typr_core/components/context/

mod.rs

pub mod config;
pub mod graph;
pub mod vartype;

use crate::components::context::config::Config;
use crate::components::context::config::Environment;
use crate::components::context::config::TargetLanguage;
use crate::components::context::graph::Graph;
use crate::components::context::unification_map::UnificationMap;
use crate::components::context::vartype::VarType;
use crate::components::error_message::help_data::HelpData;
use crate::components::language::var::Var;
use crate::components::language::var_function::VarFunction;
use crate::components::language::Lang;
use crate::components::r#type::argument_type::ArgumentType;
use crate::components::r#type::kind::Kind;
use crate::components::r#type::type_system::TypeSystem;
use crate::components::r#type::vector_type::ConstructorCategory;
use crate::components::r#type::Type;
use crate::processes::type_checking::match_types_to_generic;
use crate::processes::type_checking::type_comparison::reduce_type;
use crate::processes::type_checking::unification_map;
use crate::utils::builder;
use crate::utils::standard_library::not_in_blacklist;
use serde::Deserialize;
use serde::Serialize;
use std::collections::HashMap;
use std::collections::HashSet;
use std::iter::Rev;
use std::ops::Add;
use tap::Pipe;

/// True for the auto-generated names given to anonymous record types
/// (`Record0`, `Record1`, …), as produced by `VarType::push_alias_increment`
/// (`format!("{}{}", TypeCategory::Record, count)`).
fn is_anonymous_record_name(name: &str) -> bool {
    name.strip_prefix("Record")
        .map(|rest| !rest.is_empty() && rest.chars().all(|c| c.is_ascii_digit()))
        .unwrap_or(false)
}

#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub struct Context {
    pub typing_context: VarType,
    pub subtypes: Graph<Type>,
    /// Registry of user-declared `typeconstructor`s: (name, parameter signature, category).
    #[serde(default)]
    pub type_constructors: Vec<(String, Vec<Type>, ConstructorCategory)>,
    /// Constraints mapping a rigid generic variable name to its interface.
    /// Introduced when an interface type appears in parameter position:
    /// fn(i: I): R  ⇒  i : A  with A: I  stored here.
    #[serde(default)]
    pub interface_constraints: HashMap<String, Type>,
    /// Counter for generating unique rigid generic variable names.
    #[serde(default)]
    pub rigid_counter: u64,
    /// Flat, whole-program registry of every `type X <- list { ... }` record
    /// alias declared anywhere, including inside `mod` bodies. Unlike
    /// `typing_context.aliases`, this is never scoped away at a module
    /// boundary: R's S3 class system has no module privacy, so transpilation
    /// needs the full picture to compute structural supertypes for the class
    /// vector (see `record_field_class` callers in `processes::transpiling`).
    #[serde(default)]
    pub record_aliases: Vec<(String, Type)>,
    /// Named type embedding (`embed field: Type`): provenance of every function
    /// auto-generated by forwarding/reconstruction, as `(type_name, method_name,
    /// source_field_name)`. Used to detect a later explicit definition that
    /// collides with an inherited embedded function (E-EMBED-003).
    #[serde(default)]
    pub embedded_methods: Vec<(String, String, String)>,
    /// RFC-TR-031: lines injected at the top of a `Test { ... }` file so the
    /// test body can reach `@testable` private members of the enclosing module
    /// (e.g. `sq <- Math$.test_sq`). Set while transpiling a module body in a
    /// test build; empty otherwise. Not serialised.
    #[serde(skip)]
    pub test_preamble: Vec<String>,
    /// `Self:{ ... }` (generic_constructor.md): the type bound to the
    /// enclosing function/method's first parameter, set only while
    /// type-checking that function's body. `None` everywhere else, which is
    /// what makes `Self` invalid outside a function body.
    #[serde(skip)]
    pub self_type: Option<Type>,
    config: Config,
}

