diff --git a/.rustfmt.toml b/.rustfmt.toml
new file mode 100644
index 0000000..4d7dd9e
--- /dev/null
+++ b/.rustfmt.toml
@@ -0,0 +1,3 @@
+imports_granularity = "Crate"
+newline_style = "Unix"
+group_imports = "StdExternalCrate"
\ No newline at end of file
diff --git a/src/ast.rs b/src/ast.rs
index c2a75c4..b1b534e 100644
--- a/src/ast.rs
+++ b/src/ast.rs
@@ -3,8 +3,7 @@
 //!
 //! All AST nodes are bump allocated into the lifetime `'ast`  
 
-use crate::errors::Span;
-use crate::gc::Symbol;
+use crate::{errors::Span, gc::Symbol};
 
 #[derive(Debug, PartialEq, Eq, Hash, Clone, Copy)]
 #[cfg_attr(feature = "_debug", derive(dbg_pls::DebugPls))]
diff --git a/src/bytecode.rs b/src/bytecode.rs
index e47fde2..2e6f1a3 100644
--- a/src/bytecode.rs
+++ b/src/bytecode.rs
@@ -58,11 +58,12 @@
 //!
 //! ```
 
-use crate::errors::Span;
-use crate::vm::Value;
-use bumpalo::collections::Vec;
 use std::fmt::{Debug, Formatter};
 
+use bumpalo::collections::Vec;
+
+use crate::{errors::Span, vm::Value};
+
 /// This struct contains all data for a function.
 pub struct FnBlock<'bc> {
     /// The bytecode of the function
@@ -129,9 +130,12 @@ pub enum Instr {
 
     /// Calls the function at the top of the stack, after the parameters
     Call,
-
+    /// Returns from the function, removing that stack frame
     Return,
 
+    /// Stop the program
+    Exit,
+
     /// Shrinks the stack by `usize` elements, should always be emitted before backwards jumps
     ShrinkStack(usize),
 }
diff --git a/src/compile.rs b/src/compile.rs
index a49aed0..943d2a5 100644
--- a/src/compile.rs
+++ b/src/compile.rs
@@ -1,18 +1,20 @@
 //! The compiler that compiles the AST down to bytecode
 
-use crate::ast::{
-    Assignment, BinaryOp, BinaryOpKind, Block, Call, CallKind, Declaration, ElsePart, Expr, FnDecl,
-    Ident, IfStmt, Literal, Program, Stmt, UnaryOp, WhileStmt,
+use std::{cell::RefCell, rc::Rc};
+
+use bumpalo::{collections::Vec, Bump};
+
+use crate::{
+    ast::{
+        Assignment, BinaryOp, BinaryOpKind, Block, Call, CallKind, Declaration, ElsePart, Expr,
+        FnDecl, Ident, IfStmt, Literal, Program, Stmt, UnaryOp, WhileStmt,
+    },
+    bytecode::{FnBlock, Instr},
+    errors::{CompilerError, Span},
+    gc::Symbol,
+    vm::Value,
+    HashMap, RtAlloc,
 };
-use crate::bytecode::{FnBlock, Instr};
-use crate::errors::{CompilerError, Span};
-use crate::gc::Symbol;
-use crate::vm::Value;
-use crate::{HashMap, RtAlloc};
-use bumpalo::collections::Vec;
-use bumpalo::Bump;
-use std::cell::RefCell;
-use std::rc::Rc;
 
 type CResult<T = ()> = Result<T, CompilerError>;
 
@@ -119,8 +121,8 @@ impl<'bc, 'gc> Compiler<'bc, 'gc> {
             StackChange::Grow,
             Span::dummy(),
         );
-        // exit the program.
-        self.push_instr(Instr::Return, StackChange::None, Span::dummy());
+        // exit the program. here, we use `exit` instead of `return` because there is no stack frame
+        self.push_instr(Instr::Exit, StackChange::None, Span::dummy());
         Ok(())
     }
 
@@ -128,7 +130,7 @@ impl<'bc, 'gc> Compiler<'bc, 'gc> {
         // padding for backwards jumps
         self.push_instr(Instr::Nop, StackChange::None, block.span);
 
