diff --git a/build.rs b/build.rs
index 31abb1b..58f39f9 100644
--- a/build.rs
+++ b/build.rs
@@ -11,8 +11,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
     let mut parser_builder = CTParserBuilder::new()
         .yacckind(YaccKind::Grmtools)
         .error_on_conflicts(false);
-    let lex_rule_ids_map = parser_builder
-        .process_file_in_src("syn/parser.y")?;
+    let lex_rule_ids_map = parser_builder.process_file_in_src("syn/parser.y")?;
     if let Some((grm, _, _, conflicts)) = parser_builder.conflicts() {
         eprintln!("{}", conflicts.pp(grm));
         return Err("conflicts in parser".into());
diff --git a/src/bin/not.rs b/src/bin/not.rs
index a538966..d3aa8da 100644
--- a/src/bin/not.rs
+++ b/src/bin/not.rs
@@ -1,4 +1,4 @@
-use not_python::{syn::ast, compile::Compile, vm::Vm};
+use not_python::{compile::Compile, syn::ast, vm::Vm};
 
 use std::{fs, path::PathBuf};
 use structopt::StructOpt;
@@ -18,7 +18,6 @@ struct Options {
     #[structopt(short = "d", long)]
     disassemble: bool,
     */
-
     #[structopt(long, default_value = "run")]
     action: String,
 }
@@ -28,8 +27,8 @@ fn main() -> Result<()> {
     let text = fs::read_to_string(&opt.input)?;
     let action = &opt.action.to_lowercase();
     match action.as_str() {
-        "run" | "parse" | "dump" => {},
-        _ => eprintln!("WARNING: unknown action {}", action)
+        "run" | "parse" | "dump" => {}
+        _ => eprintln!("WARNING: unknown action {}", action),
     }
 
     let ast = match ast::parse(text.as_str()) {
@@ -40,7 +39,8 @@ fn main() -> Result<()> {
             }
             return Err("errors reported, exiting".into());
         }
-    }.unwrap();
+    }
+    .unwrap();
     if action == "parse" {
         println!("{:#?}", ast);
         return Ok(());
diff --git a/src/compile/error.rs b/src/compile/error.rs
index a8d8974..04fd678 100644
--- a/src/compile/error.rs
+++ b/src/compile/error.rs
@@ -10,4 +10,3 @@ pub enum Error {
 }
 
 pub type Result<T, E = Error> = std::result::Result<T, E>;
-
diff --git a/src/compile/locals.rs b/src/compile/locals.rs
index deb511f..4cf2da7 100644
--- a/src/compile/locals.rs
+++ b/src/compile/locals.rs
@@ -1,4 +1,8 @@
-use crate::{compile::Compile, obj::prelude::*, syn::{ast::*, visit::*}};
+use crate::{
+    compile::Compile,
+    obj::prelude::*,
+    syn::{ast::*, visit::*},
+};
 
 /// Collects local names from the given tree.
 ///
@@ -30,10 +34,18 @@ impl<'c> CollectLocals<'c> {
 impl Visit for CollectLocals<'_> {
     type Out = ();
 
-    fn visit_body(&mut self, body: &Body) -> Self::Out { DefaultAccept::default_accept(body, self); }
-    fn visit_stmt(&mut self, stmt: &Stmt) -> Self::Out { DefaultAccept::default_accept(stmt, self); }
-    fn visit_assign_stmt(&mut self, assign: &AssignStmt) -> Self::Out { DefaultAccept::default_accept(assign, self); }
-    fn visit_return_stmt(&mut self, ret: &ReturnStmt) -> Self::Out { DefaultAccept::default_accept(ret, self); }
+    fn visit_body(&mut self, body: &Body) -> Self::Out {
+        DefaultAccept::default_accept(body, self);
+    }
+    fn visit_stmt(&mut self, stmt: &Stmt) -> Self::Out {
+        DefaultAccept::default_accept(stmt, self);
+    }
+    fn visit_assign_stmt(&mut self, assign: &AssignStmt) -> Self::Out {
+        DefaultAccept::default_accept(assign, self);
+    }
+    fn visit_return_stmt(&mut self, ret: &ReturnStmt) -> Self::Out {
+        DefaultAccept::default_accept(ret, self);
+    }
     fn visit_lhs_expr(&mut self, lhs_expr: &LhsExpr) -> Self::Out {
         match lhs_expr {
             LhsExpr::Name(name) => {
@@ -43,14 +55,28 @@ impl Visit for CollectLocals<'_> {
             _ => { /* no op */ }
         }
     }
-    fn visit_expr(&mut self, expr: &Expr) -> Self::Out { DefaultAccept::default_accept(expr, self); }
-    fn visit_bin_expr(&mut self, expr: &BinExpr) -> Self::Out { DefaultAccept::default_accept(expr, self); }
-    fn visit_un_expr(&mut self, expr: &UnExpr) -> Self::Out { DefaultAccept::default_accept(expr, self); }
-    fn visit_call_expr(&mut self, expr: &CallExpr) -> Self::Out { DefaultAccept::default_accept(expr, self); }
-    fn visit_index_expr(&mut self, expr: &IndexExpr) -> Self::Out { DefaultAccept::default_accept(expr, self); }
-    fn visit_access_expr(&mut self, expr: &AccessExpr) -> Self::Out { DefaultAccept::default_accept(expr, self); }
+    fn visit_expr(&mut self, expr: &Expr) -> Self::Out {
+        DefaultAccept::default_accept(expr, self);
+    }
+    fn visit_bin_expr(&mut self, expr: &BinExpr) -> Self::Out {
+        DefaultAccept::default_accept(expr, self);
+    }
+    fn visit_un_expr(&mut self, expr: &UnExpr) -> Self::Out {
+        DefaultAccept::default_accept(expr, self);
+    }
+    fn visit_call_expr(&mut self, expr: &CallExpr) -> Self::Out {
+        DefaultAccept::default_accept(expr, self);
+    }
+    fn visit_index_expr(&mut self, expr: &IndexExpr) -> Self::Out {
+        DefaultAccept::default_accept(expr, self);
+    }
+    fn visit_access_expr(&mut self, expr: &AccessExpr) -> Self::Out {
+        DefaultAccept::default_accept(expr, self);
+    }
     fn visit_fun_expr(&mut self, _expr: &FunExpr) -> Self::Out {
         // Do not collect names for function expressions, since they have their own scope.
     }
-    fn visit_atom(&mut self, atom: &Atom) -> Self::Out { DefaultAccept::default_accept(atom, self); }
+    fn visit_atom(&mut self, atom: &Atom) -> Self::Out {
+        DefaultAccept::default_accept(atom, self);
+    }
 }
diff --git a/src/compile/mod.rs b/src/compile/mod.rs
index 8268410..ad89f39 100644
--- a/src/compile/mod.rs
+++ b/src/compile/mod.rs
@@ -4,7 +4,7 @@ mod locals;
 mod scope;
 pub mod thunk;
 
