use rustc_hash::FxHashMap;
use super::associated::LoweredAssociatedValue;
use super::checker::TypeChecker;
use super::problems::TypeProblems;
use super::traits::Implementor;
use super::ty::{Bound, GenericId, GenericParam, Lifetime, Scheme, Type};
use crate::core::ClosureKind;
use crate::core::{
AssociatedValue, BindingId, BindingKind, ReferenceKind, RustTraitImplementor, TypeBinder,
TypeBound, TypeExpr, TypeExprKind,
};
use crate::diagnostic::Diagnostic;
use crate::source::Span;
#[derive(Default)]
struct LoweredBinders {
lifetimes: Vec<BindingId>,
params: Vec<GenericParam>,
scope: FxHashMap<BindingId, GenericId>,
}
impl TypeChecker {
pub(super) fn lower_scheme(&mut self, type_expr: &TypeExpr) -> Result<Scheme, Diagnostic> {
let TypeExprKind::Where(binders, inner) = type_expr.kind() else {
return Ok(Scheme::monomorphic(
self.lower_type(type_expr, &FxHashMap::default())?,
));
};
let binders = self.lower_binders(binders)?;
Ok(Scheme {
lifetimes: binders.lifetimes,
params: binders.params,
body: self.lower_type(inner, &binders.scope)?,
})
}
pub(super) fn lower_implementor(
&mut self,
entry: &RustTraitImplementor,
trait_name: &str,
) -> Result<(Implementor, Vec<LoweredAssociatedValue>), Diagnostic> {
let implementor = &entry.implementor;
let binders = match implementor.kind() {
TypeExprKind::Where(binders, _) => self.lower_binders(binders)?,
_ => LoweredBinders::default(),
};
let (body, argument) =
self.lower_implementor_body(Self::where_body(implementor), &binders.scope)?;
Self::reject_bare_implementor(&body, implementor.span(), trait_name)?;
let values = self.lower_associated_values(&entry.associated, &binders.scope)?;
let lowered = Implementor {
scheme: Scheme {
lifetimes: binders.lifetimes,
params: binders.params,
body,
},
argument,
};
Ok((lowered, values))
}
fn where_body(implementor: &TypeExpr) -> &TypeExpr {
match implementor.kind() {
TypeExprKind::Where(_, inner) => inner,
_ => implementor,
}
}
fn lower_associated_values(
&mut self,
values: &[AssociatedValue],
scope: &FxHashMap<BindingId, GenericId>,
) -> Result<Vec<LoweredAssociatedValue>, Diagnostic> {
values
.iter()
.map(|associated| {
Ok(LoweredAssociatedValue {
projection: associated.binding,
value: self.lower_type(&associated.value, scope)?,
span: associated.span,
})
})
.collect()
}
fn lower_implementor_body(
&mut self,
type_expr: &TypeExpr,
scope: &FxHashMap<BindingId, GenericId>,
) -> Result<(Type, Option<Type>), Diagnostic> {
if let TypeExprKind::With(implementor, argument) = type_expr.kind() {
let body = self.lower_type(implementor, scope)?;
let argument = self.lower_type(argument, scope)?;
Ok((body, Some(argument)))
} else {
Ok((self.lower_type(type_expr, scope)?, None))
}
}
fn reject_bare_implementor(
body: &Type,
span: Span,
trait_name: &str,
) -> Result<(), Diagnostic> {
if matches!(body, Type::Generic(_)) {
return Err(TypeProblems::bare_implementor(trait_name, span));
}
Ok(())
}
fn lower_binders(&mut self, binders: &[TypeBinder]) -> Result<LoweredBinders, Diagnostic> {
let mut lifetimes = Vec::new();
let mut params = Vec::new();
let mut scope = FxHashMap::default();
for binder in binders {
if binder.lifetime {
lifetimes.push(binder.variable);
continue;
}
let name = self.bindings.get(binder.variable).name().to_string();
let param = self.new_generic(&name, Vec::new());
if matches!(
