diff --git a/chalk-engine/src/table.rs b/chalk-engine/src/table.rs
index bb0de48bb9d..e883cad322e 100644
--- a/chalk-engine/src/table.rs
+++ b/chalk-engine/src/table.rs
@@ -83,7 +83,7 @@ impl<I: Interner> Table<I> {
     }
 
     pub(crate) fn take_strands(&mut self) -> VecDeque<CanonicalStrand<I>> {
-        mem::replace(&mut self.strands, VecDeque::new())
+        mem::take(&mut self.strands)
     }
 
     /// Remove the next strand from the queue that meets the given criteria
diff --git a/chalk-integration/src/lowering.rs b/chalk-integration/src/lowering.rs
index dbee9a14b90..11965edf3fe 100644
--- a/chalk-integration/src/lowering.rs
+++ b/chalk-integration/src/lowering.rs
@@ -285,7 +285,7 @@ impl LowerWithEnv for (&AdtDefn, chalk_ir::AdtId<ChalkIr>) {
     fn lower(&self, env: &Env) -> LowerResult<Self::Lowered> {
         let (adt_defn, adt_id) = self;
 
-        if adt_defn.flags.fundamental && adt_defn.all_parameters().len() < 1 {
+        if adt_defn.flags.fundamental && adt_defn.all_parameters().is_empty() {
             return Err(RustIrError::InvalidFundamentalTypesParameters(
                 adt_defn.name.clone(),
             ));
@@ -669,7 +669,7 @@ impl LowerWithEnv for Ty {
         Ok(match self {
             Ty::Id { name } => {
                 let parameter = env.lookup_generic_arg(name)?;
-                parameter.ty(interner).map(|ty| ty.clone()).ok_or_else(|| {
+                parameter.ty(interner).cloned().ok_or_else(|| {
                     RustIrError::IncorrectParameterKind {
                         identifier: name.clone(),
                         expected: Kind::Ty,
diff --git a/chalk-integration/src/lowering/env.rs b/chalk-integration/src/lowering/env.rs
index 482f3364a2a..63e27a51f63 100644
--- a/chalk-integration/src/lowering/env.rs
+++ b/chalk-integration/src/lowering/env.rs
@@ -219,7 +219,7 @@ impl Env<'_> {
     ) -> LowerResult<&AssociatedTyLookup> {
         self.associated_ty_lookups
             .get(&(trait_id, ident.str.clone()))
-            .ok_or(RustIrError::MissingAssociatedType(ident.clone()))
+            .ok_or_else(|| RustIrError::MissingAssociatedType(ident.clone()))
     }
 
     /// Introduces new parameters, shifting the indices of existing
diff --git a/chalk-integration/src/program.rs b/chalk-integration/src/program.rs
index 100a8af16c6..9473ddf8d17 100644
--- a/chalk-integration/src/program.rs
+++ b/chalk-integration/src/program.rs
@@ -447,8 +447,7 @@ impl RustIrDatabase<ChalkIr> for Program {
                 let trait_ref = &impl_datum.binders.skip_binders().trait_ref;
                 trait_id == trait_ref.trait_id && {
                     assert_eq!(trait_ref.substitution.len(interner), parameters.len());
-                    <[_] as CouldMatch<[_]>>::could_match(
-                        parameters,
+                    parameters.could_match(
                         interner,
                         self.unification_database(),
                         trait_ref.substitution.as_slice(interner),
@@ -594,12 +593,11 @@ impl RustIrDatabase<ChalkIr> for Program {
     fn discriminant_type(&self, ty: Ty<ChalkIr>) -> Ty<ChalkIr> {
         let interner = self.interner();
         match ty.data(interner).kind {
-            TyKind::Adt(id, _) => {
-                let repr = self.adt_repr(id);
-                repr.int
-                    .clone()
-                    .unwrap_or(TyKind::Scalar(Scalar::Int(IntTy::Isize)).intern(interner))
-            }
+            TyKind::Adt(id, _) => self
+                .adt_repr(id)
+                .int
+                .clone()
+                .unwrap_or_else(|| TyKind::Scalar(Scalar::Int(IntTy::Isize)).intern(interner)),
             TyKind::Generator(..) => TyKind::Scalar(Scalar::Uint(UintTy::U32)).intern(interner),
             _ => TyKind::Scalar(Scalar::Uint(UintTy::U8)).intern(interner),
         }
diff --git a/chalk-recursive/src/fulfill.rs b/chalk-recursive/src/fulfill.rs
index 98156336ff7..d854dcc701c 100644
--- a/chalk-recursive/src/fulfill.rs
+++ b/chalk-recursive/src/fulfill.rs
@@ -495,7 +495,7 @@ impl<'s, I: Interner, Solver: SolveDatabase<I>> Fulfill<'s, I, Solver> {
                 }
             }
 