-use crate::{syn::ast::Body, obj::prelude::*, vm::consts::*};
+use crate::{obj::prelude::*, syn::ast::Body, vm::consts::*};
 use scope::*;
 use std::collections::HashMap;
 
@@ -29,20 +29,28 @@ impl Compile {
             .to_vec();
         // XXX TODO(compile)
         // remove this when we get returns implemented
-        main.push(crate::vm::inst::Inst::PushSym(crate::obj::reserved::NIL_NAME.sym));
+        main.push(crate::vm::inst::Inst::PushSym(
+            crate::obj::reserved::NIL_NAME.sym,
+        ));
         main.push(crate::vm::inst::Inst::Return);
-        let globals_syms: std::collections::BTreeMap<_, _> = self.pop_scope_layer().unwrap()
+        let globals_syms: std::collections::BTreeMap<_, _> = self
+            .pop_scope_layer()
+            .unwrap()
             .into_iter()
             .map(|(sym, name)| (name, sym))
             .collect();
-        let globals = globals_syms.into_iter()
+        let globals = globals_syms
+            .into_iter()
             .enumerate()
             .map(|(index, (name, sym))| {
                 assert_eq!(index, name.index());
                 sym
             })
             .collect();
-        Ok((self.const_data.const_pool, UserFun::new_obj(main, globals, 0)))
+        Ok((
+            self.const_data.const_pool,
+            UserFun::new_obj(main, globals, 0),
+        ))
     }
 
     /// Gets the constant data that is interned in this compile session.
diff --git a/src/compile/scope.rs b/src/compile/scope.rs
index 2a348f1..d19b80c 100644
--- a/src/compile/scope.rs
+++ b/src/compile/scope.rs
@@ -11,9 +11,7 @@ pub struct Scope {
 
 impl Scope {
     pub fn lookup_local(&self, sym: Sym) -> Option<Name> {
-        self.locals()
-            .and_then(|locals| locals.get(&sym))
-            .copied()
+        self.locals().and_then(|locals| locals.get(&sym)).copied()
     }
 
     pub fn lookup_global(&self, sym: Sym) -> Option<Name> {
@@ -23,8 +21,7 @@ impl Scope {
     }
 
     pub fn create_local(&mut self, sym: Sym) -> Name {
-        let locals = self.locals_mut()
-            .expect("locals");
+        let locals = self.locals_mut().expect("locals");
         if let Some(local) = locals.get(&sym).copied() {
             local
         } else {
@@ -35,8 +32,7 @@ impl Scope {
     }
 
     pub fn create_global(&mut self, sym: Sym) -> Name {
-        let globals = self.globals_mut()
-            .expect("globals");
+        let globals = self.globals_mut().expect("globals");
         if let Some(global) = globals.get(&sym).copied() {
             global
         } else {
diff --git a/src/compile/thunk.rs b/src/compile/thunk.rs
index f48e584..1430aec 100644
--- a/src/compile/thunk.rs
+++ b/src/compile/thunk.rs
@@ -106,8 +106,7 @@ impl Thunk {
     }
 
     pub fn flatten(self) -> BasicBlockList {
-        Flatten::default()
-            .flatten(self)
+        Flatten::default().flatten(self)
     }
 }
 
@@ -158,10 +157,13 @@ impl Flatten {
         match thunk {
             Thunk::Body(thunk) => {
                 let this_block = self.this_block();
-                let prev = self.blocks.insert(this_block, BasicBlock::Block {
-                    exit: next_block,
-                    block: thunk,
-                });
+                let prev = self.blocks.insert(
+                    this_block,
+                    BasicBlock::Block {
+                        exit: next_block,
+                        block: thunk,
+                    },
+                );
                 assert!(prev.is_none());
             }
             Thunk::List(thunks) => {
@@ -172,14 +174,20 @@ impl Flatten {
                 }
                 assert_eq!(next_block, self.this_block());
             }
-            Thunk::Branch { thunk_true, thunk_false, } => {
+            Thunk::Branch {
+                thunk_true,
+                thunk_false,
+            } => {
                 let branch_block = self.this_block();
                 let block_true = self.this_block() + 1;
                 let block_false = block_true + thunk_true.basic_block_count();
-                self.blocks.insert(branch_block, BasicBlock::Branch {
-                    block_true,
-                    block_false,
-                });
+                self.blocks.insert(
+                    branch_block,
+                    BasicBlock::Branch {
+                        block_true,
+                        block_false,
+                    },
+                );
                 self.flatten_next(next_block, *thunk_true);
                 self.flatten_next(next_block, *thunk_false);
                 assert_eq!(self.this_block(), next_block);
@@ -278,7 +286,10 @@ impl Visit for CompileBody<'_> {
                 if let Some(local) = self.compile.lookup_local(sym) {
                     thunk = Inst::PopLocal(Some(local)).into();
                 } else {
-                    let global = self.compile.lookup_global(sym).expect("name expected to exist someplace(?)");
+                    let global = self
+                        .compile
+                        .lookup_global(sym)
+                        .expect("name expected to exist someplace(?)");
                     thunk = Inst::PopGlobal(Some(global)).into();
                 }
             }
@@ -368,7 +379,7 @@ impl Visit for CompileBody<'_> {
         // - push const
         // (functions are unique const values so a new function will be created for every literal
         //  function defined in code)
-        
+
         // This is pretty much the only place where a new scope layer gets pushed beyond the start
         // of the program
         self.compile.push_scope_layer();
@@ -378,9 +389,7 @@ impl Visit for CompileBody<'_> {
         }
 
         // Compile function body
-        let mut code = self.visit_body(&expr.body)?
-            .flatten()
-            .to_vec();
+        let mut code = self.visit_body(&expr.body)?.flatten().to_vec();
 
         // If the last instruction is not a return, or if there are no instructions, then return
         // :nil value.
@@ -390,7 +399,9 @@ impl Visit for CompileBody<'_> {
         }
 
         // remap (Sym -> Name) to be (Name -> Sym) and make sure it's all in order.
-        let scope_locals: BTreeMap<_, _> = self.compile.pop_scope_layer()
+        let scope_locals: BTreeMap<_, _> = self
+            .compile
+            .pop_scope_layer()
             .unwrap()
             .into_iter()
             .map(|(sym, name)| (name, sym))
@@ -399,7 +410,8 @@ impl Visit for CompileBody<'_> {
         // this should be in numeric order since:
         // 1. locals are created exactly once or looked up
         // 2. scope_locals is a btreemap, keyed by names, which are in order from 0..N
-        let locals: FunLocals = scope_locals.into_iter()
+        let locals: FunLocals = scope_locals
+            .into_iter()
             .enumerate()
             .map(|(index, (name, sym))| {
                 assert_eq!(index, name.index());
@@ -407,7 +419,9 @@ impl Visit for CompileBody<'_> {
             })
             .collect();
 
-        let (hdl, _fun) = self.compile.push_const(UserFun::new_obj(code, locals, expr.params.len()));
+        let (hdl, _fun) =
+            self.compile
+                .push_const(UserFun::new_obj(code, locals, expr.params.len()));
 
         // TODO(compile) : determine return value at the end of the body (preferably at parse-time)
 
