diff --git a/src/name-resolution.md b/src/name-resolution.md index ebd44da1..3785e3aa 100644 --- a/src/name-resolution.md +++ b/src/name-resolution.md @@ -145,6 +145,23 @@ the code can be processed. Therefore, the resolution is performed in multiple stages. +## Speculative crate loading + +To give useful errors, rustc suggests importing paths into scope if they're +not found. How does it do this? It looks through every module of every crate +and looks for possible matches. This even includes crates that haven't yet +been loaded! + +Loading crates for import suggestions that haven't yet been loaded is called +_speculative crate loading_, because any errors it encounters shouldn't be +reported: resolve decided to load them, not the user. The function that does +this is `lookup_import_candidates` and lives in +`rustc_resolve/src/diagnostics.rs`. + +To tell the difference between speculative loads and loads initiated by the +user, resolve passes around a `record_used` parameter, which is `false` when +the load is speculative. + ## TODO: This is a result of the first pass of learning the code. It is definitely