Import and export improved

- Import paths are now vname and not sym
- Imports and exports accept multiple space-delimited operators in []

as a result, we can now reliably import and export the operator *

- error reporting ergonomics

src/lib.rs

@@ -34,4 +34,4 @@ pub use representations::{
   ast, from_const_tree, interpreted, sourcefile, tree, ConstTree, Literal,
   Location, PathSet, Primitive,
 };
-pub use utils::{Side, Substack, ThreadPool};
+pub use utils::{thread_pool, Side, Substack};