Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 82 insertions, 0 deletions

diff --git a/src/tools/rust-analyzer/crates/hir-ty/src/infer/closure.rs b/src/tools/rust-analyzer/crates/hir-ty/src/infer/closure.rs
new file mode 100644
index 000000000..3ead92909
--- /dev/null
+++ b/src/tools/rust-analyzer/crates/hir-ty/src/infer/closure.rs
@@ -0,0 +1,82 @@
+//! Inference of closure parameter types based on the closure's expected type.
+
+use chalk_ir::{cast::Cast, AliasEq, AliasTy, FnSubst, WhereClause};
+use hir_def::{expr::ExprId, HasModule};
+use smallvec::SmallVec;
+
+use crate::{
+    to_chalk_trait_id, utils, ChalkTraitId, DynTy, FnPointer, FnSig, Interner, Substitution, Ty,
+    TyExt, TyKind,
+};
+
+use super::{Expectation, InferenceContext};
+
+impl InferenceContext<'_> {
+    pub(super) fn deduce_closure_type_from_expectations(
+        &mut self,
+        closure_expr: ExprId,
+        closure_ty: &Ty,
+        sig_ty: &Ty,
+        expectation: &Expectation,
+    ) {
+        let expected_ty = match expectation.to_option(&mut self.table) {
+            Some(ty) => ty,
+            None => return,
+        };
+
+        // Deduction from where-clauses in scope, as well as fn-pointer coercion are handled here.
+        let _ = self.coerce(Some(closure_expr), closure_ty, &expected_ty);
+
+        // Deduction based on the expected `dyn Fn` is done separately.
+        if let TyKind::Dyn(dyn_ty) = expected_ty.kind(Interner) {
+            if let Some(sig) = self.deduce_sig_from_dyn_ty(dyn_ty) {
+                let expected_sig_ty = TyKind::Function(sig).intern(Interner);
+
+                self.unify(sig_ty, &expected_sig_ty);
+            }
+        }
+    }
+
+    fn deduce_sig_from_dyn_ty(&self, dyn_ty: &DynTy) -> Option<FnPointer> {
+        // Search for a predicate like `<$self as FnX<Args>>::Output == Ret`
+
+        let fn_traits: SmallVec<[ChalkTraitId; 3]> =
+            utils::fn_traits(self.db.upcast(), self.owner.module(self.db.upcast()).krate())
+                .map(to_chalk_trait_id)
+                .collect();
+
+        let self_ty = TyKind::Error.intern(Interner);
+        let bounds = dyn_ty.bounds.clone().substitute(Interner, &[self_ty.cast(Interner)]);
+        for bound in bounds.iter(Interner) {
+            // NOTE(skip_binders): the extracted types are rebound by the returned `FnPointer`
+            if let WhereClause::AliasEq(AliasEq { alias: AliasTy::Projection(projection), ty }) =
+                bound.skip_binders()
+            {
+                let assoc_data = self.db.associated_ty_data(projection.associated_ty_id);
+                if !fn_traits.contains(&assoc_data.trait_id) {
+                    return None;
+                }
+
+                // Skip `Self`, get the type argument.
+                let arg = projection.substitution.as_slice(Interner).get(1)?;
+                if let Some(subst) = arg.ty(Interner)?.as_tuple() {
+                    let generic_args = subst.as_slice(Interner);
+                    let mut sig_tys = Vec::new();
+                    for arg in generic_args {
+                        sig_tys.push(arg.ty(Interner)?.clone());
+                    }
+                    sig_tys.push(ty.clone());
+
+                    cov_mark::hit!(dyn_fn_param_informs_call_site_closure_signature);
+                    return Some(FnPointer {
+                        num_binders: bound.len(Interner),
+                        sig: FnSig { abi: (), safety: chalk_ir::Safety::Safe, variadic: false },
+                        substitution: FnSubst(Substitution::from_iter(Interner, sig_tys)),
+                    });
+                }
+            }
+        }
+
+        None
+    }
+}