use roc_collections::all::{default_hasher, MutMap, MutSet};
use roc_module::ident::TagName;
use roc_module::symbol::Symbol;
use roc_region::all::Region;
use roc_types::builtin_aliases::{
    bool_type, box_type, dec_type, dict_type, f32_type, f64_type, frac_type, i128_type, i16_type,
    i32_type, i64_type, i8_type, int_type, list_type, nat_type, num_type, ordering_type,
    result_type, set_type, str_type, str_utf8_byte_problem_type, u128_type, u16_type, u32_type,
    u64_type, u8_type,
};
use roc_types::solved_types::SolvedType;
use roc_types::subs::VarId;
use roc_types::types::RecordField;
use std::collections::HashMap;

lazy_static::lazy_static! {
    static ref STDLIB: StdLib = standard_stdlib();
}

/// A global static that stores our initialized standard library definitions
pub fn borrow_stdlib() -> &'static StdLib {
    &STDLIB
}

/// Example:
///
///     let_tvars! { a, b, c }
///
/// This is equivalent to:
///
///     let a = VarId::from_u32(1);
///     let b = VarId::from_u32(2);
///     let c = VarId::from_u32(3);
///
/// The idea is that this is less error-prone than assigning hardcoded IDs by hand.
macro_rules! let_tvars {
    ($($name:ident,)+) => { let_tvars!($($name),+) };
    ($($name:ident),*) => {
        let mut _current_tvar = 0;

        $(
            _current_tvar += 1;

            let $name = VarId::from_u32(_current_tvar);
        )*
    };
}

#[derive(Debug, Clone)]
pub struct StdLib {
    pub types: MutMap<Symbol, (SolvedType, Region)>,
    pub applies: MutSet<Symbol>,
}

pub fn standard_stdlib() -> StdLib {
    StdLib {
        types: types(),
        applies: vec![
            Symbol::LIST_LIST,
            Symbol::SET_SET,
            Symbol::DICT_DICT,
            Symbol::STR_STR,
        ]
        .into_iter()
        .collect(),
    }
}

/// Keep this up to date by hand! It's the number of builtin aliases that are imported by default.
const NUM_BUILTIN_IMPORTS: usize = 7;

/// These can be shared between definitions, they will get instantiated when converted to Type
const TVAR1: VarId = VarId::from_u32(1);
const TVAR2: VarId = VarId::from_u32(2);
const TVAR3: VarId = VarId::from_u32(3);
const TVAR4: VarId = VarId::from_u32(4);
pub fn types() -> MutMap<Symbol, (SolvedType, Region)> {
    let mut types = HashMap::with_capacity_and_hasher(NUM_BUILTIN_IMPORTS, default_hasher());

    macro_rules! add_type {
        ($symbol:expr, $typ:expr $(,)?) => {{
            debug_assert!(
                !types.contains_key(&$symbol),
                "Duplicate type definition for {:?}",
                $symbol
            );

            // TODO instead of using Region::zero for all of these,
            // instead use the Region where they were defined in their
            // source .roc files! This can give nicer error messages.
            types.insert($symbol, ($typ, Region::zero()));
        }};
    }

    macro_rules! add_top_level_function_type {
        ($symbol:expr, $arguments:expr, $result:expr $(,)?) => {{
            debug_assert!(
                !types.contains_key(&$symbol),
                "Duplicate type definition for {:?}",
                $symbol
            );

            let typ = SolvedType::Func(
                $arguments,
                Box::new(SolvedType::LambdaTag($symbol, vec![])),
                $result,
            );

            // TODO instead of using Region::zero for all of these,
            // instead use the Region where they were defined in their
            // source .roc files! This can give nicer error messages.
            types.insert($symbol, (typ, Region::zero()));
        }};
    }

    // Num module

    // add or (+) : Num a, Num a -> Num a
    add_top_level_function_type!(
        Symbol::NUM_ADD,
        vec![num_type(flex(TVAR1)), num_type(flex(TVAR1))],
        Box::new(num_type(flex(TVAR1))),
    );

    fn overflow() -> SolvedType {
        SolvedType::TagUnion(
            vec![(TagName("Overflow".into()), vec![])],
            Box::new(SolvedType::Wildcard),
        )
    }

    // addChecked : Num a, Num a -> Result (Num a) [Overflow]*
    add_top_level_function_type!(
        Symbol::NUM_ADD_CHECKED,
        vec![num_type(flex(TVAR1)), num_type(flex(TVAR1))],
        Box::new(result_type(num_type(flex(TVAR1)), overflow())),
    );

    // addWrap : Int range, Int range -> Int range
    add_top_level_function_type!(
        Symbol::NUM_ADD_WRAP,
        vec![int_type(flex(TVAR1)), int_type(flex(TVAR1))],
        Box::new(int_type(flex(TVAR1))),
    );

    // addSaturated : Num a, Num a -> Num a
    add_top_level_function_type!(
        Symbol::NUM_ADD_SATURATED,
        vec![int_type(flex(TVAR1)), int_type(flex(TVAR1))],
        Box::new(int_type(flex(TVAR1))),
    );

    // sub or (-) : Num a, Num a -> Num a
    add_top_level_function_type!(
        Symbol::NUM_SUB,
        vec![num_type(flex(TVAR1)), num_type(flex(TVAR1))],
        Box::new(num_type(flex(TVAR1))),
    );

    // subWrap : Int range, Int range -> Int range
    add_top_level_function_type!(
        Symbol::NUM_SUB_WRAP,
        vec![int_type(flex(TVAR1)), int_type(flex(TVAR1))],
        Box::new(int_type(flex(TVAR1))),
    );

    // subChecked : Num a, Num a -> Result (Num a) [Overflow]*
    add_top_level_function_type!(
        Symbol::NUM_SUB_CHECKED,
        vec![num_type(flex(TVAR1)), num_type(flex(TVAR1))],
        Box::new(result_type(num_type(flex(TVAR1)), overflow())),
    );

    // subSaturated : Num a, Num a -> Num a
    add_top_level_function_type!(
        Symbol::NUM_SUB_SATURATED,
        vec![int_type(flex(TVAR1)), int_type(flex(TVAR1))],
        Box::new(int_type(flex(TVAR1))),
    );

    // mul or (*) : Num a, Num a -> Num a
    add_top_level_function_type!(
        Symbol::NUM_MUL,
        vec![num_type(flex(TVAR1)), num_type(flex(TVAR1))],
        Box::new(num_type(flex(TVAR1))),
    );

    // mulWrap : Int range, Int range -> Int range
    add_top_level_function_type!(
        Symbol::NUM_MUL_WRAP,
        vec![int_type(flex(TVAR1)), int_type(flex(TVAR1))],
        Box::new(int_type(flex(TVAR1))),
    );

    // mulChecked : Num a, Num a -> Result (Num a) [Overflow]*
    add_top_level_function_type!(
        Symbol::NUM_MUL_CHECKED,
        vec![num_type(flex(TVAR1)), num_type(flex(TVAR1))],
        Box::new(result_type(num_type(flex(TVAR1)), overflow())),
    );

    // mulSaturated : Int range, Int range -> Int range
    add_top_level_function_type!(
        Symbol::NUM_MUL_SATURATED,
        vec![int_type(flex(TVAR1)), int_type(flex(TVAR1))],
        Box::new(int_type(flex(TVAR1))),
    );

    // abs : Num a -> Num a
    add_top_level_function_type!(
        Symbol::NUM_ABS,
        vec![num_type(flex(TVAR1))],
        Box::new(num_type(flex(TVAR1)))
    );

    // neg : Num a -> Num a
    add_top_level_function_type!(
        Symbol::NUM_NEG,
        vec![num_type(flex(TVAR1))],
        Box::new(num_type(flex(TVAR1)))
    );

    // isEq or (==) : a, a -> Bool
    add_top_level_function_type!(
        Symbol::BOOL_EQ,
        vec![flex(TVAR1), flex(TVAR1)],
        Box::new(bool_type())
    );

