added fresh-name fn

src/libsyntax/parse/token.rs

@@ -22,6 +22,9 @@ use core::char;
 use core::cmp::Equiv;
 use core::local_data;
 use core::str;
+use core::hashmap::HashSet;
+use core::rand;
+use core::rand::RngUtil;
 use core::to_bytes;
 
 #[deriving(Encodable, Decodable, Eq)]
@@ -559,6 +562,20 @@ pub fn gensym_ident(str : &str) -> ast::ident {
     ast::new_ident(gensym(str))
 }
 
+
+// create a fresh name. In principle, this is just a
+// gensym, but for debugging purposes, you'd like the
+// resulting name to have a suggestive stringify, without
+// paying the cost of guaranteeing that the name is
+// truly unique.  I'm going to try to strike a balance
+// by using a gensym with a name that has a random number
+// at the end. So, the gensym guarantees the uniqueness,
+// and the int helps to avoid confusion.
+pub fn fresh_name(src_name : &str) -> Name {
+    let num = rand::rng().gen_uint_range(0,0xffff);
+   gensym(fmt!("%s_%u",src_name,num))
+}
+
 /**
  * All the valid words that have meaning in the Rust language.
  *
@@ -691,3 +708,14 @@ pub fn is_reserved_keyword(tok: &Token) -> bool {
         _ => false,
     }
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use std::io;
+    #[test] fn t1() {
+        let a = fresh_name("ghi");
+        io::println(fmt!("interned name: %u,\ntextual name: %s\n",
+                         a,*interner_get(a)));
+    }
+}