31 files changed, 137 insertions, 154 deletions

diff --git a/crates/ra_assists/src/handlers/add_custom_impl.rs b/crates/ra_assists/src/handlers/add_custom_impl.rs
index 4d3a72c18..74aa4b001 100644
--- a/crates/ra_assists/src/handlers/add_custom_impl.rs
+++ b/crates/ra_assists/src/handlers/add_custom_impl.rs
@@ -43,7 +43,7 @@ pub(crate) fn add_custom_impl(ctx: AssistCtx) -> Option<Assist> {
         .clone();
 
     let trait_token =
-        ctx.token_at_offset().filter(|t| t.kind() == IDENT && *t.text() != attr_name).next()?;
+        ctx.token_at_offset().find(|t| t.kind() == IDENT && *t.text() != attr_name)?;
 
     let annotated = attr.syntax().siblings(Direction::Next).find_map(ast::Name::cast)?;
     let annotated_name = annotated.syntax().text().to_string();
@@ -86,7 +86,7 @@ pub(crate) fn add_custom_impl(ctx: AssistCtx) -> Option<Assist> {
                 .next_sibling_or_token()
                 .filter(|t| t.kind() == WHITESPACE)
                 .map(|t| t.text_range())
-                .unwrap_or(TextRange::from_to(TextUnit::from(0), TextUnit::from(0)));
+                .unwrap_or_else(|| TextRange::from_to(TextUnit::from(0), TextUnit::from(0)));
             edit.delete(line_break_range);
 
             attr_range.len() + line_break_range.len()
diff --git a/crates/ra_assists/src/handlers/move_guard.rs b/crates/ra_assists/src/handlers/move_guard.rs
index a61a2ba3e..1cc498638 100644
--- a/crates/ra_assists/src/handlers/move_guard.rs
+++ b/crates/ra_assists/src/handlers/move_guard.rs
@@ -44,7 +44,7 @@ pub(crate) fn move_guard_to_arm_body(ctx: AssistCtx) -> Option<Assist> {
         edit.target(guard.syntax().text_range());
         let offseting_amount = match space_before_guard.and_then(|it| it.into_token()) {
             Some(tok) => {
-                if let Some(_) = ast::Whitespace::cast(tok.clone()) {
+                if ast::Whitespace::cast(tok.clone()).is_some() {
                     let ele = tok.text_range();
                     edit.delete(ele);
                     ele.len()
@@ -98,11 +98,11 @@ pub(crate) fn move_arm_cond_to_match_guard(ctx: AssistCtx) -> Option<Assist> {
     let then_block = if_expr.then_branch()?;
 
     // Not support if with else branch
-    if let Some(_) = if_expr.else_branch() {
+    if if_expr.else_branch().is_some() {
         return None;
     }
     // Not support moving if let to arm guard
-    if let Some(_) = cond.pat() {
+    if cond.pat().is_some() {
         return None;
     }
 
diff --git a/crates/ra_hir/src/code_model.rs b/crates/ra_hir/src/code_model.rs
index fe9149c9d..1bdcda069 100644
--- a/crates/ra_hir/src/code_model.rs
+++ b/crates/ra_hir/src/code_model.rs
@@ -988,20 +988,17 @@ impl Type {
 
     pub fn fields(&self, db: &impl HirDatabase) -> Vec<(StructField, Type)> {
         if let Ty::Apply(a_ty) = &self.ty.value {
-            match a_ty.ctor {
-                TypeCtor::Adt(AdtId::StructId(s)) => {
-                    let var_def = s.into();
-                    return db
-                        .field_types(var_def)
-                        .iter()
-                        .map(|(local_id, ty)| {
-                            let def = StructField { parent: var_def.into(), id: local_id };
-                            let ty = ty.clone().subst(&a_ty.parameters);
-                            (def, self.derived(ty))
-                        })
-                        .collect();
-                }
-                _ => {}
+            if let TypeCtor::Adt(AdtId::StructId(s)) = a_ty.ctor {
+                let var_def = s.into();
+                return db
+                    .field_types(var_def)
+                    .iter()
+                    .map(|(local_id, ty)| {
+                        let def = StructField { parent: var_def.into(), id: local_id };
+                        let ty = ty.clone().subst(&a_ty.parameters);
+                        (def, self.derived(ty))
+                    })
+                    .collect();
             }
         };
         Vec::new()
@@ -1010,14 +1007,11 @@ impl Type {
     pub fn tuple_fields(&self, _db: &impl HirDatabase) -> Vec<Type> {
         let mut res = Vec::new();
         if let Ty::Apply(a_ty) = &self.ty.value {
-            match a_ty.ctor {
-                TypeCtor::Tuple { .. } => {
-                    for ty in a_ty.parameters.iter() {
-                        let ty = ty.clone();
-                        res.push(self.derived(ty));
-                    }
+            if let TypeCtor::Tuple { .. } = a_ty.ctor {
+                for ty in a_ty.parameters.iter() {
+                    let ty = ty.clone();
+                    res.push(self.derived(ty));
                 }
-                _ => {}
             }
         };
         res
diff --git a/crates/ra_hir_def/src/item_scope.rs b/crates/ra_hir_def/src/item_scope.rs
index f8dc06d10..6e958ca75 100644
--- a/crates/ra_hir_def/src/item_scope.rs
+++ b/crates/ra_hir_def/src/item_scope.rs
@@ -157,7 +157,7 @@ impl ItemScope {
     }
 
