Unnamed repository; edit this file 'description' to name the repository.
Diffstat (limited to 'crates/hir-ty/src/infer/mutability.rs')
| -rw-r--r-- | crates/hir-ty/src/infer/mutability.rs | 218 |
1 files changed, 218 insertions, 0 deletions
diff --git a/crates/hir-ty/src/infer/mutability.rs b/crates/hir-ty/src/infer/mutability.rs new file mode 100644 index 0000000000..4478342439 --- /dev/null +++ b/crates/hir-ty/src/infer/mutability.rs @@ -0,0 +1,218 @@ +//! Finds if an expression is an immutable context or a mutable context, which is used in selecting +//! between `Deref` and `DerefMut` or `Index` and `IndexMut` or similar. + +use chalk_ir::Mutability; +use hir_def::{ + hir::{Array, BinaryOp, BindingAnnotation, Expr, ExprId, PatId, Statement, UnaryOp}, + lang_item::LangItem, +}; +use hir_expand::name; + +use crate::{lower::lower_to_chalk_mutability, Adjust, Adjustment, AutoBorrow, OverloadedDeref}; + +use super::InferenceContext; + +impl<'a> InferenceContext<'a> { + pub(crate) fn infer_mut_body(&mut self) { + self.infer_mut_expr(self.body.body_expr, Mutability::Not); + } + + fn infer_mut_expr(&mut self, tgt_expr: ExprId, mut mutability: Mutability) { + if let Some(adjustments) = self.result.expr_adjustments.get_mut(&tgt_expr) { + for adj in adjustments.iter_mut().rev() { + match &mut adj.kind { + Adjust::NeverToAny | Adjust::Deref(None) | Adjust::Pointer(_) => (), + Adjust::Deref(Some(d)) => *d = OverloadedDeref(Some(mutability)), + Adjust::Borrow(b) => match b { + AutoBorrow::Ref(m) | AutoBorrow::RawPtr(m) => mutability = *m, + }, + } + } + } + self.infer_mut_expr_without_adjust(tgt_expr, mutability); + } + + fn infer_mut_expr_without_adjust(&mut self, tgt_expr: ExprId, mutability: Mutability) { + match &self.body[tgt_expr] { + Expr::Missing => (), + &Expr::If { condition, then_branch, else_branch } => { + self.infer_mut_expr(condition, Mutability::Not); + self.infer_mut_expr(then_branch, Mutability::Not); + if let Some(else_branch) = else_branch { + self.infer_mut_expr(else_branch, Mutability::Not); + } + } + Expr::Const(id) => { + let (_, expr) = self.db.lookup_intern_anonymous_const(*id); + self.infer_mut_expr(expr, Mutability::Not); + } + Expr::Let { pat, expr } => self.infer_mut_expr(*expr, self.pat_bound_mutability(*pat)), + Expr::Block { id: _, statements, tail, label: _ } + | Expr::Async { id: _, statements, tail } + | Expr::Unsafe { id: _, statements, tail } => { + for st in statements.iter() { + match st { + Statement::Let { pat, type_ref: _, initializer, else_branch } => { + if let Some(i) = initializer { + self.infer_mut_expr(*i, self.pat_bound_mutability(*pat)); + } + if let Some(e) = else_branch { + self.infer_mut_expr(*e, Mutability::Not); + } + } + Statement::Expr { expr, has_semi: _ } => { + self.infer_mut_expr(*expr, Mutability::Not); + } + } + } + if let Some(tail) = tail { + self.infer_mut_expr(*tail, Mutability::Not); + } + } + &Expr::While { condition: c, body, label: _ } => { + self.infer_mut_expr(c, Mutability::Not); + self.infer_mut_expr(body, Mutability::Not); + } + Expr::MethodCall { receiver: x, method_name: _, args, generic_args: _ } + | Expr::Call { callee: x, args, is_assignee_expr: _ } => { + self.infer_mut_not_expr_iter(args.iter().copied().chain(Some(*x))); + } + Expr::Match { expr, arms } => { + let m = self.pat_iter_bound_mutability(arms.iter().map(|x| x.pat)); + self.infer_mut_expr(*expr, m); + for arm in arms.iter() { + self.infer_mut_expr(arm.expr, Mutability::Not); + if let Some(g) = arm.guard { + self.infer_mut_expr(g, Mutability::Not); + } + } + } + Expr::Yield { expr } + | Expr::Yeet { expr } + | Expr::Return { expr } + | Expr::Break { expr, label: _ } => { + if let &Some(expr) = expr { + self.infer_mut_expr(expr, Mutability::Not); + } + } + Expr::RecordLit { path: _, fields, spread, ellipsis: _, is_assignee_expr: _ } => { + self.infer_mut_not_expr_iter(fields.iter().map(|x| x.expr).chain(*spread)) + } + &Expr::Index { base, index } => { + if mutability == Mutability::Mut { + if let Some((f, _)) = self.result.method_resolutions.get_mut(&tgt_expr) { + if let Some(index_trait) = self + .db + .lang_item(self.table.trait_env.krate, LangItem::IndexMut) + .and_then(|l| l.as_trait()) + { + if let Some(index_fn) = + self.db.trait_data(index_trait).method_by_name(&name![index_mut]) + { + *f = index_fn; + let base_adjustments = self + .result + .expr_adjustments + .get_mut(&base) + .and_then(|it| it.last_mut()); + if let Some(Adjustment { + kind: Adjust::Borrow(AutoBorrow::Ref(mutability)), + .. + }) = base_adjustments + { + *mutability = Mutability::Mut; + } + } + } + } + } + self.infer_mut_expr(base, mutability); + self.infer_mut_expr(index, Mutability::Not); + } + Expr::UnaryOp { expr, op: UnaryOp::Deref } => { + if let Some((f, _)) = self.result.method_resolutions.get_mut(&tgt_expr) { + if mutability == Mutability::Mut { + if let Some(deref_trait) = self + .db + .lang_item(self.table.trait_env.krate, LangItem::DerefMut) + .and_then(|l| l.as_trait()) + { + if let Some(deref_fn) = + self.db.trait_data(deref_trait).method_by_name(&name![deref_mut]) + { + *f = deref_fn; + } + } + } + } + self.infer_mut_expr(*expr, mutability); + } + Expr::Field { expr, name: _ } => { + self.infer_mut_expr(*expr, mutability); + } + Expr::UnaryOp { expr, op: _ } + | Expr::Range { lhs: Some(expr), rhs: None, range_type: _ } + | Expr::Range { rhs: Some(expr), lhs: None, range_type: _ } + | Expr::Await { expr } + | Expr::Box { expr } + | Expr::Loop { body: expr, label: _ } + | Expr::Cast { expr, type_ref: _ } => { + self.infer_mut_expr(*expr, Mutability::Not); + } + Expr::Ref { expr, rawness: _, mutability } => { + let mutability = lower_to_chalk_mutability(*mutability); + self.infer_mut_expr(*expr, mutability); + } + Expr::BinaryOp { lhs, rhs, op: Some(BinaryOp::Assignment { .. }) } => { + self.infer_mut_expr(*lhs, Mutability::Mut); + self.infer_mut_expr(*rhs, Mutability::Not); + } + Expr::Array(Array::Repeat { initializer: lhs, repeat: rhs }) + | Expr::BinaryOp { lhs, rhs, op: _ } + | Expr::Range { lhs: Some(lhs), rhs: Some(rhs), range_type: _ } => { + self.infer_mut_expr(*lhs, Mutability::Not); + self.infer_mut_expr(*rhs, Mutability::Not); + } + Expr::Closure { body, .. } => { + self.infer_mut_expr(*body, Mutability::Not); + } + Expr::Tuple { exprs, is_assignee_expr: _ } + | Expr::Array(Array::ElementList { elements: exprs, is_assignee_expr: _ }) => { + self.infer_mut_not_expr_iter(exprs.iter().copied()); + } + // These don't need any action, as they don't have sub expressions + Expr::Range { lhs: None, rhs: None, range_type: _ } + | Expr::Literal(_) + | Expr::Path(_) + | Expr::Continue { .. } + | Expr::Underscore => (), + } + } + + fn infer_mut_not_expr_iter(&mut self, exprs: impl Iterator<Item = ExprId>) { + for expr in exprs { + self.infer_mut_expr(expr, Mutability::Not); + } + } + + fn pat_iter_bound_mutability(&self, mut pat: impl Iterator<Item = PatId>) -> Mutability { + if pat.any(|p| self.pat_bound_mutability(p) == Mutability::Mut) { + Mutability::Mut + } else { + Mutability::Not + } + } + + /// Checks if the pat contains a `ref mut` binding. Such paths makes the context of bounded expressions + /// mutable. For example in `let (ref mut x0, ref x1) = *x;` we need to use `DerefMut` for `*x` but in + /// `let (ref x0, ref x1) = *x;` we should use `Deref`. + fn pat_bound_mutability(&self, pat: PatId) -> Mutability { + let mut r = Mutability::Not; + self.body.walk_bindings_in_pat(pat, |b| { + if self.body.bindings[b].mode == BindingAnnotation::RefMut { + r = Mutability::Mut; + } + }); + r + } +} |