3 files changed, 39 insertions, 2 deletions

diff --git a/crates/ra_hir/src/marks.rs b/crates/ra_hir/src/marks.rs
index 5b6400042..2d831f0d8 100644
--- a/crates/ra_hir/src/marks.rs
+++ b/crates/ra_hir/src/marks.rs
@@ -9,4 +9,5 @@ test_utils::marks!(
     glob_across_crates
     std_prelude
     match_ergonomics_ref
+    trait_resolution_on_fn_type
 );
diff --git a/crates/ra_hir/src/ty/tests.rs b/crates/ra_hir/src/ty/tests.rs
index 3c55a093f..f0793bfb4 100644
--- a/crates/ra_hir/src/ty/tests.rs
+++ b/crates/ra_hir/src/ty/tests.rs
@@ -2568,6 +2568,19 @@ fn test() { S2.into()<|>; }
     assert_eq!(t, "S1");
 }
 
+#[test]
+fn method_resolution_encountering_fn_type() {
+    covers!(trait_resolution_on_fn_type);
+    type_at(
+        r#"
+//- /main.rs
+fn foo() {}
+trait FnOnce { fn call(self); }
+fn test() { foo.call()<|>; }
+"#,
+    );
+}
+
 fn type_at_pos(db: &MockDatabase, pos: FilePosition) -> String {
     let file = db.parse(pos.file_id);
     let expr = algo::find_node_at_offset::<ast::Expr>(file.syntax(), pos.offset).unwrap();
diff --git a/crates/ra_hir/src/ty/traits/chalk.rs b/crates/ra_hir/src/ty/traits/chalk.rs
index 787970186..7bb6a4f4a 100644
--- a/crates/ra_hir/src/ty/traits/chalk.rs
+++ b/crates/ra_hir/src/ty/traits/chalk.rs
@@ -6,12 +6,13 @@ use log::debug;
 use chalk_ir::{TypeId, ImplId, TypeKindId, ProjectionTy, Parameter, Identifier, cast::Cast, PlaceholderIndex, UniverseIndex, TypeName};
 use chalk_rust_ir::{AssociatedTyDatum, TraitDatum, StructDatum, ImplDatum};
 
+use test_utils::tested_by;
 use ra_db::salsa::{InternId, InternKey};
 
 use crate::{
     Trait, HasGenericParams, ImplBlock,
     db::HirDatabase,
-    ty::{TraitRef, Ty, ApplicationTy, TypeCtor, Substs, GenericPredicate}, generics::GenericDef,
+    ty::{TraitRef, Ty, ApplicationTy, TypeCtor, Substs, GenericPredicate}, generics::GenericDef, ty::CallableDef,
 };
 use super::ChalkContext;
 
@@ -261,7 +262,29 @@ where
             }
             TypeCtor::FnPtr { num_args } => (num_args as usize + 1, vec![], true),
             TypeCtor::Tuple { cardinality } => (cardinality as usize, vec![], true),
-            TypeCtor::FnDef(_) => unimplemented!(),
+            TypeCtor::FnDef(callable) => {
+                tested_by!(trait_resolution_on_fn_type);
+                let krate = match callable {
+                    CallableDef::Function(f) => f.module(self.db).krate(self.db),
+                    CallableDef::Struct(s) => s.module(self.db).krate(self.db),
+                    CallableDef::EnumVariant(v) => {
+                        v.parent_enum(self.db).module(self.db).krate(self.db)
+                    }
+                };
+                let generic_def: GenericDef = match callable {
+                    CallableDef::Function(f) => f.into(),
+                    CallableDef::Struct(s) => s.into(),
+                    CallableDef::EnumVariant(v) => v.parent_enum(self.db).into(),
+                };
+                let generic_params = generic_def.generic_params(self.db);
+                let bound_vars = Substs::bound_vars(&generic_params);
+                let where_clauses = convert_where_clauses(self.db, generic_def, &bound_vars);
+                (
+                    generic_params.count_params_including_parent(),
+                    where_clauses,
+                    krate != Some(self.krate),
+                )
+            }
             TypeCtor::Adt(adt) => {
                 let generic_params = adt.generic_params(self.db);
                 let bound_vars = Substs::bound_vars(&generic_params);