DWARF doesn't record mut/const distinction

[tromey]

Consider code like this:

    let y : u8 = 8;
    let x : *const u8 = &y;
    let mut w : u8 = 9;
    let z : *mut u8   = & mut w;

Examining the DWARF for these, the types lose some information:

 <1><90>: Abbrev Number: 6 (DW_TAG_base_type)
    <91>   DW_AT_name        : (indirect string, offset: 0x65): u8
    <95>   DW_AT_encoding    : 7    (unsigned)
    <96>   DW_AT_byte_size   : 1
 <1><97>: Abbrev Number: 7 (DW_TAG_pointer_type)
    <98>   DW_AT_type        : <0x90>
    <9c>   DW_AT_name        : (indirect string, offset: 0x5e): *const u8
 <1><a0>: Abbrev Number: 7 (DW_TAG_pointer_type)
    <a1>   DW_AT_type        : <0x90>
    <a5>   DW_AT_name        : (indirect string, offset: 0x6c): *mut u8

Something here should be marked DW_TAG_const_type.

[tromey]

Sorry, I meant DW_TAG_const_type.

[Aatch]

@tromey just FYI, you can edit your own comments/issues

[steveklabnik]

Triage: not sure if anything has changed here, but I don't think so.

[wesleywiser]

Visited during wg-debugging. It looks like this is essentially the same issue as #37504 so we're closing this since the other issue has much more discussion and we'd like to keep it all in one place.