    // isNeq or (!=) : a, a -> Bool
    add_top_level_function_type!(
        Symbol::BOOL_NEQ,
        vec![flex(TVAR1), flex(TVAR1)],
        Box::new(bool_type())
    );

    // isLt or (<) : Num a, Num a -> Bool
    add_top_level_function_type!(
        Symbol::NUM_LT,
        vec![num_type(flex(TVAR1)), num_type(flex(TVAR1))],
        Box::new(bool_type()),
    );

    // isLte or (<=) : Num a, Num a -> Bool
    add_top_level_function_type!(
        Symbol::NUM_LTE,
        vec![num_type(flex(TVAR1)), num_type(flex(TVAR1))],
        Box::new(bool_type()),
    );

    // isGt or (>) : Num a, Num a -> Bool
    add_top_level_function_type!(
        Symbol::NUM_GT,
        vec![num_type(flex(TVAR1)), num_type(flex(TVAR1))],
        Box::new(bool_type()),
    );

    // isGte or (>=) : Num a, Num a -> Bool
    add_top_level_function_type!(
        Symbol::NUM_GTE,
        vec![num_type(flex(TVAR1)), num_type(flex(TVAR1))],
        Box::new(bool_type()),
    );

    // compare : Num a, Num a -> [LT, EQ, GT]
    add_top_level_function_type!(
        Symbol::NUM_COMPARE,
        vec![num_type(flex(TVAR1)), num_type(flex(TVAR1))],
        Box::new(ordering_type()),
    );

    // toFrac : Num * -> Frac *
    add_top_level_function_type!(
        Symbol::NUM_TO_FRAC,
        vec![num_type(flex(TVAR1))],
        Box::new(frac_type(flex(TVAR2))),
    );

    // isNegative : Num a -> Bool
    add_top_level_function_type!(
        Symbol::NUM_IS_NEGATIVE,
        vec![num_type(flex(TVAR1))],
        Box::new(bool_type())
    );

    // isPositive : Num a -> Bool
    add_top_level_function_type!(
        Symbol::NUM_IS_POSITIVE,
        vec![num_type(flex(TVAR1))],
        Box::new(bool_type())
    );

    // isZero : Num a -> Bool
    add_top_level_function_type!(
        Symbol::NUM_IS_ZERO,
        vec![num_type(flex(TVAR1))],
        Box::new(bool_type())
    );

    // isEven : Num a -> Bool
    add_top_level_function_type!(
        Symbol::NUM_IS_EVEN,
        vec![num_type(flex(TVAR1))],
        Box::new(bool_type())
    );

    // isOdd : Num a -> Bool
    add_top_level_function_type!(
        Symbol::NUM_IS_ODD,
        vec![num_type(flex(TVAR1))],
        Box::new(bool_type())
    );

    let div_by_zero = SolvedType::TagUnion(
        vec![(TagName("DivByZero".into()), vec![])],
        Box::new(SolvedType::Wildcard),
    );

    // divTrunc : Int a, Int a -> Int a
    add_top_level_function_type!(
        Symbol::NUM_DIV_TRUNC,
        vec![int_type(flex(TVAR1)), int_type(flex(TVAR1))],
        Box::new(int_type(flex(TVAR1)))
    );

    // divTruncChecked : Int a, Int a -> Result (Int a) [DivByZero]*
    add_top_level_function_type!(
        Symbol::NUM_DIV_TRUNC_CHECKED,
        vec![int_type(flex(TVAR1)), int_type(flex(TVAR1))],
        Box::new(result_type(int_type(flex(TVAR1)), div_by_zero.clone())),
    );

    // divCeil : Int a, Int a -> Int a
    add_top_level_function_type!(
        Symbol::NUM_DIV_CEIL,
        vec![int_type(flex(TVAR1)), int_type(flex(TVAR1))],
        Box::new(int_type(flex(TVAR1)))
    );

    // divCeilChecked : Int a, Int a -> Result (Int a) [DivByZero]*
    add_top_level_function_type!(
        Symbol::NUM_DIV_CEIL_CHECKED,
        vec![int_type(flex(TVAR1)), int_type(flex(TVAR1))],
        Box::new(result_type(int_type(flex(TVAR1)), div_by_zero.clone())),
    );

    // bitwiseAnd : Int a, Int a -> Int a
    add_top_level_function_type!(
        Symbol::NUM_BITWISE_AND,
        vec![int_type(flex(TVAR1)), int_type(flex(TVAR1))],
        Box::new(int_type(flex(TVAR1))),
    );

    // bitwiseXor : Int a, Int a -> Int a
    add_top_level_function_type!(
        Symbol::NUM_BITWISE_XOR,
        vec![int_type(flex(TVAR1)), int_type(flex(TVAR1))],
        Box::new(int_type(flex(TVAR1))),
    );

    // bitwiseOr : Int a, Int a -> Int a
    add_top_level_function_type!(
        Symbol::NUM_BITWISE_OR,
        vec![int_type(flex(TVAR1)), int_type(flex(TVAR1))],
        Box::new(int_type(flex(TVAR1))),
    );

    // shiftLeftBy : Int a, Int a -> Int a
    add_top_level_function_type!(
        Symbol::NUM_SHIFT_LEFT,
        vec![int_type(flex(TVAR1)), int_type(flex(TVAR1))],
        Box::new(int_type(flex(TVAR1))),
    );

    // shiftRightBy : Int a, Int a -> Int a
    add_top_level_function_type!(
        Symbol::NUM_SHIFT_RIGHT,
        vec![int_type(flex(TVAR1)), int_type(flex(TVAR1))],
        Box::new(int_type(flex(TVAR1))),
    );

    // shiftRightZfBy : Int a, Int a -> Int a
    add_top_level_function_type!(
        Symbol::NUM_SHIFT_RIGHT_ZERO_FILL,
        vec![int_type(flex(TVAR1)), int_type(flex(TVAR1))],
        Box::new(int_type(flex(TVAR1))),
    );

    // intCast : Int a -> Int b
    add_top_level_function_type!(
        Symbol::NUM_INT_CAST,
        vec![int_type(flex(TVAR1))],
        Box::new(int_type(flex(TVAR2)))
    );

    // rem : Int a, Int a -> Int a
    add_top_level_function_type!(
        Symbol::NUM_REM,
        vec![int_type(flex(TVAR1)), int_type(flex(TVAR1))],
        Box::new(int_type(flex(TVAR1))),
    );

    // remChecked : Int a, Int a -> Result (Int a) [DivByZero]*
    add_top_level_function_type!(
        Symbol::NUM_REM_CHECKED,
        vec![int_type(flex(TVAR1)), int_type(flex(TVAR1))],
        Box::new(result_type(int_type(flex(TVAR1)), div_by_zero.clone())),
    );

    // isMultipleOf : Int a, Int a -> Bool
    add_top_level_function_type!(
        Symbol::NUM_IS_MULTIPLE_OF,
        vec![int_type(flex(TVAR1)), int_type(flex(TVAR1))],
        Box::new(bool_type()),
    );

    // minI8 : I8
    add_type!(Symbol::NUM_MIN_I8, i8_type());

    // maxI8 : I8
    add_type!(Symbol::NUM_MAX_I8, i8_type());

    // minU8 : U8
    add_type!(Symbol::NUM_MIN_U8, u8_type());

    // maxU8 : U8
    add_type!(Symbol::NUM_MAX_U8, u8_type());

    // minI16 : I16
    add_type!(Symbol::NUM_MIN_I16, i16_type());

    // maxI16 : I16
    add_type!(Symbol::NUM_MAX_I16, i16_type());

    // minU16 : U16
    add_type!(Symbol::NUM_MIN_U16, u16_type());

    // maxU16 : U16
    add_type!(Symbol::NUM_MAX_U16, u16_type());

    // minI32 : I32
    add_type!(Symbol::NUM_MIN_I32, i32_type());

    // maxI32 : I32
    add_type!(Symbol::NUM_MAX_I32, i32_type());

    // minU32 : U32
    add_type!(Symbol::NUM_MIN_U32, u32_type());

