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|
//! MIR lowering for places
use super::*;
use hir_expand::name;
macro_rules! not_supported {
($x: expr) => {
return Err(MirLowerError::NotSupported(format!($x)))
};
}
impl MirLowerCtx<'_> {
fn lower_expr_to_some_place_without_adjust(
&mut self,
expr_id: ExprId,
prev_block: BasicBlockId,
) -> Result<Option<(Place, BasicBlockId)>> {
let ty = self.expr_ty(expr_id);
let place = self.temp(ty)?;
let Some(current) = self.lower_expr_to_place_without_adjust(expr_id, place.into(), prev_block)? else {
return Ok(None);
};
Ok(Some((place.into(), current)))
}
fn lower_expr_to_some_place_with_adjust(
&mut self,
expr_id: ExprId,
prev_block: BasicBlockId,
adjustments: &[Adjustment],
) -> Result<Option<(Place, BasicBlockId)>> {
let ty =
adjustments.last().map(|x| x.target.clone()).unwrap_or_else(|| self.expr_ty(expr_id));
let place = self.temp(ty)?;
let Some(current) = self.lower_expr_to_place_with_adjust(expr_id, place.into(), prev_block, adjustments)? else {
return Ok(None);
};
Ok(Some((place.into(), current)))
}
pub(super) fn lower_expr_as_place_with_adjust(
&mut self,
current: BasicBlockId,
expr_id: ExprId,
upgrade_rvalue: bool,
adjustments: &[Adjustment],
) -> Result<Option<(Place, BasicBlockId)>> {
let try_rvalue = |this: &mut MirLowerCtx<'_>| {
if !upgrade_rvalue {
return Err(MirLowerError::MutatingRvalue);
}
this.lower_expr_to_some_place_with_adjust(expr_id, current, adjustments)
};
if let Some((last, rest)) = adjustments.split_last() {
match last.kind {
Adjust::Deref(None) => {
let Some(mut x) = self.lower_expr_as_place_with_adjust(
current,
expr_id,
upgrade_rvalue,
rest,
)? else {
return Ok(None);
};
x.0.projection.push(ProjectionElem::Deref);
Ok(Some(x))
}
Adjust::Deref(Some(od)) => {
let Some((r, current)) = self.lower_expr_as_place_with_adjust(
current,
expr_id,
upgrade_rvalue,
rest,
)? else {
return Ok(None);
};
self.lower_overloaded_deref(
current,
r,
rest.last()
.map(|x| x.target.clone())
.unwrap_or_else(|| self.expr_ty(expr_id)),
last.target.clone(),
expr_id.into(),
match od.0 {
Some(Mutability::Mut) => true,
Some(Mutability::Not) => false,
None => {
not_supported!("implicit overloaded deref with unknown mutability")
}
},
)
}
Adjust::NeverToAny | Adjust::Borrow(_) | Adjust::Pointer(_) => try_rvalue(self),
}
} else {
self.lower_expr_as_place_without_adjust(current, expr_id, upgrade_rvalue)
}
}
pub(super) fn lower_expr_as_place(
&mut self,
current: BasicBlockId,
expr_id: ExprId,
upgrade_rvalue: bool,
) -> Result<Option<(Place, BasicBlockId)>> {
match self.infer.expr_adjustments.get(&expr_id) {
Some(a) => self.lower_expr_as_place_with_adjust(current, expr_id, upgrade_rvalue, a),
None => self.lower_expr_as_place_without_adjust(current, expr_id, upgrade_rvalue),
}
}
pub(super) fn lower_expr_as_place_without_adjust(
&mut self,
current: BasicBlockId,
expr_id: ExprId,
upgrade_rvalue: bool,
) -> Result<Option<(Place, BasicBlockId)>> {
let try_rvalue = |this: &mut MirLowerCtx<'_>| {
if !upgrade_rvalue {
return Err(MirLowerError::MutatingRvalue);
}
this.lower_expr_to_some_place_without_adjust(expr_id, current)
};
match &self.body.exprs[expr_id] {
Expr::Path(p) => {
let resolver = resolver_for_expr(self.db.upcast(), self.owner, expr_id);
let Some(pr) = resolver.resolve_path_in_value_ns(self.db.upcast(), p.mod_path()) else {
return Err(MirLowerError::unresolved_path(self.db, p));
};
let pr = match pr {
ResolveValueResult::ValueNs(v) => v,
ResolveValueResult::Partial(..) => return try_rvalue(self),
};
match pr {
ValueNs::LocalBinding(pat_id) => {
Ok(Some((self.result.binding_locals[pat_id].into(), current)))
}
_ => try_rvalue(self),
}
}
Expr::UnaryOp { expr, op } => match op {
hir_def::expr::UnaryOp::Deref => {
if !matches!(
self.expr_ty(*expr).kind(Interner),
TyKind::Ref(..) | TyKind::Raw(..)