/// The canonical sentinel nodes seeded into every subtype `Graph` so the
/// kind-sigil generic categories materialize as intermediate levels of the
/// lattice. Because `is_subtype_raw` already gives `RecordN <: %_ <: Generic
/// <: Any` (a concrete Record is a subtype of a record-kinded `KindedGen`, and
/// any generic is a subtype of the bare `Generic`), seeding one anchor per
/// kind makes every monomorphized record/interface/char/bool/number auto-nest
/// under its `G*` node. These sentinels all answer `has_generic() == true`, so
/// `get_classes` filters them out of generated R `class = c(...)` vectors —
/// they are a compile-time organisation of the hierarchy only.
fn generic_sentinels() -> Vec<Type> {
    let h = HelpData::default();
    let name = "_".to_string();
    vec![
        Type::Generic(name.clone(), h.clone()),
        Type::KindedGen(Kind::Record, name.clone(), h.clone()),
        Type::KindedGen(Kind::Interface, name.clone(), h.clone()),
        Type::KindedGen(Kind::String, name.clone(), h.clone()),
        Type::KindedGen(Kind::Boolean, name.clone(), h.clone()),
        Type::IndexGen(name, h),
    ]
}

/// A fresh subtype graph pre-seeded with the kind-sigil generic sentinels
/// (see [`generic_sentinels`]). Built against `Context::empty()` since the
/// sentinel ordering only exercises the structural `is_subtype_raw` arms
/// (`(_, Generic)`, `(_, Any)`, the `KindedGen`/`IndexGen` arms) and needs no
/// typing context.
fn seeded_subtype_graph() -> Graph<Type> {
    Graph::new().add_types(&generic_sentinels(), &Context::empty())
}

impl Default for Context {
    fn default() -> Self {
        let config = Config::default();
        Context {
            config: config.clone(),
            typing_context: VarType::from_config(config),
            subtypes: seeded_subtype_graph(),
            type_constructors: Vec::new(),
            interface_constraints: HashMap::new(),
            rigid_counter: 0,
            record_aliases: Vec::new(),
            embedded_methods: Vec::new(),
            test_preamble: Vec::new(),
            self_type: None,
        }
    }
}

impl From<Vec<(Lang, Type)>> for Context {
    fn from(val: Vec<(Lang, Type)>) -> Self {
        let val2: Vec<(Var, Type)> = val
            .iter()
            .map(|(lan, typ)| (Var::from_language(lan.clone()).unwrap(), typ.clone()))
            .collect();
        Context {
            typing_context: val2.into(),
            ..Context::default()
        }
    }
}

impl Context {
    pub fn new(types: Vec<(Var, Type)>) -> Context {
        Context {
            typing_context: types.into(),
            ..Context::default()
        }
    }

    pub fn empty() -> Self {
        Context {
            config: Config::default(),
            typing_context: VarType::new(),
            subtypes: Graph::new(),
            type_constructors: Vec::new(),
            interface_constraints: HashMap::new(),
            rigid_counter: 0,
            record_aliases: Vec::new(),
            embedded_methods: Vec::new(),
            test_preamble: Vec::new(),
            self_type: None,
        }
    }

    pub fn set_config(self, config: Config) -> Self {
        Self { config, ..self }
    }

    pub fn set_as_module_context(self) -> Context {
        Self {
            config: self.config.set_as_module(),
            ..self
        }
    }

    pub fn set_test_mode(self, val: bool) -> Context {
        Self {
            config: self.config.set_test_mode(val),
            ..self
        }
    }

    pub fn get_test_mode(&self) -> bool {
        self.config.test_mode
    }

    pub fn set_test_preamble(self, lines: Vec<String>) -> Context {
        Self {
            test_preamble: lines,
            ..self
        }
    }

    /// `Self:{ ... }` (generic_constructor.md §4.1): bind/clear the type
    /// denoted by `Self` for the duration of typing a function body.
    pub fn set_self_type(self, self_type: Option<Type>) -> Context {
        Self { self_type, ..self }
    }

    pub fn set_in_module_body(self) -> Self {
        Self {
            config: self.config.set_in_module_body(true),
            ..self
        }
    }

    pub fn is_in_module_body(&self) -> bool {
        self.config.in_module_body
    }

    /// Retourne un nouveau Context avec le Graph de sous-typage mis à jour
    pub fn with_subtypes(self, subtypes: Graph<Type>) -> Self {
        Self { subtypes, ..self }
    }

    pub fn get_members(&self) -> Vec<(Var, Type)> {
        self.typing_context
            .variables()
            .chain(self.aliases())
            .cloned()
            .collect::<Vec<_>>()
    }

    pub fn variable_exist(&self, var: Var) -> Option<Var> {
        self.typing_context.variable_exist(var)
    }