    // maxU32 : U32
    add_type!(Symbol::NUM_MAX_U32, u32_type());

    // minI64 : I64
    add_type!(Symbol::NUM_MIN_I64, i64_type());

    // maxI64 : I64
    add_type!(Symbol::NUM_MAX_I64, i64_type());

    // minU64 : U64
    add_type!(Symbol::NUM_MIN_U64, u64_type());

    // maxU64 : U64
    add_type!(Symbol::NUM_MAX_U64, u64_type());

    // minI128 : I128
    add_type!(Symbol::NUM_MIN_I128, i128_type());

    // maxI128 : I128
    add_type!(Symbol::NUM_MAX_I128, i128_type());

    // toI8 : Int * -> I8
    add_top_level_function_type!(
        Symbol::NUM_TO_I8,
        vec![int_type(flex(TVAR1))],
        Box::new(i8_type()),
    );

    let out_of_bounds = SolvedType::TagUnion(
        vec![(TagName("OutOfBounds".into()), vec![])],
        Box::new(SolvedType::Wildcard),
    );

    // toI8Checked : Int * -> Result I8 [OutOfBounds]*
    add_top_level_function_type!(
        Symbol::NUM_TO_I8_CHECKED,
        vec![int_type(flex(TVAR1))],
        Box::new(result_type(i8_type(), out_of_bounds.clone())),
    );

    // toI16 : Int * -> I16
    add_top_level_function_type!(
        Symbol::NUM_TO_I16,
        vec![int_type(flex(TVAR1))],
        Box::new(i16_type()),
    );

    // toI16Checked : Int * -> Result I16 [OutOfBounds]*
    add_top_level_function_type!(
        Symbol::NUM_TO_I16_CHECKED,
        vec![int_type(flex(TVAR1))],
        Box::new(result_type(i16_type(), out_of_bounds.clone())),
    );

    // toI32 : Int * -> I32
    add_top_level_function_type!(
        Symbol::NUM_TO_I32,
        vec![int_type(flex(TVAR1))],
        Box::new(i32_type()),
    );

    // toI32Checked : Int * -> Result I32 [OutOfBounds]*
    add_top_level_function_type!(
        Symbol::NUM_TO_I32_CHECKED,
        vec![int_type(flex(TVAR1))],
        Box::new(result_type(i32_type(), out_of_bounds.clone())),
    );

    // toI64 : Int * -> I64
    add_top_level_function_type!(
        Symbol::NUM_TO_I64,
        vec![int_type(flex(TVAR1))],
        Box::new(i64_type()),
    );

    // toI64Checked : Int * -> Result I64 [OutOfBounds]*
    add_top_level_function_type!(
        Symbol::NUM_TO_I64_CHECKED,
        vec![int_type(flex(TVAR1))],
        Box::new(result_type(i64_type(), out_of_bounds.clone())),
    );

    // toI128 : Int * -> I128
    add_top_level_function_type!(
        Symbol::NUM_TO_I128,
        vec![int_type(flex(TVAR1))],
        Box::new(i128_type()),
    );

    // toI128Checked : Int * -> Result I128 [OutOfBounds]*
    add_top_level_function_type!(
        Symbol::NUM_TO_I128_CHECKED,
        vec![int_type(flex(TVAR1))],
        Box::new(result_type(i128_type(), out_of_bounds)),
    );

    // toU8 : Int * -> U8
    add_top_level_function_type!(
        Symbol::NUM_TO_U8,
        vec![int_type(flex(TVAR1))],
        Box::new(u8_type()),
    );

    let out_of_bounds = SolvedType::TagUnion(
        vec![(TagName("OutOfBounds".into()), vec![])],
        Box::new(SolvedType::Wildcard),
    );

    // toU8Checked : Int * -> Result U8 [OutOfBounds]*
    add_top_level_function_type!(
        Symbol::NUM_TO_U8_CHECKED,
        vec![int_type(flex(TVAR1))],
        Box::new(result_type(u8_type(), out_of_bounds.clone())),
    );

    // toU16 : Int * -> U16
    add_top_level_function_type!(
        Symbol::NUM_TO_U16,
        vec![int_type(flex(TVAR1))],
        Box::new(u16_type()),
    );

    // toU16Checked : Int * -> Result U16 [OutOfBounds]*
    add_top_level_function_type!(
        Symbol::NUM_TO_U16_CHECKED,
        vec![int_type(flex(TVAR1))],
        Box::new(result_type(u16_type(), out_of_bounds.clone())),
    );

    // toU32 : Int * -> U32
    add_top_level_function_type!(
        Symbol::NUM_TO_U32,
        vec![int_type(flex(TVAR1))],
        Box::new(u32_type()),
    );

    // toU32Checked : Int * -> Result U32 [OutOfBounds]*
    add_top_level_function_type!(
        Symbol::NUM_TO_U32_CHECKED,
        vec![int_type(flex(TVAR1))],
        Box::new(result_type(u32_type(), out_of_bounds.clone())),
    );

    // toU64 : Int * -> U64
    add_top_level_function_type!(
        Symbol::NUM_TO_U64,
        vec![int_type(flex(TVAR1))],
        Box::new(u64_type()),
    );

    // toU64Checked : Int * -> Result U64 [OutOfBounds]*
    add_top_level_function_type!(
        Symbol::NUM_TO_U64_CHECKED,
        vec![int_type(flex(TVAR1))],
        Box::new(result_type(u64_type(), out_of_bounds.clone())),
    );

    // toU128 : Int * -> U128
    add_top_level_function_type!(
        Symbol::NUM_TO_U128,
        vec![int_type(flex(TVAR1))],
        Box::new(u128_type()),
    );

    // toU128Checked : Int * -> Result U128 [OutOfBounds]*
    add_top_level_function_type!(
        Symbol::NUM_TO_U128_CHECKED,
        vec![int_type(flex(TVAR1))],
        Box::new(result_type(u128_type(), out_of_bounds.clone())),
    );

    // toNat : Int * -> Nat
    add_top_level_function_type!(
        Symbol::NUM_TO_NAT,
        vec![int_type(flex(TVAR1))],
        Box::new(nat_type()),
    );

    // toNatChecked : Int * -> Result Nat [OutOfBounds]*
    add_top_level_function_type!(
        Symbol::NUM_TO_NAT_CHECKED,
        vec![int_type(flex(TVAR1))],
        Box::new(result_type(nat_type(), out_of_bounds.clone())),
    );

    // toF32 : Num * -> F32
    add_top_level_function_type!(
        Symbol::NUM_TO_F32,
        vec![num_type(flex(TVAR1))],
        Box::new(f32_type()),
    );

    // toF32Checked : Num * -> Result F32 [OutOfBounds]*
    add_top_level_function_type!(
        Symbol::NUM_TO_F32_CHECKED,
        vec![num_type(flex(TVAR1))],
        Box::new(result_type(f32_type(), out_of_bounds.clone())),
    );

    // toF64 : Num * -> F64
    add_top_level_function_type!(
        Symbol::NUM_TO_F64,
        vec![num_type(flex(TVAR1))],
        Box::new(f64_type()),
    );

    // toF64Checked : Num * -> Result F64 [OutOfBounds]*
    add_top_level_function_type!(
        Symbol::NUM_TO_F64_CHECKED,
        vec![num_type(flex(TVAR1))],
        Box::new(result_type(f64_type(), out_of_bounds)),
    );

    // toStr : Num a -> Str
    add_top_level_function_type!(
        Symbol::NUM_TO_STR,
        vec![num_type(flex(TVAR1))],
        Box::new(str_type())
    );

    // Frac module

    // div : Frac a, Frac a -> Frac a
    add_top_level_function_type!(
        Symbol::NUM_DIV_FRAC,
        vec![frac_type(flex(TVAR1)), frac_type(flex(TVAR1))],
        Box::new(frac_type(flex(TVAR1)))
    );

