DBG: Show the contents of references and pointers with LLDB

[artemmukhin]

Fixes #9050.
Partially fixes #9252 (LLDB only).

This PR brings automatic dereferencing of Rust references and pointers when debugging with LLDB. For example, now the debugger renders the contents of &Vec, *const Vec and *mut Vec, in addition to previously supported Vec.

Technical information

Previously, for each Rust type regex $type (for String, Vec, etc.), we ran the following LLDB commands:

(lldb) type summary add -F lldb_lookup.summary_lookup -e -x -h $type --category Rust
(lldb) type synthetic add -l lldb_lookup.synthetic_lookup -x $type --category Rust

They attach summary_lookup and synthetic_lookup Python functions as summary/synthetic providers for the given types. Actual providers are invoked by these lookup functions. This was done for two main reasons:

• for consistency, as GDB pretty-printing API requires us to use lookup functions (https://sourceware.org/gdb/onlinedocs/gdb/Writing-a-Pretty_002dPrinter.html);
• for flexibility, for example, to be able to choose the provider depending not only on the type regex, but also on its type class (eTypeClassStruct, eTypeClassPointer, etc.).

It turned out, however, that such flexibility is not needed for LLDB anymore. Moreover, it appeared that the current implementation breaks the automatic dereferencing of pointers provided by LLDB by default when registering pretty-printers just by regex.

So now, for each pair of $type and the corresponding $provider, we run these LLDB commands instead:

(lldb) type summary add -F lldb_formatters.lldb_providers.$provider -e -x -h $type --category Rust
(lldb) type synthetic add -l lldb_formatters.lldb_providers.$provider -x $type --category Rust

changelog: Show the contents of references and pointers when debugging with LLDB

[Undin]

Could you resolve merge conflicts, please?

[artemmukhin]

@Undin I've resolved merge conflicts and reordered the regexes for readability

[Undin]

Works for me!

Don't forget before merge:

• drop changes on CI
• describe that multiple dereferences don't work after these changes

[Undin]

Why did it change and how does it affect users? I can't see any difference with macOS lldb but didn't check with MSVC lldb

[artemmukhin]

I should not affect users, so the UI representation for HashMap is supposed to be the same.

@intellij-rust/qa Please pay attention to this ^

[artemmukhin]

Note: this PR affects how the debugger renders "references to references" &&T and "pointers to pointers" and, more generally, multiple references and pointers. Consider this example:

fn main() {
    let vec = vec![1,2,3];
    let vec_ref = &vec;
    let vec_ref_ref = &vec_ref;

    let s = String::from("abc");
    let s_ref = &s;
    let s_ref_ref = &s_ref;

    println!(); // break
}

Before	After

Once this PR is merged, I will open an issue with a more detailed overview.

[artemmukhin]

bors r=Undin

[bors]

Build succeeded:

• check

[mili-l]

rust-lang/rust#106679

macOS LLDB	MSVC LLDB