@@ -427,7 +441,10 @@ impl Visit for CompileBody<'_> {
                 // This checks to make sure that it's both a local variable and that there's more
                 // than one scope layer.
                 let sym = global_sym(ident.to_string());
-                if let (true, Some(local)) = (self.compile.scope().layers_len() > 1, self.compile.lookup_local(sym)) {
+                if let (true, Some(local)) = (
+                    self.compile.scope().layers_len() > 1,
+                    self.compile.lookup_local(sym),
+                ) {
                     // get local
                     Inst::LoadLocal(local).into()
                 } else {
@@ -466,25 +483,20 @@ fn test_flatten_thunk() {
     let init_body = vec![
         Inst::PushSym(Sym::new(0)),
         Inst::PushSym(Sym::new(1)),
-        Inst::Call(1)
+        Inst::Call(1),
     ];
     let true_body = vec![Inst::PushSym(Sym::new(2))];
     let false_body = vec![Inst::PushSym(Sym::new(3))];
-    let end_body = vec![
-        Inst::PushSym(Sym::new(1)),
-        Inst::Call(1)
-    ];
+    let end_body = vec![Inst::PushSym(Sym::new(1)), Inst::Call(1)];
 
     let thunk = Thunk::List(vec![
         // do something before
         Thunk::Body(init_body.clone()),
-
         // branch
         Thunk::Branch {
             thunk_true: Thunk::Body(true_body.clone()).into(),
             thunk_false: Thunk::Body(false_body.clone()).into(),
         },
-
         // do something after
         Thunk::Body(end_body.clone()),
     ]);
@@ -495,10 +507,55 @@ fn test_flatten_thunk() {
     assert_eq!(blocks.len(), block_count);
 
     let mut iter = blocks.into_iter();
-    assert_eq!(iter.next().unwrap(), (0, BasicBlock::Block { exit: 1, block: init_body, }));
-    assert_eq!(iter.next().unwrap(), (1, BasicBlock::Branch { block_true: 2, block_false: 3, }));
-    assert_eq!(iter.next().unwrap(), (2, BasicBlock::Block { exit: 4, block: true_body, }));
-    assert_eq!(iter.next().unwrap(), (3, BasicBlock::Block { exit: 4, block: false_body, }));
-    assert_eq!(iter.next().unwrap(), (4, BasicBlock::Block { exit: 5, block: end_body, }));
+    assert_eq!(
+        iter.next().unwrap(),
+        (
+            0,
+            BasicBlock::Block {
+                exit: 1,
+                block: init_body,
+            }
+        )
+    );
+    assert_eq!(
+        iter.next().unwrap(),
+        (
+            1,
+            BasicBlock::Branch {
+                block_true: 2,
+                block_false: 3,
+            }
+        )
+    );
+    assert_eq!(
+        iter.next().unwrap(),
+        (
+            2,
+            BasicBlock::Block {
+                exit: 4,
+                block: true_body,
+            }
+        )
+    );
+    assert_eq!(
+        iter.next().unwrap(),
+        (
+            3,
+            BasicBlock::Block {
+                exit: 4,
+                block: false_body,
+            }
+        )
+    );
+    assert_eq!(
+        iter.next().unwrap(),
+        (
+            4,
+            BasicBlock::Block {
+                exit: 5,
+                block: end_body,
+            }
+        )
+    );
     assert!(iter.next().is_none());
 }
diff --git a/src/lib.rs b/src/lib.rs
index 6ef273b..a404eac 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,6 +3,6 @@
 
 #[macro_use]
 pub mod obj;
-pub mod syn;
 pub mod compile;
+pub mod syn;
 pub mod vm;
diff --git a/src/obj/attrs.rs b/src/obj/attrs.rs
index c04051a..f912ed8 100644
--- a/src/obj/attrs.rs
+++ b/src/obj/attrs.rs
@@ -1,6 +1,9 @@
-use crate::obj::{ObjRef, sym::Sym};
+use crate::obj::{sym::Sym, ObjRef};
 use shredder::{Gc, Scan};
-use std::{collections::BTreeMap, ops::{Deref, DerefMut}};
+use std::{
+    collections::BTreeMap,
+    ops::{Deref, DerefMut},
+};
 
 pub type Attrs = BTreeMap<Sym, ObjRef>;
 pub type VtableAttrs = Gc<Attrs>;
@@ -12,7 +15,9 @@ pub struct Vtable {
 
 impl Vtable {
     pub fn new(attrs: Attrs) -> Self {
-        Self { attrs: Gc::new(attrs), }
+        Self {
+            attrs: Gc::new(attrs),
+        }
     }
 }
 
diff --git a/src/obj/builtin.rs b/src/obj/builtin.rs
index 4b4e109..7e8e12c 100644
--- a/src/obj/builtin.rs
+++ b/src/obj/builtin.rs
@@ -1,49 +1,72 @@
-use crate::{obj::{prelude::*, reserved::*}, vm::{error::*, signal::*}};
+use crate::{
+    obj::{prelude::*, reserved::*},
+    vm::{error::*, signal::*},
+};
 use maplit::btreemap;
 use once_cell::sync::Lazy;
 use std::collections::BTreeMap;
 
-pub static PRINTLN_BUILTIN_FUN: Lazy<NativeFunRef> = Lazy::new(|| NativeFun::new_obj(1, |_, vm, args| {
-    // TODO : use __get_attr__ when it gets added
-    let to_string = {
-        let obj_ref = &args[0];
-        read_obj!(let obj = obj_ref);
-        obj.get_attr(STR_MEMBER_NAME.sym)
-            .ok_or(Error::MissingAttr { attr: STR_MEMBER_NAME.sym })?
-    };
-    let return_value = vm.call(to_string, vec![])?;
-    {
-        read_obj!(let str_obj = return_value);
-        let str_obj: &Str = str_obj.as_any().downcast_ref()
-            .ok_or_else(|| Error::ValueError { error: "expected str value".to_string(), })?; 
-        println!("{}", str_obj.value());
-    }
+pub static PRINTLN_BUILTIN_FUN: Lazy<NativeFunRef> = Lazy::new(|| {
+    NativeFun::new_obj(1, |_, vm, args| {
+        // TODO : use __get_attr__ when it gets added
+        let to_string = {
+            let obj_ref = &args[0];
+            read_obj!(let obj = obj_ref);
+            obj.get_attr(STR_MEMBER_NAME.sym)
+                .ok_or(Error::MissingAttr {
+                    attr: STR_MEMBER_NAME.sym,
+                })?
+        };
+        let return_value = vm.call(to_string, vec![])?;
+        {
+            read_obj!(let str_obj = return_value);
+            let str_obj: &Str =
+                str_obj
+                    .as_any()
+                    .downcast_ref()
+                    .ok_or_else(|| Error::ValueError {
+                        error: "expected str value".to_string(),
+                    })?;
+            println!("{}", str_obj.value());
+        }
 