    // divChecked : Frac a, Frac a -> Result (Frac a) [DivByZero]*
    add_top_level_function_type!(
        Symbol::NUM_DIV_FRAC_CHECKED,
        vec![frac_type(flex(TVAR1)), frac_type(flex(TVAR1))],
        Box::new(result_type(frac_type(flex(TVAR1)), div_by_zero)),
    );

    // sqrt : Frac a -> Frac a
    add_top_level_function_type!(
        Symbol::NUM_SQRT,
        vec![frac_type(flex(TVAR1))],
        Box::new(frac_type(flex(TVAR1))),
    );

    // sqrtChecked : Frac a -> Result (Frac a) [SqrtOfNegative]*
    let sqrt_of_negative = SolvedType::TagUnion(
        vec![(TagName("SqrtOfNegative".into()), vec![])],
        Box::new(SolvedType::Wildcard),
    );

    add_top_level_function_type!(
        Symbol::NUM_SQRT_CHECKED,
        vec![frac_type(flex(TVAR1))],
        Box::new(result_type(frac_type(flex(TVAR1)), sqrt_of_negative)),
    );

    // log : Frac a -> Frac a
    add_top_level_function_type!(
        Symbol::NUM_LOG,
        vec![frac_type(flex(TVAR1))],
        Box::new(frac_type(flex(TVAR1))),
    );

    // logChecked : Frac a -> Result (Frac a) [LogNeedsPositive]*
    let log_needs_positive = SolvedType::TagUnion(
        vec![(TagName("LogNeedsPositive".into()), vec![])],
        Box::new(SolvedType::Wildcard),
    );

    add_top_level_function_type!(
        Symbol::NUM_LOG_CHECKED,
        vec![frac_type(flex(TVAR1))],
        Box::new(result_type(frac_type(flex(TVAR1)), log_needs_positive)),
    );

    // round : Frac a -> Int b
    add_top_level_function_type!(
        Symbol::NUM_ROUND,
        vec![frac_type(flex(TVAR1))],
        Box::new(int_type(flex(TVAR2))),
    );

    // sin : Frac a -> Frac a
    add_top_level_function_type!(
        Symbol::NUM_SIN,
        vec![frac_type(flex(TVAR1))],
        Box::new(frac_type(flex(TVAR1))),
    );

    // cos : Frac a -> Frac a
    add_top_level_function_type!(
        Symbol::NUM_COS,
        vec![frac_type(flex(TVAR1))],
        Box::new(frac_type(flex(TVAR1))),
    );

    // tan : Frac a -> Frac a
    add_top_level_function_type!(
        Symbol::NUM_TAN,
        vec![frac_type(flex(TVAR1))],
        Box::new(frac_type(flex(TVAR1))),
    );

    // pow : Frac a, Frac a -> Frac a
    add_top_level_function_type!(
        Symbol::NUM_POW,
        vec![frac_type(flex(TVAR1)), frac_type(flex(TVAR1))],
        Box::new(frac_type(flex(TVAR1))),
    );

    // ceiling : Frac a -> Int b
    add_top_level_function_type!(
        Symbol::NUM_CEILING,
        vec![frac_type(flex(TVAR1))],
        Box::new(int_type(flex(TVAR2))),
    );

    // powInt : Int a, Int a -> Int a
    add_top_level_function_type!(
        Symbol::NUM_POW_INT,
        vec![int_type(flex(TVAR1)), int_type(flex(TVAR1))],
        Box::new(int_type(flex(TVAR1))),
    );

    // floor : Frac a -> Int b
    add_top_level_function_type!(
        Symbol::NUM_FLOOR,
        vec![frac_type(flex(TVAR1))],
        Box::new(int_type(flex(TVAR2))),
    );

    // atan : Frac a -> Frac a
    add_top_level_function_type!(
        Symbol::NUM_ATAN,
        vec![frac_type(flex(TVAR1))],
        Box::new(frac_type(flex(TVAR1))),
    );

    // acos : Frac a -> Frac a
    add_top_level_function_type!(
        Symbol::NUM_ACOS,
        vec![frac_type(flex(TVAR1))],
        Box::new(frac_type(flex(TVAR1))),
    );

    // asin : Frac a -> Frac a
    add_top_level_function_type!(
        Symbol::NUM_ASIN,
        vec![frac_type(flex(TVAR1))],
        Box::new(frac_type(flex(TVAR1))),
    );

    // bytesToU16 : List U8, Nat -> Result U16 [OutOfBounds]
    {
        let position_out_of_bounds = SolvedType::TagUnion(
            vec![(TagName("OutOfBounds".into()), vec![])],
            Box::new(SolvedType::Wildcard),
        );
        add_top_level_function_type!(
            Symbol::NUM_BYTES_TO_U16,
            vec![list_type(u8_type()), nat_type()],
            Box::new(result_type(u16_type(), position_out_of_bounds)),
        );
    }

    // bytesToU32 : List U8, Nat -> Result U32 [OutOfBounds]
    {
        let position_out_of_bounds = SolvedType::TagUnion(
            vec![(TagName("OutOfBounds".into()), vec![])],
            Box::new(SolvedType::Wildcard),
        );
        add_top_level_function_type!(
            Symbol::NUM_BYTES_TO_U32,
            vec![list_type(u8_type()), nat_type()],
            Box::new(result_type(u32_type(), position_out_of_bounds)),
        );
    }

    // Bool module

    // and : Bool, Bool -> Bool
    add_top_level_function_type!(
        Symbol::BOOL_AND,
        vec![bool_type(), bool_type()],
        Box::new(bool_type())
    );

    // or : Bool, Bool -> Bool
    add_top_level_function_type!(
        Symbol::BOOL_OR,
        vec![bool_type(), bool_type()],
        Box::new(bool_type())
    );

    // xor : Bool, Bool -> Bool
    add_top_level_function_type!(
        Symbol::BOOL_XOR,
        vec![bool_type(), bool_type()],
        Box::new(bool_type())
    );

    // not : Bool -> Bool
    add_top_level_function_type!(Symbol::BOOL_NOT, vec![bool_type()], Box::new(bool_type()));

    // Str module

    // Str.split : Str, Str -> List Str
    add_top_level_function_type!(
        Symbol::STR_SPLIT,
        vec![str_type(), str_type()],
        Box::new(list_type(str_type())),
    );

    // Str.concat : Str, Str -> Str
    add_top_level_function_type!(
        Symbol::STR_CONCAT,
        vec![str_type(), str_type()],
        Box::new(str_type()),
    );

    // Str.joinWith : List Str, Str -> Str
    add_top_level_function_type!(
        Symbol::STR_JOIN_WITH,
        vec![list_type(str_type()), str_type()],
        Box::new(str_type()),
    );

    // Str.toScalars : Str -> List U32
    add_top_level_function_type!(
        Symbol::STR_TO_SCALARS,
        vec![str_type()],
        Box::new(list_type(u32_type())),
    );

    // isEmpty : Str -> Bool
    add_top_level_function_type!(
        Symbol::STR_IS_EMPTY,
        vec![str_type()],
        Box::new(bool_type())
    );

    // startsWith : Str, Str -> Bool
    add_top_level_function_type!(
        Symbol::STR_STARTS_WITH,
        vec![str_type(), str_type()],
        Box::new(bool_type())
    );

    // startsWithScalar : Str, U32 -> Bool
    add_top_level_function_type!(
        Symbol::STR_STARTS_WITH_SCALAR,
        vec![str_type(), u32_type()],
        Box::new(bool_type())
    );

    // endsWith : Str, Str -> Bool
    add_top_level_function_type!(
        Symbol::STR_ENDS_WITH,
        vec![str_type(), str_type()],
        Box::new(bool_type())
    );

    // countGraphemes : Str -> Nat
    add_top_level_function_type!(
        Symbol::STR_COUNT_GRAPHEMES,
        vec![str_type()],
        Box::new(nat_type())
    );

    // repeat : Str, Nat -> Str
    add_top_level_function_type!(
        Symbol::STR_REPEAT,
        vec![str_type(), nat_type()],
        Box::new(str_type())
    );

