libproc_macro: Implement FromStr for TokenStream

Implement FromStr for TokenStream rust interface type.

ChangeLog:

	* librust/proc_macro/rust/bridge/token_stream.rs: Add FromStr
	implementation on internal type.
	* librust/proc_macro/rust/lib.rs: Implement FromStr.

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

2 files changed, 24 insertions, 8 deletions

diff --git a/librust/proc_macro/rust/bridge/token_stream.rs b/librust/proc_macro/rust/bridge/token_stream.rs
index eca0902..c33806f 100644
--- a/librust/proc_macro/rust/bridge/token_stream.rs
+++ b/librust/proc_macro/rust/bridge/token_stream.rs
@@ -1,11 +1,21 @@
 use bridge::{group::Group, ident::Ident, literal::Literal, punct::Punct};
 use std::convert::TryInto;
+use std::ffi::c_uchar;
 use std::fmt;
 use std::slice;
+use std::str::FromStr;
+use LexError;
 
 type ExternalTokenTree = crate::TokenTree;
 type ExternalTokenStream = crate::TokenStream;
 
+extern "C" {
+    fn TokenStream__new() -> TokenStream;
+    fn TokenStream__with_capacity(capacity: u64) -> TokenStream;
+    fn TokenStream__push(stream: *mut TokenStream, tree: TokenTree);
+    fn TokenStream__from_string(str: *const c_uchar, ts: *mut TokenStream) -> bool;
+}
+
 // TODO: There surely is a better way to achieve this. I don't like this
 // "duplication" of the TokenTree enumeration. But I cannot use the public
 // one since it's underlying types (public Group, Ident...) are not ffi safe.
@@ -41,12 +51,6 @@ impl From<ExternalTokenTree> for TokenTree {
     }
 }
 
-extern "C" {
-    fn TokenStream__new() -> TokenStream;
-    fn TokenStream__with_capacity(capacity: u64) -> TokenStream;
-    fn TokenStream__push(stream: *mut TokenStream, tree: TokenTree);
-}
-
 #[repr(C)]
 #[derive(Debug, Clone)]
 pub struct TokenStream {
@@ -129,3 +133,15 @@ impl fmt::Display for TokenStream {
         Ok(())
     }
 }
+
+impl FromStr for TokenStream {
+    type Err = LexError;
+    fn from_str(string: &str) -> Result<Self, LexError> {
+        let mut ts = TokenStream::new();
+        if unsafe { TokenStream__from_string(string.as_ptr(), &mut ts as *mut TokenStream) } {
+            Err(LexError)
+        } else {
+            Ok(ts)
+        }
+    }
+}
diff --git a/librust/proc_macro/rust/lib.rs b/librust/proc_macro/rust/lib.rs
index 59b4929..a1be0ac 100644
--- a/librust/proc_macro/rust/lib.rs
+++ b/librust/proc_macro/rust/lib.rs
@@ -168,8 +168,8 @@ impl fmt::Debug for TokenStream {
 impl FromStr for TokenStream {
     type Err = LexError;
 
-    fn from_str(_src: &str) -> Result<Self, LexError> {
-        todo!("Implement this function")
+    fn from_str(src: &str) -> Result<Self, LexError> {
+        bridge::token_stream::TokenStream::from_str(src).map(TokenStream)
     }
 }