[BUG] Debugging when using Optional[String](None) shows a JIT error

[osawyerr]

Bug description

Running the program below in debug mode throws shows a JIT error

Steps to reproduce

Run the code below in VSCode in debug mode

fn main() :
    var val1 = 2
    var val2 = Optional[String](None)
 
    print("foo", "bar", "baz") # set breakpoint here

error: JIT(0x300000000)(0x0000000300000000) The parsed MLIR structure type '!kgen.variant, struct<(struct<(pointer, index, index) memoryOnly>) memoryOnly>>' has not byte size. The MLIR type won't be used and regular MLIR-agnostic DWARF parsing will be performed.
error: JIT(0x300000000)(0x0000000300000000) [MojoDWARFParser::ParseTypeFromDWARF]: Unhandled type tag. Die = 0x3c0, tag = DW_TAG_variant_part, name = DW_TAG_variant_part
error: JIT(0x300000000)(0x0000000300000000) [MojoDWARFParser::CompleteTypeFromDWARF]: Couldn't complete the struct type '!kgen.variant, struct<(struct<(pointer, index, index) memoryOnly>) memoryOnly>>' because one of its fields has no size. Die = 0x3a6, member die = 0x3ad.
error: JIT(0x300000000)(0x0000000300000000) [MojoDWARFParser::CompleteTypeFromDWARF]: The struct type 'pkg stdlib::pkg utils::module variant::struct Variant[`variadic>`]<`:variadic> [[@"stdlib::collections::optional::_NoneType" : anystruct<@"stdlib::collections::optional::_NoneType">, {"__copyinit__" : (!lit.ref<@"stdlib::collections::optional::_NoneType", mut *[0,0]> init_self, !lit.ref<@"stdlib::collections::optional::_NoneType", imm *[0,1]> borrow_in_mem) -> !kgen.none = @"stdlib::collections::optional::_NoneType::__copyinit__(stdlib::collections::optional::_NoneType=&,stdlib::collections::optional::_NoneType)", "__del__" : (!lit.ref<@"stdlib::collections::optional::_NoneType", mut *[0,0]> owned_in_mem) -> !kgen.none = @"stdlib::collections::optional::_NoneType::__del__(stdlib::collections::optional::_NoneType)", "__moveinit__" : (!lit.ref<@"stdlib::collections::optional::_NoneType", mut *[0,0]> init_self, !lit.ref<@"stdlib::collections::optional::_NoneType", mut *[0,1]> owned_in_mem) -> !kgen.none = @"stdlib::collections::optional::_NoneType::__moveinit__(stdlib::collections::optional::_NoneType=&,stdlib::collections::optional::_NoneType)"}], [@"stdlib::builtin::string::String" : anystruct<@"stdlib::builtin::string::String">, {"__copyinit__" : (!lit.ref<@"stdlib::builtin::string::String", mut *[0,0]> init_self, !lit.ref<@"stdlib::builtin::string::String", imm *[0,1]> borrow_in_mem) -> !kgen.none = @"stdlib::builtin::string::String::__copyinit__(stdlib::builtin::string::String=&,stdlib::builtin::string::String)", "__del__" : (!lit.ref<@"stdlib::builtin::string::String", mut *[0,0]> owned_in_mem) -> !kgen.none = @"stdlib::builtin::string::String::__del__(stdlib::builtin::string::String)", "__moveinit__" : (!lit.ref<@"stdlib::builtin::string::String", mut *[0,0]> init_self, !lit.ref<@"stdlib::builtin::string::String", mut *[0,1]> owned_in_mem) -> !kgen.none = @"stdlib::builtin::string::String::__moveinit__(stdlib::builtin::string::String=&,stdlib::builtin::string::String)"}]]`>' doesn't have the same size as reported in the DWARF after type completion. Die = 0x253c.
error: JIT(0x300000000)(0x0000000300000000) [MojoDWARFParser::CompleteTypeFromDWARF]: The struct type 'pkg stdlib::pkg collections::module optional::struct Optional[`trait<@stdlib::@builtin::@value::@CollectionElement>`]<`:trait<@"stdlib::builtin::value::CollectionElement"> [@"stdlib::builtin::string::String" : anystruct<@"stdlib::builtin::string::String">, {"__copyinit__" : (!lit.ref<@"stdlib::builtin::string::String", mut *[0,0]> init_self, !lit.ref<@"stdlib::builtin::string::String", imm *[0,1]> borrow_in_mem) -> !kgen.none = @"stdlib::builtin::string::String::__copyinit__(stdlib::builtin::string::String=&,stdlib::builtin::string::String)", "__del__" : (!lit.ref<@"stdlib::builtin::string::String", mut *[0,0]> owned_in_mem) -> !kgen.none = @"stdlib::builtin::string::String::__del__(stdlib::builtin::string::String)", "__moveinit__" : (!lit.ref<@"stdlib::builtin::string::String", mut *[0,0]> init_self, !lit.ref<@"stdlib::builtin::string::String", mut *[0,1]> owned_in_mem) -> !kgen.none = @"stdlib::builtin::string::String::__moveinit__(stdlib::builtin::string::String=&,stdlib::builtin::string::String)"}]`>' doesn't have the same size as reported in the DWARF after type completion. Die = 0x2529.
foo bar baz

System information

- What OS did you do install Mojo on ? = MacOS Apple Silicon M3
- Provide version information for Mojo by pasting the output of `mojo -v` = mojo 24.3.0 (9882e19d)
- Provide Modular CLI version by pasting the output of `modular -v` = modular 0.8.0 (39a426b5)

[walter-erquinigo]

Thanks for reporting this! I'll revisit our handling of optional and variant types and fix this issue.