# @value
struct MyPet:
    var name: String
    var age: Int

    fn __init__(inout self, owned n: String, a: Int):
        self.name = n^
        self.age = a
        print(self.name,  ": ", self.age)

    fn __copyinit__(inout self, rhs: MyPet):
        self.name = rhs.name
        self.age = rhs.age

    fn __moveinit__(inout self, rhs: MyPet):
        self.name = rhs.name^
        self.age = rhs.age

    fn __del__(owned self):
        print("\tDestruct", self.name)

fn pets():
    var a = MyPet("Loki", 4)
    var b = MyPet("Sylvie", 2)
    print(a.name)
    # Zn: @value is a little confusing as it doe not mean immutable class. 
    # Zn: how to define a immutable struct in Mojo?
    a.name = "fake"
    # a.__del__() runs here for "Loki"

    a = MyPet("Charlie", 8)
    # a.__del__() runs immediately because "Charlie" is never used

    print(b.name)
    # b.__del__() runs here

fn main():
    pets()

(base) nings-mbp:del ningzhang$ '/Users/ningzhang/.modular/pkg/packages.modular.com_max/bin/mojo' '/Users/ningzhang/test/mojo_max/del/del.mojo'
/Users/ningzhang/test/mojo_max/del/del.mojo:15:33: error: existing value argument must be passed as owned
    fn __moveinit__(inout self, rhs: MyPet):
                                ^
Please submit a bug report to https://github.com/modularml/mojo/issues and include the crash backtrace along with all the relevant source codes.
Stack dump:
0.      Program arguments: /Users/ningzhang/.modular/pkg/packages.modular.com_max/bin/mojo /Users/ningzhang/test/mojo_max/del/del.mojo
1.      Crash resolving decl body at loc("/Users/ningzhang/test/mojo_max/del/del.mojo":2:8)
    >> struct MyPet:
              ^.....
    >>     var name: String
    >>     var age: Int
    >> 
    >>     fn __init__(inout self, owned n: String, a: Int):
Stack dump without symbol names (ensure you have llvm-symbolizer in your PATH or set the environment var `LLVM_SYMBOLIZER_PATH` to point to it):
0  mojo                     0x0000000102f00c04 llvm_strlcpy   51480
1  mojo                     0x0000000102efeef0 llvm_strlcpy   44036
2  mojo                     0x0000000102f012a4 llvm_strlcpy   53176
3  libsystem_platform.dylib 0x000000019d58f584 _sigtramp   56
4  mojo                     0x0000000103244488 __jit_debug_register_code   709568
5  mojo                     0x0000000103244bbc __jit_debug_register_code   711412
6  mojo                     0x00000001031be52c __jit_debug_register_code   160868
7  mojo                     0x00000001031cacb0 __jit_debug_register_code   211944
8  mojo                     0x00000001031cb17c __jit_debug_register_code   213172
9  mojo                     0x00000001031d4788 __jit_debug_register_code   251584
10 mojo                     0x00000001031d49a8 __jit_debug_register_code   252128
11 mojo                     0x0000000102e4e8c8
12 mojo                     0x0000000102e606b0
13 mojo                     0x0000000102e49940
14 dyld                     0x000000019d1d60e0 start   2360
mojo crashed!
Please file a bug report.
[30546:4088829:20240712,155400.429252:WARNING crash_report_exception_handler.cc:257] UniversalExceptionRaise: (os/kern) failure (5)
Segmentation fault: 11