libproc_macro: Add TokenStream type interface

Add the TokenStream rust type interface to libproc_macro. Note that the
token_stream module containing the iterator operations implemented on
the TokenStream type is missing.

ChangeLog:

	* librust/proc_macro/rust/lib.rs: Add TokenStream type.

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

1 files changed, 45 insertions, 1 deletions

diff --git a/librust/proc_macro/rust/lib.rs b/librust/proc_macro/rust/lib.rs
index fa1160e..f270b79 100644
--- a/librust/proc_macro/rust/lib.rs
+++ b/librust/proc_macro/rust/lib.rs
@@ -3,7 +3,7 @@ pub use literal::Literal;
 pub use punct::{Punct, Spacing};
 pub use span::Span;
 use std::error;
-use std::fmt;
+use std::{fmt, str::FromStr};
 
 mod ident;
 mod literal;
@@ -34,3 +34,47 @@ impl fmt::Display for LexError {
 }
 
 impl error::Error for LexError {}
+
+/// An abstract sequence of token trees.
+///
+/// This type provides interfaces for iterating over those token trees. This
+/// is both the input and the output of `#[proc_macro]`,
+/// `#[proc_macro_attribute]` and `#[proc_macro_derive]` definitions.
+#[derive(Clone)]
+pub struct TokenStream {
+    // Internal implementation details
+}
+
+impl TokenStream {
+    // TODO: Add experimental API functions for this type
+
+    /// Creates an empty `TokenStream` containing no token trees.
+    pub fn new() -> Self {
+        todo!("Implement this function")
+    }
+
+    /// Checks if this `TokenStream` is empty.
+    pub fn is_empty(&self) -> bool {
+        todo!("Implement this function")
+    }
+}
+
+impl fmt::Display for TokenStream {
+    fn fmt(&self, _f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        todo!("Implement this function")
+    }
+}
+
+impl fmt::Debug for TokenStream {
+    fn fmt(&self, _f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        todo!("Implement this function")
+    }
+}
+
+impl FromStr for TokenStream {
+    type Err = LexError;
+
+    fn from_str(_src: &str) -> Result<Self, LexError> {
+        todo!("Implement this function")
+    }
+}