-        self.compile_stmts(&block.stmts)
+        self.compile_stmts(block.stmts)
     }
 
     fn compile_stmts(&mut self, stmts: &[Stmt]) -> CResult {
@@ -222,7 +224,7 @@ impl<'bc, 'gc> Compiler<'bc, 'gc> {
                 .push(decl.params.len() + CALLCONV_OFFSET_DATA);
         }
 
-        self.compile_stmts(&decl.body.stmts)?;
+        self.compile_stmts(decl.body.stmts)?;
 
         self.push_instr(Instr::PushVal(Value::Null), StackChange::Grow, decl.span);
         self.push_instr(Instr::Return, StackChange::None, decl.span);
@@ -380,7 +382,7 @@ impl<'bc, 'gc> Compiler<'bc, 'gc> {
         let next_env = Env::new_inner(self.env.clone(), OuterEnvKind::Block);
         self.env = next_env;
 
-        self.compile_stmts(&block.stmts)?;
+        self.compile_stmts(block.stmts)?;
 
         let outer = self.env.borrow().outer.clone().expect("outer env got lost");
         self.env = outer;
diff --git a/src/gc.rs b/src/gc.rs
index b3b8cdd..38284ba 100644
--- a/src/gc.rs
+++ b/src/gc.rs
@@ -2,14 +2,17 @@
 //!
 //! The structure of the GC might change, but for now it's simply a `LinkedList` of `Object`s.
 
-use crate::vm::Value;
-use crate::{HashMap, HashSet};
+use std::{
+    collections::LinkedList,
+    fmt::{Debug, Formatter},
+    hash::{Hash, Hasher},
+    ops::Deref,
+    ptr::NonNull,
+};
+
 use dbg_pls::DebugPls;
-use std::collections::LinkedList;
-use std::fmt::{Debug, Formatter};
-use std::hash::{Hash, Hasher};
-use std::ops::Deref;
-use std::ptr::NonNull;
+
+use crate::{vm::Value, HashMap, HashSet};
 
 /// A pointer to a garbage collected value. This pointer *must* always be valid, and a value
 /// is only allowed to be freed once no Gc is pointing at it anymore. This is achieved through
diff --git a/src/lex.rs b/src/lex.rs
index 04e205c..3a66144 100644
--- a/src/lex.rs
+++ b/src/lex.rs
@@ -4,11 +4,13 @@
 //! For error handling, there is a single `Error` token, which contains the error. The lexer
 //! is an iterator, and can therefore be used without any allocations
 
-use crate::errors::{CompilerError, Span};
-use crate::gc::Symbol;
-use crate::RtAlloc;
-use std::iter::Peekable;
-use std::str::CharIndices;
+use std::{iter::Peekable, str::CharIndices};
+
+use crate::{
+    errors::{CompilerError, Span},
+    gc::Symbol,
+    RtAlloc,
+};
 
 ///
 /// A single token generated from the lexer
@@ -360,8 +362,7 @@ fn is_valid_ident_start(char: char) -> bool {
 
 #[cfg(test)]
 mod test {
-    use crate::lex::Lexer;
-    use crate::RtAlloc;
+    use crate::{lex::Lexer, RtAlloc};
 
     type StdString = std::string::String;
 
diff --git a/src/lib.rs b/src/lib.rs
index 8b29407..acce4f4 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,4 +1,4 @@
-#![deny(clippy::disallowed_type)]
+#![deny(clippy::disallowed_types)]
 
 mod ast;
 mod bytecode;
@@ -10,14 +10,14 @@ mod parse;
 mod util;
 mod vm;
 
-use crate::ast::Program;
-use crate::gc::RtAlloc;
 use std::io::Write;
 
 pub use bumpalo::Bump;
 pub use lex::*;
 pub use parse::*;
 
+use crate::{ast::Program, gc::RtAlloc};
+
 #[cfg(not(feature = "fxhash"))]
 #[allow(clippy::disallowed_types)]
 type HashMap<K, V> = std::collections::HashMap<K, V>;
@@ -73,8 +73,8 @@ fn process_ast(program: &str, ast: &Program, mut runtime: RtAlloc, cfg: &mut Con
             }
 
             let result = vm::execute(code, runtime, cfg);
-            if let Err(result) = result {
-                eprintln!("error: {}", result);
+            if let Err(msg) = result {
+                eprintln!("error: {msg}");
             }
         }
         Err(err) => errors::display_error(program, err),
diff --git a/src/main.rs b/src/main.rs
index dfe7190..c782988 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,6 +1,7 @@
-use dilaria::Config;
 use std::io;
 
