tsz_solver/intern/

mod.rs

//! Type interning for structural deduplication.
//!
//! This module implements the type interning engine that converts
//! `TypeData` structures into lightweight `TypeId` handles.
//!
//! Benefits:
//! - O(1) type equality (just compare `TypeId` values)
//! - Memory efficient (each unique structure stored once)
//! - Cache-friendly (work with u32 arrays instead of heap objects)
//!
//! # Concurrency Strategy
//!
//! The `TypeInterner` uses a sharded DashMap-based architecture for lock-free
//! concurrent access:
//!
//! - **Sharded Type Storage**: 64 shards based on hash of `TypeData` to minimize contention
//! - **`DashMap` for Interning**: Each shard uses `DashMap` for lock-free read/write operations
//! - **Arc for Immutability**: Type data is stored in Arc<T> for cheap cloning
//! - **No `RwLock`<Vec<T>>**: Avoids the read-then-write deadlock pattern
//!
//! This design allows true parallel type checking without lock contention.

use crate::def::DefId;
#[cfg(test)]
use crate::types::*;
use crate::types::{
    CallSignature, CallableShape, CallableShapeId, ConditionalType, ConditionalTypeId,
    FunctionShape, FunctionShapeId, IndexSignature, IntrinsicKind, LiteralValue, MappedType,
    MappedTypeId, ObjectFlags, ObjectShape, ObjectShapeId, OrderedFloat, PropertyInfo,
    PropertyLookup, SymbolRef, TemplateLiteralId, TemplateSpan, TupleElement, TupleListId,
    TypeApplication, TypeApplicationId, TypeData, TypeId, TypeListId, TypeParamInfo, Visibility,
};
use crate::visitor::is_identity_comparable_type;
use dashmap::DashMap;
use dashmap::mapref::entry::Entry;
use rustc_hash::{FxBuildHasher, FxHashMap, FxHashSet, FxHasher};
use smallvec::SmallVec;
use std::hash::{Hash, Hasher};
use std::sync::{
    Arc, OnceLock,
    atomic::{AtomicU32, Ordering},
};
use tsz_common::interner::{Atom, ShardedInterner};

mod intersection;
mod normalize;
mod template;

const SHARD_BITS: u32 = 6;
const SHARD_COUNT: usize = 1 << SHARD_BITS; // 64 shards
const SHARD_MASK: u32 = (SHARD_COUNT as u32) - 1;
pub(crate) const PROPERTY_MAP_THRESHOLD: usize = 24;
const TYPE_LIST_INLINE: usize = 8;

/// Maximum template literal expansion limit.
/// WASM environments have limited linear memory, so we use a much lower limit
/// to prevent OOM. Native CLI can handle more.
#[cfg(target_arch = "wasm32")]
pub(crate) const TEMPLATE_LITERAL_EXPANSION_LIMIT: usize = 2_000;
#[cfg(not(target_arch = "wasm32"))]
pub(crate) const TEMPLATE_LITERAL_EXPANSION_LIMIT: usize = 100_000;

/// Maximum number of interned types before aborting.
/// WASM linear memory cannot grow indefinitely, so we cap at 500k types.
#[cfg(target_arch = "wasm32")]
pub(crate) const MAX_INTERNED_TYPES: usize = 500_000;
#[cfg(not(target_arch = "wasm32"))]
pub(crate) const MAX_INTERNED_TYPES: usize = 5_000_000;

pub(crate) type TypeListBuffer = SmallVec<[TypeId; TYPE_LIST_INLINE]>;
type ObjectPropertyIndex = DashMap<ObjectShapeId, Arc<FxHashMap<Atom, usize>>, FxBuildHasher>;
type ObjectPropertyMap = OnceLock<ObjectPropertyIndex>;

/// Inner data for a `TypeShard`, lazily initialized.
struct TypeShardInner {
    /// Map from `TypeData` to local index within this shard
    key_to_index: DashMap<TypeData, u32, FxBuildHasher>,
    /// Map from local index to `TypeData` (using Arc for shared access)
    index_to_key: DashMap<u32, Arc<TypeData>, FxBuildHasher>,
}

/// A single shard of the type interned storage.
///
/// Uses `OnceLock` for lazy initialization - `DashMaps` are only allocated
/// when the shard is first accessed, reducing startup overhead.
struct TypeShard {
    /// Lazily initialized inner maps
    inner: OnceLock<TypeShardInner>,
    /// Atomic counter for allocating new indices in this shard
    /// Kept outside `OnceLock` for fast checks without initialization
    next_index: AtomicU32,
}

impl TypeShard {
    const fn new() -> Self {
        Self {
            inner: OnceLock::new(),
            next_index: AtomicU32::new(0),
        }
    }

    /// Get the inner maps, initializing on first access
    #[inline]
    fn get_inner(&self) -> &TypeShardInner {
        self.inner.get_or_init(|| TypeShardInner {
            key_to_index: DashMap::with_hasher(FxBuildHasher),
            index_to_key: DashMap::with_hasher(FxBuildHasher),
        })
    }

    /// Check if a key exists without initializing the shard
    #[inline]
    fn is_empty(&self) -> bool {
        self.next_index.load(Ordering::Relaxed) == 0
    }
}

/// Inner data for `ConcurrentSliceInterner`, lazily initialized.
struct SliceInternerInner<T> {
    items: DashMap<u32, Arc<[T]>, FxBuildHasher>,
    map: DashMap<Arc<[T]>, u32, FxBuildHasher>,
}

/// Lock-free slice interner using `DashMap` for concurrent access.
/// Uses lazy initialization to defer `DashMap` allocation until first use.
struct ConcurrentSliceInterner<T> {
    inner: OnceLock<SliceInternerInner<T>>,
    next_id: AtomicU32,
}

impl<T> ConcurrentSliceInterner<T>
where
    T: Eq + Hash + Clone + Send + Sync + 'static,
{
    const fn new() -> Self {
        Self {
            inner: OnceLock::new(),
            next_id: AtomicU32::new(1), // Reserve 0 for empty
        }
    }

    #[inline]
    fn get_inner(&self) -> &SliceInternerInner<T> {
        self.inner.get_or_init(|| {
            let items = DashMap::with_hasher(FxBuildHasher);
            let map = DashMap::with_hasher(FxBuildHasher);
            let empty: Arc<[T]> = Arc::from(Vec::new());
            items.insert(0, std::sync::Arc::clone(&empty));
            map.insert(empty, 0);
            SliceInternerInner { items, map }
        })
    }

    fn intern(&self, items_slice: &[T]) -> u32 {
        if items_slice.is_empty() {
            return 0;
        }

        let inner = self.get_inner();
        let temp_arc: Arc<[T]> = Arc::from(items_slice.to_vec());

