python_instruction_dsl_proc/

lib.rs

extern crate proc_macro;
use heck::ToUpperCamelCase;
use proc_macro::TokenStream;
use quote::quote;
use syn::{
    Expr, Ident, LitInt, Token, bracketed, parenthesized, parse::Parse, parse_macro_input,
    spanned::Spanned,
};

#[derive(Clone)]
enum StackItem {
    Name(Ident),
    NameCounted(Ident, Expr),
    /// Amount of unused (and unnamed) stack items
    Unused(Expr),
}

#[derive(Clone)]
struct StackEffect {
    pops: Vec<StackItem>,
    pushes: Vec<StackItem>,
}

#[derive(Clone)]
struct Opcode {
    name: Ident,
    number: LitInt,
    stack_effect: Option<StackEffect>,
}

struct Exception {
    stack_effect: StackEffect,
}

impl Parse for Opcode {
    fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
        // Example: LOAD_CONST = 100 ( -- constant)
        // You may also use ( / ) to indicate this opcode has no stack description.
        let name: Ident = input.parse()?;
        input.parse::<Token![=]>()?;
        let number: LitInt = input.parse()?;

        let inner_stack_effect;

        parenthesized!(inner_stack_effect in input);

        let mut stack_effect = StackEffect {
            pops: vec![],
            pushes: vec![],
        };

        if inner_stack_effect.parse::<Token![/]>().is_ok() {
            // This opcode does not have a stack description
            return Ok(Opcode {
                name,
                number,
                stack_effect: None,
            });
        }

        // Pops
        while inner_stack_effect.peek(Ident) {
            let name: Ident = inner_stack_effect.parse()?;

            stack_effect.pops.push(
                // This name is special, see the reference document on GitHub.
                if name == "unused" {
                    if inner_stack_effect.peek(syn::token::Bracket) {
                        let inner_bracket;
                        bracketed!(inner_bracket in inner_stack_effect);
                        let size: Expr = inner_bracket.parse()?;
                        StackItem::Unused(size)
                    } else {
                        StackItem::Unused(Expr::Lit(syn::ExprLit {
                            attrs: vec![],
                            lit: syn::Lit::Int(LitInt::new(
                                "1",
                                proc_macro::Span::call_site().into(),
                            )),
                        }))
                    }
                } else {
                    if inner_stack_effect.peek(syn::token::Bracket) {
                        let inner_bracket;
                        bracketed!(inner_bracket in inner_stack_effect);
                        let size: Expr = inner_bracket.parse()?;
                        StackItem::NameCounted(name, size)
                    } else {
                        StackItem::Name(name)
                    }
                },
            );

            if inner_stack_effect.parse::<Token![,]>().is_err() {
                break;
            }
        }

        inner_stack_effect.parse::<Token![-]>()?;
        inner_stack_effect.parse::<Token![-]>()?;

        while inner_stack_effect.peek(Ident) {
            let name: Ident = inner_stack_effect.parse()?;

            stack_effect.pushes.push(
                // This name is special, see the reference document on GitHub.
                if name == "unused" {
                    if inner_stack_effect.peek(syn::token::Bracket) {
                        let inner_bracket;
                        bracketed!(inner_bracket in inner_stack_effect);
                        let size: Expr = inner_bracket.parse()?;
                        StackItem::Unused(size)
                    } else {
                        StackItem::Unused(Expr::Lit(syn::ExprLit {
                            attrs: vec![],
                            lit: syn::Lit::Int(LitInt::new(
                                "1",
                                proc_macro::Span::call_site().into(),
                            )),
                        }))
                    }
                } else {
                    if inner_stack_effect.peek(syn::token::Bracket) {
                        let inner_bracket;
                        bracketed!(inner_bracket in inner_stack_effect);
                        let size: Expr = inner_bracket.parse()?;
                        StackItem::NameCounted(name, size)
                    } else {
                        StackItem::Name(name)
                    }
                },
            );

            if inner_stack_effect.parse::<Token![,]>().is_err() {
                break;
            }
        }

        Ok(Opcode {
            name,
            number,
            stack_effect: Some(stack_effect),
        })
    }
}

impl Parse for Exception {
    fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
        // Special parsing for custom exception specification
        // Example: *EXCEPTION ( -- lasti[if lasti {1} else {0}], exception)

        input.parse::<Token![*]>()?;
        syn::custom_keyword!(EXCEPTION);
        input.parse::<EXCEPTION>()?;

        let inner_stack_effect;

        parenthesized!(inner_stack_effect in input);

        let mut stack_effect = StackEffect {
            pops: vec![],
            pushes: vec![],
        };