     pub(crate) fn resolutions<'a>(&'a self) -> impl Iterator<Item = (Name, PerNs)> + 'a {
-        self.visible.iter().map(|(name, res)| (name.clone(), res.clone()))
+        self.visible.iter().map(|(name, res)| (name.clone(), *res))
     }
 
     pub(crate) fn collect_legacy_macros(&self) -> FxHashMap<Name, MacroDefId> {
diff --git a/crates/ra_hir_def/src/lib.rs b/crates/ra_hir_def/src/lib.rs
index aa0b558b8..564b5fec5 100644
--- a/crates/ra_hir_def/src/lib.rs
+++ b/crates/ra_hir_def/src/lib.rs
@@ -460,7 +460,7 @@ impl AsMacroCall for AstIdWithPath<ast::MacroCall> {
         resolver: impl Fn(path::ModPath) -> Option<MacroDefId>,
     ) -> Option<MacroCallId> {
         let def = resolver(self.path.clone())?;
-        Some(def.as_call_id(db, MacroCallKind::FnLike(self.ast_id.clone())))
+        Some(def.as_call_id(db, MacroCallKind::FnLike(self.ast_id)))
     }
 }
 
@@ -471,6 +471,6 @@ impl AsMacroCall for AstIdWithPath<ast::ModuleItem> {
         resolver: impl Fn(path::ModPath) -> Option<MacroDefId>,
     ) -> Option<MacroCallId> {
         let def = resolver(self.path.clone())?;
-        Some(def.as_call_id(db, MacroCallKind::Attr(self.ast_id.clone())))
+        Some(def.as_call_id(db, MacroCallKind::Attr(self.ast_id)))
     }
 }
diff --git a/crates/ra_hir_expand/src/builtin_macro.rs b/crates/ra_hir_expand/src/builtin_macro.rs
index 4adaa9b07..f2bb0bddb 100644
--- a/crates/ra_hir_expand/src/builtin_macro.rs
+++ b/crates/ra_hir_expand/src/builtin_macro.rs
@@ -155,14 +155,11 @@ fn compile_error_expand(
     tt: &tt::Subtree,
 ) -> Result<tt::Subtree, mbe::ExpandError> {
     if tt.count() == 1 {
-        match &tt.token_trees[0] {
-            tt::TokenTree::Leaf(tt::Leaf::Literal(it)) => {
-                let s = it.text.as_str();
-                if s.contains('"') {
-                    return Ok(quote! { loop { #it }});
-                }
+        if let tt::TokenTree::Leaf(tt::Leaf::Literal(it)) = &tt.token_trees[0] {
+            let s = it.text.as_str();
+            if s.contains('"') {
+                return Ok(quote! { loop { #it }});
             }
-            _ => {}
         };
     }
 
diff --git a/crates/ra_hir_expand/src/quote.rs b/crates/ra_hir_expand/src/quote.rs
index b54e00b68..57e7eebf9 100644
--- a/crates/ra_hir_expand/src/quote.rs
+++ b/crates/ra_hir_expand/src/quote.rs
@@ -15,14 +15,13 @@ macro_rules! __quote {
     ( @SUBTREE $delim:ident $($tt:tt)* ) => {
         {
             let children = $crate::__quote!($($tt)*);
-            let subtree = tt::Subtree {
+            tt::Subtree {
                 delimiter: Some(tt::Delimiter {
                     kind: tt::DelimiterKind::$delim,
                     id: tt::TokenId::unspecified(),
                 }),
                 token_trees: $crate::quote::IntoTt::to_tokens(children),
-            };
-            subtree
+            }
         }
     };
 
