Clean up some comments on lint implementation

compiler/rustc_lint/src/late.rs

@@ -1,18 +1,7 @@
-//! Implementation of lint checking.
+//! Implementation of the late lint pass.
 //!
-//! The lint checking is mostly consolidated into one pass which runs
-//! after all other analyses. Throughout compilation, lint warnings
-//! can be added via the `add_lint` method on the Session structure. This
-//! requires a span and an ID of the node that the lint is being added to. The
-//! lint isn't actually emitted at that time because it is unknown what the
-//! actual lint level at that location is.
-//!
-//! To actually emit lint warnings/errors, a separate pass is used.
-//! A context keeps track of the current state of all lint levels.
-//! Upon entering a node of the ast which can modify the lint settings, the
-//! previous lint state is pushed onto a stack and the ast is then recursed
-//! upon. As the ast is traversed, this keeps track of the current lint level
-//! for all lint attributes.
+//! The late lint pass Works on HIR nodes, towards the end of analysis (after
+//! borrow checking, etc.). These lints have full type information available.
 
 use std::any::Any;
 use std::cell::Cell;