        // Pops
        while inner_stack_effect.peek(Ident) {
            let name: Ident = inner_stack_effect.parse()?;

            stack_effect.pops.push(
                // This name is special, see the reference document on GitHub.
                if name == "unused" {
                    if inner_stack_effect.peek(syn::token::Bracket) {
                        let inner_bracket;
                        bracketed!(inner_bracket in inner_stack_effect);
                        let size: Expr = inner_bracket.parse()?;
                        StackItem::Unused(size)
                    } else {
                        StackItem::Unused(Expr::Lit(syn::ExprLit {
                            attrs: vec![],
                            lit: syn::Lit::Int(LitInt::new(
                                "1",
                                proc_macro::Span::call_site().into(),
                            )),
                        }))
                    }
                } else {
                    if inner_stack_effect.peek(syn::token::Bracket) {
                        let inner_bracket;
                        bracketed!(inner_bracket in inner_stack_effect);
                        let size: Expr = inner_bracket.parse()?;
                        StackItem::NameCounted(name, size)
                    } else {
                        StackItem::Name(name)
                    }
                },
            );

            if inner_stack_effect.parse::<Token![,]>().is_err() {
                break;
            }
        }

        inner_stack_effect.parse::<Token![-]>()?;
        inner_stack_effect.parse::<Token![-]>()?;

        while inner_stack_effect.peek(Ident) {
            let name: Ident = inner_stack_effect.parse()?;

            stack_effect.pushes.push(
                // This name is special, see the reference document on GitHub.
                if name == "unused" {
                    if inner_stack_effect.peek(syn::token::Bracket) {
                        let inner_bracket;
                        bracketed!(inner_bracket in inner_stack_effect);
                        let size: Expr = inner_bracket.parse()?;
                        StackItem::Unused(size)
                    } else {
                        StackItem::Unused(Expr::Lit(syn::ExprLit {
                            attrs: vec![],
                            lit: syn::Lit::Int(LitInt::new(
                                "1",
                                proc_macro::Span::call_site().into(),
                            )),
                        }))
                    }
                } else {
                    if inner_stack_effect.peek(syn::token::Bracket) {
                        let inner_bracket;
                        bracketed!(inner_bracket in inner_stack_effect);
                        let size: Expr = inner_bracket.parse()?;
                        StackItem::NameCounted(name, size)
                    } else {
                        StackItem::Name(name)
                    }
                },
            );

            if inner_stack_effect.parse::<Token![,]>().is_err() {
                break;
            }
        }

        Ok(Exception { stack_effect })
    }
}

struct Opcodes {
    opcodes: Vec<Opcode>,
    exception: Option<Exception>,
}

impl Parse for Opcodes {
    fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
        let mut opcodes = vec![];
        let mut exception = None;

        loop {
            if input.peek(Token![*]) {
                exception = Some(Exception::parse(input)?);
            } else {
                opcodes.push(Opcode::parse(input)?);
            }

            if input.parse::<Token![,]>().is_err() || input.is_empty() {
                break;
            }
        }

        Ok(Opcodes { opcodes, exception })
    }
}

fn sum_items(items: &[StackItem]) -> Expr {
    if items.is_empty() {
        // 0 if empty
        Expr::Lit(syn::ExprLit {
            attrs: vec![],
            lit: syn::Lit::Int(LitInt::new("0", proc_macro::Span::call_site().into())),
        })
    } else {
        items
            .iter()
            .map(|p| match p {
                StackItem::Name(_) => Expr::Lit(syn::ExprLit {
                    attrs: vec![],
                    lit: syn::Lit::Int(LitInt::new("1", proc_macro::Span::call_site().into())),
                }),
                StackItem::NameCounted(_, size) => size.clone(),
                StackItem::Unused(size) => size.clone(),
            })
            .reduce(|left, right| {
                syn::Expr::Binary(syn::ExprBinary {
                    attrs: vec![],
                    left: Box::new(left),
                    op: syn::BinOp::Add(syn::token::Plus {
                        spans: [proc_macro::Span::call_site().into()],
                    }),
                    right: Box::new(right),
                })
            })
            .expect("Something is wrong with the format")
    }
}