    // trimLeft : Str -> Str
    add_top_level_function_type!(
        Symbol::STR_TRIM_LEFT,
        vec![str_type()],
        Box::new(str_type())
    );

    // trimRight : Str -> Str
    add_top_level_function_type!(
        Symbol::STR_TRIM_RIGHT,
        vec![str_type()],
        Box::new(str_type())
    );

    // trim : Str -> Str
    add_top_level_function_type!(Symbol::STR_TRIM, vec![str_type()], Box::new(str_type()));

    // fromUtf8 : List U8 -> Result Str [BadUtf8 Utf8Problem]*
    {
        let bad_utf8 = SolvedType::TagUnion(
            vec![(
                TagName("BadUtf8".into()),
                vec![str_utf8_byte_problem_type(), nat_type()],
            )],
            Box::new(SolvedType::Wildcard),
        );

        add_top_level_function_type!(
            Symbol::STR_FROM_UTF8,
            vec![list_type(u8_type())],
            Box::new(result_type(str_type(), bad_utf8)),
        );
    }

    // fromUtf8Range : List U8, { start : Nat, count : Nat } -> Result Str [BadUtf8 Utf8Problem, OutOfBounds]*
    {
        let bad_utf8 = SolvedType::TagUnion(
            vec![
                (
                    TagName("BadUtf8".into()),
                    vec![str_utf8_byte_problem_type(), nat_type()],
                ),
                (TagName("OutOfBounds".into()), vec![]),
            ],
            Box::new(SolvedType::Wildcard),
        );

        add_top_level_function_type!(
            Symbol::STR_FROM_UTF8_RANGE,
            vec![
                list_type(u8_type()),
                SolvedType::Record {
                    fields: vec![
                        ("start".into(), RecordField::Required(nat_type())),
                        ("count".into(), RecordField::Required(nat_type())),
                    ],
                    ext: Box::new(SolvedType::EmptyRecord),
                }
            ],
            Box::new(result_type(str_type(), bad_utf8)),
        );
    }

    // toUtf8 : Str -> List U8
    add_top_level_function_type!(
        Symbol::STR_TO_UTF8,
        vec![str_type()],
        Box::new(list_type(u8_type()))
    );

    // toNum : Str -> Result (Num a) [InvalidNumStr]
    // Because toNum doesn't work with floats & decimals by default without
    // a point of usage to be able to infer the proper layout
    // we decided that separate functions for each sub num type
    // is the best approach. These below all end up mapping to
    // `str_to_num` in can `builtins.rs`
    let invalid_str = || {
        SolvedType::TagUnion(
            vec![(TagName("InvalidNumStr".into()), vec![])],
            Box::new(SolvedType::Wildcard),
        )
    };

    // toDec : Str -> Result Dec [InvalidNumStr]
    add_top_level_function_type!(
        Symbol::STR_TO_DEC,
        vec![str_type()],
        Box::new(result_type(dec_type(), invalid_str()))
    );

    // toF64 : Str -> Result F64 [InvalidNumStr]
    add_top_level_function_type!(
        Symbol::STR_TO_F64,
        vec![str_type()],
        Box::new(result_type(f64_type(), invalid_str()))
    );

    // toF32 : Str -> Result F32 [InvalidNumStr]
    add_top_level_function_type!(
        Symbol::STR_TO_F32,
        vec![str_type()],
        Box::new(result_type(f32_type(), invalid_str()))
    );

    // toNat : Str -> Result Nat [InvalidNumStr]
    add_top_level_function_type!(
        Symbol::STR_TO_NAT,
        vec![str_type()],
        Box::new(result_type(nat_type(), invalid_str()))
    );

    // toU128 : Str -> Result U128 [InvalidNumStr]
    add_top_level_function_type!(
        Symbol::STR_TO_U128,
        vec![str_type()],
        Box::new(result_type(u128_type(), invalid_str()))
    );

    // toI128 : Str -> Result I128 [InvalidNumStr]
    add_top_level_function_type!(
        Symbol::STR_TO_I128,
        vec![str_type()],
        Box::new(result_type(i128_type(), invalid_str()))
    );

    // toU64 : Str -> Result U64 [InvalidNumStr]
    add_top_level_function_type!(
        Symbol::STR_TO_U64,
        vec![str_type()],
        Box::new(result_type(u64_type(), invalid_str()))
    );

    // toI64 : Str -> Result I64 [InvalidNumStr]
    add_top_level_function_type!(
        Symbol::STR_TO_I64,
        vec![str_type()],
        Box::new(result_type(i64_type(), invalid_str()))
    );

    // toU32 : Str -> Result U32 [InvalidNumStr]
    add_top_level_function_type!(
        Symbol::STR_TO_U32,
        vec![str_type()],
        Box::new(result_type(u32_type(), invalid_str()))
    );

    // toI32 : Str -> Result I32 [InvalidNumStr]
    add_top_level_function_type!(
        Symbol::STR_TO_I32,
        vec![str_type()],
        Box::new(result_type(i32_type(), invalid_str()))
    );

    // toU16 : Str -> Result U16 [InvalidNumStr]
    add_top_level_function_type!(
        Symbol::STR_TO_U16,
        vec![str_type()],
        Box::new(result_type(u16_type(), invalid_str()))
    );

    // toI16 : Str -> Result I16 [InvalidNumStr]
    add_top_level_function_type!(
        Symbol::STR_TO_I16,
        vec![str_type()],
        Box::new(result_type(i16_type(), invalid_str()))
    );

    // toU8 : Str -> Result U8 [InvalidNumStr]
    add_top_level_function_type!(
        Symbol::STR_TO_U8,
        vec![str_type()],
        Box::new(result_type(u8_type(), invalid_str()))
    );

    // toI8 : Str -> Result I8 [InvalidNumStr]
    add_top_level_function_type!(
        Symbol::STR_TO_I8,
        vec![str_type()],
        Box::new(result_type(i8_type(), invalid_str()))
    );

    // List module

    // get : List elem, Nat -> Result elem [OutOfBounds]*
    let index_out_of_bounds = SolvedType::TagUnion(
        vec![(TagName("OutOfBounds".into()), vec![])],
        Box::new(SolvedType::Wildcard),
    );

    add_top_level_function_type!(
        Symbol::LIST_GET,
        vec![list_type(flex(TVAR1)), nat_type()],
        Box::new(result_type(flex(TVAR1), index_out_of_bounds)),
    );

    // first : List elem -> Result elem [ListWasEmpty]*
    let list_was_empty = SolvedType::TagUnion(
        vec![(TagName("ListWasEmpty".into()), vec![])],
        Box::new(SolvedType::Wildcard),
    );

    add_top_level_function_type!(
        Symbol::LIST_FIRST,
        vec![list_type(flex(TVAR1))],
        Box::new(result_type(flex(TVAR1), list_was_empty.clone())),
    );

    // last : List elem -> Result elem [ListWasEmpty]*
    add_top_level_function_type!(
        Symbol::LIST_LAST,
        vec![list_type(flex(TVAR1))],
        Box::new(result_type(flex(TVAR1), list_was_empty.clone())),
    );

    // replace : List elem, Nat, elem -> { list: List elem, value: elem }
    add_top_level_function_type!(
        Symbol::LIST_REPLACE,
        vec![list_type(flex(TVAR1)), nat_type(), flex(TVAR1)],
        Box::new(SolvedType::Record {
            fields: vec![
                ("list".into(), RecordField::Required(list_type(flex(TVAR1)))),
                ("value".into(), RecordField::Required(flex(TVAR1))),
            ],
            ext: Box::new(SolvedType::EmptyRecord),
        }),
    );

    // set : List elem, Nat, elem -> List elem
    add_top_level_function_type!(
        Symbol::LIST_SET,
        vec![list_type(flex(TVAR1)), nat_type(), flex(TVAR1)],
        Box::new(list_type(flex(TVAR1))),
    );

    // concat : List elem, List elem -> List elem
    add_top_level_function_type!(
        Symbol::LIST_CONCAT,
        vec![list_type(flex(TVAR1)), list_type(flex(TVAR1))],
        Box::new(list_type(flex(TVAR1))),
    );