diff --git a/crates/ra_hir_ty/src/diagnostics.rs b/crates/ra_hir_ty/src/diagnostics.rs
index 5054189cc..6eafdc8f6 100644
--- a/crates/ra_hir_ty/src/diagnostics.rs
+++ b/crates/ra_hir_ty/src/diagnostics.rs
@@ -40,7 +40,7 @@ impl Diagnostic for MissingFields {
         use std::fmt::Write;
         let mut message = String::from("Missing structure fields:\n");
         for field in &self.missed_fields {
-            write!(message, "- {}\n", field).unwrap();
+            writeln!(message, "- {}", field).unwrap();
         }
         message
     }
diff --git a/crates/ra_hir_ty/src/expr.rs b/crates/ra_hir_ty/src/expr.rs
index f752a9f09..0d11b537c 100644
--- a/crates/ra_hir_ty/src/expr.rs
+++ b/crates/ra_hir_ty/src/expr.rs
@@ -138,7 +138,7 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
             _ => return,
         };
 
-        if params.len() == 2 && &params[0] == &mismatch.actual {
+        if params.len() == 2 && params[0] == mismatch.actual {
             let (_, source_map) = db.body_with_source_map(self.func.into());
 
             if let Some(source_ptr) = source_map.expr_syntax(id) {
diff --git a/crates/ra_hir_ty/src/infer/coerce.rs b/crates/ra_hir_ty/src/infer/coerce.rs
index 4a0eabdfc..fb6a51b12 100644
--- a/crates/ra_hir_ty/src/infer/coerce.rs
+++ b/crates/ra_hir_ty/src/infer/coerce.rs
@@ -26,7 +26,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
     /// Note that it is only possible that one type are coerced to another.
     /// Coercing both types to another least upper bound type is not possible in rustc,
     /// which will simply result in "incompatible types" error.
-    pub(super) fn coerce_merge_branch<'t>(&mut self, ty1: &Ty, ty2: &Ty) -> Ty {
+    pub(super) fn coerce_merge_branch(&mut self, ty1: &Ty, ty2: &Ty) -> Ty {
         if self.coerce(ty1, ty2) {
             ty2.clone()
         } else if self.coerce(ty2, ty1) {
@@ -252,15 +252,14 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 let unsize_generic_index = {
                     let mut index = None;
                     let mut multiple_param = false;
-                    field_tys[last_field_id].value.walk(&mut |ty| match ty {
-                        &Ty::Bound(idx) => {
+                    field_tys[last_field_id].value.walk(&mut |ty| {
+                        if let &Ty::Bound(idx) = ty {
                             if index.is_none() {
                                 index = Some(idx);
                             } else if Some(idx) != index {
                                 multiple_param = true;
                             }
                         }
-                        _ => {}
                     });
 
                     if multiple_param {
diff --git a/crates/ra_hir_ty/src/infer/expr.rs b/crates/ra_hir_ty/src/infer/expr.rs
index 0af94ae32..9d5f75625 100644
--- a/crates/ra_hir_ty/src/infer/expr.rs
+++ b/crates/ra_hir_ty/src/infer/expr.rs
@@ -35,8 +35,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 TypeMismatch { expected: expected.ty.clone(), actual: ty.clone() },
             );
         }
-        let ty = self.resolve_ty_as_possible(ty);
-        ty
+        self.resolve_ty_as_possible(ty)
     }
 
     /// Infer type of expression with possibly implicit coerce to the expected type.
@@ -155,8 +154,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 };
                 self.register_obligations_for_call(&callee_ty);
                 self.check_call_arguments(args, &param_tys);
-                let ret_ty = self.normalize_associated_types_in(ret_ty);
-                ret_ty
+                self.normalize_associated_types_in(ret_ty)
             }
             Expr::MethodCall { receiver, args, method_name, generic_args } => self
                 .infer_method_call(tgt_expr, *receiver, &args, &method_name, generic_args.as_ref()),
@@ -280,14 +278,11 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             }
             Expr::Await { expr } => {
                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
-                let ty =
-                    self.resolve_associated_type(inner_ty, self.resolve_future_future_output());
-                ty
+                self.resolve_associated_type(inner_ty, self.resolve_future_future_output())
             }
             Expr::Try { expr } => {
                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
-                let ty = self.resolve_associated_type(inner_ty, self.resolve_ops_try_ok());
-                ty
+                self.resolve_associated_type(inner_ty, self.resolve_ops_try_ok())
             }
             Expr::Cast { expr, type_ref } => {
                 let _inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
@@ -611,8 +606,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         self.unify(&expected_receiver_ty, &actual_receiver_ty);
 
         self.check_call_arguments(args, &param_tys);
-        let ret_ty = self.normalize_associated_types_in(ret_ty);
-        ret_ty
+        self.normalize_associated_types_in(ret_ty)
     }
 