fn collect_stack_effect<'a, T>(
    stack_items: T,
    index_offset: Option<proc_macro2::TokenStream>,
) -> (Vec<proc_macro2::TokenStream>, proc_macro2::TokenStream)
where
    T: DoubleEndedIterator<Item = &'a StackItem>,
{
    let mut index = if let Some(ref index_offset) = index_offset {
        index_offset.clone()
    } else {
        quote! { 0 }
    };

    let mut fields = vec![];

    for item in stack_items.rev() {
        let count = match item {
            StackItem::Name(name) => {
                let name = name.to_string();

                let new_index = if index_offset.is_none() {
                    quote! { (#index) - 1 }
                } else {
                    index.clone()
                };

                fields.push(quote! { StackItem { name: #name, count: 1, index: #new_index } });
                quote! { 1 }
            }
            StackItem::NameCounted(name, count) => {
                let name = name.to_string();

                let new_index = if index_offset.is_none() {
                    quote! { (#index) - (#count) }
                } else {
                    index.clone()
                };

                fields.push(
                    quote! { StackItem { name: #name, count: (#count) as u32, index: #new_index } },
                );
                quote! { #count }
            }
            StackItem::Unused(count) => quote! { #count },
        };

        if index_offset.is_none() {
            index = quote! { (#index) - (#count) };
        } else {
            index = quote! { (#index) + (#count) };
        }
    }

    if index_offset.is_none() {
        fields.reverse();
    }

    (fields, index)
}

#[proc_macro]
pub fn define_opcodes(input: TokenStream) -> TokenStream {
    let Opcodes { opcodes, exception } = parse_macro_input!(input as Opcodes);

    let opcodes_with_stack: Vec<_> = opcodes
        .iter()
        .filter(|o| o.stack_effect.is_some())
        .collect();

    let names: Vec<_> = opcodes.iter().map(|o| &o.name).collect();
    let camel_names: Vec<Ident> = names
        .iter()
        .map(|ident| {
            let camel = ident.to_string().to_upper_camel_case();
            Ident::new(&camel, ident.span())
        })
        .collect();

    let names_with_stack: Vec<_> = opcodes_with_stack.iter().map(|o| &o.name).collect();

    let numbers: Vec<_> = opcodes.iter().map(|o| &o.number).collect();

    let pops: Vec<_> = opcodes_with_stack
        .iter()
        .map(|o| sum_items(&o.stack_effect.as_ref().unwrap().pops))
        .collect();

    let pushes: Vec<_> = opcodes_with_stack
        .iter()
        .map(|o| sum_items(&o.stack_effect.as_ref().unwrap().pushes))
        .collect();

    let mut expanded = quote! {
        #[allow(non_camel_case_types)]
        #[allow(clippy::upper_case_acronyms)]
        #[derive(Debug, Clone, PartialEq, Eq)]
        pub enum Opcode {
            #( #names ),*,
            INVALID_OPCODE(u8),
        }

        impl From<u8> for Opcode {
            fn from(value: u8) -> Self {
                match value {
                    #( #numbers => Opcode::#names, )*
                    _ => Opcode::INVALID_OPCODE(value),
                }
            }
        }

        impl From<Opcode> for u8 {
            fn from(value: Opcode) -> Self {
                match value {
                    #( Opcode::#names => #numbers , )*
                    Opcode::INVALID_OPCODE(value) => value,
                }
            }
        }

        impl From<(Opcode, u8)> for Instruction {
            fn from(value: (Opcode, u8)) -> Self {
                match value.0 {
                    #(
                        Opcode::#names => Instruction::#camel_names(value.1),
                    )*
                    Opcode::INVALID_OPCODE(opcode) => {
                        if !cfg!(test) {
                            Instruction::InvalidOpcode((opcode, value.1))
                        } else {
                            panic!("Testing environment should not come across invalid opcodes")
                        }
                    },
                }
            }
        }

        impl Opcode {
            pub fn from_instruction(instruction: &Instruction) -> Self {
                match instruction {
                    #(
                        Instruction::#camel_names(_) => Opcode::#names ,
                    )*
                    Instruction::InvalidOpcode((opcode, _)) => Opcode::INVALID_OPCODE(*opcode),
                }
            }
        }

        impl StackEffectTrait for Opcode {
            fn stack_effect(&self, oparg: u32, jump: bool, calculate_max: bool) -> StackEffect {
                match &self {
                    #(
                        Opcode::#names_with_stack => StackEffect { pops: #pops, pushes: #pushes },
                    )*
                    Opcode::INVALID_OPCODE(_) => StackEffect { pops: 0, pushes: 0 },

