New gdb with Rust support does not honor rust-gdb's pretty printers

[DemiMarie]

gdb git HEAD, when invoked via rust-gdb, does not honor the Rust pretty-printers. This results in bad printing of types like Vec.

[michaelwoerister]

cc @tromey

[tromey]

It's most useful if you can report the version of rustc that you are using. I was able to reproduce the problem with stable. I'll look into it.

[tromey]

The older gdb says the type of a vec variable is:

(gdb) whatis x
type = struct Vec<i32>

However git gdb says:

(gdb) whatis x
type = collections::vec::Vec<i32>

The rust pretty-printers assume that the type tag holds the unqualified name (see GdbType.get_unqualified_type_name), but in git gdb, this is not the case:

(gdb) python print (val.type.tag)
collections::vec::Vec<i32>

Perhaps the Rust gdb scripts could be updated to recognize this name, though I'm not 100% certain this will work in all cases.