core: Make sure every module at least has a one-line description

src/libcore/cast.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+//! Unsafe casting functions
+
 pub mod rusti {
     #[abi = "rust-intrinsic"]
     #[link_name = "rusti"]

src/libcore/cell.rs

@@ -8,13 +8,17 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+//! A mutable, nullable memory location
+
 use cast::transmute;
 use option;
 use prelude::*;
 
-/// A dynamic, mutable location.
-///
-/// Similar to a mutable option type, but friendlier.
+/*
+A dynamic, mutable location.
+
+Similar to a mutable option type, but friendlier.
+*/
 
 pub struct Cell<T> {
     mut value: Option<T>

src/libcore/clone.rs

@@ -8,9 +8,20 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-/**
-Clonable types are copied with the clone method
+/*! The Clone trait for types that cannot be "implicitly copied"
+
+In Rust, some simple types are "implicitly copyable" and when you
+assign them or pass them as arguments, the receiver will get a copy,
+leaving the original value in place. These types do not require
+allocation to copy and do not have finalizers (i.e. they do not
+contain owned pointers or implement `Drop`), so the compiler considers
+them cheap and safe to copy and automatically implements the `Copy`
+trait for them. For other types copies must be made explicitly,
+by convention implementing the `Clone` trait and calling the
+`clone` method.
+
 */
+
 pub trait Clone {
     fn clone(&self) -> Self;
 }

src/libcore/comm.rs

@@ -8,6 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+/*!
+Message passing
+*/
+
 use cast;
 use either::{Either, Left, Right};
 use kinds::Owned;

src/libcore/condition.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+/*! Condition handling */
+
 use prelude::*;
 use task;
 use task::local_data::{local_data_pop, local_data_set};

src/libcore/rt/mod.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#[doc(hidden)];
+
 use libc::c_char;
 
 // Some basic logging