+use dilaria::Config;
+
 fn main() {
     let mut args = std::env::args();
 
diff --git a/src/parse.rs b/src/parse.rs
index 49d46da..5e1209a 100644
--- a/src/parse.rs
+++ b/src/parse.rs
@@ -6,13 +6,16 @@
 #[cfg(test)]
 mod test;
 
-use crate::ast::*;
-use crate::errors::{CompilerError, Span};
-use crate::lex::{Token, TokenKind};
-use bumpalo::collections::Vec;
-use bumpalo::Bump;
 use std::iter::Peekable;
 
+use bumpalo::{collections::Vec, Bump};
+
+use crate::{
+    ast::*,
+    errors::{CompilerError, Span},
+    lex::{Token, TokenKind},
+};
+
 #[derive(Debug)]
 struct Parser<'ast, I>
 where
diff --git a/src/parse/test.rs b/src/parse/test.rs
index be1fcee..a1b90c8 100644
--- a/src/parse/test.rs
+++ b/src/parse/test.rs
@@ -3,16 +3,17 @@
 //! These tests are horrible and break all the time. Never do it like this again.
 //! That said it's too late to fix it.
 
-use crate::errors::Span;
-use crate::parse::Parser;
-use crate::RtAlloc;
 use bumpalo::Bump;
 use prelude::*;
 
+use crate::{errors::Span, parse::Parser, RtAlloc};
+
 mod prelude {
     pub(super) use super::{parser, rt, test_literal_bin_op, test_number_literal, token};
-    pub(super) use crate::ast::{Expr, Stmt};
-    pub(super) use crate::lex::TokenKind::*;
+    pub(super) use crate::{
+        ast::{Expr, Stmt},
+        lex::TokenKind::*,
+    };
     pub type Token = crate::lex::Token;
     pub type TokenType = crate::lex::TokenKind;
     pub(super) use bumpalo::Bump;
@@ -58,9 +59,10 @@ fn test_number_literal<F: FnOnce(Vec<Token>, &Bump) -> Expr>(parser: F) {
 }
 
 mod assignment {
+    use bumpalo::Bump;
+
     use super::prelude::*;
     use crate::parse::test::rt;
-    use bumpalo::Bump;
 
     fn parse_assignment(tokens: Vec<Token>, alloc: &Bump) -> Stmt {
         let mut parser = parser(tokens, alloc);
diff --git a/src/util.rs b/src/util.rs
index d6767b3..242bd16 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -6,9 +6,10 @@ macro_rules! assert_size {
     };
 }
 
-pub(crate) use assert_size;
 use std::fmt::Display;
 
+pub(crate) use assert_size;
+
 #[cfg(feature = "_debug")]
 pub fn dbg(prefix: impl Display, x: impl dbg_pls::DebugPls) {
     eprintln!("{prefix}{}", dbg_pls::color(&x))
diff --git a/src/vm.rs b/src/vm.rs
index 395b4c6..0f8252d 100644
--- a/src/vm.rs
+++ b/src/vm.rs
@@ -1,21 +1,36 @@
-use crate::bytecode::{FnBlock, Function, Instr};
-use crate::gc::{Object, RtAlloc, Symbol};
-use crate::util;
-use crate::Config;
-use std::fmt::{Debug, Display, Formatter};
-use std::io::{Read, Write};
+use std::{
+    fmt::{Debug, Display, Formatter},
+    io::{Read, Write},
+};
+
+use crate::{
+    bytecode::{FnBlock, Function, Instr},
+    gc::{Object, RtAlloc, Symbol},
+    util, Config,
+};
+
+type ActualBackingVmError = &'static str;
+
+type VmError = Box<VmErrorInner>;
+
+#[derive(Debug)]
+enum VmErrorInner {
+    Exit,
+    Error(ActualBackingVmError),
+}
 
-type VmError = Box<&'static str>;
 type VmResult = Result<(), VmError>;
 
 // never get bigger than a machine word.
 util::assert_size!(VmResult <= std::mem::size_of::<usize>());
 