    pub fn get_type_from_variable(&self, var: &Var) -> Result<Type, String> {
        let res = self
            .variables()
            .flat_map(|(var2, typ)| {
                let conditions = (var.name == var2.name)
                    && (var.is_opaque == var2.is_opaque)
                    && var.related_type.is_subtype(&var2.related_type, self).0;
                if conditions {
                    Some(typ.clone())
                } else {
                    None
                }
            })
            .reduce(|acc, x| if x.is_subtype(&acc, self).0 { x } else { acc });
        match res {
            Some(typ) => Ok(typ),
            _ => Err(format!(
                "Didn't find {} in the context: {}",
                var.get_name(),
                self.display_typing_context()
            )),
        }
    }

    pub fn get_types_from_name(&self, name: &str) -> Vec<Type> {
        self.variables()
            .filter(|(var, _)| var.get_name() == name)
            .map(|(_, typ)| typ.clone())
            .collect()
    }

    pub fn get_type_from_aliases(&self, var: &Var) -> Option<Type> {
        self.aliases()
            .flat_map(|(var2, type_)| {
                let conditions = (var.name == var2.name)
                    && (var.is_opaque == var2.is_opaque)
                    && var.related_type.is_subtype(&var2.related_type, self).0;
                if conditions {
                    Some(type_.clone())
                } else {
                    None
                }
            })
            .next()
    }

    fn is_matching_alias(&self, var1: &Var, var2: &Var) -> bool {
        var1.name == var2.name
    }

    pub fn get_matching_alias_signature(&self, var: &Var) -> Option<(Type, Vec<Type>)> {
        self.aliases()
            .find(|(var2, _)| self.is_matching_alias(var, var2))
            .map(|(var2, target_type)| {
                if var2.is_opaque() {
                    (var2.clone().to_alias_type(), vec![])
                } else if let Type::Params(types, _) = var2.get_type() {
                    (target_type.clone(), types.clone())
                } else {
                    panic!("The related type is not Params([...])");
                }
            })
    }

    pub fn variables(&self) -> Rev<std::vec::IntoIter<&(Var, Type)>> {
        self.typing_context.variables()
    }

    pub fn aliases(&self) -> Rev<std::vec::IntoIter<&(Var, Type)>> {
        self.typing_context.aliases()
    }

    /// Generate a fresh rigid generic variable name (immutable builder pattern).
    pub fn fresh_rigid_name(self) -> (String, Self) {
        let name = format!("__rigid_{}", self.rigid_counter);
        (
            name,
            Self {
                rigid_counter: self.rigid_counter + 1,
                ..self
            },
        )
    }

    /// Register a constraint: rigid variable → interface type.
    pub fn add_interface_constraint(mut self, rigid_name: String, interface: Type) -> Context {
        self.interface_constraints.insert(rigid_name, interface);
        self
    }

    /// Look up the interface constraint for a rigid variable.
    pub fn get_interface_constraint(&self, name: &str) -> Option<&Type> {
        self.interface_constraints.get(name)
    }

    /// Check if a name is a constrained rigid variable.
    pub fn is_rigid_constrained(&self, name: &str) -> bool {
        self.interface_constraints.contains_key(name)
    }

    pub fn push_var_type(self, lang: Var, typ: Type, context: &Context) -> Context {
        let reduced_type = typ.reduce(context);
        let types = reduced_type.extract_types();
        let var_type = self
            .typing_context
            .clone()
            .pipe(|vt| {
                if reduced_type.is_interface() && lang.is_variable() {
                    vt.clone()
                        .push_interface(lang.clone(), reduced_type, typ.clone(), context)
                } else {
                    vt.push_var_type(&[(lang.clone(), typ.clone())])
                }
            })
            .push_types(&types);
        let new_subtypes = self.subtypes.add_types(&types, context);
        Context {
            typing_context: var_type,
            subtypes: new_subtypes,
            ..self
        }
    }

    pub fn replace_or_push_var_type(self, lang: Var, typ: Type, context: &Context) -> Context {
        let types = typ.reduce(context).extract_types();
        let var_type = self
            .typing_context
            .clone()
            .replace_or_push_var_type(&[(lang.clone(), typ.clone())])
            .push_types(&types);
        let new_subtypes = self.subtypes.add_types(&types, context);
        Context {
            typing_context: var_type,
            subtypes: new_subtypes,
            ..self
        }
    }