self.bindings.get(binder.variable).kind(),
BindingKind::AssociatedType
) {
self.associated_generics
.insert(param.id, std::rc::Rc::from(name.as_str()));
}
scope.insert(binder.variable, param.id);
params.push(param);
}
for (binder, param) in binders
.iter()
.filter(|binder| !binder.lifetime)
.zip(&mut params)
{
let bounds = self.lower_bounds(binder, &scope)?;
self.replace_bounds(param, bounds);
}
Ok(LoweredBinders {
lifetimes,
params,
scope,
})
}
fn lower_bounds(
&mut self,
binder: &TypeBinder,
scope: &FxHashMap<BindingId, GenericId>,
) -> Result<Vec<Bound>, Diagnostic> {
binder
.bounds
.iter()
.map(|bound| self.lower_type_bound(bound, scope))
.collect()
}
pub(super) fn lower_type_bound(
&mut self,
bound: &TypeBound,
scope: &FxHashMap<BindingId, GenericId>,
) -> Result<Bound, Diagnostic> {
let Some(argument) = &bound.argument else {
return Ok(Bound::plain(bound.binding));
};
self.check_trait_argument(bound.binding, argument.span())?;
let argument = self.lower_type(argument, scope)?;
Ok(Bound::with_argument(bound.binding, argument))
}
fn check_trait_argument(&self, binding: BindingId, span: Span) -> Result<(), Diagnostic> {
if self.trait_takes_argument(binding) {
return Ok(());
}
Err(TypeProblems::trait_takes_no_argument(
self.bindings.get(binding).name(),
span,
))
}
fn replace_bounds(&mut self, param: &mut GenericParam, bounds: Vec<Bound>) {
param.bounds = bounds.clone();
self.generics.insert(param.id, param.clone());
self.unifier.register_generic(param.id, bounds);
}
pub(super) fn lower_type(
&mut self,
type_expr: &TypeExpr,
scope: &FxHashMap<BindingId, GenericId>,
) -> Result<Type, Diagnostic> {
self.lower_type_kind(type_expr.kind(), type_expr, scope)
}
fn lower_type_kind(
&mut self,
kind: &TypeExprKind,
type_expr: &TypeExpr,
scope: &FxHashMap<BindingId, GenericId>,
) -> Result<Type, Diagnostic> {
match kind {
TypeExprKind::Where(..) | TypeExprKind::With(..) | TypeExprKind::Trait(_) => {
self.lower_invalid_type(kind, type_expr)
}
_ => self.lower_plain_type(kind, type_expr, scope),
}
}
fn lower_plain_type(
&mut self,
kind: &TypeExprKind,
type_expr: &TypeExpr,
scope: &FxHashMap<BindingId, GenericId>,
) -> Result<Type, Diagnostic> {
match kind {
TypeExprKind::Primitive(primitive) => Ok(Type::Primitive(*primitive)),
TypeExprKind::Named(binding, arguments) => {
self.lower_named(*binding, arguments, type_expr.span(), scope)
}
TypeExprKind::Function(kind, parameters, result) => {
self.lower_function(*kind, parameters, result, scope)
}
TypeExprKind::Reference(kind, lifetime, inner) => {
self.lower_reference(*kind, *lifetime, inner, scope)
}
TypeExprKind::Hole => Ok(self.unifier.fresh()),
_ => unreachable!("the caller matches a plain type"),
}
}
fn lower_invalid_type(
&mut self,
kind: &TypeExprKind,
type_expr: &TypeExpr,
) -> Result<Type, Diagnostic> {
match kind {
TypeExprKind::Where(..) => Err(TypeProblems::misplaced_where(type_expr.span())),
TypeExprKind::With(..) => Err(TypeProblems::misplaced_with(type_expr.span())),
TypeExprKind::Trait(binding) => Err(TypeProblems::trait_outside_box(
self.bindings.get(*binding).name(),
type_expr.span(),
)),
_ => unreachable!("the caller matches an invalid type"),
}
}
fn lower_function(
&mut self,
kind: ClosureKind,
parameters: &[TypeExpr],
result: &TypeExpr,
scope: &FxHashMap<BindingId, GenericId>,
) -> Result<Type, Diagnostic> {