+type PublicVmError = ActualBackingVmError;
+
 pub fn execute<'bc>(
     bytecode: &'bc [FnBlock<'bc>],
     alloc: RtAlloc,
     cfg: &mut Config,
-) -> Result<(), VmError> {
+) -> Result<(), PublicVmError> {
     let mut vm = Vm {
         blocks: bytecode,
         current: bytecode.first().ok_or("no bytecode found")?,
@@ -28,7 +43,13 @@ pub fn execute<'bc>(
         step: cfg.step,
     };
 
-    vm.execute_function()
+    match vm.execute_function() {
+        Ok(()) => Ok(()),
+        Err(boxed) => match *boxed {
+            VmErrorInner::Exit => Ok(()),
+            VmErrorInner::Error(err) => Err(err),
+        },
+    }
 }
 
 #[derive(Debug, Clone, Copy)]
@@ -86,7 +107,7 @@ impl<'bc> Vm<'bc, '_> {
                 None => return Ok(()),
             }
             if self.pc > 0 {
-                //debug_assert_eq!(self.current.stack_sizes[self.pc - 1], self.stack.len());
+                // debug_assert_eq!(self.current.stack_sizes[self.pc - 1], self.stack.len());
             }
         }
     }
@@ -109,56 +130,56 @@ impl<'bc> Vm<'bc, '_> {
                 match val {
                     Value::Bool(bool) => self.stack.push(Value::Bool(!bool)),
                     Value::Num(float) => self.stack.push(Value::Num(-float)),
-                    _ => return Err(self.type_error()),
+                    _ => return Err(err("bad type")),
                 }
             }
             Instr::BinAdd => self.bin_op(|lhs, rhs| match (lhs, rhs) {
                 (Value::Num(a), Value::Num(b)) => Ok(Value::Num(a + b)),
-                _ => Err("bad type".into()),
+                _ => Err(err("bad type")),
             })?,
             Instr::BinSub => self.bin_op(|lhs, rhs| match (lhs, rhs) {
                 (Value::Num(a), Value::Num(b)) => Ok(Value::Num(a - b)),
-                _ => Err("bad type".into()),
+                _ => Err(err("bad type")),
             })?,
             Instr::BinMul => self.bin_op(|lhs, rhs| match (lhs, rhs) {
                 (Value::Num(a), Value::Num(b)) => Ok(Value::Num(a * b)),
-                _ => Err("bad type".into()),
+                _ => Err(err("bad type")),
             })?,
             Instr::BinDiv => self.bin_op(|lhs, rhs| match (lhs, rhs) {
                 (Value::Num(a), Value::Num(b)) => Ok(Value::Num(a / b)),
-                _ => Err("bad type".into()),
+                _ => Err(err("bad type")),
             })?,
             Instr::BinMod => self.bin_op(|lhs, rhs| match (lhs, rhs) {
                 (Value::Num(a), Value::Num(b)) => Ok(Value::Num(a % b)),
-                _ => Err("bad type".into()),
+                _ => Err(err("bad type")),
             })?,
             Instr::BinAnd => self.bin_op(|lhs, rhs| match (lhs, rhs) {
                 (Value::Bool(a), Value::Bool(b)) => Ok(Value::Bool(a && b)),
-                _ => Err("bad type".into()),
+                _ => Err(err("bad type")),
             })?,
             Instr::BinOr => self.bin_op(|lhs, rhs| match (lhs, rhs) {
                 (Value::Bool(a), Value::Bool(b)) => Ok(Value::Bool(a || b)),
-                _ => Err("bad type".into()),
+                _ => Err(err("bad type")),
             })?,
             Instr::CmpGreater => self.bin_op(|lhs, rhs| match (lhs, rhs) {
                 (Value::Num(a), Value::Num(b)) => Ok(Value::Bool(a > b)),
                 (Value::String(a), Value::String(b)) => Ok(Value::Bool(a.as_str() > b.as_str())),
-                _ => Err("bad type".into()),
+                _ => Err(err("bad type")),
             })?,
             Instr::CmpGreaterEq => self.bin_op(|lhs, rhs| match (lhs, rhs) {
                 (Value::Num(a), Value::Num(b)) => Ok(Value::Bool(a >= b)),
                 (Value::String(a), Value::String(b)) => Ok(Value::Bool(a.as_str() >= b.as_str())),
-                _ => Err("bad type".into()),
+                _ => Err(err("bad type")),
             })?,