-    vm.push(NIL_NAME.sym_ref());
-    Ok(Signal::Return)
-}));
-
-pub static PRINT_BUILTIN_FUN: Lazy<NativeFunRef> = Lazy::new(|| NativeFun::new_obj(1, |_, vm, args| {
-    // TODO : use __get_attr__ when it gets added
-    let to_string = {
-        let obj_ref = &args[0];
-        read_obj!(let obj = obj_ref);
-        obj.get_attr(STR_MEMBER_NAME.sym)
-            .ok_or(Error::MissingAttr { attr: STR_MEMBER_NAME.sym })?
-    };
-    let return_value = vm.call(to_string, vec![])?;
-    {
-        read_obj!(let str_obj = return_value);
-        let str_obj: &Str = str_obj.as_any().downcast_ref()
-            .ok_or_else(|| Error::ValueError { error: "expected str value".to_string(), })?;
-        print!("{}", str_obj.value());
-    }
-
-    vm.push(NIL_NAME.sym_ref());
-    Ok(Signal::Return)
-}));
-
-pub static BUILTIN_OBJS: Lazy<BTreeMap<Sym, ObjRef>> = Lazy::new(|| btreemap! {
-    PRINTLN_BUILTIN_NAME.sym => PRINTLN_BUILTIN_FUN.clone() as _,
-    PRINT_BUILTIN_NAME.sym => PRINT_BUILTIN_FUN.clone() as _,
+        vm.push(NIL_NAME.sym_ref());
+        Ok(Signal::Return)
+    })
+});
+
+pub static PRINT_BUILTIN_FUN: Lazy<NativeFunRef> = Lazy::new(|| {
+    NativeFun::new_obj(1, |_, vm, args| {
+        // TODO : use __get_attr__ when it gets added
+        let to_string = {
+            let obj_ref = &args[0];
+            read_obj!(let obj = obj_ref);
+            obj.get_attr(STR_MEMBER_NAME.sym)
+                .ok_or(Error::MissingAttr {
+                    attr: STR_MEMBER_NAME.sym,
+                })?
+        };
+        let return_value = vm.call(to_string, vec![])?;
+        {
+            read_obj!(let str_obj = return_value);
+            let str_obj: &Str =
+                str_obj
+                    .as_any()
+                    .downcast_ref()
+                    .ok_or_else(|| Error::ValueError {
+                        error: "expected str value".to_string(),
+                    })?;
+            print!("{}", str_obj.value());
+        }
+
+        vm.push(NIL_NAME.sym_ref());
+        Ok(Signal::Return)
+    })
+});
+
+pub static BUILTIN_OBJS: Lazy<BTreeMap<Sym, ObjRef>> = Lazy::new(|| {
+    btreemap! {
+        PRINTLN_BUILTIN_NAME.sym => PRINTLN_BUILTIN_FUN.clone() as _,
+        PRINT_BUILTIN_NAME.sym => PRINT_BUILTIN_FUN.clone() as _,
+    }
 });
diff --git a/src/obj/fun.rs b/src/obj/fun.rs
index 7bd7bbf..064ef15 100644
--- a/src/obj/fun.rs
+++ b/src/obj/fun.rs
@@ -1,7 +1,14 @@
-use crate::{obj::{reserved::*, prelude::*}, vm::{consts::ConstPool, error::*, frame::*, inst::Inst, signal::*, Vm}};
+use crate::{
+    obj::{prelude::*, reserved::*},
+    vm::{consts::ConstPool, error::*, frame::*, inst::Inst, signal::*, Vm},
+};
 use once_cell::sync::Lazy;
 use shredder::{GcSafeWrapper, Scan};
-use std::{fmt::{Debug, Formatter, self}, io::{self, Write}, sync::Arc};
+use std::{
+    fmt::{self, Debug, Formatter},
+    io::{self, Write},
+    sync::Arc,
+};
 
 pub type FunLocals = Vec<Sym>;
 
@@ -49,9 +56,13 @@ impl Obj for Method {
         Some(&mut self.attrs)
     }
 
-    fn as_any(&self) -> &dyn std::any::Any { self }
+    fn as_any(&self) -> &dyn std::any::Any {
+        self
+    }
 
-    fn as_fun(&self) -> Option<&dyn Fun> { Some(self) }
+    fn as_fun(&self) -> Option<&dyn Fun> {
+        Some(self)
+    }
 }
 
 impl Fun for Method {
@@ -110,7 +121,12 @@ impl UserFun {
         &self.locals
     }
 
-    pub fn dump(&self, writer: &mut dyn Write, const_pool: &ConstPool, globals: &FunLocals) -> io::Result<()> {
+    pub fn dump(
+        &self,
+        writer: &mut dyn Write,
+        const_pool: &ConstPool,
+        globals: &FunLocals,
+    ) -> io::Result<()> {
         fn num_digits(n: usize, radix: usize) -> usize {
             ((n as f64) + 1.0).log(radix as f64).ceil() as usize
         }
@@ -126,21 +142,22 @@ impl UserFun {
                     sym.index().to_string(),
                     global_sym_lookup(*sym).unwrap().to_string(),
                 ),
-                Inst::PushConst(hdl) => (
-                    hdl.index().to_string(),
-                    {
-                        let obj_ref = const_pool.get(*hdl);
-                        read_obj!(let obj = obj_ref);
-                        format!("{:?}", obj)
-                    },
-                ),
+                Inst::PushConst(hdl) => (hdl.index().to_string(), {
+                    let obj_ref = const_pool.get(*hdl);
+                    read_obj!(let obj = obj_ref);
+                    format!("{:?}", obj)
+                }),
                 Inst::LoadLocal(local) => (
                     local.index().to_string(),
-                    global_sym_lookup(self.locals()[local.index()]).unwrap().to_string(),
+                    global_sym_lookup(self.locals()[local.index()])
+                        .unwrap()
+                        .to_string(),
                 ),
                 Inst::LoadGlobal(global) => (
                     global.index().to_string(),
-                    global_sym_lookup(globals[global.index()]).unwrap().to_string(),
+                    global_sym_lookup(globals[global.index()])
+                        .unwrap()
+                        .to_string(),
                 ),
                 Inst::PopLocal(local) => {
                     if let Some(local) = local {
@@ -153,7 +170,7 @@ impl UserFun {
                     }
                 }
                 Inst::PopGlobal(global) => {
-                    if let Some(global) = global{
+                    if let Some(global) = global {
                         let index = global.index();
                         let sym = globals[index];
                         let name = global_sym_lookup(sym).unwrap().to_string();
@@ -162,14 +179,8 @@ impl UserFun {
                         ("(discarded)".to_string(), String::new())
                     }
                 }
-                Inst::Jump(addr) | Inst::JumpTrue(addr) => (
-                    addr.to_string(),
-                    String::new(),
-                ),
-                Inst::Call(argc) => (
-                    argc.to_string(),
-                    String::new(),
-                ),
+                Inst::Jump(addr) | Inst::JumpTrue(addr) => (addr.to_string(), String::new()),
+                Inst::Call(argc) => (argc.to_string(), String::new()),
                 _ => (String::new(), String::new()),
             };
 