                    _ => unimplemented!("stack_effect not implemented for {:?}", self),
                }
            }
        }
    };

    let mut input_sirs = vec![];
    let mut output_sirs = vec![];
    let mut stack_deltas = vec![];

    for (opcode, name) in opcodes.iter().zip(names) {
        let mut input_constructor_fields = vec![];
        let mut output_constructor_fields = vec![];
        let mut stack_delta = quote! { 0 };

        if let Some(stack_effect) = &opcode.stack_effect {
            let input_offset;
            (input_constructor_fields, input_offset) =
                collect_stack_effect(stack_effect.pops.iter(), None);

            (output_constructor_fields, _) =
                collect_stack_effect(stack_effect.pushes.iter().rev(), Some(input_offset));

            let pushes = sum_items(&stack_effect.pushes);
            let pops = sum_items(&stack_effect.pops);

            stack_delta = quote! { (#pushes) as isize - (#pops) as isize};
        }

        input_sirs.push(quote! { Opcode::#name => vec![
            #(
                #input_constructor_fields
            ),*
        ] });

        output_sirs.push(quote! { Opcode::#name => vec![
            #(
                #output_constructor_fields
            ),*
        ] });

        stack_deltas.push(quote! { Opcode::#name => #stack_delta });
    }

    let sir_exception = if let Some(exception) = exception {
        let (input_fields, input_offset) =
            collect_stack_effect(exception.stack_effect.pops.iter(), None);

        let (output_fields, _) = collect_stack_effect(
            exception.stack_effect.pushes.iter().rev(),
            Some(input_offset),
        );

        let pushes = sum_items(&exception.stack_effect.pushes);
        let pops = sum_items(&exception.stack_effect.pops);

        let stack_delta = quote! { (#pushes) as isize - (#pops) as isize};

        quote! {
            #[derive(PartialEq, Debug, Clone)]
            pub struct SIRException {
                pub lasti: bool,
                pub stack_depth: usize,
                pub input: Vec<StackItem>,
                pub output: Vec<StackItem>,
                pub net_stack_delta: isize
            }

            impl SIRException {
                pub fn new(lasti: bool, stack_depth: usize, jump: bool) -> Self {
                    let input = vec![
                        #(
                            #input_fields
                        ),*
                    ];

                    let output = vec![
                        #(
                            #output_fields
                        ),*
                    ];

                    let net_stack_delta = #stack_delta;

                    Self {
                        lasti,
                        stack_depth,
                        input,
                        output,
                        net_stack_delta,
                    }
                }
            }

            impl GenericSIRException for SIRException {
                type Opcode = Opcode;

                fn new(lasti: bool, stack_depth: usize, jump: bool) -> Self {
                    SIRException::new(lasti, stack_depth, jump)
                }

                fn get_outputs(&self) -> &[StackItem] {
                    &self.output
                }

                fn get_inputs(&self) -> &[StackItem] {
                    &self.input
                }

                fn get_net_stack_delta(&self) -> isize {
                    self.net_stack_delta
                }

                fn get_stack_depth(&self) -> usize {
                    self.stack_depth
                }
            }

            impl std::fmt::Display for ExceptionCall<SIRNode> {
                fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
                    let mut inputs = self
                        .stack_inputs
                        .iter()
                        .map(|input| format!("{}", input))
                        .collect::<Vec<_>>();

                    inputs.push(format!("{}", self.exception.lasti));

                    write!(f, "EXCEPTION({})", inputs.join(", "))
                }
            }
        }
    } else {
        quote! {#[derive(PartialEq, Debug, Clone)]
            /// This does not exist in versions without an exception_table
            /// So we generate an empty version of it
            pub struct SIRException {
            }

            impl std::fmt::Display for ExceptionCall<SIRNode> {
                fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
                    unreachable!()
                }
            }

            impl GenericSIRException for SIRException {
                type Opcode = Opcode;