let parameters = parameters
.iter()
.map(|parameter| self.lower_type(parameter, scope))
.collect::<Result<Vec<Type>, Diagnostic>>()?;
let result = self.lower_type(result, scope)?;
Ok(Type::Function(kind, parameters, Box::new(result)))
}
fn lower_reference(
&mut self,
kind: ReferenceKind,
lifetime: Option<BindingId>,
inner: &TypeExpr,
scope: &FxHashMap<BindingId, GenericId>,
) -> Result<Type, Diagnostic> {
let lifetime = lifetime.map_or(Lifetime::Elided, Lifetime::written);
let inner = Box::new(self.lower_type(inner, scope)?);
Ok(match kind {
ReferenceKind::Shared => Type::Ref(lifetime, inner),
ReferenceKind::Mutable => Type::Mut(lifetime, inner),
})
}
pub(super) fn instantiate(&mut self, scheme: &Scheme, span: Span) -> Type {
let fresh: Vec<Type> = scheme
.params
.iter()
.map(|param| self.fresh_instance(param.id))
.collect();
let replacements: FxHashMap<GenericId, Type> = scheme
.params
.iter()
.zip(&fresh)
.map(|(param, value)| (param.id, value.clone()))
.collect();
for (param, value) in scheme.params.iter().zip(&fresh) {
if let Type::Var(var) = value {
let implied = self.implied_bounds.get(¶m.id).into_iter().flatten();
let bounds = param
.bounds
.iter()
.chain(implied)
.map(|bound| bound.substituted(&replacements))
.collect();
self.unifier.set_bounds(*var, bounds, span);
}
}
scheme.body.substitute(&replacements)
}
fn fresh_instance(&mut self, generic: GenericId) -> Type {
match self.literal_generics.get(&generic) {
Some(literal) => self.unifier.fresh_literal(*literal),
None => self.unifier.fresh(),
}
}
fn lower_named(
&mut self,
binding: BindingId,
arguments: &[TypeExpr],
span: Span,
scope: &FxHashMap<BindingId, GenericId>,
) -> Result<Type, Diagnostic> {
self.check_type_argument_count(binding, arguments.len(), span)?;
let arguments = self.lower_named_arguments(binding, arguments, scope)?;
let lowered = self.apply_named(binding, arguments, scope);
self.record_written_projection(&lowered, span);
Ok(lowered)
}
fn lower_named_arguments(
&mut self,
binding: BindingId,
arguments: &[TypeExpr],
scope: &FxHashMap<BindingId, GenericId>,
) -> Result<Vec<Type>, Diagnostic> {
arguments
.iter()
.map(|argument| {
if self.rust_types.is_box(binding) {
self.lower_box_argument(argument, scope)
} else {
self.lower_type(argument, scope)
}
})
.collect()
}
fn apply_named(
&mut self,
binding: BindingId,
arguments: Vec<Type>,
scope: &FxHashMap<BindingId, GenericId>,
) -> Type {
match (self.bindings.get(binding).kind(), scope.get(&binding)) {
(BindingKind::TypeVariable | BindingKind::AssociatedType, Some(generic)) => {
Type::Generic(*generic)
}
(BindingKind::TypeVariable, None) => self.unifier.fresh(),
_ => Type::Named(binding, arguments),
}
}
fn lower_box_argument(
&mut self,
argument: &TypeExpr,
scope: &FxHashMap<BindingId, GenericId>,
) -> Result<Type, Diagnostic> {
match argument.kind() {
TypeExprKind::Trait(binding) => {
self.check_boxable(*binding, argument.span());
Ok(Type::TraitObject(*binding))
}
_ => self.lower_type(argument, scope),
}
}
fn check_type_argument_count(
&self,
binding: BindingId,
found: usize,
span: Span,
) -> Result<(), Diagnostic> {
let expected = self.type_arities.get(&binding).copied().unwrap_or_default();
if found == expected {
return Ok(());
}
Err(TypeProblems::wrong_type_argument_count(
self.bindings.get(binding).name(),
expected,
found,
span,
))
}
}