@@ -224,12 +235,13 @@ impl Fun for UserFun {
                 got: args.len(),
             });
         }
-        let bindings: FrameBindings = args.into_iter()
-            .enumerate()
-            .collect();
-        Ok(Frame::User(
-            UserFrame::new(callee, bindings, vm.pc(), Arc::clone(&self.code))
-        ))
+        let bindings: FrameBindings = args.into_iter().enumerate().collect();
+        Ok(Frame::User(UserFrame::new(
+            callee,
+            bindings,
+            vm.pc(),
+            Arc::clone(&self.code),
+        )))
     }
 }
 
@@ -294,7 +306,10 @@ impl NativeFun {
 impl Debug for NativeFun {
     fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
         fmt.debug_struct("NativeFun")
-            .field("fun", &format!("(function at {:x})", &self.fun as *const _ as usize))
+            .field(
+                "fun",
+                &format!("(function at {:x})", &self.fun as *const _ as usize),
+            )
             .field("attrs", &self.attrs)
             .finish()
     }
@@ -330,9 +345,7 @@ impl Fun for NativeFun {
                 got: args.len(),
             });
         }
-        Ok(Frame::Native(
-            NativeFrame::new(callee, *self.fun, args)
-        ))
+        Ok(Frame::Native(NativeFrame::new(callee, *self.fun, args)))
     }
 }
 
diff --git a/src/obj/int.rs b/src/obj/int.rs
index 79670c8..a32ce5d 100644
--- a/src/obj/int.rs
+++ b/src/obj/int.rs
@@ -1,7 +1,10 @@
-use crate::{obj::{prelude::*, reserved::*}, vm::error::*};
+use crate::{
+    obj::{prelude::*, reserved::*},
+    vm::error::*,
+};
 use once_cell::sync::Lazy;
 use shredder::Scan;
-use std::fmt::{Debug, Formatter, self};
+use std::fmt::{self, Debug, Formatter};
 
 pub type IntRef = ObjRef<Int>;
 pub type IntValue = i128;
@@ -43,9 +46,7 @@ impl_obj_readonly!(Int);
 
 impl Debug for Int {
     fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
-        fmt.debug_struct("Int")
-            .field("value", &self.value)
-            .finish()
+        fmt.debug_struct("Int").field("value", &self.value).finish()
     }
 }
 
diff --git a/src/obj/intern.rs b/src/obj/intern.rs
index d8a873f..25e7893 100644
--- a/src/obj/intern.rs
+++ b/src/obj/intern.rs
@@ -9,14 +9,12 @@ pub struct Interner<T: Hash + Eq> {
 
 impl<T: Hash + Eq> Interner<T> {
     pub fn new(forward: Vec<Arc<T>>) -> Self {
-        let reverse = forward.iter()
+        let reverse = forward
+            .iter()
             .enumerate()
             .map(|(i, s)| (Arc::clone(s), Sym::new(i)))
             .collect();
-        Self {
-            forward,
-            reverse,
-        }
+        Self { forward, reverse }
     }
 
     pub fn forward(&self) -> &Vec<Arc<T>> {
@@ -41,18 +39,19 @@ impl<T: Hash + Eq> Interner<T> {
     }
 
     pub fn lookup(&self, sym: Sym) -> Option<Arc<T>> {
-        self.forward.get(sym.index())
-            .map(Arc::clone)
+        self.forward.get(sym.index()).map(Arc::clone)
     }
 
     pub fn lookup_sym(&self, value: impl std::borrow::Borrow<T>) -> Option<Sym> {
-        self.reverse.get(value.borrow())
-            .copied()
+        self.reverse.get(value.borrow()).copied()
     }
 }
 
 impl<T: Hash + Eq> Default for Interner<T> {
     fn default() -> Self {
-        Interner { forward: Default::default(), reverse: Default::default(), }
+        Interner {
+            forward: Default::default(),
+            reverse: Default::default(),
+        }
     }
 }
diff --git a/src/obj/macros.rs b/src/obj/macros.rs
index 86ea908..e3f6471 100644
--- a/src/obj/macros.rs
+++ b/src/obj/macros.rs
@@ -14,7 +14,7 @@ macro_rules! impl_obj {
             fn attrs_mut(&mut self) -> Option<&mut $crate::obj::attrs::Attrs> {
                 Some(&mut self.$attrs)
             }
-            
+
             fn as_any(&self) -> &dyn std::any::Any {
                 self
             }
@@ -23,7 +23,7 @@ macro_rules! impl_obj {
 
     ($ty:ty) => {
         impl_obj!($ty, vtable, attrs);
-    }
+    };
 }
 
 #[macro_export]
diff --git a/src/obj/mod.rs b/src/obj/mod.rs
index 70f6307..5c82dfd 100644
--- a/src/obj/mod.rs
+++ b/src/obj/mod.rs
@@ -40,7 +40,7 @@ macro_rules! obj_attr {
         fn $name(&self) -> Option<ObjRef> {
             self.get_attr($attr.sym)
         }
-    }
+    };
 }
 
 pub trait Obj: Scan + Debug {
@@ -58,7 +58,9 @@ pub trait Obj: Scan + Debug {
     fn as_any(&self) -> &dyn std::any::Any;
 
     /// Gets this object as a `dyn Fun` reference.
-    fn as_fun(&self) -> Option<&dyn Fun> { None }
+    fn as_fun(&self) -> Option<&dyn Fun> {
+        None
+    }
 
     obj_attr!(get_ty, TY_MEMBER_NAME);
     obj_attr!(get_call, CALL_MEMBER_NAME);
@@ -140,7 +142,8 @@ where
 // impl Debug for ObjRef
 //
 impl<T> Debug for ObjRef<T>
-    where T: Obj + ?Sized + Send + Sync + 'static,
+where
+    T: Obj + ?Sized + Send + Sync + 'static,
 {
     fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
         read_obj!(let obj: &T = self);
diff --git a/src/obj/reserved.rs b/src/obj/reserved.rs
index 4b8c471..31dc835 100644
--- a/src/obj/reserved.rs
+++ b/src/obj/reserved.rs
@@ -1,6 +1,6 @@
 //! Reserved names for object members.
 