    // contains : List elem, elem -> Bool
    add_top_level_function_type!(
        Symbol::LIST_CONTAINS,
        vec![list_type(flex(TVAR1)), flex(TVAR1)],
        Box::new(bool_type()),
    );

    // min :  List (Num a) -> Result (Num a) [ListWasEmpty]*
    add_top_level_function_type!(
        Symbol::LIST_MIN,
        vec![list_type(num_type(flex(TVAR1)))],
        Box::new(result_type(num_type(flex(TVAR1)), list_was_empty.clone())),
    );

    // max :  List (Num a) -> Result (Num a) [ListWasEmpty]*
    add_top_level_function_type!(
        Symbol::LIST_MAX,
        vec![list_type(num_type(flex(TVAR1)))],
        Box::new(result_type(num_type(flex(TVAR1)), list_was_empty)),
    );

    // sum :  List (Num a) -> Num a
    add_top_level_function_type!(
        Symbol::LIST_SUM,
        vec![list_type(num_type(flex(TVAR1)))],
        Box::new(num_type(flex(TVAR1))),
    );

    // product :  List (Num a) -> Num a
    add_top_level_function_type!(
        Symbol::LIST_PRODUCT,
        vec![list_type(num_type(flex(TVAR1)))],
        Box::new(num_type(flex(TVAR1))),
    );

    // walk : List elem, state, (state, elem -> state) -> state
    add_top_level_function_type!(
        Symbol::LIST_WALK,
        vec![
            list_type(flex(TVAR1)),
            flex(TVAR2),
            closure(vec![flex(TVAR2), flex(TVAR1)], TVAR3, Box::new(flex(TVAR2))),
        ],
        Box::new(flex(TVAR2)),
    );

    // walkBackwards : List elem, state, (state, elem -> state) -> state
    add_top_level_function_type!(
        Symbol::LIST_WALK_BACKWARDS,
        vec![
            list_type(flex(TVAR1)),
            flex(TVAR2),
            closure(vec![flex(TVAR2), flex(TVAR1)], TVAR3, Box::new(flex(TVAR2))),
        ],
        Box::new(flex(TVAR2)),
    );

    fn until_type(content: SolvedType) -> SolvedType {
        // [Continue, Break]
        SolvedType::TagUnion(
            vec![
                (TagName("Continue".into()), vec![content.clone()]),
                (TagName("Break".into()), vec![content]),
            ],
            Box::new(SolvedType::EmptyTagUnion),
        )
    }

    // walkUntil : List elem, state, (state, elem -> [Continue state, Stop state]) -> state
    add_top_level_function_type!(
        Symbol::LIST_WALK_UNTIL,
        vec![
            list_type(flex(TVAR1)),
            flex(TVAR2),
            closure(
                vec![flex(TVAR2), flex(TVAR1)],
                TVAR3,
                Box::new(until_type(flex(TVAR2))),
            ),
        ],
        Box::new(flex(TVAR2)),
    );

    // keepIf : List elem, (elem -> Bool) -> List elem
    add_top_level_function_type!(
        Symbol::LIST_KEEP_IF,
        vec![
            list_type(flex(TVAR1)),
            closure(vec![flex(TVAR1)], TVAR2, Box::new(bool_type())),
        ],
        Box::new(list_type(flex(TVAR1))),
    );

    // keepOks : List before, (before -> Result after *) -> List after
    {
        let_tvars! { star, cvar, before, after};
        add_top_level_function_type!(
            Symbol::LIST_KEEP_OKS,
            vec![
                list_type(flex(before)),
                closure(
                    vec![flex(before)],
                    cvar,
                    Box::new(result_type(flex(after), flex(star))),
                ),
            ],
            Box::new(list_type(flex(after))),
        )
    };

    // keepErrs: List before, (before -> Result * after) -> List after
    {
        let_tvars! { star, cvar, before, after};

        add_top_level_function_type!(
            Symbol::LIST_KEEP_ERRS,
            vec![
                list_type(flex(before)),
                closure(
                    vec![flex(before)],
                    cvar,
                    Box::new(result_type(flex(star), flex(after))),
                ),
            ],
            Box::new(list_type(flex(after))),
        )
    };

    // range : Int a, Int a -> List (Int a)
    add_top_level_function_type!(
        Symbol::LIST_RANGE,
        vec![int_type(flex(TVAR1)), int_type(flex(TVAR1))],
        Box::new(list_type(int_type(flex(TVAR1)))),
    );

    // joinMap : List before, (before -> List after) -> List after
    {
        let_tvars! { cvar, before, after }
        add_top_level_function_type!(
            Symbol::LIST_JOIN_MAP,
            vec![
                list_type(flex(before)),
                closure(vec![flex(before)], cvar, Box::new(list_type(flex(after)))),
            ],
            Box::new(list_type(flex(after))),
        );
    }

    // map : List before, (before -> after) -> List after
    add_top_level_function_type!(
        Symbol::LIST_MAP,
        vec![
            list_type(flex(TVAR1)),
            closure(vec![flex(TVAR1)], TVAR3, Box::new(flex(TVAR2))),
        ],
        Box::new(list_type(flex(TVAR2))),
    );

    // mapWithIndex : List before, (before, Nat -> after) -> List after
    {
        let_tvars! { cvar, before, after};
        add_top_level_function_type!(
            Symbol::LIST_MAP_WITH_INDEX,
            vec![
                list_type(flex(before)),
                closure(vec![flex(before), nat_type()], cvar, Box::new(flex(after))),
            ],
            Box::new(list_type(flex(after))),
        )
    };

    // map2 : List a, List b, (a, b -> c) -> List c
    {
        let_tvars! {a, b, c, cvar};
        add_top_level_function_type!(
            Symbol::LIST_MAP2,
            vec![
                list_type(flex(a)),
                list_type(flex(b)),
                closure(vec![flex(a), flex(b)], cvar, Box::new(flex(c))),
            ],
            Box::new(list_type(flex(c))),
        )
    };

    {
        let_tvars! {a, b, c, d, cvar};

        // map3 : List a, List b, List c, (a, b, c -> d) -> List d
        add_top_level_function_type!(
            Symbol::LIST_MAP3,
            vec![
                list_type(flex(a)),
                list_type(flex(b)),
                list_type(flex(c)),
                closure(vec![flex(a), flex(b), flex(c)], cvar, Box::new(flex(d))),
            ],
            Box::new(list_type(flex(d))),
        )
    };

    {
        let_tvars! {a, b, c, d, e, cvar};

        // map4 : List a, List b, List c, List d, (a, b, c, d -> e) -> List e
        add_top_level_function_type!(
            Symbol::LIST_MAP4,
            vec![
                list_type(flex(a)),
                list_type(flex(b)),
                list_type(flex(c)),
                list_type(flex(d)),
                closure(
                    vec![flex(a), flex(b), flex(c), flex(d)],
                    cvar,
                    Box::new(flex(e))
                ),
            ],
            Box::new(list_type(flex(e))),
        )
    };

    // append : List elem, elem -> List elem
    add_top_level_function_type!(
        Symbol::LIST_APPEND,
        vec![list_type(flex(TVAR1)), flex(TVAR1)],
        Box::new(list_type(flex(TVAR1))),
    );

    // takeFirst : List elem, Nat -> List elem
    add_top_level_function_type!(
        Symbol::LIST_TAKE_FIRST,
        vec![list_type(flex(TVAR1)), nat_type()],
        Box::new(list_type(flex(TVAR1))),
    );

    // takeLast : List elem, Nat -> List elem
    add_top_level_function_type!(
        Symbol::LIST_TAKE_LAST,
        vec![list_type(flex(TVAR1)), nat_type()],
        Box::new(list_type(flex(TVAR1))),
    );

