feature request: exporting bindings' name mappings

(this is a feature request)

Hello,

I was wondering you were interested in letting bindgen::Builder provide a HashMap<String, String>, or something similar, mapping the original name of a C-type to its Rust rust-bindgen generated binding. This would give a mapping like:

// C => Rust
"type_A" => "type_A" // for a typedef type
"struct type_B" => "type_B" // for a normal struct type

I could also build this mapping myself if the bindgen::callbacks::ParseCallbacks trait had a callback method providing both the "original" name and the final "binding" name but this is currently not the case.

Use case

I am working on a library that imports some structs from a C library using rust-bindgen, defines some functions that return the imported types and are made available to C using cbindgen through the cargo-c crate.

My issue is that the types in the function signatures exported by cbindgen are not the same as the one imported (see example):
struct MySuperStruct becomes MySuperStruct in Rust and stay MySuperStruct when re-exported to C. This unnecessarily duplicates all type definitions.

This is however only partially a cbindgen issue since this happens because depending on whether the type was declared using a typedef or not. cbindgen has no way to know what the original name was.
cbindgen however provides a way to rename types by manually providing a new name for some types, which works.

My goal would be to get the mapping from rust-bindgen and generate a rename config for cbindgen

Example:

the C header

struct MySuperStruct {
   ...
}

the Rust bindings from rust-bindgen

#[repr(C, packed)]
pub struct MySuperStruct {
   ...
}

my Rust function

#[no_mangle]
pub extern "C" fn my_super_function() -> MySuperStruct {
   ...
}

the C function generated by cbindgen

// this is a header generated by cbindgen
MySuperStruct my_super_function();

Notice that the type loses the struct keyword here and thus requires an additional unwanted typedef / cast to the correct type.

The issue names bindgen::Builder and callbacks::ParseCallbacks as entry points; start by tracing how C names become final Rust binding names. Done means exposing an original-to-generated-name mapping that can be used to configure cbindgen renames; no test or file is named in the issue.