Dynamic-wind (#52)

* Implement dynamic wind, fix bug with environment cloning

* Adjust readme

* I think this is correct now

README.md

@@ -22,7 +22,6 @@ That is obviously a long way away.
 ## Features currently unsupported by scheme-rs: 
 
 - Exceptions and error handling
-- Dynamic winding 
 - Ports and IO operations
 - Most API functions are not implemented
 - A large portion of lexical structures are missing; there's no way to specify recursive data structures
@@ -39,17 +38,17 @@ in the repo's root directory (examples taken from wikipedia):
 ~/scheme-rs> cargo run
     Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.03s
      Running `target/debug/scheme-rs`
->>> (let loop ((n 1))
-...   (if (> n 10)
-...       '()
-...       (cons n
-...     (loop (+ n 1)))))
+> (let loop ((n 1))
+   (if (> n 10)
+       '()
+       (cons n
+         (loop (+ n 1)))))
 $1 = (1 2 3 4 5 6 7 8 9 10)
 >>> (let* ((yin
-...          ((lambda (cc) (display "@") cc) (call-with-current-continuation (lambda (c) c))))
-...        (yang
-...          ((lambda (cc) (display "*") cc) (call-with-current-continuation (lambda (c) c)))))
-...     (yin yang))
+            ((lambda (cc) (display "@") cc) (call-with-current-continuation (lambda (c) c))))
+           (yang
+            ((lambda (cc) (display "*") cc) (call-with-current-continuation (lambda (c) c)))))
+     (yin yang))
 @*@**@***@****@*****@******@*******@********@*********@**********@***********@**********...^C
 ```
 

proc-macros/src/lib.rs

@@ -291,14 +291,14 @@ fn derive_trace_enum(name: Ident, data_enum: DataEnum) -> proc_macro2::TokenStre
         unsafe impl ::scheme_rs::gc::Trace for #name {
             unsafe fn visit_children(&self, visitor: unsafe fn(::scheme_rs::gc::OpaqueGcPtr)) {
                 match self {
-                    #( #visit_match_clauses )*,
+                    #( #visit_match_clauses, )*
                     _ => (),
                 }
             }
 
             unsafe fn finalize(&mut self) {
                 match self {
-                    #( #finalize_match_clauses )*,
+                    #( #finalize_match_clauses, )*
                     _ => (),
                 }
             }

src/ast/parse.rs

@@ -18,7 +18,7 @@ use std::{
     sync::Arc,
 };
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Trace)]
 pub enum ParseAstError {
     BadForm(Span),
     UnexpectedEmptyList(Span),