-            self.obligations.extend(obligations.drain(..));
+            self.obligations.append(&mut obligations);
             debug!("end of round, {} obligations left", self.obligations.len());
         }
 
diff --git a/chalk-solve/src/clauses.rs b/chalk-solve/src/clauses.rs
index 37e741cea1e..e795c8fd63e 100644
--- a/chalk-solve/src/clauses.rs
+++ b/chalk-solve/src/clauses.rs
@@ -1089,12 +1089,11 @@ fn match_alias_ty<I: Interner>(
     environment: &Environment<I>,
     alias: &AliasTy<I>,
 ) {
-    match alias {
-        AliasTy::Projection(projection_ty) => builder
+    if let AliasTy::Projection(projection_ty) = alias {
+        builder
             .db
             .associated_ty_data(projection_ty.associated_ty_id)
-            .to_program_clauses(builder, environment),
-        _ => (),
+            .to_program_clauses(builder, environment)
     }
 }
 
diff --git a/chalk-solve/src/infer/unify.rs b/chalk-solve/src/infer/unify.rs
index 038297f32b7..e5e169fdc75 100644
--- a/chalk-solve/src/infer/unify.rs
+++ b/chalk-solve/src/infer/unify.rs
@@ -184,11 +184,11 @@ impl<'t, I: Interner> Unifier<'t, I> {
             (_, &TyKind::Alias(ref alias)) => self.relate_alias_ty(variance.invert(), alias, a),
             (&TyKind::Alias(ref alias), _) => self.relate_alias_ty(variance, alias, b),
 
-            (&TyKind::InferenceVar(var, kind), ty_data @ _) => {
+            (&TyKind::InferenceVar(var, kind), ty_data) => {
                 let ty = ty_data.clone().intern(interner);
                 self.relate_var_ty(variance, var, kind, &ty)
             }
-            (ty_data @ _, &TyKind::InferenceVar(var, kind)) => {
+            (ty_data, &TyKind::InferenceVar(var, kind)) => {
                 // We need to invert the variance if inference var is `b` because we pass it in
                 // as `a` to relate_var_ty
                 let ty = ty_data.clone().intern(interner);
diff --git a/chalk-solve/src/logging_db.rs b/chalk-solve/src/logging_db.rs
index 00408a28a0c..f736e103c76 100644
--- a/chalk-solve/src/logging_db.rs
+++ b/chalk-solve/src/logging_db.rs
@@ -210,7 +210,9 @@ where
         well_known_trait: crate::rust_ir::WellKnownTrait,
     ) -> Option<TraitId<I>> {
         let trait_id = self.ws.db().well_known_trait_id(well_known_trait);
-        trait_id.map(|id| self.record(id));
+        if let Some(id) = trait_id {
+            self.record(id);
+        }
         trait_id
     }
 
diff --git a/src/main.rs b/src/main.rs
index 3a2c145b1cd..577835bc017 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -71,7 +71,7 @@ impl LoadedProgram {
         let goal = lower_goal(&*chalk_parse::parse_goal(text)?, &*program)?;
         let peeled_goal = goal.into_peeled_goal(self.db.interner());
         if multiple_answers {
-            if self.db.solve_multiple(&peeled_goal, &mut |v, has_next| {
+            let no_more_solutions = self.db.solve_multiple(&peeled_goal, &mut |v, has_next| {
                 println!("{}\n", v.as_ref().map(|v| v.display(ChalkIr)));
                 if has_next {
                     if let Some(ref mut rl) = rl {
@@ -94,7 +94,8 @@ impl LoadedProgram {
                 } else {
                     true
                 }
-            }) {
+            });
+            if no_more_solutions {
                 println!("No more solutions");
             }
         } else {
@@ -290,7 +291,7 @@ fn read_program(rl: &mut rustyline::Editor<()>) -> Result<String> {
 