     fn check_call_arguments(&mut self, args: &[ExprId], param_tys: &[Ty]) {
diff --git a/crates/ra_hir_ty/src/infer/unify.rs b/crates/ra_hir_ty/src/infer/unify.rs
index 1dc842f40..9c7996572 100644
--- a/crates/ra_hir_ty/src/infer/unify.rs
+++ b/crates/ra_hir_ty/src/infer/unify.rs
@@ -140,13 +140,12 @@ where
 impl<T> Canonicalized<T> {
     pub fn decanonicalize_ty(&self, mut ty: Ty) -> Ty {
         ty.walk_mut_binders(
-            &mut |ty, binders| match ty {
-                &mut Ty::Bound(idx) => {
+            &mut |ty, binders| {
+                if let &mut Ty::Bound(idx) = ty {
                     if idx as usize >= binders && (idx as usize - binders) < self.free_vars.len() {
                         *ty = Ty::Infer(self.free_vars[idx as usize - binders]);
                     }
                 }
-                _ => {}
             },
             0,
         );
diff --git a/crates/ra_hir_ty/src/lib.rs b/crates/ra_hir_ty/src/lib.rs
index 302bb8aa2..13c5e6c6b 100644
--- a/crates/ra_hir_ty/src/lib.rs
+++ b/crates/ra_hir_ty/src/lib.rs
@@ -763,8 +763,8 @@ pub trait TypeWalk {
         Self: Sized,
     {
         self.walk_mut_binders(
-            &mut |ty, binders| match ty {
-                &mut Ty::Bound(idx) => {
+            &mut |ty, binders| {
+                if let &mut Ty::Bound(idx) = ty {
                     if idx as usize >= binders && (idx as usize - binders) < substs.len() {
                         *ty = substs.0[idx as usize - binders].clone();
                     } else if idx as usize >= binders + substs.len() {
@@ -772,7 +772,6 @@ pub trait TypeWalk {
                         *ty = Ty::Bound(idx - substs.len() as u32);
                     }
                 }
-                _ => {}
             },
             0,
         );
diff --git a/crates/ra_hir_ty/src/op.rs b/crates/ra_hir_ty/src/op.rs
index ae253ca04..54e2bd05a 100644
--- a/crates/ra_hir_ty/src/op.rs
+++ b/crates/ra_hir_ty/src/op.rs
@@ -30,20 +30,18 @@ pub(super) fn binary_op_return_ty(op: BinaryOp, lhs_ty: Ty, rhs_ty: Ty) -> Ty {
 pub(super) fn binary_op_rhs_expectation(op: BinaryOp, lhs_ty: Ty) -> Ty {
     match op {
         BinaryOp::LogicOp(..) => Ty::simple(TypeCtor::Bool),
-        BinaryOp::Assignment { op: None } | BinaryOp::CmpOp(CmpOp::Eq { negated: _ }) => {
-            match lhs_ty {
-                Ty::Apply(ApplicationTy { ctor, .. }) => match ctor {
-                    TypeCtor::Int(..)
-                    | TypeCtor::Float(..)
-                    | TypeCtor::Str
-                    | TypeCtor::Char
-                    | TypeCtor::Bool => lhs_ty,
-                    _ => Ty::Unknown,
-                },
-                Ty::Infer(InferTy::IntVar(..)) | Ty::Infer(InferTy::FloatVar(..)) => lhs_ty,
+        BinaryOp::Assignment { op: None } | BinaryOp::CmpOp(CmpOp::Eq { .. }) => match lhs_ty {
+            Ty::Apply(ApplicationTy { ctor, .. }) => match ctor {
+                TypeCtor::Int(..)
+                | TypeCtor::Float(..)
+                | TypeCtor::Str
+                | TypeCtor::Char
+                | TypeCtor::Bool => lhs_ty,
                 _ => Ty::Unknown,
-            }
-        }
+            },
+            Ty::Infer(InferTy::IntVar(..)) | Ty::Infer(InferTy::FloatVar(..)) => lhs_ty,
+            _ => Ty::Unknown,
+        },
         BinaryOp::ArithOp(ArithOp::Shl) | BinaryOp::ArithOp(ArithOp::Shr) => Ty::Unknown,
         BinaryOp::CmpOp(CmpOp::Ord { .. })
         | BinaryOp::Assignment { op: Some(_) }
diff --git a/crates/ra_hir_ty/src/test_db.rs b/crates/ra_hir_ty/src/test_db.rs
index 1a31b587b..c794f7b84 100644
--- a/crates/ra_hir_ty/src/test_db.rs
+++ b/crates/ra_hir_ty/src/test_db.rs
@@ -86,15 +86,14 @@ impl TestDB {
     pub fn diagnostics(&self) -> String {
         let mut buf = String::new();
         let crate_graph = self.crate_graph();
-        for krate in crate_graph.iter().next() {
+        for krate in crate_graph.iter() {
             let crate_def_map = self.crate_def_map(krate);
 