    // Remove variables from the context
    // For removing added variables for evaluating a function's body
    pub fn remove_vars(self, vars: &[Var]) -> Context {
        Context {
            typing_context: self.typing_context.remove_vars(vars),
            ..self
        }
    }

    pub fn push_types(self, types: &[Type]) -> Self {
        Self {
            typing_context: self.typing_context.push_types(types),
            ..self
        }
    }

    pub fn get_type_from_existing_variable(&self, var: Var) -> Type {
        if let Type::UnknownFunction(_) = var.get_type() {
            var.get_type()
        } else {
            self.typing_context
                .variables()
                .find(|(v, _)| var.match_with(v, self))
                .map(|(_, ty)| ty)
                // Return Any type instead of panicking if variable not found
                .unwrap_or(&Type::Any(var.get_help_data()))
                .clone()
        }
    }

    pub fn get_true_variable(&self, var: &Var) -> Var {
        let res = self
            .typing_context
            .variables()
            .find(|(v, _)| var.match_with(v, self))
            .map(|(v, _)| v);
        match res {
            Some(vari) => vari.clone(),
            _ => {
                // Return the variable with UnknownFunction type if it's a standard function
                // Otherwise return with Any type to allow error collection
                if self.is_an_untyped_function(&var.get_name()) {
                    var.clone()
                        .set_type(Type::UnknownFunction(var.get_help_data()))
                } else {
                    var.clone().set_type(Type::Any(var.get_help_data()))
                }
            }
        }
    }

    fn is_a_standard_function(&self, name: &str) -> bool {
        !self.typing_context.name_exists_outside_of_std(name)
    }

    pub fn is_an_untyped_function(&self, name: &str) -> bool {
        self.is_a_standard_function(name)
    }

    pub fn get_class(&self, t: &Type) -> String {
        // For a named alias whose underlying type is a record, return the alias name directly.
        // push_types may have also registered the same record with an auto-generated "Record0"
        // name; searching aliases by type value would find that first (insertion-order) and
        // return the wrong name.
        if let Type::Alias(name, _, false, _) = t {
            if let Some((_, underlying)) = self.aliases().find(|(v, _)| v.get_name() == *name) {
                if matches!(underlying, Type::Record(_, _)) {
                    return "'".to_string() + name + "'";
                }
            }
        }
        let reduced = t.reduce(self);
        if matches!(reduced, Type::Any(_)) {
            if let Type::Alias(name, _, _, _) = t {
                return "'".to_string() + name + "'";
            }
        }
        self.typing_context.get_class(&reduced)
    }

    pub fn get_class_unquoted(&self, t: &Type) -> String {
        // Same rationale as get_class: bypass the record-type alias search for named aliases.
        if let Type::Alias(name, _, false, _) = t {
            if let Some((_, underlying)) = self.aliases().find(|(v, _)| v.get_name() == *name) {
                if matches!(underlying, Type::Record(_, _)) {
                    return name.clone();
                }
            }
        }
        let reduced = t.reduce(self);
        if matches!(reduced, Type::Any(_)) {
            if let Type::Alias(name, _, _, _) = t {
                return name.clone();
            }
        }
        self.typing_context.get_class_unquoted(&reduced)
    }

    pub fn module_aliases(&self) -> Vec<(Var, Type)> {
        self.variables()
            .flat_map(|(_, typ)| typ.clone().to_module_type())
            .flat_map(|module| module.get_aliases())
            .collect()
    }

    pub fn get_type_anotations(&self) -> String {
        self.aliases()
            .chain(
                [
                    (Var::from_name("Integer"), builder::integer_type_default()),
                    (
                        Var::from_name("Character"),
                        builder::character_type_default(),
                    ),
                    (Var::from_name("Number"), builder::number_type()),
                    (Var::from_name("Boolean"), builder::boolean_type()),
                ]
                .iter(),
            )
            .cloned()
            .chain(self.module_aliases())
            .filter(|(_, typ)| typ.clone().to_module_type().is_err())
            // Records that have a user-given alias are excluded: their `as.X` cast
            // is emitted by the inline constructor/validator pipeline. Anonymous
            // records (auto-named `Record0`, `Record1`, …) have no constructor, so
            // they still need their `as.RecordN` annotation generated here.
            .filter(|(var, typ)| {
                !matches!(typ, Type::Record(_, _)) || is_anonymous_record_name(&var.get_name())
            })
            // Aliases whose underlying type still mentions an unresolved generic
            // (e.g. `type Animator<%T> <- %T & list { ... }`) have no single
            // fixed runtime class — there's no monomorphization, so a static
            // `as.Animator` cast can't be generated. Without this, get_class
            // panics trying to render `%T` as an R class name.
            .filter(|(_, typ)| !typ.has_generic())
            .map(|(var, typ)| (typ, var.get_name()))
            .map(|(typ, name)| {
                let name0 = if ["Integer", "Character", "Boolean", "Number"]
                    .iter()
                    .any(|x| name == *x)
                {
                    format!("'{}', ", name)
                } else {
                    Default::default()
                };
                let class_str = self.get_class(&typ);
                let prefix = if name0.is_empty() && class_str != format!("'{}'", name) {
                    format!("'{}', ", name)
                } else {
                    name0
                };
                format!(
                    "as.{} <- function(x) x |> struct(c({}{}, {}))",
                    name,
                    prefix,
                    class_str,
                    self.get_classes(&typ).unwrap()
                )
            })
            .collect::<Vec<_>>()
            .join("\n")
    }