-use crate::obj::sym::{Sym, SymRef, global_sym, global_sym_ref};
+use crate::obj::sym::{global_sym, global_sym_ref, Sym, SymRef};
 use once_cell::sync::Lazy;
 
 macro_rules! name {
@@ -8,9 +8,9 @@ macro_rules! name {
         pub static $name: Lazy<NameInfo> = Lazy::new(|| {
             let name = $text;
             let sym = global_sym(name.to_string());
-            NameInfo { name, sym, }
+            NameInfo { name, sym }
         });
-    }
+    };
 }
 
 pub struct NameInfo {
@@ -79,4 +79,3 @@ name!(PLUS_OP_NAME, "__add__");
 name!(MINUS_OP_NAME, "__sub__");
 name!(TIMES_OP_NAME, "__mul__");
 name!(DIV_OP_NAME, "__div__");
-
diff --git a/src/obj/str.rs b/src/obj/str.rs
index 27503be..bfd727b 100644
--- a/src/obj/str.rs
+++ b/src/obj/str.rs
@@ -1,7 +1,10 @@
-use crate::{obj::{prelude::*, reserved::*}, vm::error::*};
+use crate::{
+    obj::{prelude::*, reserved::*},
+    vm::error::*,
+};
 use once_cell::sync::Lazy;
 use shredder::Scan;
-use std::fmt::{Debug, Formatter, self};
+use std::fmt::{self, Debug, Formatter};
 
 pub type StrRef = ObjRef<Str>;
 
@@ -37,9 +40,7 @@ impl_obj_readonly!(Str);
 
 impl Debug for Str {
     fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
-        fmt.debug_struct("Str")
-            .field("value", &self.value)
-            .finish()
+        fmt.debug_struct("Str").field("value", &self.value).finish()
     }
 }
 
@@ -86,8 +87,9 @@ static STR_INT_FUN: Lazy<NativeFunRef> = Lazy::new(|| {
             error: "expected Str value".to_string(),
         })?;
 
-        let int: IntValue = str_obj.value.parse()
-            .map_err(|_| Error::ValueError { error: "invalid Int value".to_string(), })?;
+        let int: IntValue = str_obj.value.parse().map_err(|_| Error::ValueError {
+            error: "invalid Int value".to_string(),
+        })?;
         vm.push(Int::new_obj(int));
 
         Ok(crate::vm::signal::Signal::Return)
diff --git a/src/obj/sym.rs b/src/obj/sym.rs
index 0eed22d..b5f1855 100644
--- a/src/obj/sym.rs
+++ b/src/obj/sym.rs
@@ -1,6 +1,9 @@
-use crate::obj::{intern::Interner, reserved::*, prelude::*};
+use crate::obj::{intern::Interner, prelude::*, reserved::*};
 use once_cell::sync::Lazy;
-use std::{collections::BTreeMap, sync::{Arc, Mutex}};
+use std::{
+    collections::BTreeMap,
+    sync::{Arc, Mutex},
+};
 
 //
 // struct Sym
diff --git a/src/obj/ty.rs b/src/obj/ty.rs
index d9c5976..ef62076 100644
--- a/src/obj/ty.rs
+++ b/src/obj/ty.rs
@@ -1,4 +1,4 @@
-use crate::obj::{reserved::*, prelude::*};
+use crate::obj::{prelude::*, reserved::*};
 use once_cell::sync::Lazy;
 use shredder::Scan;
 
diff --git a/src/syn/ast.rs b/src/syn/ast.rs
index b313614..4d5851c 100644
--- a/src/syn/ast.rs
+++ b/src/syn/ast.rs
@@ -13,10 +13,9 @@ impl<V: Visit> Accept<V> for Body {
     }
 }
 
-impl<V: Visit<Out=()>> DefaultAccept<V> for Body {
+impl<V: Visit<Out = ()>> DefaultAccept<V> for Body {
     fn default_accept(&self, visitor: &mut V) -> V::Out {
-        self.iter()
-            .for_each(|stmt| visitor.visit_stmt(stmt));
+        self.iter().for_each(|stmt| visitor.visit_stmt(stmt));
     }
 }
 
@@ -67,7 +66,7 @@ impl<V: Visit> Accept<V> for AssignStmt {
 //
 // impl DefaultAccept for AssignStmt
 //
-impl<V: Visit<Out=()>> DefaultAccept<V> for AssignStmt {
+impl<V: Visit<Out = ()>> DefaultAccept<V> for AssignStmt {
     fn default_accept(&self, visitor: &mut V) -> V::Out {
         self.lhs.accept(visitor);
         self.rhs.accept(visitor);
@@ -92,11 +91,11 @@ impl<V: Visit> Accept<V> for LhsExpr {
 //
 // impl DefaultAccept for LhsExpr
 //
-impl<V: Visit<Out=()>> DefaultAccept<V> for LhsExpr {
+impl<V: Visit<Out = ()>> DefaultAccept<V> for LhsExpr {
     fn default_accept(&self, visitor: &mut V) -> V::Out {
         match self {
             LhsExpr::SetAttr(a) => a.accept(visitor),
-            LhsExpr::Name(_) => {},
+            LhsExpr::Name(_) => {}
         }
     }
 }
@@ -115,7 +114,7 @@ impl<V: Visit> Accept<V> for ReturnStmt {
     }
 }
 
-impl<V: Visit<Out=()>> DefaultAccept<V> for ReturnStmt {
+impl<V: Visit<Out = ()>> DefaultAccept<V> for ReturnStmt {
     fn default_accept(&self, visitor: &mut V) -> V::Out {
         if let Some(expr) = self.expr.as_ref() {
             expr.accept(visitor)
@@ -123,7 +122,6 @@ impl<V: Visit<Out=()>> DefaultAccept<V> for ReturnStmt {
     }
 }
 
-
 //
 // struct Expr
 //
@@ -237,7 +235,7 @@ pub struct BinExpr {
 
 impl BinExpr {
     pub fn new_expr(lhs: Expr, op: BinOp, rhs: Expr) -> Expr {
-        Self { lhs, op, rhs, }.into()
+        Self { lhs, op, rhs }.into()
     }
 }
 
@@ -253,7 +251,7 @@ impl<V: Visit> Accept<V> for BinExpr {
 //
 // impl DefaultAccept for BinExpr
 //
-impl<V: Visit<Out=()>> DefaultAccept<V> for BinExpr {
+impl<V: Visit<Out = ()>> DefaultAccept<V> for BinExpr {
     fn default_accept(&self, visitor: &mut V) -> V::Out {
         visitor.visit_expr(&self.lhs);
         visitor.visit_expr(&self.rhs);
@@ -326,11 +324,10 @@ impl<V: Visit> Accept<V> for CallExpr {
 //
 // impl DefaultAccept for CallExpr
 //
-impl<V: Visit<Out=()>> DefaultAccept<V> for CallExpr {
+impl<V: Visit<Out = ()>> DefaultAccept<V> for CallExpr {
     fn default_accept(&self, visitor: &mut V) -> V::Out {
         visitor.visit_expr(&self.expr);
-        self.args.iter()
-            .for_each(|arg| visitor.visit_expr(arg));
+        self.args.iter().for_each(|arg| visitor.visit_expr(arg));
     }
 }
 
@@ -345,7 +342,7 @@ pub struct IndexExpr {
 
 impl IndexExpr {
     pub fn new_expr(expr: Expr, index: Expr) -> Expr {
-        Self { expr, index, }.into()
+        Self { expr, index }.into()
     }
 }
 
@@ -361,7 +358,7 @@ impl<V: Visit> Accept<V> for IndexExpr {
 //
 // impl DefaultAccept for IndexExpr
 //
-impl<V: Visit<Out=()>> DefaultAccept<V> for IndexExpr {
+impl<V: Visit<Out = ()>> DefaultAccept<V> for IndexExpr {
     fn default_accept(&self, visitor: &mut V) -> V::Out {
         visitor.visit_expr(&self.expr);
         visitor.visit_expr(&self.index);
@@ -379,7 +376,7 @@ pub struct AccessExpr {
 
 impl AccessExpr {
     pub fn new_expr(expr: Expr, access: String) -> Expr {
-        Self { expr, access, }.into()
+        Self { expr, access }.into()
     }
 }
 