) {
let Some(_) = self.lower_expr_as_place(current, *expr, true)? else {
return Ok(None);
};
not_supported!("explicit overloaded deref");
}
let Some((mut r, current)) = self.lower_expr_as_place(current, *expr, true)? else {
return Ok(None);
};
r.projection.push(ProjectionElem::Deref);
Ok(Some((r, current)))
}
_ => try_rvalue(self),
},
Expr::Field { expr, .. } => {
let Some((mut r, current)) = self.lower_expr_as_place(current, *expr, true)? else {
return Ok(None);
};
self.push_field_projection(&mut r, expr_id)?;
Ok(Some((r, current)))
}
Expr::Index { base, index } => {
let base_ty = self.expr_ty_after_adjustments(*base);
let index_ty = self.expr_ty_after_adjustments(*index);
if index_ty != TyBuilder::usize()
|| !matches!(base_ty.kind(Interner), TyKind::Array(..) | TyKind::Slice(..))
{
not_supported!("overloaded index");
}
let Some((mut p_base, current)) =
self.lower_expr_as_place(current, *base, true)? else {
return Ok(None);
};
let l_index = self.temp(self.expr_ty_after_adjustments(*index))?;
let Some(current) = self.lower_expr_to_place(*index, l_index.into(), current)? else {
return Ok(None);
};
p_base.projection.push(ProjectionElem::Index(l_index));
Ok(Some((p_base, current)))
}
_ => try_rvalue(self),
}
}
fn lower_overloaded_deref(
&mut self,
current: BasicBlockId,
place: Place,
source_ty: Ty,
target_ty: Ty,
span: MirSpan,
mutability: bool,
) -> Result<Option<(Place, BasicBlockId)>> {
let (chalk_mut, trait_lang_item, trait_method_name, borrow_kind) = if !mutability {
(Mutability::Not, LangItem::Deref, name![deref], BorrowKind::Shared)
} else {
(
Mutability::Mut,
LangItem::DerefMut,
name![deref_mut],
BorrowKind::Mut { allow_two_phase_borrow: false },
)
};
let ty_ref = TyKind::Ref(chalk_mut, static_lifetime(), source_ty.clone()).intern(Interner);
let target_ty_ref = TyKind::Ref(chalk_mut, static_lifetime(), target_ty).intern(Interner);
let ref_place: Place = self.temp(ty_ref)?.into();
self.push_assignment(current, ref_place.clone(), Rvalue::Ref(borrow_kind, place), span);
let deref_trait = self
.resolve_lang_item(trait_lang_item)?
.as_trait()
.ok_or(MirLowerError::LangItemNotFound(trait_lang_item))?;
let deref_fn = self
.db
.trait_data(deref_trait)
.method_by_name(&trait_method_name)
.ok_or(MirLowerError::LangItemNotFound(trait_lang_item))?;
let deref_fn_op = Operand::const_zst(
TyKind::FnDef(
self.db.intern_callable_def(CallableDefId::FunctionId(deref_fn)).into(),
Substitution::from1(Interner, source_ty),
)
.intern(Interner),
);
let mut result: Place = self.temp(target_ty_ref)?.into();
let Some(current) = self.lower_call(deref_fn_op, vec![Operand::Copy(ref_place)], result.clone(), current, false)? else {
return Ok(None);
};
result.projection.push(ProjectionElem::Deref);
Ok(Some((result, current)))
}
}
|