    pub fn get_type_anotation(&self, t: &Type) -> String {
        self.typing_context.get_type_anotation(t)
    }

    pub fn get_type_anotation_no_parentheses(&self, t: &Type) -> String {
        self.typing_context.get_type_anotation_no_parentheses(t)
    }

    pub fn get_classes(&self, t: &Type) -> Option<String> {
        let res = self
            .subtypes
            .get_supertypes(t, self)
            .iter()
            .filter(|typ| (*typ).clone().to_module_type().is_err())
            .filter(|typ| !typ.is_empty())
            // A supertype that still mentions an unresolved generic (e.g. a
            // record-kinded `%T` picked up structurally from a generic alias
            // like `Animator<%T> <- %T & list {...}`) has no R class name —
            // it's a compile-time-only constraint, never render it.
            .filter(|typ| !typ.has_generic())
            .map(|typ| self.get_class(typ))
            .collect::<Vec<_>>()
            .join(", ");
        if res.is_empty() {
            Some("'None'".to_string())
        } else {
            Some(res)
        }
    }

    pub fn get_functions(&self, var1: Var) -> Vec<(Var, Type)> {
        self.typing_context
            .variables()
            .filter(|(var2, typ)| {
                let reduced_type1 = var1.get_type().reduce(self);
                let reduced_type2 = var2.get_type().reduce(self);
                var1.get_name() == var2.get_name()
                    && typ.is_function()
                    && reduced_type1.is_subtype(&reduced_type2, self).0
            })
            .cloned()
            .collect()
    }

    pub fn get_all_generic_functions(&self) -> Vec<(Var, Type)> {
        let res = self
            .typing_context
            .variables()
            .filter(|(_, typ)| typ.is_function())
            .filter(|(var, _)| not_in_blacklist(&var.get_name()))
            .filter(|(var, _)| !var.get_type().is_any())
            .collect::<HashSet<_>>();
        res.iter()
            .map(|(var, typ)| (var.clone().add_backticks_if_percent(), typ.clone()))
            .collect()
    }

    pub fn get_first_matching_function(&self, var1: Var) -> Type {
        let res = self.typing_context.variables().find(|(var2, typ)| {
            let reduced_type1 = var1.get_type().reduce(self);
            let reduced_type2 = var2.get_type().reduce(self);
            var1.get_name() == var2.get_name()
                && typ.is_function()
                && (reduced_type1.is_subtype(&reduced_type2, self).0
                    || reduced_type1.is_upperrank_of(&reduced_type2))
        });
        if let Some(res) = res {
            res.1.clone()
        } else {
            self.typing_context
                .standard_library()
                .iter()
                .find(|(var2, _)| var2.get_name() == var1.get_name())
                .unwrap_or_else(|| {
                    panic!(
                        "Can't find var {} in the context:\n {}",
                        var1,
                        self.display_typing_context()
                    )
                })
                .1
                .clone()
        }
    }

    pub fn get_matching_typed_functions(&self, var1: Var) -> Vec<Type> {
        self.typing_context
            .variables()
            .filter(|(var2, typ)| {
                let reduced_type1 = var1.get_type().reduce(self);
                let reduced_type2 = var2.get_type().reduce(self);
                var1.get_name() == var2.get_name()
                    && typ.is_function()
                    && (reduced_type1.is_subtype(&reduced_type2, self).0
                        || reduced_type1.is_upperrank_of(&reduced_type2))
            })
            .map(|(_, typ)| typ.clone())
            .collect::<Vec<_>>()
    }