             let mut fns = Vec::new();
             for (module_id, _) in crate_def_map.modules.iter() {
                 for decl in crate_def_map[module_id].scope.declarations() {
-                    match decl {
-                        ModuleDefId::FunctionId(f) => fns.push(f),
-                        _ => (),
+                    if let ModuleDefId::FunctionId(f) = decl {
+                        fns.push(f)
                     }
                 }
 
diff --git a/crates/ra_hir_ty/src/tests.rs b/crates/ra_hir_ty/src/tests.rs
index d1f10e675..240cc03a2 100644
--- a/crates/ra_hir_ty/src/tests.rs
+++ b/crates/ra_hir_ty/src/tests.rs
@@ -101,9 +101,9 @@ fn infer_with_mismatches(content: &str, include_mismatches: bool) -> String {
                 (src_ptr.value.range(), node.text().to_string().replace("\n", " "))
             };
             let macro_prefix = if src_ptr.file_id != file_id.into() { "!" } else { "" };
-            write!(
+            writeln!(
                 acc,
-                "{}{} '{}': {}\n",
+                "{}{} '{}': {}",
                 macro_prefix,
                 range,
                 ellipsize(text, 15),
@@ -118,9 +118,9 @@ fn infer_with_mismatches(content: &str, include_mismatches: bool) -> String {
             for (src_ptr, mismatch) in &mismatches {
                 let range = src_ptr.value.range();
                 let macro_prefix = if src_ptr.file_id != file_id.into() { "!" } else { "" };
-                write!(
+                writeln!(
                     acc,
-                    "{}{}: expected {}, got {}\n",
+                    "{}{}: expected {}, got {}",
                     macro_prefix,
                     range,
                     mismatch.expected.display(&db),
diff --git a/crates/ra_hir_ty/src/traits.rs b/crates/ra_hir_ty/src/traits.rs
index ff8e75b48..e83449957 100644
--- a/crates/ra_hir_ty/src/traits.rs
+++ b/crates/ra_hir_ty/src/traits.rs
@@ -248,12 +248,9 @@ fn solution_from_chalk(
         let value = subst
             .value
             .into_iter()
-            .map(|p| {
-                let ty = match p.ty() {
-                    Some(ty) => from_chalk(db, ty.clone()),
-                    None => unimplemented!(),
-                };
-                ty
+            .map(|p| match p.ty() {
+                Some(ty) => from_chalk(db, ty.clone()),
+                None => unimplemented!(),
             })
             .collect();
         let result = Canonical { value, num_vars: subst.binders.len() };
diff --git a/crates/ra_hir_ty/src/traits/builtin.rs b/crates/ra_hir_ty/src/traits/builtin.rs
index 67120abf6..a537420a5 100644
--- a/crates/ra_hir_ty/src/traits/builtin.rs
+++ b/crates/ra_hir_ty/src/traits/builtin.rs
@@ -122,7 +122,7 @@ fn closure_fn_trait_impl_datum(
         substs: Substs::build_for_def(db, trait_).push(self_ty).push(arg_ty).build(),
     };
 
-    let output_ty_id = AssocTyValue::ClosureFnTraitImplOutput(data.clone());
+    let output_ty_id = AssocTyValue::ClosureFnTraitImplOutput(data);
 
     BuiltinImplData {
         num_vars: num_args as usize + 1,
@@ -137,7 +137,7 @@ fn closure_fn_trait_output_assoc_ty_value(
     krate: CrateId,
     data: super::ClosureFnTraitImplData,
 ) -> BuiltinImplAssocTyValueData {
-    let impl_ = Impl::ClosureFnTraitImpl(data.clone());
+    let impl_ = Impl::ClosureFnTraitImpl(data);
 
     let num_args: u16 = match &db.body(data.def)[data.expr] {
         Expr::Lambda { args, .. } => args.len() as u16,
diff --git a/crates/ra_hir_ty/src/traits/chalk.rs b/crates/ra_hir_ty/src/traits/chalk.rs
index 306909ec2..1bdf13e48 100644
--- a/crates/ra_hir_ty/src/traits/chalk.rs
+++ b/crates/ra_hir_ty/src/traits/chalk.rs
@@ -409,8 +409,7 @@ where
     fn to_chalk(self, db: &impl HirDatabase) -> chalk_ir::Canonical<T::Chalk> {
         let parameter = chalk_ir::ParameterKind::Ty(chalk_ir::UniverseIndex::ROOT);
         let value = self.value.to_chalk(db);
-        let canonical = chalk_ir::Canonical { value, binders: vec![parameter; self.num_vars] };
-        canonical
+        chalk_ir::Canonical { value, binders: vec![parameter; self.num_vars] }
     }
 