        // Try to get existing ID via reverse map — O(1)
        if let Some(ref_entry) = inner.map.get(&temp_arc) {
            return *ref_entry.value();
        }

        // Allocate new ID
        let id = self.next_id.fetch_add(1, Ordering::Relaxed);

        // Double-check: another thread might have inserted while we allocated
        match inner.map.entry(std::sync::Arc::clone(&temp_arc)) {
            dashmap::mapref::entry::Entry::Vacant(e) => {
                e.insert(id);
                inner.items.insert(id, temp_arc);
                id
            }
            dashmap::mapref::entry::Entry::Occupied(e) => *e.get(),
        }
    }

    fn get(&self, id: u32) -> Option<Arc<[T]>> {
        // For id 0 (empty), we can return without initializing
        if id == 0 {
            return Some(Arc::from(Vec::new()));
        }
        self.inner
            .get()?
            .items
            .get(&id)
            .map(|e| std::sync::Arc::clone(e.value()))
    }

    fn empty(&self) -> Arc<[T]> {
        Arc::from(Vec::new())
    }
}

/// Inner data for `ConcurrentValueInterner`, lazily initialized.
struct ValueInternerInner<T> {
    items: DashMap<u32, Arc<T>, FxBuildHasher>,
    map: DashMap<Arc<T>, u32, FxBuildHasher>,
}

/// Lock-free value interner using `DashMap` for concurrent access.
/// Uses lazy initialization to defer `DashMap` allocation until first use.
struct ConcurrentValueInterner<T> {
    inner: OnceLock<ValueInternerInner<T>>,
    next_id: AtomicU32,
}

impl<T> ConcurrentValueInterner<T>
where
    T: Eq + Hash + Clone + Send + Sync + 'static,
{
    const fn new() -> Self {
        Self {
            inner: OnceLock::new(),
            next_id: AtomicU32::new(0),
        }
    }

    #[inline]
    fn get_inner(&self) -> &ValueInternerInner<T> {
        self.inner.get_or_init(|| ValueInternerInner {
            items: DashMap::with_hasher(FxBuildHasher),
            map: DashMap::with_hasher(FxBuildHasher),
        })
    }

    fn intern(&self, value: T) -> u32 {
        let inner = self.get_inner();
        let value_arc = Arc::new(value);

        // Try to get existing ID
        if let Some(ref_entry) = inner.map.get(&value_arc) {
            return *ref_entry.value();
        }

        // Allocate new ID
        let id = self.next_id.fetch_add(1, Ordering::Relaxed);

        // Double-check: another thread might have inserted while we allocated
        match inner.map.entry(std::sync::Arc::clone(&value_arc)) {
            Entry::Vacant(e) => {
                e.insert(id);
                inner.items.insert(id, value_arc);
                id
            }
            Entry::Occupied(e) => *e.get(),
        }
    }

    fn get(&self, id: u32) -> Option<Arc<T>> {
        self.inner
            .get()?
            .items
            .get(&id)
            .map(|e| std::sync::Arc::clone(e.value()))
    }
}

/// Type interning table with lock-free concurrent access.
///
/// Uses sharded `DashMap` structures for all internal storage, enabling
/// true parallel type checking without lock contention.
///
/// All internal structures use lazy initialization via `OnceLock` to minimize
/// startup overhead - `DashMaps` are only allocated when first accessed.
pub struct TypeInterner {
    /// Sharded storage for user-defined types (lazily initialized)
    shards: Vec<TypeShard>,
    /// String interner for property names and string literals (already lock-free)
    pub string_interner: ShardedInterner,
    /// Concurrent interners for type components (lazily initialized)
    type_lists: ConcurrentSliceInterner<TypeId>,
    tuple_lists: ConcurrentSliceInterner<TupleElement>,
    template_lists: ConcurrentSliceInterner<TemplateSpan>,
    object_shapes: ConcurrentValueInterner<ObjectShape>,
    /// Object property maps: lazily initialized `DashMap`
    object_property_maps: ObjectPropertyMap,
    function_shapes: ConcurrentValueInterner<FunctionShape>,
    callable_shapes: ConcurrentValueInterner<CallableShape>,
    conditional_types: ConcurrentValueInterner<ConditionalType>,
    mapped_types: ConcurrentValueInterner<MappedType>,
    applications: ConcurrentValueInterner<TypeApplication>,
    /// Cache for `is_identity_comparable_type` checks (memoized O(1) lookup after first computation)
    identity_comparable_cache: DashMap<TypeId, bool, FxBuildHasher>,
    /// The global Array base type (e.g., Array<T> from lib.d.ts)
    array_base_type: OnceLock<TypeId>,
    /// Type parameters for the Array base type
    array_base_type_params: OnceLock<Vec<TypeParamInfo>>,
    /// Boxed interface types for primitives (e.g., String interface for `string`).
    /// Registered from lib.d.ts during primordial type setup.
    boxed_types: DashMap<IntrinsicKind, TypeId, FxBuildHasher>,
}

impl std::fmt::Debug for TypeInterner {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("TypeInterner")
            .field("shards", &self.shards.len())
            .finish_non_exhaustive()
    }
}

impl TypeInterner {
    /// Create a new type interner with pre-registered intrinsics.
    ///
    /// Uses lazy initialization for all `DashMap` structures to minimize
    /// startup overhead. `DashMaps` are only allocated when first accessed.
    pub fn new() -> Self {
        let shards: Vec<TypeShard> = (0..SHARD_COUNT).map(|_| TypeShard::new()).collect();

        Self {
            shards,
            // String interner - common strings are interned on-demand for faster startup
            string_interner: ShardedInterner::new(),
            type_lists: ConcurrentSliceInterner::new(),
            tuple_lists: ConcurrentSliceInterner::new(),
            template_lists: ConcurrentSliceInterner::new(),
            object_shapes: ConcurrentValueInterner::new(),
            object_property_maps: OnceLock::new(),
            function_shapes: ConcurrentValueInterner::new(),
            callable_shapes: ConcurrentValueInterner::new(),
            conditional_types: ConcurrentValueInterner::new(),
            mapped_types: ConcurrentValueInterner::new(),
            applications: ConcurrentValueInterner::new(),
            identity_comparable_cache: DashMap::with_hasher(FxBuildHasher),
            array_base_type: OnceLock::new(),
            array_base_type_params: OnceLock::new(),
            boxed_types: DashMap::with_hasher(FxBuildHasher),
        }
    }