    pub fn get_matching_untyped_functions(&self, var: Var) -> Result<Vec<Type>, String> {
        let name1 = var.get_name();
        let std_lib = self.typing_context.standard_library();
        let res = std_lib
            .iter()
            .find(|(var2, _)| var2.get_name() == name1)
            .map(|(_, typ)| typ);
        match res {
            Some(val) => Ok(vec![val.clone()]),
            _ => Err(format!(
                "Can't find var {} in the context:\n {}",
                var,
                self.display_typing_context()
            )),
        }
    }

    pub fn get_matching_functions(&self, var: Var) -> Result<Vec<Type>, String> {
        let res = self.get_matching_typed_functions(var.clone());
        if res.is_empty() {
            self.get_matching_untyped_functions(var)
        } else {
            Ok(res)
        }
    }

    pub fn get_type_from_class(&self, class: &str) -> Type {
        self.typing_context.get_type_from_class(class)
    }

    pub fn add_arg_types(&self, params: &[ArgumentType]) -> Context {
        let param_types = params
            .iter()
            .map(|arg_typ| reduce_type(self, &arg_typ.get_type()).for_var())
            .map(|typ| match typ.to_owned() {
                Type::Function(typs, _, _) => {
                    if !typs.is_empty() {
                        typs[0].get_type()
                    } else {
                        typ
                    }
                }
                t => t,
            })
            .collect::<Vec<_>>();
        params
            .iter()
            .zip(param_types.clone())
            .map(|(arg_typ, par_typ): (&ArgumentType, Type)| {
                (
                    Var::from_name(&arg_typ.get_argument_str())
                        .set_type(reduce_type(self, &par_typ)),
                    reduce_type(self, &arg_typ.get_type()),
                )
            })
            .fold(self.clone(), |cont: Context, (var, typ): (Var, Type)| {
                cont.clone().push_var_type(var, typ, &cont)
            })
    }

    pub fn set_environment(&self, e: Environment) -> Context {
        Context {
            config: self.config.set_environment(e),
            ..self.clone()
        }
    }

    pub fn display_typing_context(&self) -> String {
        let res = self
            .variables()
            .chain(self.aliases())
            .map(|(var, typ)| format!("{} ==> {}", var, typ))
            .collect::<Vec<_>>()
            .join("\n");
        format!("CONTEXT:\n{}", res)
    }

    pub fn error(&self, msg: String) -> String {
        format!("{}{}", msg, self.display_typing_context())
    }

    pub fn push_alias(self, alias_name: String, typ: Type) -> Self {
        Context {
            typing_context: self.typing_context.push_alias(alias_name, typ),
            ..self
        }
    }

    /// Register a user-declared `typeconstructor` in the registry.
    pub fn push_type_constructor(
        self,
        name: String,
        parameters: Vec<Type>,
        category: ConstructorCategory,
    ) -> Self {
        let mut type_constructors = self.type_constructors.clone();
        // Last declaration wins: drop any previous entry with the same name.
        type_constructors.retain(|(n, _, _)| n != &name);
        type_constructors.push((name, parameters, category));
        Context {
            type_constructors,
            ..self
        }
    }

    /// Look up a declared `typeconstructor` by name.
    pub fn get_type_constructor(
        &self,
        name: &str,
    ) -> Option<&(String, Vec<Type>, ConstructorCategory)> {
        self.type_constructors.iter().find(|(n, _, _)| n == name)
    }

    /// Register a `type X <- list { ... }` record alias in the whole-program
    /// registry, regardless of the current module scope. No-op for non-record
    /// aliases. Last declaration for a given name wins.
    pub fn push_record_alias(self, name: String, typ: Type) -> Self {
        if !matches!(typ, Type::Record(_, _)) {
            return self;
        }
        let mut record_aliases = self.record_aliases.clone();
        record_aliases.retain(|(n, _)| n != &name);
        record_aliases.push((name, typ));
        Context {
            record_aliases,
            ..self
        }
    }

    /// Merge another context's whole-program record-alias registry into this
    /// one. Used at module boundaries, where the rest of the inner typing
    /// context is intentionally discarded for encapsulation but this registry
    /// must still bubble up (see `Lang::Module` in `processes::type_checking`).
    pub fn merge_record_aliases(self, other: &Context) -> Self {
        let mut record_aliases = self.record_aliases.clone();
        for (name, typ) in &other.record_aliases {
            if !record_aliases.iter().any(|(n, _)| n == name) {
                record_aliases.push((name.clone(), typ.clone()));
            }
        }
        Context {
            record_aliases,
            ..self
        }
    }