 impl Args {
     fn solver_choice(&self) -> SolverChoice {
-        match self.flag_solver.as_ref().map(String::as_str) {
+        match self.flag_solver.as_deref() {
             None | Some("slg") => SolverChoice::SLG {
                 max_size: self.flag_overflow_depth,
                 expected_answers: None,
diff --git a/tests/display/util.rs b/tests/display/util.rs
index 2e55d702ef2..1f40313b4a0 100644
--- a/tests/display/util.rs
+++ b/tests/display/util.rs
@@ -74,9 +74,7 @@ pub fn program_item_ids(program: &Program) -> impl Iterator<Item = RecordedItemI
 
     // then discard the RawId since the RecordedItemId has the same information,
     // and is what we actually want to consume.
-    let ids = ids.into_iter().map(|(_, id)| id);
-
-    ids
+    ids.into_iter().map(|(_, id)| id)
 }
 
 /// Sends all items in a `chalk_integration::Program` through `display` code and
@@ -146,9 +144,9 @@ fn program_diff(original: &impl Debug, produced: &impl Debug) -> String {
     let produced = format!("{:#?}", produced);
     for line in diff::lines(&original, &produced) {
         match line {
-            diff::Result::Left(l) => write!(out, "-{}\n", l),
-            diff::Result::Both(l, _) => write!(out, " {}\n", l),
-            diff::Result::Right(r) => write!(out, "+{}\n", r),
+            diff::Result::Left(l) => writeln!(out, "-{}", l),
+            diff::Result::Both(l, _) => writeln!(out, " {}", l),
+            diff::Result::Right(r) => writeln!(out, "+{}", r),
         }
         .expect("writing to string never fails");
     }
diff --git a/tests/logging_db/util.rs b/tests/logging_db/util.rs
index 2e4d23643e2..ca00e9a24ff 100644
--- a/tests/logging_db/util.rs
+++ b/tests/logging_db/util.rs
@@ -35,7 +35,7 @@ pub fn logging_db_output_sufficient(
 
     let goals = goals
         .iter()
-        .flat_map(|(a, bs, c)| bs.into_iter().map(move |b| (a, b, c)));
+        .flat_map(|(a, bs, c)| bs.iter().map(move |b| (a, b, c)));
 
     let output_text = {
         let db = ChalkDatabase::with(
diff --git a/tests/test/mod.rs b/tests/test/mod.rs
index 88ccc18e4d5..824b00cd598 100644
--- a/tests/test/mod.rs
+++ b/tests/test/mod.rs
@@ -24,17 +24,14 @@ mod wf_lowering;
 
 fn format_solution(mut result: Option<Solution<ChalkIr>>, interner: ChalkIr) -> String {
     // sort constraints, since the different solvers may output them in different order
-    match &mut result {
-        Some(Solution::Unique(solution)) => {
-            let mut sorted = solution.value.constraints.as_slice(interner).to_vec();
-            sorted.sort_by_key(|c| format!("{:?}", c));
-            solution.value.constraints = Constraints::from_iter(interner, sorted);
-        }
-        _ => {}
+    if let Some(Solution::Unique(solution)) = &mut result {
+        let mut sorted = solution.value.constraints.as_slice(interner).to_vec();
+        sorted.sort_by_key(|c| format!("{:?}", c));
+        solution.value.constraints = Constraints::from_iter(interner, sorted);
     }
     match result {
-        Some(v) => format!("{}", v.display(ChalkIr)),
-        None => format!("No possible solution"),
+        Some(v) => v.display(ChalkIr).to_string(),
+        None => "No possible solution".to_string(),
     }
 }
 
@@ -310,7 +307,7 @@ fn solve_goal(
                         assert_result(result, expected, db.interner());
                     }
                     TestGoal::All(expected) => {
-                        let mut expected = expected.into_iter();
+                        let mut expected = expected.iter();
                         assert!(
                             db.solve_multiple(&peeled_goal, &mut |result, next_result| {
                                 match expected.next() {
@@ -334,7 +331,7 @@ fn solve_goal(
                         }
                     }
                     TestGoal::First(expected) => {
-                        let mut expected = expected.into_iter();
+                        let mut expected = expected.iter();
                         db.solve_multiple(&peeled_goal, &mut |result, next_result| match expected
                             .next()
                         {