             Instr::CmpLess => self.bin_op(|lhs, rhs| match (lhs, rhs) {
                 (Value::Num(a), Value::Num(b)) => Ok(Value::Bool(a < b)),
                 (Value::String(a), Value::String(b)) => Ok(Value::Bool(a.as_str() < b.as_str())),
-                _ => Err("bad type".into()),
+                _ => Err(err("bad type")),
             })?,
             Instr::CmpLessEq => self.bin_op(|lhs, rhs| match (lhs, rhs) {
                 (Value::Num(a), Value::Num(b)) => Ok(Value::Bool(a <= b)),
                 (Value::String(a), Value::String(b)) => Ok(Value::Bool(a.as_str() <= b.as_str())),
-                _ => Err("bad type".into()),
+                _ => Err(err("bad type")),
             })?,
             Instr::CmpEq => self.bin_op(|lhs, rhs| match (lhs, rhs) {
                 (Value::Null, Value::Null) => Ok(TRUE),
@@ -166,7 +187,7 @@ impl<'bc> Vm<'bc, '_> {
                 (Value::String(a), Value::String(b)) => Ok(Value::Bool(a == b)),
                 (Value::Object(_a), Value::Object(_b)) => todo!(),
                 (Value::Array, Value::Array) => Ok(TRUE),
-                _ => Err("bad type".into()),
+                _ => Err(err("bad type")),
             })?,
             Instr::CmpNotEq => self.bin_op(|lhs, rhs| match (lhs, rhs) {
                 (Value::Null, Value::Null) => Ok(FALSE),
@@ -174,23 +195,24 @@ impl<'bc> Vm<'bc, '_> {
                 (Value::String(a), Value::String(b)) => Ok(Value::Bool(a != b)),
                 (Value::Object(_a), Value::Object(_b)) => todo!(),
                 (Value::Array, Value::Array) => Ok(FALSE),
-                _ => Err("bad type".into()),
+                _ => Err(err("bad type")),
             })?,
             Instr::Print => {
                 let val = self.stack.pop().unwrap();
-                writeln!(self.stdout, "{}", val).map_err(|_| "failed to write to stdout")?;
+                writeln!(self.stdout, "{}", val).map_err(|_| err("failed to write to stdout"))?;
             }
             Instr::JmpFalse(pos) => {
                 let val = self.stack.pop().unwrap();
                 match val {
                     Value::Bool(false) => self.pc = (self.pc as isize + pos) as usize,
                     Value::Bool(true) => {}
-                    _ => return Err("bad type".into()),
+                    _ => return Err(err("bad type")),
                 }
             }
             Instr::Jmp(pos) => self.pc = (self.pc as isize + pos) as usize,
             Instr::Call => self.call()?,
             Instr::Return => self.ret()?,
+            Instr::Exit => return Err(Box::new(VmErrorInner::Exit)),
             Instr::ShrinkStack(size) => {
                 assert!(self.stack.len() >= size);
                 let new_len = self.stack.len() - size;
@@ -246,6 +268,8 @@ impl<'bc> Vm<'bc, '_> {
 
         let bookkeeping_offset = self.stack_offset + current_arity;
 
+        let inner_stack_offset = self.stack_offset;
+
         // now, we get all the bookkeeping info out
         let old_stack_offset = self.stack[bookkeeping_offset].unwrap_native_int();
         let old_pc = self.stack[bookkeeping_offset + 1].unwrap_native_int();
@@ -259,15 +283,14 @@ impl<'bc> Vm<'bc, '_> {
 
         // and kill the function stack frame
         // note: don't emit a return instruction from the whole global script.
-        todo!();
+        unsafe { self.stack.set_len(inner_stack_offset) };
+
+        // everything that remains...
+        self.stack.push(return_value);
 
         Ok(())
     }
 
-    fn type_error(&self) -> VmError {
-        "bad type".into()
-    }
-
     fn step_debug(&self, current_instr: Instr) {
         let curr_stack_size = self.stack.len();
         // at this point, we've always incremented the pc already
@@ -320,3 +343,7 @@ impl Display for Value {
         }
     }
 }
+
+fn err(msg: &'static str) -> VmError {
+    Box::new(VmErrorInner::Error(msg))
+}