    /// Record that `method_name` on `type_name` was auto-generated by named type
    /// embedding (`embed field: Type`), forwarded from `field_name`. See
    /// `processes::type_checking::embedding`.
    pub fn push_embedded_method(
        self,
        type_name: String,
        method_name: String,
        field_name: String,
    ) -> Self {
        let mut embedded_methods = self.embedded_methods.clone();
        embedded_methods.push((type_name, method_name, field_name));
        Context {
            embedded_methods,
            ..self
        }
    }

    /// If `method_name` on `type_name` was inherited via named type embedding,
    /// return the source field name it was forwarded from.
    pub fn get_embedded_method(&self, type_name: &str, method_name: &str) -> Option<String> {
        self.embedded_methods
            .iter()
            .find(|(t, m, _)| t == type_name && m == method_name)
            .map(|(_, _, field)| field.clone())
    }

    pub fn push_alias2(self, alias_var: Var, typ: Type) -> Self {
        Context {
            typing_context: self.typing_context.push_alias2(alias_var, typ),
            ..self
        }
    }

    pub fn in_a_project(&self) -> bool {
        self.config.environment == Environment::Project
    }

    pub fn get_unification_map(
        &self,
        entered_types: &[Type],
        param_types: &[Type],
    ) -> Option<UnificationMap> {
        let res = entered_types
            .iter()
            .zip(param_types.iter())
            .map(|(val_typ, par_typ)| match_types_to_generic(self, &val_typ.clone(), par_typ))
            .collect::<Option<Vec<_>>>();

        let val = res
            .map(|vec| vec.iter().flatten().cloned().collect::<Vec<_>>())
            .map(UnificationMap::new);

        val
    }

    fn s3_type_definition(&self, var: &Var, typ: &Type) -> String {
        let first_part = format!("{} <- function(x) x |> ", var.get_name());
        match typ {
            Type::RClass(v, _) => format!(
                "{} struct(c({}))",
                first_part,
                v.iter().cloned().collect::<Vec<_>>().join(", ")
            ),
            _ => {
                let class = if typ.is_primitive() {
                    format!("'{}'", var.get_name())
                } else {
                    self.get_class(typ)
                };
                format!("{} struct(c({}))", first_part, class)
            }
        }
    }

    fn get_primitive_type_definition(&self) -> Vec<String> {
        let primitives = [
            ("Integer", builder::integer_type_default()),
            ("Character", builder::character_type_default()),
            ("Number", builder::number_type()),
            ("Boolean", builder::boolean_type()),
        ];
        let new_context = self.clone().push_types(
            &primitives
                .iter()
                .map(|(_, typ)| typ)
                .cloned()
                .collect::<Vec<_>>(),
        );
        primitives
            .iter()
            .map(|(name, prim)| {
                (
                    name,
                    new_context.get_classes(prim).unwrap(),
                    new_context.get_class(prim),
                )
            })
            .map(|(name, cls, cl)| {
                format!("{} <- function(x) x |> struct(c({}, {}))", name, cls, cl)
            })
            .collect::<Vec<_>>()
    }

    pub fn get_related_functions(&self, typ: &Type, functions: &VarFunction) -> Vec<Lang> {
        let names = self.typing_context.get_related_functions(typ);
        functions.get_bodies(&names)
    }

    pub fn get_functions_from_type(&self, typ: &Type) -> Vec<(Var, Type)> {
        self.variables()
            .filter(|&(var, typ2)| typ2.is_function() && var.get_type() == *typ)
            .cloned()
            .collect()
    }

    pub fn get_functions_from_name(&self, name: &str) -> Vec<(Var, Type)> {
        self.variables()
            .filter(|&(var, typ2)| typ2.is_function() && var.get_name() == name)
            .cloned()
            .collect()
    }

    pub fn get_type_definition(&self, _functions: &VarFunction) -> String {
        match self.get_target_language() {
            TargetLanguage::R => self
                .typing_context
                .aliases
                .iter()
                .map(|(var, typ)| self.s3_type_definition(var, typ))
                .chain(self.get_primitive_type_definition().iter().cloned())
                .collect::<Vec<_>>()
                .join("\n"),
            TargetLanguage::JS => {
                todo!();
            }
        }
    }

    pub fn update_variable(self, var: Var) -> Self {
        Self {
            typing_context: self.typing_context.update_variable(var),
            ..self
        }
    }

    pub fn set_target_language(self, language: TargetLanguage) -> Self {
        Self {
            config: self.config.set_target_language(language),
            typing_context: self.typing_context.source(language),
            ..self
        }
    }