    /// Set the global Array base type (e.g., Array<T> from lib.d.ts).
    ///
    /// This should be called once during primordial type setup when lib.d.ts is processed.
    /// Once set, the value cannot be changed (`OnceLock` enforces this).
    pub fn set_array_base_type(&self, type_id: TypeId, params: Vec<TypeParamInfo>) {
        let _ = self.array_base_type.set(type_id);
        let _ = self.array_base_type_params.set(params);
    }

    /// Get the global Array base type, if it has been set.
    #[inline]
    pub fn get_array_base_type(&self) -> Option<TypeId> {
        self.array_base_type.get().copied()
    }

    /// Get the type parameters for the global Array base type, if it has been set.
    #[inline]
    pub fn get_array_base_type_params(&self) -> &[TypeParamInfo] {
        self.array_base_type_params
            .get()
            .map_or(&[], |v| v.as_slice())
    }

    /// Set a boxed interface type for a primitive intrinsic kind.
    ///
    /// Called during primordial type setup when lib.d.ts is processed.
    /// For example, `set_boxed_type(IntrinsicKind::String, type_id_of_String_interface)`
    /// enables property access on `string` values to resolve through the String interface.
    pub fn set_boxed_type(&self, kind: IntrinsicKind, type_id: TypeId) {
        self.boxed_types.insert(kind, type_id);
    }

    /// Get the boxed interface type for a primitive intrinsic kind.
    #[inline]
    pub fn get_boxed_type(&self, kind: IntrinsicKind) -> Option<TypeId> {
        self.boxed_types.get(&kind).map(|r| *r)
    }

    /// Get the object property maps, initializing on first access
    #[inline]
    fn get_object_property_maps(&self) -> &ObjectPropertyIndex {
        self.object_property_maps
            .get_or_init(|| DashMap::with_hasher(FxBuildHasher))
    }

    /// Check if a type can be compared by `TypeId` identity alone (O(1) equality).
    /// Results are cached for O(1) lookup after first computation.
    /// This is used for optimization in BCT and subtype checking.
    #[inline]
    pub fn is_identity_comparable_type(&self, type_id: TypeId) -> bool {
        // Fast path: check cache first
        if let Some(cached) = self.identity_comparable_cache.get(&type_id) {
            return *cached;
        }
        // Compute and cache
        let result = is_identity_comparable_type(self, type_id);
        self.identity_comparable_cache.insert(type_id, result);
        result
    }

    /// Intern a string into an Atom.
    /// This is used when constructing types with property names or string literals.
    pub fn intern_string(&self, s: &str) -> Atom {
        self.string_interner.intern(s)
    }

    /// Resolve an Atom back to its string value.
    /// This is used when formatting types for error messages.
    pub fn resolve_atom(&self, atom: Atom) -> String {
        self.string_interner.resolve(atom).to_string()
    }

    /// Resolve an Atom without allocating a new String.
    pub fn resolve_atom_ref(&self, atom: Atom) -> Arc<str> {
        self.string_interner.resolve(atom)
    }

    pub fn type_list(&self, id: TypeListId) -> Arc<[TypeId]> {
        self.type_lists
            .get(id.0)
            .unwrap_or_else(|| self.type_lists.empty())
    }

    pub fn tuple_list(&self, id: TupleListId) -> Arc<[TupleElement]> {
        self.tuple_lists
            .get(id.0)
            .unwrap_or_else(|| self.tuple_lists.empty())
    }

    pub fn template_list(&self, id: TemplateLiteralId) -> Arc<[TemplateSpan]> {
        self.template_lists
            .get(id.0)
            .unwrap_or_else(|| self.template_lists.empty())
    }

    pub fn object_shape(&self, id: ObjectShapeId) -> Arc<ObjectShape> {
        self.object_shapes.get(id.0).unwrap_or_else(|| {
            Arc::new(ObjectShape {
                flags: ObjectFlags::empty(),
                properties: Vec::new(),
                string_index: None,
                number_index: None,
                symbol: None,
            })
        })
    }

    pub fn object_property_index(&self, shape_id: ObjectShapeId, name: Atom) -> PropertyLookup {
        let shape = self.object_shape(shape_id);
        if shape.properties.len() < PROPERTY_MAP_THRESHOLD {
            return PropertyLookup::Uncached;
        }

        match self.object_property_map(shape_id, &shape) {
            Some(map) => match map.get(&name) {
                Some(&idx) => PropertyLookup::Found(idx),
                None => PropertyLookup::NotFound,
            },
            None => PropertyLookup::Uncached,
        }
    }

    /// Get or create a property map for an object shape.
    ///
    /// This uses a lock-free pattern with `DashMap` to avoid the read-then-write
    /// deadlock that existed in the previous `RwLock`<Vec> implementation.
    fn object_property_map(
        &self,
        shape_id: ObjectShapeId,
        shape: &ObjectShape,
    ) -> Option<Arc<FxHashMap<Atom, usize>>> {
        if shape.properties.len() < PROPERTY_MAP_THRESHOLD {
            return None;
        }

        let maps = self.get_object_property_maps();

        // Try to get existing map (lock-free read)
        if let Some(map) = maps.get(&shape_id) {
            return Some(std::sync::Arc::clone(&map));
        }

        // Build the property map
        let mut map = FxHashMap::default();
        for (idx, prop) in shape.properties.iter().enumerate() {
            map.insert(prop.name, idx);
        }
        let map = Arc::new(map);