@@ -415,7 +412,7 @@ pub struct FunExpr {
 //
 impl FunExpr {
     pub fn new_expr(params: Vec<String>, body: Body) -> Expr {
-        Self { params, body, }.into()
+        Self { params, body }.into()
     }
 }
 
@@ -462,8 +459,8 @@ impl<V: Visit> Accept<V> for Atom {
 // impl DefaultAccept for Atom
 //
 
-impl<V: Visit<Out=()>> DefaultAccept<V> for Atom {
-    fn default_accept(&self, _visitor: &mut V) -> V::Out { }
+impl<V: Visit<Out = ()>> DefaultAccept<V> for Atom {
+    fn default_accept(&self, _visitor: &mut V) -> V::Out {}
 }
 
 pub fn parse(text: &str) -> Result<Option<Vec<Stmt>>, Vec<String>> {
@@ -473,9 +470,10 @@ pub fn parse(text: &str) -> Result<Option<Vec<Stmt>>, Vec<String>> {
     let (res, errors) = parser::parse(&lexer);
 
     if !errors.is_empty() {
-        return Err(errors.into_iter()
+        return Err(errors
+            .into_iter()
             .map(|e| e.pp(&lexer, &parser::token_epp))
-            .collect())
+            .collect());
     }
 
     Ok(res.transpose().unwrap())
diff --git a/src/syn/mod.rs b/src/syn/mod.rs
index 8116462..53649c1 100644
--- a/src/syn/mod.rs
+++ b/src/syn/mod.rs
@@ -1,18 +1,18 @@
-#![macro_use] mod macros;
+#![macro_use]
 pub mod ast;
+mod macros;
 pub mod visit;
 
 pub mod lexer {
     lrlex_mod!("syn/lexer.l");
-    use lrlex::lrlex_mod;
     pub use self::lexer_l::*;
-
+    use lrlex::lrlex_mod;
 }
 
 pub mod parser {
     lrpar_mod!("syn/parser.y");
-    use lrpar::lrpar_mod;
     pub use self::parser_y::*;
+    use lrpar::lrpar_mod;
 }
 
 //pub use lexer_l as lexer;
diff --git a/src/vm/consts.rs b/src/vm/consts.rs
index 0fbf54d..1c9fdfe 100644
--- a/src/vm/consts.rs
+++ b/src/vm/consts.rs
@@ -8,7 +8,7 @@ pub struct ConstPool {
 }
 
 // Constant pools are constant, and live for the lifetime of the entire program.
-impl shredder::EmptyScan for ConstPool { }
+impl shredder::EmptyScan for ConstPool {}
 
 impl ConstPool {
     pub fn new() -> Self {
diff --git a/src/vm/error.rs b/src/vm/error.rs
index 6fd8a2a..79ccf93 100644
--- a/src/vm/error.rs
+++ b/src/vm/error.rs
@@ -4,20 +4,17 @@ use snafu::Snafu;
 #[derive(Debug, Snafu)]
 pub enum Error {
     #[snafu(display("missing attribute: {}", global_sym_lookup(*attr).unwrap()))]
-    MissingAttr {
-        attr: Sym,
-    },
+    MissingAttr { attr: Sym },
 
     #[snafu(display("{}", error))]
-    ValueError {
-        error: String,
-    },
+    ValueError { error: String },
 
-    #[snafu(display("incorrect function arity; expected {} but got {} instead", expected, got))]
-    ArityError {
-        expected: usize,
-        got: usize,
-    },
+    #[snafu(display(
+        "incorrect function arity; expected {} but got {} instead",
+        expected,
+        got
+    ))]
+    ArityError { expected: usize, got: usize },
 }
 
 pub type Result<T, E = Error> = std::result::Result<T, E>;
diff --git a/src/vm/frame.rs b/src/vm/frame.rs
index 8d2b99e..4f55b4f 100644
--- a/src/vm/frame.rs
+++ b/src/vm/frame.rs
@@ -1,6 +1,6 @@
 use crate::{obj::prelude::*, vm::inst::Inst};
+use std::fmt::{self, Debug, Formatter};
 use std::{collections::BTreeMap, sync::Arc};
-use std::fmt::{self, Formatter, Debug};
 
 pub type FrameBindings = BTreeMap<usize, ObjRef>;
 
@@ -53,8 +53,18 @@ pub struct UserFrame {
 }
 
 impl UserFrame {
-    pub fn new(callee: ObjRef, bindings: FrameBindings, last_pc: usize, code: Arc<Vec<Inst>>) -> Self {
-        Self { callee, bindings, last_pc, code, }
+    pub fn new(
+        callee: ObjRef,
+        bindings: FrameBindings,
+        last_pc: usize,
+        code: Arc<Vec<Inst>>,
+    ) -> Self {
+        Self {
+            callee,
+            bindings,
+            last_pc,
+            code,
+        }
     }
 
     pub fn bindings(&self) -> &FrameBindings {
@@ -86,7 +96,11 @@ pub struct NativeFrame {
 
 impl NativeFrame {
     pub fn new(callee: ObjRef, fun_ptr: NativeFunPtr, args: Vec<ObjRef>) -> Self {
-        Self { callee, fun_ptr, args }
+        Self {
+            callee,
+            fun_ptr,
+            args,
+        }
     }
 
     pub fn fun_ptr(&self) -> &NativeFunPtr {
@@ -105,7 +119,10 @@ impl NativeFrame {
 impl Debug for NativeFrame {
     fn fmt(&self, fmt: &mut Formatter) -> fmt::Result {
         fmt.debug_struct("NativeFrame")
-            .field("fun_ptr", &format!("{:#x}", &self.fun_ptr as *const _ as usize))
+            .field(
+                "fun_ptr",
+                &format!("{:#x}", &self.fun_ptr as *const _ as usize),
+            )
             .finish()
     }
 }
diff --git a/src/vm/inst.rs b/src/vm/inst.rs
index a8d534d..69e561c 100644
--- a/src/vm/inst.rs
+++ b/src/vm/inst.rs
@@ -154,4 +154,4 @@ impl Inst {
     }
 }
 
-impl EmptyScan for Inst { }
+impl EmptyScan for Inst {}
diff --git a/src/vm/mod.rs b/src/vm/mod.rs
index 0a83b3e..c4db78f 100644
--- a/src/vm/mod.rs
+++ b/src/vm/mod.rs
@@ -5,7 +5,7 @@ pub mod inst;
 pub mod signal;
 
 use crate::{
-    obj::{builtin::BUILTIN_OBJS, reserved::*, prelude::*},
+    obj::{builtin::BUILTIN_OBJS, prelude::*, reserved::*},
     vm::{consts::ConstPool, error::*, frame::*, inst::*, signal::*},
 };
 
