compilation is awfully slow

Hello! On my M3 Pro it takes 22 seconds to compile octorust (excluding dependencies). This timing seems insensitive to features (same result with default and --no-default-features).

I can't attach the HTML report generated by cargo build --timings -p octorust --no-default-features but here's a snippet:

I tried profiling the compiler:

cargo install --git https://github.com/rust-lang/measureme summarize
cd github
cargo +nightly rustc -- -Z self-profile
summarize summarize ../octorust-*.mm_profdata | head -n11

+-------------------------------------------------------------------------+-----------+-----------------+----------+------------+---------------------------------+
| Item                                                                    | Self time | % of total time | Time     | Item count | Incremental result hashing time |
+-------------------------------------------------------------------------+-----------+-----------------+----------+------------+---------------------------------+
| LLVM_module_codegen_emit_obj                                            | 6.43s     | 19.772          | 6.43s    | 186        | 0.00ns                          |
+-------------------------------------------------------------------------+-----------+-----------------+----------+------------+---------------------------------+
| typeck                                                                  | 4.77s     | 14.649          | 5.29s    | 30934      | 387.19ms                        |
+-------------------------------------------------------------------------+-----------+-----------------+----------+------------+---------------------------------+
| mir_borrowck                                                            | 3.01s     | 9.260           | 5.76s    | 30934      | 3.85ms                          |
+-------------------------------------------------------------------------+-----------+-----------------+----------+------------+---------------------------------+
| LLVM_passes                                                             | 1.59s     | 4.880           | 1.59s    | 1          | 0.00ns                          |
+-------------------------------------------------------------------------+-----------+-----------------+----------+------------+---------------------------------+

I don't find this particularly telling, but it's a start. Is it possible there's a lot of duplication in the generated code? I haven't looked deeply.

Reproduce the report with cargo build --timings -p octorust --no-default-features, then compare it with the default-feature build. Review the cargo +nightly rustc -- -Z self-profile output using summarize and investigate the reported LLVM code generation, type checking, and borrow-checking time. Done should identify the source of the slow compilation and document or implement a justified improvement.