The "1:1" assumption is a massive unjustified assumption. Rust and Zig have different memory models, so it's possible to do a "1:1" translation of Zig code to Rust and end up with undefined behavior in Rust.
For example, Zig code might make assumptions about lifetimes based on implicit knowledge of which allocator was used for some memory. That could cause problems in Rust if you erase the lifetime https://github.com/oven-sh/bun/blob/main/src/bun_core/string...
It's not, that's clear from this kind of bug popping up. Functionally this bug exists because `PathString` was converted into a "safe" Rust API but still works the same internally as the original Zig code did (via using `unsafe`), that introduces UB that wasn't there in the Zig code.
If it was attempting to be a 1:1 with no behavior changes (like c2Rust attempts to do) then this would not have been turned into a "safe" Rust API like this.