    // sublist : List elem, { start : Nat, len : Nat } -> List elem
    add_top_level_function_type!(
        Symbol::LIST_SUBLIST,
        vec![
            list_type(flex(TVAR1)),
            SolvedType::Record {
                fields: vec![
                    ("start".into(), RecordField::Required(nat_type())),
                    ("len".into(), RecordField::Required(nat_type())),
                ],
                ext: Box::new(SolvedType::EmptyRecord),
            },
        ],
        Box::new(list_type(flex(TVAR1))),
    );

    // split : List elem, Nat -> { before: List elem, others: List elem }
    add_top_level_function_type!(
        Symbol::LIST_SPLIT,
        vec![list_type(flex(TVAR1)), nat_type(),],
        Box::new(SolvedType::Record {
            fields: vec![
                (
                    "before".into(),
                    RecordField::Required(list_type(flex(TVAR1)))
                ),
                (
                    "others".into(),
                    RecordField::Required(list_type(flex(TVAR1)))
                ),
            ],
            ext: Box::new(SolvedType::EmptyRecord),
        },),
    );

    // drop : List elem, Nat -> List elem
    add_top_level_function_type!(
        Symbol::LIST_DROP,
        vec![list_type(flex(TVAR1)), nat_type()],
        Box::new(list_type(flex(TVAR1))),
    );

    // dropAt : List elem, Nat -> List elem
    add_top_level_function_type!(
        Symbol::LIST_DROP_AT,
        vec![list_type(flex(TVAR1)), nat_type()],
        Box::new(list_type(flex(TVAR1))),
    );

    // dropLast : List elem -> List elem
    add_top_level_function_type!(
        Symbol::LIST_DROP_LAST,
        vec![list_type(flex(TVAR1))],
        Box::new(list_type(flex(TVAR1))),
    );

    // dropFirst : List elem -> List elem
    add_top_level_function_type!(
        Symbol::LIST_DROP_FIRST,
        vec![list_type(flex(TVAR1))],
        Box::new(list_type(flex(TVAR1))),
    );

    // dropIf : List elem, (elem -> Bool) -> List elem
    add_top_level_function_type!(
        Symbol::LIST_DROP_IF,
        vec![
            list_type(flex(TVAR1)),
            closure(vec![flex(TVAR1)], TVAR2, Box::new(bool_type())),
        ],
        Box::new(list_type(flex(TVAR1))),
    );

    // swap : List elem, Nat, Nat -> List elem
    add_top_level_function_type!(
        Symbol::LIST_SWAP,
        vec![list_type(flex(TVAR1)), nat_type(), nat_type()],
        Box::new(list_type(flex(TVAR1))),
    );

    // prepend : List elem, elem -> List elem
    add_top_level_function_type!(
        Symbol::LIST_PREPEND,
        vec![list_type(flex(TVAR1)), flex(TVAR1)],
        Box::new(list_type(flex(TVAR1))),
    );

    // join : List (List elem) -> List elem
    add_top_level_function_type!(
        Symbol::LIST_JOIN,
        vec![list_type(list_type(flex(TVAR1)))],
        Box::new(list_type(flex(TVAR1))),
    );

    // single : a -> List a
    add_top_level_function_type!(
        Symbol::LIST_SINGLE,
        vec![flex(TVAR1)],
        Box::new(list_type(flex(TVAR1)))
    );

    // repeat : elem, Nat -> List elem
    add_top_level_function_type!(
        Symbol::LIST_REPEAT,
        vec![flex(TVAR1), nat_type()],
        Box::new(list_type(flex(TVAR1))),
    );

    // reverse : List elem -> List elem
    add_top_level_function_type!(
        Symbol::LIST_REVERSE,
        vec![list_type(flex(TVAR1))],
        Box::new(list_type(flex(TVAR1))),
    );

    // len : List * -> Nat
    add_top_level_function_type!(
        Symbol::LIST_LEN,
        vec![list_type(flex(TVAR1))],
        Box::new(nat_type())
    );

    // isEmpty : List * -> Bool
    add_top_level_function_type!(
        Symbol::LIST_IS_EMPTY,
        vec![list_type(flex(TVAR1))],
        Box::new(bool_type())
    );

    // any: List elem, (elem -> Bool) -> Bool
    add_top_level_function_type!(
        Symbol::LIST_ANY,
        vec![
            list_type(flex(TVAR1)),
            closure(vec![flex(TVAR1)], TVAR2, Box::new(bool_type())),
        ],
        Box::new(bool_type()),
    );

    // all: List elem, (elem -> Bool) -> Bool
    add_top_level_function_type!(
        Symbol::LIST_ALL,
        vec![
            list_type(flex(TVAR1)),
            closure(vec![flex(TVAR1)], TVAR2, Box::new(bool_type())),
        ],
        Box::new(bool_type()),
    );

    // sortWith : List a, (a, a -> Ordering) -> List a
    add_top_level_function_type!(
        Symbol::LIST_SORT_WITH,
        vec![
            list_type(flex(TVAR1)),
            closure(
                vec![flex(TVAR1), flex(TVAR1)],
                TVAR2,
                Box::new(ordering_type()),
            ),
        ],
        Box::new(list_type(flex(TVAR1))),
    );

    // sortAsc : List (Num a) -> List (Num a)
    add_top_level_function_type!(
        Symbol::LIST_SORT_ASC,
        vec![list_type(num_type(flex(TVAR1)))],
        Box::new(list_type(num_type(flex(TVAR1))))
    );

    // sortDesc : List (Num a) -> List (Num a)
    add_top_level_function_type!(
        Symbol::LIST_SORT_DESC,
        vec![list_type(num_type(flex(TVAR1)))],
        Box::new(list_type(num_type(flex(TVAR1))))
    );

    // find : List elem, (elem -> Bool) -> Result elem [NotFound]*
    {
        let not_found = SolvedType::TagUnion(
            vec![(TagName("NotFound".into()), vec![])],
            Box::new(SolvedType::Wildcard),
        );
        let (elem, cvar) = (TVAR1, TVAR2);
        add_top_level_function_type!(
            Symbol::LIST_FIND,
            vec![
                list_type(flex(elem)),
                closure(vec![flex(elem)], cvar, Box::new(bool_type())),
            ],
            Box::new(result_type(flex(elem), not_found)),
        )
    }

    // intersperse : List elem, elem -> List elem
    add_top_level_function_type!(
        Symbol::LIST_INTERSPERSE,
        vec![list_type(flex(TVAR1)), flex(TVAR1)],
        Box::new(list_type(flex(TVAR1))),
    );

    // Dict module

    // len : Dict * * -> Nat
    add_top_level_function_type!(
        Symbol::DICT_LEN,
        vec![dict_type(flex(TVAR1), flex(TVAR2))],
        Box::new(nat_type()),
    );

    // empty : Dict * *
    add_type!(Symbol::DICT_EMPTY, dict_type(flex(TVAR1), flex(TVAR2)));

    // single : k, v -> Dict k v
    add_top_level_function_type!(
        Symbol::DICT_SINGLE,
        vec![flex(TVAR1), flex(TVAR2)],
        Box::new(dict_type(flex(TVAR1), flex(TVAR2))),
    );

    // get : Dict k v, k -> Result v [KeyNotFound]*
    let key_not_found = SolvedType::TagUnion(
        vec![(TagName("KeyNotFound".into()), vec![])],
        Box::new(SolvedType::Wildcard),
    );

    add_top_level_function_type!(
        Symbol::DICT_GET,
        vec![dict_type(flex(TVAR1), flex(TVAR2)), flex(TVAR1)],
        Box::new(result_type(flex(TVAR2), key_not_found)),
    );

    // Dict.insert : Dict k v, k, v -> Dict k v
    add_top_level_function_type!(
        Symbol::DICT_INSERT,
        vec![
            dict_type(flex(TVAR1), flex(TVAR2)),
            flex(TVAR1),
            flex(TVAR2),
        ],
        Box::new(dict_type(flex(TVAR1), flex(TVAR2))),
    );

    // Dict.remove : Dict k v, k -> Dict k v
    add_top_level_function_type!(
        Symbol::DICT_REMOVE,
        vec![dict_type(flex(TVAR1), flex(TVAR2)), flex(TVAR1)],
        Box::new(dict_type(flex(TVAR1), flex(TVAR2))),
    );

