From b93a8315f2fcff479a99e0694309fe12dbe095d5 Mon Sep 17 00:00:00 2001 From: Joshua Nelson Date: Tue, 15 Sep 2020 08:40:10 -0400 Subject: [PATCH] Add a comment why rustdoc loads crates from the sysroot --- src/librustdoc/lib.rs | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs index 94e51d91b542a..7762e8f8d4fb1 100644 --- a/src/librustdoc/lib.rs +++ b/src/librustdoc/lib.rs @@ -21,7 +21,11 @@ extern crate tracing; // N.B. these need `extern crate` even in 2018 edition // because they're loaded implicitly from the sysroot. -// Dependencies listed in Cargo.toml do not need extern crate. +// The reason they're loaded from the sysroot is because +// the rustdoc artifacts aren't stored in rustc's cargo target directory. +// So if `rustc` was specified in Cargo.toml, this would spuriously rebuild crates. +// +// Dependencies listed in Cargo.toml do not need `extern crate`. extern crate rustc_ast; extern crate rustc_ast_pretty; extern crate rustc_attr;