
        {
            res++
            defer {
                res++
                assert res == 3
            }
        } // <- Block 2 ends. Defer 3 executes. res = 3.
    } // <- Block 1 ends. Defer 2 executes. res = 4.
} // <- 'test_scoped_defer' ends. Defer 1 executes. res = 5.

fn test_defer_with_comptime_if() {
    mut c := 0
    defer { assert c == 3 }
    defer { c++ }
    $if tinyc || gcc || clang || msvc || mingw {
        defer { c++ }
        c++
    } $else {
        c = 0
    }
}

fn test_defer_with_comptime_match() {
    mut c := 0
    defer { assert c == 3 }
    defer { c++ }
    $match @CCOMPILER {
        'tinyc', 'gcc', 'clang', 'msvc', 'mingw' {
            defer { c++ }
            c++
        }
        $else {
            c = 0
        }
    }
}

fn test_defer_with_comptime_for() {
    mut c := 0
    $for f in Data.fields {
        defer {
            if f.name == 'counter' {
                c++
            }
        }
    }
    assert c == 1

    $for m in Data.methods {
        defer {
            if m.name in ['operation', 'run_operation'] {
                c++
            }
        }
    }
    assert c == 3
}

fn test_defer_fn_with_inner_var() {
    mut x := 0
    defer {
        assert x == 1
    }
    {
        a := 1
        defer(fn) {
            x = a
        }
    }
}

fn test_scoped_defer_can_use_inner_var_declared_in_loop() {
    mut values := []int{}
    for i := 0; i < 3; i++ {
        defer {
            j := i
            values << j
        }
    }
    assert values == [0, 1, 2]
}