    // Dict.contains : Dict k v, k -> Bool
    add_top_level_function_type!(
        Symbol::DICT_CONTAINS,
        vec![dict_type(flex(TVAR1), flex(TVAR2)), flex(TVAR1)],
        Box::new(bool_type()),
    );

    // Dict.keys : Dict k v -> List k
    add_top_level_function_type!(
        Symbol::DICT_KEYS,
        vec![dict_type(flex(TVAR1), flex(TVAR2))],
        Box::new(list_type(flex(TVAR1))),
    );

    // Dict.values : Dict k v -> List v
    add_top_level_function_type!(
        Symbol::DICT_VALUES,
        vec![dict_type(flex(TVAR1), flex(TVAR2))],
        Box::new(list_type(flex(TVAR2))),
    );

    // Dict.union : Dict k v, Dict k v -> Dict k v
    add_top_level_function_type!(
        Symbol::DICT_UNION,
        vec![
            dict_type(flex(TVAR1), flex(TVAR2)),
            dict_type(flex(TVAR1), flex(TVAR2)),
        ],
        Box::new(dict_type(flex(TVAR1), flex(TVAR2))),
    );

    // Dict.intersection : Dict k v, Dict k v -> Dict k v
    add_top_level_function_type!(
        Symbol::DICT_INTERSECTION,
        vec![
            dict_type(flex(TVAR1), flex(TVAR2)),
            dict_type(flex(TVAR1), flex(TVAR2)),
        ],
        Box::new(dict_type(flex(TVAR1), flex(TVAR2))),
    );

    // Dict.difference : Dict k v, Dict k v -> Dict k v
    add_top_level_function_type!(
        Symbol::DICT_DIFFERENCE,
        vec![
            dict_type(flex(TVAR1), flex(TVAR2)),
            dict_type(flex(TVAR1), flex(TVAR2)),
        ],
        Box::new(dict_type(flex(TVAR1), flex(TVAR2))),
    );

    // Dict.walk : Dict k v, state, (state, k, v -> state) -> state
    add_top_level_function_type!(
        Symbol::DICT_WALK,
        vec![
            dict_type(flex(TVAR1), flex(TVAR2)),
            flex(TVAR3),
            closure(
                vec![flex(TVAR3), flex(TVAR1), flex(TVAR2)],
                TVAR4,
                Box::new(flex(TVAR3)),
            ),
        ],
        Box::new(flex(TVAR3)),
    );

    // Set module

    // empty : Set a
    add_type!(Symbol::SET_EMPTY, set_type(flex(TVAR1)));

    // single : a -> Set a
    add_top_level_function_type!(
        Symbol::SET_SINGLE,
        vec![flex(TVAR1)],
        Box::new(set_type(flex(TVAR1)))
    );

    // len : Set * -> Nat
    add_top_level_function_type!(
        Symbol::SET_LEN,
        vec![set_type(flex(TVAR1))],
        Box::new(nat_type())
    );

    // toList : Set a -> List a
    add_top_level_function_type!(
        Symbol::SET_TO_LIST,
        vec![set_type(flex(TVAR1))],
        Box::new(list_type(flex(TVAR1))),
    );

    // fromList : List a -> Set a
    add_top_level_function_type!(
        Symbol::SET_FROM_LIST,
        vec![list_type(flex(TVAR1))],
        Box::new(set_type(flex(TVAR1))),
    );

    // union : Set a, Set a -> Set a
    add_top_level_function_type!(
        Symbol::SET_UNION,
        vec![set_type(flex(TVAR1)), set_type(flex(TVAR1))],
        Box::new(set_type(flex(TVAR1))),
    );

    // difference : Set a, Set a -> Set a
    add_top_level_function_type!(
        Symbol::SET_DIFFERENCE,
        vec![set_type(flex(TVAR1)), set_type(flex(TVAR1))],
        Box::new(set_type(flex(TVAR1))),
    );

    // intersection : Set a, Set a -> Set a
    add_top_level_function_type!(
        Symbol::SET_INTERSECTION,
        vec![set_type(flex(TVAR1)), set_type(flex(TVAR1))],
        Box::new(set_type(flex(TVAR1))),
    );

    // Set.walk : Set a, (b, a -> b), b -> b
    add_top_level_function_type!(
        Symbol::SET_WALK,
        vec![
            set_type(flex(TVAR1)),
            flex(TVAR2),
            closure(vec![flex(TVAR2), flex(TVAR1)], TVAR3, Box::new(flex(TVAR2))),
        ],
        Box::new(flex(TVAR2)),
    );

    add_top_level_function_type!(
        Symbol::SET_INSERT,
        vec![set_type(flex(TVAR1)), flex(TVAR1)],
        Box::new(set_type(flex(TVAR1))),
    );

    add_top_level_function_type!(
        Symbol::SET_REMOVE,
        vec![set_type(flex(TVAR1)), flex(TVAR1)],
        Box::new(set_type(flex(TVAR1))),
    );

    add_top_level_function_type!(
        Symbol::SET_CONTAINS,
        vec![set_type(flex(TVAR1)), flex(TVAR1)],
        Box::new(bool_type()),
    );

    // Result module

    // map : Result a err, (a -> b) -> Result b err
    add_top_level_function_type!(
        Symbol::RESULT_MAP,
        vec![
            result_type(flex(TVAR1), flex(TVAR3)),
            closure(vec![flex(TVAR1)], TVAR4, Box::new(flex(TVAR2))),
        ],
        Box::new(result_type(flex(TVAR2), flex(TVAR3))),
    );

    // mapErr : Result a x, (x -> y) -> Result a x
    add_top_level_function_type!(
        Symbol::RESULT_MAP_ERR,
        vec![
            result_type(flex(TVAR1), flex(TVAR3)),
            closure(vec![flex(TVAR3)], TVAR4, Box::new(flex(TVAR2))),
        ],
        Box::new(result_type(flex(TVAR1), flex(TVAR2))),
    );

    // after : Result a err, (a -> Result b err) -> Result b err
    add_top_level_function_type!(
        Symbol::RESULT_AFTER,
        vec![
            result_type(flex(TVAR1), flex(TVAR3)),
            closure(
                vec![flex(TVAR1)],
                TVAR4,
                Box::new(result_type(flex(TVAR2), flex(TVAR3))),
            ),
        ],
        Box::new(result_type(flex(TVAR2), flex(TVAR3))),
    );

    // withDefault : Result a x, a -> a
    add_top_level_function_type!(
        Symbol::RESULT_WITH_DEFAULT,
        vec![result_type(flex(TVAR1), flex(TVAR3)), flex(TVAR1)],
        Box::new(flex(TVAR1)),
    );

    // isOk : Result * * -> bool
    add_top_level_function_type!(
        Symbol::RESULT_IS_OK,
        vec![result_type(flex(TVAR1), flex(TVAR3))],
        Box::new(bool_type()),
    );

    // isErr : Result * * -> bool
    add_top_level_function_type!(
        Symbol::RESULT_IS_ERR,
        vec![result_type(flex(TVAR1), flex(TVAR3))],
        Box::new(bool_type()),
    );

    // Box.box : a -> Box a
    add_top_level_function_type!(
        Symbol::BOX_BOX_FUNCTION,
        vec![flex(TVAR1)],
        Box::new(box_type(flex(TVAR1))),
    );

    // Box.unbox : Box a -> a
    add_top_level_function_type!(
        Symbol::BOX_UNBOX,
        vec![box_type(flex(TVAR1))],
        Box::new(flex(TVAR1)),
    );

    types
}

#[inline(always)]
fn flex(tvar: VarId) -> SolvedType {
    SolvedType::Flex(tvar)
}

#[inline(always)]
fn closure(arguments: Vec<SolvedType>, closure_var: VarId, ret: Box<SolvedType>) -> SolvedType {
    SolvedType::Func(arguments, Box::new(SolvedType::Flex(closure_var)), ret)
}