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Reblogged by rust@octodon.social ("Rust tips"):

mo8it@fosstodon.org ("Mo :ferris: :tux:") wrote:

#RustLang lint idea and performance tip 🚀

Warn about a repeated call of `Path::join` ⚠️

This allocates a new `PathBuf` each time. Then `Path::join` is called on the new `PathBuf` because of the `Deref` implementation.

Instead, you should use extend like in the screenshot (preferably with a capacity hint).

You can also use `.collect::()` on an iterator instead:
https://doc.rust-lang.org/stable/std/path/struct.PathBuf.html#impl-FromIterator%3CP%3E-for-PathBuf

Attachments:

• ```rust let sysroot_src = Path::new(toolchain) .join("lib") .join("rustlib") .join("src") .join("rust") .join("library"); ``` (remote)
• ```rust let mut sysroot_src = PathBuf::with_capacity(256); sysroot_src.extend([toolchain, "lib", "rustlib", "src", "rust", "library"]); ``` (remote)