     fn from_chalk(db: &impl HirDatabase, canonical: chalk_ir::Canonical<T::Chalk>) -> Canonical<T> {
diff --git a/crates/ra_ide/src/call_info.rs b/crates/ra_ide/src/call_info.rs
index f2b29306e..7c6322cb4 100644
--- a/crates/ra_ide/src/call_info.rs
+++ b/crates/ra_ide/src/call_info.rs
@@ -128,7 +128,7 @@ impl FnCallNode {
             }),
 
             FnCallNode::MethodCallExpr(call_expr) => {
-                call_expr.syntax().children().filter_map(ast::NameRef::cast).nth(0)
+                call_expr.syntax().children().filter_map(ast::NameRef::cast).next()
             }
 
             FnCallNode::MacroCallExpr(call_expr) => call_expr.path()?.segment()?.name_ref(),
diff --git a/crates/ra_ide/src/completion/complete_trait_impl.rs b/crates/ra_ide/src/completion/complete_trait_impl.rs
index 6ff10c017..83628e35c 100644
--- a/crates/ra_ide/src/completion/complete_trait_impl.rs
+++ b/crates/ra_ide/src/completion/complete_trait_impl.rs
@@ -59,7 +59,7 @@ pub(crate) fn complete_trait_impl(acc: &mut Completions, ctx: &CompletionContext
         .as_ref()
         .and_then(|node| node.parent())
         .and_then(|node| node.parent())
-        .and_then(|node| ast::ImplBlock::cast(node));
+        .and_then(ast::ImplBlock::cast);
 
     if let (Some(trigger), Some(impl_block)) = (trigger, impl_block) {
         match trigger.kind() {
@@ -110,17 +110,17 @@ fn add_function_impl(
     ctx: &CompletionContext,
     func: &hir::Function,
 ) {
-    let display = FunctionSignature::from_hir(ctx.db, func.clone());
+    let display = FunctionSignature::from_hir(ctx.db, *func);
 
     let fn_name = func.name(ctx.db).to_string();
 
-    let label = if func.params(ctx.db).len() > 0 {
+    let label = if !func.params(ctx.db).is_empty() {
         format!("fn {}(..)", fn_name)
     } else {
         format!("fn {}()", fn_name)
     };
 
-    let builder = CompletionItem::new(CompletionKind::Magic, ctx.source_range(), label.clone())
+    let builder = CompletionItem::new(CompletionKind::Magic, ctx.source_range(), label)
         .lookup_by(fn_name)
         .set_documentation(func.docs(ctx.db));
 
diff --git a/crates/ra_ide/src/completion/completion_item.rs b/crates/ra_ide/src/completion/completion_item.rs
index 93f336370..61867c0ff 100644
--- a/crates/ra_ide/src/completion/completion_item.rs
+++ b/crates/ra_ide/src/completion/completion_item.rs
@@ -159,7 +159,7 @@ impl CompletionItem {
 
     /// Short one-line additional information, like a type
     pub fn detail(&self) -> Option<&str> {
-        self.detail.as_ref().map(|it| it.as_str())
+        self.detail.as_deref()
     }
     /// A doc-comment
     pub fn documentation(&self) -> Option<Documentation> {
@@ -167,7 +167,7 @@ impl CompletionItem {
     }
     /// What string is used for filtering.
     pub fn lookup(&self) -> &str {
-        self.lookup.as_ref().map(|it| it.as_str()).unwrap_or_else(|| self.label())
+        self.lookup.as_deref().unwrap_or_else(|| self.label())
     }
 
     pub fn kind(&self) -> Option<CompletionItemKind> {
diff --git a/crates/ra_ide/src/display/function_signature.rs b/crates/ra_ide/src/display/function_signature.rs
index c23e08e9a..b85fd8075 100644
--- a/crates/ra_ide/src/display/function_signature.rs
+++ b/crates/ra_ide/src/display/function_signature.rs
@@ -54,9 +54,8 @@ impl FunctionSignature {
 
     pub(crate) fn from_struct(db: &RootDatabase, st: hir::Struct) -> Option<Self> {
         let node: ast::StructDef = st.source(db).value;
-        match node.kind() {
-            ast::StructKind::Record(_) => return None,
-            _ => (),
+        if let ast::StructKind::Record(_) = node.kind() {
+            return None;
         };
 
         let params = st
diff --git a/crates/ra_ide/src/display/navigation_target.rs b/crates/ra_ide/src/display/navigation_target.rs
index 906aab1eb..096c41c81 100644
--- a/crates/ra_ide/src/display/navigation_target.rs
+++ b/crates/ra_ide/src/display/navigation_target.rs
@@ -64,11 +64,11 @@ impl NavigationTarget {
     }
 
     pub fn docs(&self) -> Option<&str> {
-        self.docs.as_ref().map(String::as_str)
+        self.docs.as_deref()
     }
 
     pub fn description(&self) -> Option<&str> {
-        self.description.as_ref().map(String::as_str)
+        self.description.as_deref()
     }
 