    pub fn set_default_var_types(self) -> Self {
        Self {
            typing_context: self.typing_context.set_default_var_types(),
            ..self
        }
    }

    pub fn get_target_language(&self) -> TargetLanguage {
        self.config.get_target_language()
    }

    pub fn set_new_aliase_signature(self, alias: &str, related_type: Type) -> Self {
        let alias = Var::from_type(alias.parse::<Type>().unwrap()).unwrap();
        self.clone().push_alias2(alias, related_type)
    }

    pub fn extract_module_as_vartype(&self, module_name: &str) -> Self {
        let typ = self
            .get_type_from_variable(&Var::from_name(module_name))
            .expect("The module name was not found");
        let empty_context = Context::default();
        let new_context = match typ.clone() {
            Type::Module(args, _) => {
                args.iter()
                    .rev()
                    .map(|arg_type| {
                        (
                            Var::try_from(arg_type.0.clone()).unwrap(),
                            arg_type.1.clone(),
                        )
                    }) //TODO: Differenciate between pushing variable and
                    //aliases
                    .fold(empty_context.clone(), |acc, (var, typ)| {
                        acc.clone().push_var_type(var, typ, &acc)
                    })
            }
            _ => panic!("{} is not a module", module_name),
        };
        new_context
            .clone()
            .push_var_type(Var::from_name(module_name), typ, &new_context)
    }

    pub fn get_vartype(&self) -> VarType {
        self.clone().typing_context
    }

    pub fn get_environment(&self) -> Environment {
        self.config.environment
    }
    pub fn extend_typing_context(self, var_types: VarType) -> Self {
        Self {
            typing_context: self.typing_context + var_types,
            ..self
        }
    }
}

impl Add for Context {
    type Output = Self;

    fn add(self, other: Self) -> Self::Output {
        let mut type_constructors = self.type_constructors;
        for (name, params, cat) in other.type_constructors {
            type_constructors.retain(|(n, _, _)| n != &name);
            type_constructors.push((name, params, cat));
        }
        let mut interface_constraints = self.interface_constraints;
        interface_constraints.extend(other.interface_constraints);
        let rigid_counter = self.rigid_counter.max(other.rigid_counter);
        let mut test_preamble = self.test_preamble;
        test_preamble.extend(other.test_preamble);
        let mut record_aliases = self.record_aliases;
        for entry in other.record_aliases {
            if !record_aliases.contains(&entry) {
                record_aliases.push(entry);
            }
        }
        let mut embedded_methods = self.embedded_methods;
        for entry in other.embedded_methods {
            if !embedded_methods.contains(&entry) {
                embedded_methods.push(entry);
            }
        }
        Context {
            typing_context: self.typing_context + other.typing_context,
            subtypes: self.subtypes + other.subtypes,
            type_constructors,
            interface_constraints,
            rigid_counter,
            record_aliases,
            embedded_methods,
            test_preamble,
            self_type: None,
            config: self.config,
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_default_context1() {
        let context = Context::default();
        assert!(!context.display_typing_context().is_empty());
    }

    #[test]
    fn test_record_nests_under_grecord_sentinel() {
        let ctx = Context::default();
        let rec = builder::record_type(&[("x".to_string(), builder::integer_type_default())]);
        let graph = ctx.subtypes.clone().add_type(rec.clone(), &ctx);
        let supers = graph.get_supertypes(&rec, &ctx);
        assert!(
            supers
                .iter()
                .any(|t| matches!(t, Type::KindedGen(Kind::Record, _, _))),
            "a record must nest under the GRecord (%_) sentinel; supers = {:?}",
            supers
        );
        assert!(
            supers.iter().any(|t| matches!(t, Type::Generic(_, _))),
            "GRecord must itself sit under the bare Generic sentinel; supers = {:?}",
            supers
        );
    }

    #[test]
    fn test_generic_sentinels_absent_from_r_classes() {
        let ctx = Context::default();
        let rec = builder::record_type(&[("x".to_string(), builder::integer_type_default())]);
        let graph = ctx.subtypes.clone().add_type(rec.clone(), &ctx);
        let ctx = ctx.with_subtypes(graph);
        let classes = ctx.get_classes(&rec).unwrap();
        assert!(
            !classes.contains("GRecord") && !classes.contains('%') && !classes.contains("Generic"),
            "generic sentinels must be filtered out of generated R classes, got: {}",
            classes
        );
    }
}