        // Try to insert - if another thread inserted first, use theirs
        match maps.entry(shape_id) {
            Entry::Vacant(e) => {
                e.insert(std::sync::Arc::clone(&map));
                Some(map)
            }
            Entry::Occupied(e) => Some(std::sync::Arc::clone(e.get())),
        }
    }

    pub fn function_shape(&self, id: FunctionShapeId) -> Arc<FunctionShape> {
        self.function_shapes.get(id.0).unwrap_or_else(|| {
            Arc::new(FunctionShape {
                type_params: Vec::new(),
                params: Vec::new(),
                this_type: None,
                return_type: TypeId::ERROR,
                type_predicate: None,
                is_constructor: false,
                is_method: false,
            })
        })
    }

    pub fn callable_shape(&self, id: CallableShapeId) -> Arc<CallableShape> {
        self.callable_shapes.get(id.0).unwrap_or_else(|| {
            Arc::new(CallableShape {
                call_signatures: Vec::new(),
                construct_signatures: Vec::new(),
                properties: Vec::new(),
                ..Default::default()
            })
        })
    }

    pub fn conditional_type(&self, id: ConditionalTypeId) -> Arc<ConditionalType> {
        self.conditional_types.get(id.0).unwrap_or_else(|| {
            Arc::new(ConditionalType {
                check_type: TypeId::ERROR,
                extends_type: TypeId::ERROR,
                true_type: TypeId::ERROR,
                false_type: TypeId::ERROR,
                is_distributive: false,
            })
        })
    }

    pub fn mapped_type(&self, id: MappedTypeId) -> Arc<MappedType> {
        self.mapped_types.get(id.0).unwrap_or_else(|| {
            Arc::new(MappedType {
                type_param: TypeParamInfo {
                    is_const: false,
                    name: self.intern_string("_"),
                    constraint: None,
                    default: None,
                },
                constraint: TypeId::ERROR,
                name_type: None,
                template: TypeId::ERROR,
                readonly_modifier: None,
                optional_modifier: None,
            })
        })
    }

    pub fn type_application(&self, id: TypeApplicationId) -> Arc<TypeApplication> {
        self.applications.get(id.0).unwrap_or_else(|| {
            Arc::new(TypeApplication {
                base: TypeId::ERROR,
                args: Vec::new(),
            })
        })
    }

    /// Intern a type key and return its `TypeId`.
    /// If the key already exists, returns the existing `TypeId`.
    /// Otherwise, creates a new `TypeId` and stores the key.
    ///
    /// This uses a lock-free pattern with `DashMap` for concurrent access.
    pub fn intern(&self, key: TypeData) -> TypeId {
        if let Some(id) = self.get_intrinsic_id(&key) {
            return id;
        }

        // Circuit breaker: prevent OOM by limiting total interned types
        // This is especially important for WASM where linear memory is limited.
        // We do a cheap approximate check (summing shard indices) to avoid
        // iterating all shards on every intern call.
        if self.approximate_count() > MAX_INTERNED_TYPES {
            return TypeId::ERROR;
        }

        let mut hasher = FxHasher::default();
        key.hash(&mut hasher);
        let shard_idx = (hasher.finish() as usize) & (SHARD_COUNT - 1);
        let shard = &self.shards[shard_idx];
        let inner = shard.get_inner();

        // Try to get existing ID (lock-free read)
        if let Some(entry) = inner.key_to_index.get(&key) {
            let local_index = *entry.value();
            return self.make_id(local_index, shard_idx as u32);
        }

        // Allocate new index
        let local_index = shard.next_index.fetch_add(1, Ordering::Relaxed);
        if local_index > (u32::MAX >> SHARD_BITS) {
            // Return error type instead of panicking
            return TypeId::ERROR;
        }

        // Double-check: another thread might have inserted while we allocated
        match inner.key_to_index.entry(key.clone()) {
            Entry::Vacant(e) => {
                e.insert(local_index);
                let key_arc = Arc::new(key);
                inner.index_to_key.insert(local_index, key_arc);
                self.make_id(local_index, shard_idx as u32)
            }
            Entry::Occupied(e) => {
                // Another thread inserted first, use their ID
                let existing_index = *e.get();
                self.make_id(existing_index, shard_idx as u32)
            }
        }
    }

    /// Look up the `TypeData` for a given `TypeId`.
    ///
    /// This uses lock-free `DashMap` access with lazy shard initialization.
    pub fn lookup(&self, id: TypeId) -> Option<TypeData> {
        if id.is_intrinsic() || id.is_error() {
            return self.get_intrinsic_key(id);
        }

        let raw_val = id.0.checked_sub(TypeId::FIRST_USER)?;
        let shard_idx = (raw_val & SHARD_MASK) as usize;
        let local_index = raw_val >> SHARD_BITS;

        let shard = self.shards.get(shard_idx)?;
        // If shard is empty, no types have been interned there yet
        if shard.is_empty() {
            return None;
        }
        shard
            .get_inner()
            .index_to_key
            .get(&{ local_index })
            .map(|r| r.value().as_ref().clone())
    }

    fn intern_type_list(&self, members: Vec<TypeId>) -> TypeListId {
        TypeListId(self.type_lists.intern(&members))
    }

    fn intern_tuple_list(&self, elements: Vec<TupleElement>) -> TupleListId {
        TupleListId(self.tuple_lists.intern(&elements))
    }

    pub(crate) fn intern_template_list(&self, spans: Vec<TemplateSpan>) -> TemplateLiteralId {
        TemplateLiteralId(self.template_lists.intern(&spans))
    }

    pub fn intern_object_shape(&self, shape: ObjectShape) -> ObjectShapeId {
        ObjectShapeId(self.object_shapes.intern(shape))
    }

    fn intern_function_shape(&self, shape: FunctionShape) -> FunctionShapeId {
        FunctionShapeId(self.function_shapes.intern(shape))
    }

    fn intern_callable_shape(&self, shape: CallableShape) -> CallableShapeId {
        CallableShapeId(self.callable_shapes.intern(shape))
    }

    fn intern_conditional_type(&self, conditional: ConditionalType) -> ConditionalTypeId {
        ConditionalTypeId(self.conditional_types.intern(conditional))
    }

    fn intern_mapped_type(&self, mapped: MappedType) -> MappedTypeId {
        MappedTypeId(self.mapped_types.intern(mapped))
    }

    fn intern_application(&self, application: TypeApplication) -> TypeApplicationId {
        TypeApplicationId(self.applications.intern(application))
    }

    /// Get the number of interned types (lock-free read)
    pub fn len(&self) -> usize {
        let mut total = TypeId::FIRST_USER as usize;
        for shard in &self.shards {
            total += shard.next_index.load(Ordering::Relaxed) as usize;
        }
        total
    }

    /// Check if the interner is empty (only has intrinsics)
    pub fn is_empty(&self) -> bool {
        self.len() <= TypeId::FIRST_USER as usize
    }