     /// A "most interesting" range withing the `full_range`.
diff --git a/crates/ra_ide/src/references.rs b/crates/ra_ide/src/references.rs
index de924fad2..97c08ade5 100644
--- a/crates/ra_ide/src/references.rs
+++ b/crates/ra_ide/src/references.rs
@@ -268,7 +268,7 @@ fn decl_access(
     };
 
     let stmt = find_node_at_offset::<ast::LetStmt>(syntax, range.start())?;
-    if let Some(_) = stmt.initializer() {
+    if stmt.initializer().is_some() {
         let pat = stmt.pat()?;
         if let ast::Pat::BindPat(it) = pat {
             if it.name()?.text().as_str() == name {
diff --git a/crates/ra_ide/src/ssr.rs b/crates/ra_ide/src/ssr.rs
index 14eb0b8b2..902c29fc6 100644
--- a/crates/ra_ide/src/ssr.rs
+++ b/crates/ra_ide/src/ssr.rs
@@ -85,8 +85,11 @@ impl FromStr for SsrQuery {
     fn from_str(query: &str) -> Result<SsrQuery, SsrError> {
         let mut it = query.split("==>>");
         let pattern = it.next().expect("at least empty string").trim();
-        let mut template =
-            it.next().ok_or(SsrError("Cannot find delemiter `==>>`".into()))?.trim().to_string();
+        let mut template = it
+            .next()
+            .ok_or_else(|| SsrError("Cannot find delemiter `==>>`".into()))?
+            .trim()
+            .to_string();
         if it.next().is_some() {
             return Err(SsrError("More than one delimiter found".into()));
         }
@@ -131,11 +134,12 @@ fn traverse(node: &SyntaxNode, go: &mut impl FnMut(&SyntaxNode) -> bool) {
 }
 
 fn split_by_var(s: &str) -> Result<(&str, &str, &str), SsrError> {
-    let end_of_name = s.find(":").ok_or(SsrError("Use $<name>:expr".into()))?;
+    let end_of_name = s.find(':').ok_or_else(|| SsrError("Use $<name>:expr".into()))?;
     let name = &s[0..end_of_name];
     is_name(name)?;
     let type_begin = end_of_name + 1;
-    let type_length = s[type_begin..].find(|c| !char::is_ascii_alphanumeric(&c)).unwrap_or(s.len());
+    let type_length =
+        s[type_begin..].find(|c| !char::is_ascii_alphanumeric(&c)).unwrap_or_else(|| s.len());
     let type_name = &s[type_begin..type_begin + type_length];
     Ok((name, type_name, &s[type_begin + type_length..]))
 }
@@ -182,7 +186,7 @@ fn find(pattern: &SsrPattern, code: &SyntaxNode) -> SsrMatches {
                 pattern.text() == code.text()
             }
             (SyntaxElement::Node(ref pattern), SyntaxElement::Node(ref code)) => {
-                if placeholders.iter().find(|&n| n.0.as_str() == pattern.text()).is_some() {
+                if placeholders.iter().any(|n| n.0.as_str() == pattern.text()) {
                     match_.binding.insert(Var(pattern.text().to_string()), code.clone());
                     true
                 } else {
diff --git a/crates/ra_mbe/src/parser.rs b/crates/ra_mbe/src/parser.rs
index 1cdebc216..10a6f300a 100644
--- a/crates/ra_mbe/src/parser.rs
+++ b/crates/ra_mbe/src/parser.rs
@@ -45,15 +45,15 @@ impl PartialEq for Separator {
     }
 }
 
-pub(crate) fn parse_template<'a>(
-    template: &'a tt::Subtree,
-) -> impl Iterator<Item = Result<Op<'a>, ExpandError>> {
+pub(crate) fn parse_template(
+    template: &tt::Subtree,
+) -> impl Iterator<Item = Result<Op<'_>, ExpandError>> {
     parse_inner(template, Mode::Template)
 }
 