@@ -19,7 +19,7 @@ pub struct Vm<'c> {
 }
 
 impl<'c> Vm<'c> {
-    pub fn new(const_pool: &'c ConstPool,) -> Self {
+    pub fn new(const_pool: &'c ConstPool) -> Self {
         Self {
             stack: Default::default(),
             frames: vec![],
@@ -122,9 +122,7 @@ impl<'c> Vm<'c> {
                     let args = fun.args().clone();
                     (*fun.fun_ptr())(callee, self, args)?
                 }
-                Frame::User(_) => {
-                    self.resume_user_fun()
-                }
+                Frame::User(_) => self.resume_user_fun(),
             };
             self.handle_signal(signal)?;
         }
@@ -148,8 +146,11 @@ impl<'c> Vm<'c> {
         match signal {
             Signal::Call(callee, args) => {
                 read_obj!(let callee_obj = callee);
-                let frame = callee_obj.as_fun()
-                    .ok_or_else(|| Error::ValueError { error: "cannot call this object".to_string() })?
+                let frame = callee_obj
+                    .as_fun()
+                    .ok_or_else(|| Error::ValueError {
+                        error: "cannot call this object".to_string(),
+                    })?
                     .create_frame(callee.clone(), self, args)?;
                 // Jump to the first address of the new function call if it's a user function
                 if let Frame::User(_) = &frame {
@@ -207,19 +208,20 @@ impl<'c> Vm<'c> {
                 self.push(obj_ref);
             }
             Inst::LoadLocal(local) => {
-                let value = self.get_local(local)
+                let value = self
+                    .get_local(local)
                     .expect("TODO: throw error for missing local");
                 self.push(value);
             }
             Inst::LoadGlobal(global) => {
-                let value = self.get_global(global)
+                let value = self
+                    .get_global(global)
                     .or_else(|| self.get_builtin(global))
                     .expect("TODO: throw error for missing global");
                 self.push(value);
             }
             Inst::PopLocal(name) => {
-                let tos = self.pop()
-                    .expect("stack underflow");
+                let tos = self.pop().expect("stack underflow");
                 // pop into name
                 if let Some(name) = name {
                     self.set_local(name, tos);
@@ -227,8 +229,7 @@ impl<'c> Vm<'c> {
                 // else discard
             }
             Inst::PopGlobal(name) => {
-                let tos = self.pop()
-                    .expect("stack underflow");
+                let tos = self.pop().expect("stack underflow");
                 // pop into name
                 if let Some(name) = name {
                     self.set_global(name, tos);
@@ -244,10 +245,8 @@ impl<'c> Vm<'c> {
                 self.push(attr);
             }
             Inst::SetAttr(sym) => {
-                let target = self.pop()
-                    .expect("no target available for SetAttr");
-                let source = self.pop()
-                    .expect("no source available for SetAttr");
+                let target = self.pop().expect("no target available for SetAttr");
+                let source = self.pop().expect("no source available for SetAttr");
                 write_obj!(let target = target);
                 if let Some(attrs) = target.attrs_mut() {
                     attrs.insert(sym, source);
@@ -266,15 +265,17 @@ impl<'c> Vm<'c> {
             Inst::Call(argc) => {
                 let stack_top = self.stack.len() - argc;
                 let args = self.stack.split_off(stack_top);
-                let tos = self.pop()
-                    .expect("stack underflow");
+                let tos = self.pop().expect("stack underflow");
                 read_obj!(let tos = tos);
-                let callee = tos.get_call()
+                let callee = tos
+                    .get_call()
                     .expect("TODO: throw an error for missing __call__ attr");
                 signal = Some(Signal::Call(callee, args));
             }
             Inst::Index => todo!(),
-            Inst::Return => { signal = Some(Signal::Return); }
+            Inst::Return => {
+                signal = Some(Signal::Return);
+            }
             Inst::UnNeg => todo!(),
             Inst::UnPos => todo!(),
             Inst::BinPlus => {
@@ -282,7 +283,8 @@ impl<'c> Vm<'c> {
                 let lhs = self.pop().unwrap();
                 let fun = {
                     read_obj!(let lhs = lhs);
-                    lhs.get_plus().expect("TODO: throw an error for missing __add__ attr")
+                    lhs.get_plus()
+                        .expect("TODO: throw an error for missing __add__ attr")
                 };
                 signal = Some(Signal::Call(fun, vec![rhs]));
             }
@@ -291,7 +293,8 @@ impl<'c> Vm<'c> {
                 let lhs = self.pop().unwrap();
                 let fun = {
                     read_obj!(let lhs = lhs);
-                    lhs.get_minus().expect("TODO: throw an error for missing __sub__ attr")
+                    lhs.get_minus()
+                        .expect("TODO: throw an error for missing __sub__ attr")
                 };
                 signal = Some(Signal::Call(fun, vec![rhs]));
             }
@@ -300,7 +303,8 @@ impl<'c> Vm<'c> {
                 let lhs = self.pop().unwrap();
                 let fun = {
                     read_obj!(let lhs = lhs);
-                    lhs.get_mul().expect("TODO: throw an error for missing __mul__ attr")
+                    lhs.get_mul()
+                        .expect("TODO: throw an error for missing __mul__ attr")
                 };
                 signal = Some(Signal::Call(fun, vec![rhs]));
             }
@@ -309,7 +313,8 @@ impl<'c> Vm<'c> {
                 let lhs = self.pop().unwrap();
                 let fun = {
                     read_obj!(let lhs = lhs);
-                    lhs.get_div().expect("TODO: throw an error for missing __div__ attr")
+                    lhs.get_div()
+                        .expect("TODO: throw an error for missing __div__ attr")
                 };
                 signal = Some(Signal::Call(fun, vec![rhs]));
             }
@@ -318,7 +323,8 @@ impl<'c> Vm<'c> {
                 let lhs = self.pop().unwrap();
                 let fun = {
                     read_obj!(let lhs = lhs);
-                    lhs.get_eq().expect("TODO: throw an error for missing __eq__ attr")
+                    lhs.get_eq()
+                        .expect("TODO: throw an error for missing __eq__ attr")
                 };
                 signal = Some(Signal::Call(fun, vec![rhs]));
             }
@@ -342,7 +348,7 @@ impl<'c> Vm<'c> {
             .get(&name.index())
             .cloned()
     }
-    
+
     fn set_local(&mut self, name: Name, value: ObjRef) {
         let frame = self
             .frame_mut()
@@ -363,7 +369,8 @@ impl<'c> Vm<'c> {
     }
 
     fn set_global(&mut self, name: Name, value: ObjRef) {
-        let frame = self.frames_mut()
+        let frame = self
+            .frames_mut()
             .first_mut()
             .expect("global stack frame")
             .user_frame_mut()
diff --git a/src/vm/signal.rs b/src/vm/signal.rs
index 8475137..44f90b1 100644
--- a/src/vm/signal.rs
+++ b/src/vm/signal.rs
@@ -6,4 +6,3 @@ pub enum Signal {
     Call(ObjRef, Vec<ObjRef>),
     Return,
 }
-