    /// Get an approximate count of interned types.
    /// This is cheaper than `len()` as it samples only a few shards.
    /// Used for the circuit breaker to avoid OOM.
    #[inline]
    fn approximate_count(&self) -> usize {
        // Sample first 4 shards and extrapolate (assumes uniform distribution)
        let mut sample_total: usize = 0;
        for shard in self.shards.iter().take(4) {
            sample_total += shard.next_index.load(Ordering::Relaxed) as usize;
        }
        // Extrapolate to all 64 shards
        (sample_total * SHARD_COUNT / 4) + TypeId::FIRST_USER as usize
    }

    #[inline]
    fn make_id(&self, local_index: u32, shard_idx: u32) -> TypeId {
        let raw_val = (local_index << SHARD_BITS) | (shard_idx & SHARD_MASK);
        let id = TypeId(TypeId::FIRST_USER + raw_val);

        // SAFETY: Assert that we're not overflowing into the local ID space (MSB=1).
        // Global TypeIds must have MSB=0 (0x7FFFFFFF-) to allow ScopedTypeInterner
        // to use the upper half (0x80000000+) for ephemeral types.
        debug_assert!(
            id.is_global(),
            "Global TypeId overflow: {id:?} - would conflict with local ID space"
        );

        id
    }

    const fn get_intrinsic_id(&self, key: &TypeData) -> Option<TypeId> {
        match key {
            TypeData::Intrinsic(kind) => Some(kind.to_type_id()),
            TypeData::Error => Some(TypeId::ERROR),
            // Map boolean literals to their intrinsic IDs to avoid duplicates
            TypeData::Literal(LiteralValue::Boolean(true)) => Some(TypeId::BOOLEAN_TRUE),
            TypeData::Literal(LiteralValue::Boolean(false)) => Some(TypeId::BOOLEAN_FALSE),
            _ => None,
        }
    }

    const fn get_intrinsic_key(&self, id: TypeId) -> Option<TypeData> {
        match id {
            TypeId::NONE | TypeId::ERROR => Some(TypeData::Error),
            TypeId::NEVER => Some(TypeData::Intrinsic(IntrinsicKind::Never)),
            TypeId::UNKNOWN => Some(TypeData::Intrinsic(IntrinsicKind::Unknown)),
            TypeId::ANY => Some(TypeData::Intrinsic(IntrinsicKind::Any)),
            TypeId::VOID => Some(TypeData::Intrinsic(IntrinsicKind::Void)),
            TypeId::UNDEFINED => Some(TypeData::Intrinsic(IntrinsicKind::Undefined)),
            TypeId::NULL => Some(TypeData::Intrinsic(IntrinsicKind::Null)),
            TypeId::BOOLEAN => Some(TypeData::Intrinsic(IntrinsicKind::Boolean)),
            TypeId::NUMBER => Some(TypeData::Intrinsic(IntrinsicKind::Number)),
            TypeId::STRING => Some(TypeData::Intrinsic(IntrinsicKind::String)),
            TypeId::BIGINT => Some(TypeData::Intrinsic(IntrinsicKind::Bigint)),
            TypeId::SYMBOL => Some(TypeData::Intrinsic(IntrinsicKind::Symbol)),
            TypeId::OBJECT | TypeId::PROMISE_BASE => {
                Some(TypeData::Intrinsic(IntrinsicKind::Object))
            }
            TypeId::BOOLEAN_TRUE => Some(TypeData::Literal(LiteralValue::Boolean(true))),
            TypeId::BOOLEAN_FALSE => Some(TypeData::Literal(LiteralValue::Boolean(false))),
            TypeId::FUNCTION => Some(TypeData::Intrinsic(IntrinsicKind::Function)),
            _ => None,
        }
    }

    // =========================================================================
    // Convenience methods for common type constructions
    // =========================================================================

    /// Intern an intrinsic type
    pub const fn intrinsic(&self, kind: IntrinsicKind) -> TypeId {
        kind.to_type_id()
    }

    /// Intern a literal string type
    pub fn literal_string(&self, value: &str) -> TypeId {
        let atom = self.intern_string(value);
        self.intern(TypeData::Literal(LiteralValue::String(atom)))
    }

    /// Intern a literal string type from an already-interned Atom
    pub fn literal_string_atom(&self, atom: Atom) -> TypeId {
        self.intern(TypeData::Literal(LiteralValue::String(atom)))
    }

    /// Intern a literal number type
    pub fn literal_number(&self, value: f64) -> TypeId {
        self.intern(TypeData::Literal(LiteralValue::Number(OrderedFloat(value))))
    }

    /// Intern a literal boolean type
    pub fn literal_boolean(&self, value: bool) -> TypeId {
        self.intern(TypeData::Literal(LiteralValue::Boolean(value)))
    }

    /// Intern a literal bigint type
    pub fn literal_bigint(&self, value: &str) -> TypeId {
        let atom = self.intern_string(&self.normalize_bigint_literal(value));
        self.intern(TypeData::Literal(LiteralValue::BigInt(atom)))
    }

    /// Intern a literal bigint type, allowing a sign prefix without extra clones.
    pub fn literal_bigint_with_sign(&self, negative: bool, digits: &str) -> TypeId {
        let normalized = self.normalize_bigint_literal(digits);
        if normalized == "0" {
            return self.literal_bigint(&normalized);
        }
        if !negative {
            return self.literal_bigint(&normalized);
        }

        let mut value = String::with_capacity(normalized.len() + 1);
        value.push('-');
        value.push_str(&normalized);
        let atom = self.string_interner.intern_owned(value);
        self.intern(TypeData::Literal(LiteralValue::BigInt(atom)))
    }

    fn normalize_bigint_literal(&self, value: &str) -> String {
        let stripped = value.replace('_', "");
        if stripped.is_empty() {
            return "0".to_string();
        }

        let (base, digits) = if stripped.starts_with("0x") || stripped.starts_with("0X") {
            (16, &stripped[2..])
        } else if stripped.starts_with("0o") || stripped.starts_with("0O") {
            (8, &stripped[2..])
        } else if stripped.starts_with("0b") || stripped.starts_with("0B") {
            (2, &stripped[2..])
        } else {
            (10, stripped.as_str())
        };

        if digits.is_empty() {
            return "0".to_string();
        }

        if base == 10 {
            let normalized = digits.trim_start_matches('0');
            return if normalized.is_empty() {
                "0".to_string()
            } else {
                normalized.to_string()
            };
        }

        let mut decimal: Vec<u8> = vec![0];
        for ch in digits.chars() {
            let Some(digit) = ch.to_digit(base) else {
                return "0".to_string();
            };
            let digit = digit as u16;
            let mut carry = digit;
            let base = base as u16;
            for dec in decimal.iter_mut() {
                let value = u16::from(*dec) * base + carry;
                *dec = (value % 10) as u8;
                carry = value / 10;
            }
            while carry > 0 {
                decimal.push((carry % 10) as u8);
                carry /= 10;
            }
        }

        while decimal.len() > 1 && *decimal.last().unwrap_or(&0) == 0 {
            decimal.pop();
        }

        let mut out = String::with_capacity(decimal.len());
        for digit in decimal.iter().rev() {
            out.push(char::from(b'0' + *digit));
        }
        out
    }