                fn new(lasti: bool, stack_depth: usize, jump: bool) -> Self {
                    SIRException {}
                }

                fn get_outputs(&self) -> &[StackItem] {
                    &[]
                }

                fn get_inputs(&self) -> &[StackItem] {
                    &[]
                }

                fn get_net_stack_delta(&self) -> isize {
                    0
                }

                fn get_stack_depth(&self) -> usize {
                    0
                }
            }
        }
    };

    let sir = quote! {
        #[cfg(feature = "sir")]
        pub mod sir {
            use super::{Opcode};
            use crate::sir::{SIR, StackItem, SIRStatement, ExceptionCall, Call, SIRExpression, AuxVar};
            use crate::traits::{GenericSIRNode, SIROwned, GenericSIRException};


            #[derive(PartialEq, Debug, Clone)]
            pub struct SIRNode {
                pub opcode: Opcode,
                pub oparg: u32,
                pub input: Vec<StackItem>,
                pub output: Vec<StackItem>,
                pub net_stack_delta: isize
            }

            impl SIRNode {
                pub fn new(opcode: Opcode, oparg: u32, jump: bool) -> Self {
                    // This comes from the Python DSL where it is used to calculate the max stack usage possible. We intentionally disable it here.
                    let calculate_max = false;
                    let oparg = oparg as isize;

                    let input = match opcode {
                        #(
                            #input_sirs
                        ),*,
                        Opcode::INVALID_OPCODE(_) => vec![],
                    };

                    let output = match opcode {
                        #(
                            #output_sirs
                        ),*,
                        Opcode::INVALID_OPCODE(_) => vec![],
                    };

                    let net_stack_delta = match opcode {
                        #(
                            #stack_deltas
                        ),*,
                        Opcode::INVALID_OPCODE(_) => 0,
                    };

                    Self {
                        opcode,
                        oparg: oparg as u32,
                        input,
                        output,
                        net_stack_delta
                    }
                }
            }

            #sir_exception

            impl GenericSIRNode for SIRNode {
                type Opcode = Opcode;
                type SIRException = SIRException;

                fn new(opcode: Self::Opcode, oparg: u32, jump: bool) -> Self {
                    SIRNode::new(opcode, oparg, jump)
                }

                fn get_outputs(&self) -> &[StackItem] {
                    &self.output
                }

                fn get_inputs(&self) -> &[StackItem] {
                    &self.input
                }

                fn get_net_stack_delta(&self) -> isize {
                    self.net_stack_delta
                }
            }

            impl SIROwned<SIRNode> for SIR<SIRNode> {
                fn new(statements: Vec<SIRStatement<SIRNode>>) -> Self {
                    SIR(statements)
                }
            }

            impl std::fmt::Display for SIR<SIRNode> {
                fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
                    for statement in &self.0 {
                        match statement {
                            SIRStatement::Assignment(aux_var, call) => {
                                writeln!(f, "{} = {}", aux_var.name, call)?;
                            }
                            SIRStatement::TupleAssignment(aux_vars, call) => {
                                let vars = aux_vars.iter().map(|v| v.name.clone()).collect::<Vec<_>>().join(", ");
                                writeln!(f, "({}) = {}", vars, call)?;
                            }
                            SIRStatement::DisregardCall(call) => {
                                writeln!(f, "{}", call)?;
                            }
                            SIRStatement::UseVar(aux_var) => {
                                write!(f, "UseVar({})", aux_var.name.clone())?;
                            },
                        }
                    }
                    Ok(())
                }
            }

            impl std::fmt::Display for Call<SIRNode> {
                fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
                    let mut inputs = self
                        .stack_inputs
                        .iter()
                        .map(|input| format!("{}", input))
                        .collect::<Vec<_>>();

                    inputs.push(format!("{}", self.node.oparg));

                    write!(f, "{:#?}({})", self.node.opcode, inputs.join(", "))
                }
            }

            impl std::fmt::Display for SIRExpression<SIRNode> {
                fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
                    match self {
                        SIRExpression::Call(call) => write!(f, "{}", call),
                        SIRExpression::Exception(exception_call) => write!(f, "{}", exception_call),
                        SIRExpression::PhiNode(phi) => write!(f, "phi({})", phi.iter().map(|v| &v.name).cloned().collect::<Vec<_>>().join(", ")),
                        SIRExpression::GeneratorStart => write!(f, "GenStart()"),
                    }
                }
            }
        }
    };

    expanded.extend(sir);

    expanded.into()
}

#[cfg(test)]
mod tests {
    use proc_macro2::Span;
    use syn::Ident;

    use crate::StackItem;

