libproc_macro: Move Spacing type to punct module

The spacing type is inherently linked to the Punct type and can
therefore be moved to the punct module. This commit also add some
documentation to the spacing type.

ChangeLog:

	* librust/proc_macro/rust/lib.rs: Remove Spacing type.
	* librust/proc_macro/rust/punct.rs: Add Spacing type.

Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>

2 files changed, 16 insertions, 9 deletions

diff --git a/librust/proc_macro/rust/lib.rs b/librust/proc_macro/rust/lib.rs
index 1bb8e247..f79342e 100644
--- a/librust/proc_macro/rust/lib.rs
+++ b/librust/proc_macro/rust/lib.rs
@@ -1,6 +1,6 @@
 pub use ident::Ident;
 pub use literal::Literal;
-pub use punct::Punct;
+pub use punct::{Punct, Spacing};
 pub use span::Span;
 use std::error;
 use std::fmt;
@@ -29,9 +29,3 @@ impl fmt::Display for LexError {
 }
 
 impl error::Error for LexError {}
-
-#[derive(Copy, Clone, Debug, PartialEq, Eq)]
-pub enum Spacing {
-    Alone,
-    Joint,
-}
diff --git a/librust/proc_macro/rust/punct.rs b/librust/proc_macro/rust/punct.rs
index 1389122..24d6acb 100644
--- a/librust/proc_macro/rust/punct.rs
+++ b/librust/proc_macro/rust/punct.rs
@@ -1,14 +1,27 @@
 use std::fmt;
-use Spacing;
 use Span;
 
+/// Describes the context of a [`Punct`] relatively to the next token.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum Spacing {
+    /// A [`Punct`] is not immediately followed by another `Punct`.
+    Alone,
+    /// A [`Punct`] is immediately followed by another `Punct` and can be
+    /// combined into a multi-character operator.
+    Joint,
+}
+
+/// Single punctuation character such as `+`, `-` or `#`.
+///
+/// Multi-character operators like `+=` are represented as two instances of
+/// `Punct` with different forms of `Spacing` returned.
 #[derive(Clone)]
 pub struct Punct {
     // Internal implementation details.
 }
 
 impl Punct {
-    /// Creates a new [Punct] from a given character and spacing.
+    /// Creates a new `Punct` from a given character and spacing.
     ///
     /// # Arguments
     ///