Module fastlink 

Zero-install fast linker.

rustup ships LLVM’s linkers inside every toolchain, next to the target’s std: <sysroot>/lib/rustlib/<host>/bin/gcc-ld/ contains ld.lld (ELF), lld-link (COFF/MSVC) and the Apple/WebAssembly variants. No mold, no lld package, no clang needed.

epicenter setup --fast wires that directory into Cargo:

• GNU/ELF hosts keep the system C compiler as the linker driver and pass -C link-arg=-fuse-ld=lld -C link-arg=-B<gcc-ld> — a flag GCC and Clang both understand, with -B making the bundled ld.lld discoverable.
• MSVC hosts cannot use -fuse-ld (the driver is link.exe): rustc is pointed directly at the bundled lld-link.exe with -C linker=….

Apple’s ld64.lld is not a drop-in for the system linker, so --fast refuses macOS instead of producing fragile builds.

Structs

FastLinker

The bundled LLD for the active rustup toolchain.

Enums

Flavor

How the bundled LLD is invoked on this host.

Functions

detect

Detect the bundled LLD for the active toolchain’s host.

locate

Pure detection against a known sysroot/host (unit-testable).