    #[test]
    fn test_stack_effect() {
        let inputs = [
            StackItem::Name(Ident::new("first", Span::call_site())),
            StackItem::Name(Ident::new("second", Span::call_site())),
        ];

        let outputs = [
            StackItem::Name(Ident::new("out", Span::call_site())),
            StackItem::Name(Ident::new("out2", Span::call_site())),
        ];

        let (input_fields, input_offset) = crate::collect_stack_effect(inputs.iter(), None);

        let (output_fields, _) =
            crate::collect_stack_effect(outputs.iter().rev(), Some(input_offset));

        for input_field in input_fields {
            println!("{}", input_field);
        }

        assert_eq!(
            format!("{}", output_fields[0]),
            "StackItem { name : \"out\" , count : 1 , index : ((0) - (1)) - (1) }"
        );

        assert_eq!(
            format!("{}", output_fields[1]),
            "StackItem { name : \"out2\" , count : 1 , index : (((0) - (1)) - (1)) + (1) }"
        );

        for output_field in output_fields {
            println!("{}", output_field);
        }
    }

    #[test]
    fn test_stack_effect2() {
        let inputs = [
            StackItem::NameCounted(
                Ident::new("first", Span::call_site()),
                syn::Expr::Lit(syn::ExprLit {
                    attrs: vec![],
                    lit: syn::Lit::Int(syn::LitInt::new("5", Span::call_site().into())),
                }),
            ),
            StackItem::Name(Ident::new("second", Span::call_site())),
        ];

        let outputs = [
            StackItem::NameCounted(
                Ident::new("out", Span::call_site()),
                syn::Expr::Lit(syn::ExprLit {
                    attrs: vec![],
                    lit: syn::Lit::Int(syn::LitInt::new("5", Span::call_site().into())),
                }),
            ),
            StackItem::Name(Ident::new("out2", Span::call_site())),
        ];

        let (input_fields, input_offset) = crate::collect_stack_effect(inputs.iter(), None);

        let (output_fields, _) =
            crate::collect_stack_effect(outputs.iter().rev(), Some(input_offset));

        for input_field in input_fields {
            println!("{}", input_field);
        }

        assert_eq!(
            format!("{}", output_fields[0]),
            "StackItem { name : \"out\" , count : (5) as u32 , index : ((0) - (1)) - (5) }"
        );

        assert_eq!(
            format!("{}", output_fields[1]),
            "StackItem { name : \"out2\" , count : 1 , index : (((0) - (1)) - (5)) + (5) }"
        );

        for output_field in output_fields {
            println!("{}", output_field);
        }
    }

    #[test]
    fn test_stack_effect_copy() {
        // Emulates the `COPY 3`` instruction
        let inputs = [
            StackItem::Name(Ident::new("bottom", Span::call_site())),
            StackItem::Unused(syn::Expr::Lit(syn::ExprLit {
                attrs: vec![],
                lit: syn::Lit::Int(syn::LitInt::new("2", Span::call_site().into())),
            })),
        ];

        let outputs = [
            StackItem::Name(Ident::new("bottom", Span::call_site())),
            StackItem::Unused(syn::Expr::Lit(syn::ExprLit {
                attrs: vec![],
                lit: syn::Lit::Int(syn::LitInt::new("2", Span::call_site().into())),
            })),
            StackItem::Name(Ident::new("top", Span::call_site())),
        ];

        let (input_fields, input_offset) = crate::collect_stack_effect(inputs.iter(), None);

        let (output_fields, _) =
            crate::collect_stack_effect(outputs.iter().rev(), Some(input_offset));

        for input_field in input_fields {
            println!("{}", input_field);
        }

        assert_eq!(
            format!("{}", output_fields[0]),
            "StackItem { name : \"bottom\" , count : 1 , index : ((0) - (2)) - (1) }"
        );

        assert_eq!(
            format!("{}", output_fields[1]),
            "StackItem { name : \"top\" , count : 1 , index : ((((0) - (2)) - (1)) + (1)) + (2) }"
        );

        for output_field in output_fields {
            println!("{}", output_field);
        }
    }
}