    /// Intern a union type, normalizing and deduplicating members
    pub fn union(&self, members: Vec<TypeId>) -> TypeId {
        self.union_from_iter(members)
    }

    /// Intern a union type from a vector that is already sorted and deduped.
    /// This is an O(N) operation that avoids redundant sorting.
    pub fn union_from_sorted_vec(&self, flat: Vec<TypeId>) -> TypeId {
        if flat.is_empty() {
            return TypeId::NEVER;
        }
        if flat.len() == 1 {
            return flat[0];
        }

        let list_id = self.intern_type_list(flat);
        self.intern(TypeData::Union(list_id))
    }

    /// Intern a union type while preserving member structure.
    ///
    /// This keeps unknown/literal members intact for property access checks.
    pub fn union_preserve_members(&self, members: Vec<TypeId>) -> TypeId {
        if members.is_empty() {
            return TypeId::NEVER;
        }

        let mut flat: TypeListBuffer = SmallVec::new();
        for member in members {
            if let Some(TypeData::Union(inner)) = self.lookup(member) {
                let members = self.type_list(inner);
                flat.extend(members.iter().copied());
            } else {
                flat.push(member);
            }
        }

        flat.sort_by_key(|id| id.0);
        flat.dedup();
        flat.retain(|id| *id != TypeId::NEVER);

        if flat.is_empty() {
            return TypeId::NEVER;
        }
        if flat.len() == 1 {
            return flat[0];
        }

        let list_id = self.intern_type_list(flat.into_vec());
        self.intern(TypeData::Union(list_id))
    }

    /// Fast path for unions that already fit in registers.
    pub fn union2(&self, left: TypeId, right: TypeId) -> TypeId {
        // Fast paths to avoid expensive normalize_union for trivial cases
        if left == right {
            return left;
        }
        if left == TypeId::NEVER {
            return right;
        }
        if right == TypeId::NEVER {
            return left;
        }
        self.union_from_iter([left, right])
    }

    /// Fast path for three-member unions without heap allocations.
    pub fn union3(&self, first: TypeId, second: TypeId, third: TypeId) -> TypeId {
        self.union_from_iter([first, second, third])
    }

    fn union_from_iter<I>(&self, members: I) -> TypeId
    where
        I: IntoIterator<Item = TypeId>,
    {
        let mut iter = members.into_iter();
        let Some(first) = iter.next() else {
            return TypeId::NEVER;
        };
        let Some(second) = iter.next() else {
            return first;
        };

        let mut flat: TypeListBuffer = SmallVec::new();
        self.push_union_member(&mut flat, first);
        self.push_union_member(&mut flat, second);
        for member in iter {
            self.push_union_member(&mut flat, member);
        }

        self.normalize_union(flat)
    }

    fn push_union_member(&self, flat: &mut TypeListBuffer, member: TypeId) {
        if let Some(TypeData::Union(inner)) = self.lookup(member) {
            let members = self.type_list(inner);
            flat.extend(members.iter().copied());
        } else {
            flat.push(member);
        }
    }

    fn normalize_union(&self, mut flat: TypeListBuffer) -> TypeId {
        // Deduplicate and sort for consistent hashing
        flat.sort_by_key(|id| id.0);
        flat.dedup();

        // Handle special cases
        if flat.contains(&TypeId::ERROR) {
            return TypeId::ERROR;
        }
        if flat.is_empty() {
            return TypeId::NEVER;
        }
        if flat.len() == 1 {
            return flat[0];
        }
        // If any member is `any`, the union is `any`
        if flat.contains(&TypeId::ANY) {
            return TypeId::ANY;
        }
        // If any member is `unknown`, the union is `unknown`
        if flat.contains(&TypeId::UNKNOWN) {
            return TypeId::UNKNOWN;
        }
        // Remove `never` from unions
        flat.retain(|id| *id != TypeId::NEVER);
        if flat.is_empty() {
            return TypeId::NEVER;
        }
        if flat.len() == 1 {
            return flat[0];
        }

        // Absorb literal types into their corresponding primitive types
        // e.g., "a" | string | number => string | number
        // e.g., 1 | 2 | number => number
        // e.g., true | boolean => boolean
        self.absorb_literals_into_primitives(&mut flat);

        if flat.is_empty() {
            return TypeId::NEVER;
        }
        if flat.len() == 1 {
            return flat[0];
        }

        // Reduce union using subtype checks (e.g., {a: 1} | {a: 1 | number} => {a: 1 | number})
        // Skip reduction if union contains complex types (TypeParameters, Lazy, etc.)
        let has_complex = flat.iter().any(|&id| {
            matches!(
                self.lookup(id),
                Some(TypeData::TypeParameter(_) | TypeData::Lazy(_))
            )
        });
        if !has_complex {
            self.reduce_union_subtypes(&mut flat);
        }

        if flat.is_empty() {
            return TypeId::NEVER;
        }
        if flat.len() == 1 {
            return flat[0];
        }

        let list_id = self.intern_type_list(flat.into_vec());
        self.intern(TypeData::Union(list_id))
    }

    /// Intern an intersection type, normalizing and deduplicating members
    pub fn intersection(&self, members: Vec<TypeId>) -> TypeId {
        self.intersection_from_iter(members)
    }

    /// Fast path for two-member intersections.
    pub fn intersection2(&self, left: TypeId, right: TypeId) -> TypeId {
        self.intersection_from_iter([left, right])
    }

    /// Create an intersection type WITHOUT triggering `normalize_intersection`
    ///
    /// This is a low-level operation used by the `SubtypeChecker` to merge
    /// properties from intersection members without causing infinite recursion.
    ///
    /// # Safety
    /// Only use this when you need to synthesize a type for intermediate checking.
    /// Do NOT use for final compiler output (like .d.ts generation) as the
    /// resulting type will be "unsimplified".
    pub fn intersect_types_raw(&self, members: Vec<TypeId>) -> TypeId {
        // Use SmallVec to keep stack allocation benefits
        let mut flat: TypeListBuffer = SmallVec::new();

        for member in members {
            // Structural flattening is safe and cheap
            if let Some(TypeData::Intersection(inner)) = self.lookup(member) {
                let inner_members = self.type_list(inner);
                flat.extend(inner_members.iter().copied());
            } else {
                flat.push(member);
            }
        }

