Add implementations for parsing assign statements, forgot to do this

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

src/syn/parser.y

@@ -19,12 +19,12 @@ Body -> Result<Vec<Stmt>>:
 
 Stmt -> Result<Stmt>:
         Expr { Ok(Stmt::Expr($1?)) }
-    |   Assign { todo!() }
+    |   Assign { Ok(Stmt::Assign($1?)) }
     ;
 
 Assign -> Result<AssignStmt>:
         LhsExpr '=' Expr {
-            todo!()
+            Ok(AssignStmt { lhs: $1?, rhs: $3? })
         }
     ;
 
@@ -32,7 +32,7 @@ LhsExpr -> Result<LhsExpr>:
         AccessExpr {
             let lhs = match $1? {
                 Expr::Access(access) => LhsExpr::SetAttr(*access),
-                Expr::Atom(Atom::Ident(local)) => LhsExpr::Local(local),
+                Expr::Atom(Atom::Ident(local)) => LhsExpr::Name(local),
                 _ => todo!("TODO : invalid syntax, raise error"),
             };
             Ok(lhs)