        // Abort reduction if any member is a Lazy type.
        // The interner (Judge) cannot resolve symbols, so if we have unresolved types,
        // we must preserve the intersection as-is without attempting to merge or reduce.
        let has_unresolved = flat
            .iter()
            .any(|&id| matches!(self.lookup(id), Some(TypeData::Lazy(_))));
        if has_unresolved {
            // Basic dedup without any simplification
            flat.sort_by_key(|id| id.0);
            flat.dedup();
            let list_id = self.intern_type_list(flat.into_vec());
            return self.intern(TypeData::Intersection(list_id));
        }

        // =========================================================
        // Canonicalization: Handle callable order preservation
        // =========================================================
        // In TypeScript, intersections of functions represent overloads, and
        // order matters. We need to separate callables from non-callables.

        let has_callables = flat.iter().any(|&id| self.is_callable_type(id));

        if !has_callables {
            // Fast path: No callables, sort everything for canonicalization
            flat.sort_by_key(|id| id.0);
            flat.dedup();
        } else {
            // Slow path: Separate callables and others to preserve order
            let mut callables = SmallVec::<[TypeId; 4]>::new();

            // Retain only non-callables in 'flat', move callables to 'callables'
            // This preserves the order of callables as they are extracted
            let mut i = 0;
            while i < flat.len() {
                if self.is_callable_type(flat[i]) {
                    callables.push(flat.remove(i));
                } else {
                    i += 1;
                }
            }

            // Sort and dedup non-callables
            flat.sort_by_key(|id| id.0);
            flat.dedup();

            // Deduplicate callables (preserving order)
            let mut seen = FxHashSet::default();
            callables.retain(|id| seen.insert(*id));

            // Merge: Put non-callables first (canonical), then callables (ordered)
            flat.extend(callables);
        }

        // =========================================================
        // O(1) Fast Paths (Safe to do without recursion)
        // =========================================================

        // 1. If any member is Never, the result is Never
        if flat.contains(&TypeId::NEVER) {
            return TypeId::NEVER;
        }

        // 2. If any member is Any, the result is Any (unless Never is present)
        if flat.contains(&TypeId::ANY) {
            return TypeId::ANY;
        }

        // 3. Remove Unknown (Identity element for intersection)
        flat.retain(|id| *id != TypeId::UNKNOWN);

        // 4. Check for disjoint primitives (e.g., string & number = never)
        // If we have multiple intrinsic primitive types that are disjoint, return never
        if self.has_disjoint_primitives(&flat) {
            return TypeId::NEVER;
        }

        // =========================================================
        // Final Construction
        // =========================================================

        if flat.is_empty() {
            return TypeId::UNKNOWN;
        }
        if flat.len() == 1 {
            return flat[0];
        }

        // Create the intersection directly without calling normalize_intersection
        let list_id = self.intern_type_list(flat.into_vec());
        self.intern(TypeData::Intersection(list_id))
    }

    /// Convenience wrapper for raw intersection of two types
    pub fn intersect_types_raw2(&self, a: TypeId, b: TypeId) -> TypeId {
        self.intersect_types_raw(vec![a, b])
    }

    fn intersection_from_iter<I>(&self, members: I) -> TypeId
    where
        I: IntoIterator<Item = TypeId>,
    {
        let mut iter = members.into_iter();
        let Some(first) = iter.next() else {
            return TypeId::UNKNOWN;
        };
        let Some(second) = iter.next() else {
            return first;
        };

        let mut flat: TypeListBuffer = SmallVec::new();
        self.push_intersection_member(&mut flat, first);
        self.push_intersection_member(&mut flat, second);
        for member in iter {
            self.push_intersection_member(&mut flat, member);
        }

        self.normalize_intersection(flat)
    }

    fn push_intersection_member(&self, flat: &mut TypeListBuffer, member: TypeId) {
        if let Some(TypeData::Intersection(inner)) = self.lookup(member) {
            let members = self.type_list(inner);
            flat.extend(members.iter().copied());
        } else {
            flat.push(member);
        }
    }

    /// Check if a type is a function or callable (order-sensitive in intersections).
    ///
    /// In TypeScript, intersection types are commutative for structural types
    /// (objects, primitives) but non-commutative for call signatures.
    /// For example: `((a: string) => void) & ((a: number) => void)` has a different
    /// overload order than the reverse.
    fn is_callable_type(&self, id: TypeId) -> bool {
        matches!(
            self.lookup(id),
            Some(TypeData::Function(_) | TypeData::Callable(_))
        )
    }

    // Intersection normalization, empty object elimination, callable/object
    // merging, and distribution are in `intersection.rs`.

    /// Intern an array type
    pub fn array(&self, element: TypeId) -> TypeId {
        self.intern(TypeData::Array(element))
    }

    /// Canonical `this` type.
    pub fn this_type(&self) -> TypeId {
        self.intern(TypeData::ThisType)
    }

    /// Intern a readonly array type
    /// Returns a distinct type from mutable arrays to enforce readonly semantics
    pub fn readonly_array(&self, element: TypeId) -> TypeId {
        let array_type = self.array(element);
        self.intern(TypeData::ReadonlyType(array_type))
    }

    /// Intern a tuple type
    pub fn tuple(&self, elements: Vec<TupleElement>) -> TypeId {
        let list_id = self.intern_tuple_list(elements);
        self.intern(TypeData::Tuple(list_id))
    }

    /// Intern a readonly tuple type
    /// Returns a distinct type from mutable tuples to enforce readonly semantics
    pub fn readonly_tuple(&self, elements: Vec<TupleElement>) -> TypeId {
        let tuple_type = self.tuple(elements);
        self.intern(TypeData::ReadonlyType(tuple_type))
    }

    /// Wrap any type in a `ReadonlyType` marker
    /// This is used for the `readonly` type operator
    pub fn readonly_type(&self, inner: TypeId) -> TypeId {
        self.intern(TypeData::ReadonlyType(inner))
    }

    /// Wrap a type in a `NoInfer` marker.
    pub fn no_infer(&self, inner: TypeId) -> TypeId {
        self.intern(TypeData::NoInfer(inner))
    }

    /// Create a `unique symbol` type for a symbol declaration.
    pub fn unique_symbol(&self, symbol: SymbolRef) -> TypeId {
        self.intern(TypeData::UniqueSymbol(symbol))
    }

    /// Create an `infer` binder with the provided info.
    pub fn infer(&self, info: TypeParamInfo) -> TypeId {
        self.intern(TypeData::Infer(info))
    }

    pub fn bound_parameter(&self, index: u32) -> TypeId {
        self.intern(TypeData::BoundParameter(index))
    }

    pub fn recursive(&self, depth: u32) -> TypeId {
        self.intern(TypeData::Recursive(depth))
    }

    /// Wrap a type in a `KeyOf` marker.
    pub fn keyof(&self, inner: TypeId) -> TypeId {
        self.intern(TypeData::KeyOf(inner))
    }

    /// Build an indexed access type (`T[K]`).
    pub fn index_access(&self, object_type: TypeId, index_type: TypeId) -> TypeId {
        self.intern(TypeData::IndexAccess(object_type, index_type))
    }

    /// Build a nominal enum type that preserves `DefId` identity and carries
    /// structural member information for compatibility with primitive relations.
    pub fn enum_type(&self, def_id: DefId, structural_type: TypeId) -> TypeId {
        self.intern(TypeData::Enum(def_id, structural_type))
    }

    /// Intern an object type with properties.
    pub fn object(&self, properties: Vec<PropertyInfo>) -> TypeId {
        self.object_with_flags(properties, ObjectFlags::empty())
    }

    /// Intern a fresh object type with properties.
    pub fn object_fresh(&self, properties: Vec<PropertyInfo>) -> TypeId {
        self.object_with_flags(properties, ObjectFlags::FRESH_LITERAL)
    }

    /// Intern an object type with properties and custom flags.
    pub fn object_with_flags(
        &self,
        mut properties: Vec<PropertyInfo>,
        flags: ObjectFlags,
    ) -> TypeId {
        // Sort by property name for consistent hashing
        properties.sort_by_key(|a| a.name);
        let shape_id = self.intern_object_shape(ObjectShape {
            flags,
            properties,
            string_index: None,
            number_index: None,
            symbol: None,
        });
        self.intern(TypeData::Object(shape_id))
    }

    /// Intern an object type with properties, custom flags, and optional symbol.
    /// This is used for interfaces that need symbol tracking but no index signatures.
    pub fn object_with_flags_and_symbol(
        &self,
        mut properties: Vec<PropertyInfo>,
        flags: ObjectFlags,
        symbol: Option<tsz_binder::SymbolId>,
    ) -> TypeId {
        // Sort by property name for consistent hashing
        properties.sort_by_key(|a| a.name);
        let shape_id = self.intern_object_shape(ObjectShape {
            flags,
            properties,
            string_index: None,
            number_index: None,
            symbol,
        });
        self.intern(TypeData::Object(shape_id))
    }

    /// Intern an object type with index signatures.
    pub fn object_with_index(&self, mut shape: ObjectShape) -> TypeId {
        // Sort properties by name for consistent hashing
        shape.properties.sort_by_key(|a| a.name);
        let shape_id = self.intern_object_shape(shape);
        self.intern(TypeData::ObjectWithIndex(shape_id))
    }

    /// Intern a function type
    pub fn function(&self, shape: FunctionShape) -> TypeId {
        let shape_id = self.intern_function_shape(shape);
        self.intern(TypeData::Function(shape_id))
    }

    /// Intern a callable type with overloaded signatures
    pub fn callable(&self, shape: CallableShape) -> TypeId {
        let shape_id = self.intern_callable_shape(shape);
        self.intern(TypeData::Callable(shape_id))
    }

    /// Intern a conditional type
    pub fn conditional(&self, conditional: ConditionalType) -> TypeId {
        let conditional_id = self.intern_conditional_type(conditional);
        self.intern(TypeData::Conditional(conditional_id))
    }

    /// Intern a mapped type
    pub fn mapped(&self, mapped: MappedType) -> TypeId {
        let mapped_id = self.intern_mapped_type(mapped);
        self.intern(TypeData::Mapped(mapped_id))
    }

    /// Build a string intrinsic (`Uppercase`, `Lowercase`, etc.) marker.
    pub fn string_intrinsic(
        &self,
        kind: crate::types::StringIntrinsicKind,
        type_arg: TypeId,
    ) -> TypeId {
        self.intern(TypeData::StringIntrinsic { kind, type_arg })
    }

    /// Intern a type reference (deprecated - use `lazy()` with `DefId` instead).
    ///
    /// This method is kept for backward compatibility with tests and legacy code.
    /// It converts `SymbolRef` to `DefId` and creates `TypeData::Lazy`.
    ///
    /// Deprecated: new code should use `lazy(def_id)` instead.
    pub fn reference(&self, symbol: SymbolRef) -> TypeId {
        // Convert SymbolRef to DefId by wrapping the raw u32 value
        // This maintains the same identity while using the new TypeData::Lazy variant
        let def_id = DefId(symbol.0);
        self.intern(TypeData::Lazy(def_id))
    }

    /// Intern a lazy type reference (DefId-based).
    ///
    /// This is the replacement for `reference()` that uses Solver-owned
    /// `DefIds` instead of Binder-owned `SymbolRefs`.
    ///
    /// Use this method for all new type references
    /// to enable O(1) type equality across Binder and Solver boundaries.
    pub fn lazy(&self, def_id: DefId) -> TypeId {
        self.intern(TypeData::Lazy(def_id))
    }

    /// Intern a type parameter.
    pub fn type_param(&self, info: TypeParamInfo) -> TypeId {
        self.intern(TypeData::TypeParameter(info))
    }

    /// Intern a type query (`typeof value`) marker.
    pub fn type_query(&self, symbol: SymbolRef) -> TypeId {
        self.intern(TypeData::TypeQuery(symbol))
    }

    /// Intern a generic type application
    pub fn application(&self, base: TypeId, args: Vec<TypeId>) -> TypeId {
        let app_id = self.intern_application(TypeApplication { base, args });
        self.intern(TypeData::Application(app_id))
    }
}

impl Default for TypeInterner {
    fn default() -> Self {
        Self::new()
    }
}

#[cfg(test)]
#[path = "../../tests/intern_tests.rs"]
mod tests;

#[cfg(test)]
#[path = "../../tests/concurrent_tests.rs"]
mod concurrent_tests;