-pub(crate) fn parse_pattern<'a>(
-    pattern: &'a tt::Subtree,
-) -> impl Iterator<Item = Result<Op<'a>, ExpandError>> {
+pub(crate) fn parse_pattern(
+    pattern: &tt::Subtree,
+) -> impl Iterator<Item = Result<Op<'_>, ExpandError>> {
     parse_inner(pattern, Mode::Pattern)
 }
 
@@ -63,10 +63,7 @@ enum Mode {
     Template,
 }
 
-fn parse_inner<'a>(
-    src: &'a tt::Subtree,
-    mode: Mode,
-) -> impl Iterator<Item = Result<Op<'a>, ExpandError>> {
+fn parse_inner(src: &tt::Subtree, mode: Mode) -> impl Iterator<Item = Result<Op<'_>, ExpandError>> {
     let mut src = TtIter::new(src);
     std::iter::from_fn(move || {
         let first = src.next()?;
diff --git a/crates/ra_parser/src/grammar/items.rs b/crates/ra_parser/src/grammar/items.rs
index 54284c933..f8b43866c 100644
--- a/crates/ra_parser/src/grammar/items.rs
+++ b/crates/ra_parser/src/grammar/items.rs
@@ -21,7 +21,7 @@ use super::*;
 // struct S;
 pub(super) fn mod_contents(p: &mut Parser, stop_on_r_curly: bool) {
     attributes::inner_attributes(p);
-    while !p.at(EOF) && !(stop_on_r_curly && p.at(T!['}'])) {
+    while !(stop_on_r_curly && p.at(T!['}']) || p.at(EOF)) {
         item_or_macro(p, stop_on_r_curly, ItemFlavor::Mod)
     }
 }
diff --git a/crates/ra_parser/src/parser.rs b/crates/ra_parser/src/parser.rs
index 1071c46dc..76e2d4f7d 100644
--- a/crates/ra_parser/src/parser.rs
+++ b/crates/ra_parser/src/parser.rs
@@ -126,13 +126,13 @@ impl<'t> Parser<'t> {
     }
 
     fn at_composite2(&self, n: usize, k1: SyntaxKind, k2: SyntaxKind) -> bool {
-        let t1 = self.token_source.lookahead_nth(n + 0);
+        let t1 = self.token_source.lookahead_nth(n);
         let t2 = self.token_source.lookahead_nth(n + 1);
         t1.kind == k1 && t1.is_jointed_to_next && t2.kind == k2
     }
 
     fn at_composite3(&self, n: usize, k1: SyntaxKind, k2: SyntaxKind, k3: SyntaxKind) -> bool {
-        let t1 = self.token_source.lookahead_nth(n + 0);
+        let t1 = self.token_source.lookahead_nth(n);
         let t2 = self.token_source.lookahead_nth(n + 1);
         let t3 = self.token_source.lookahead_nth(n + 2);
         (t1.kind == k1 && t1.is_jointed_to_next)
diff --git a/crates/ra_project_model/src/cargo_workspace.rs b/crates/ra_project_model/src/cargo_workspace.rs
index 34fd73bb7..4fea459d5 100644
--- a/crates/ra_project_model/src/cargo_workspace.rs
+++ b/crates/ra_project_model/src/cargo_workspace.rs
@@ -197,7 +197,7 @@ impl CargoWorkspace {
             let pkg_data = &mut packages[pkg];
             pkg_by_id.insert(id, pkg);
             for meta_tgt in meta_pkg.targets {
-                let is_proc_macro = meta_tgt.kind.as_slice() == &["proc-macro"];
+                let is_proc_macro = meta_tgt.kind.as_slice() == ["proc-macro"];
                 let tgt = targets.alloc(TargetData {
                     pkg,
                     name: meta_tgt.name,
diff --git a/crates/ra_project_model/src/lib.rs b/crates/ra_project_model/src/lib.rs
index 9e67d2498..e35f7fbbc 100644
--- a/crates/ra_project_model/src/lib.rs
+++ b/crates/ra_project_model/src/lib.rs
@@ -197,8 +197,9 @@ impl ProjectWorkspace {
                         if let (Some(&from), Some(&to)) =
                             (crates.get(&from_crate_id), crates.get(&to_crate_id))
                         {
-                            if let Err(_) =
-                                crate_graph.add_dep(from, CrateName::new(&dep.name).unwrap(), to)
+                            if crate_graph
+                                .add_dep(from, CrateName::new(&dep.name).unwrap(), to)
+                                .is_err()
                             {
                                 log::error!(
                                     "cyclic dependency {:?} -> {:?}",
@@ -237,8 +238,7 @@ impl ProjectWorkspace {
                         if let (Some(&from), Some(&to)) =
                             (sysroot_crates.get(&from), sysroot_crates.get(&to))
                         {
-                            if let Err(_) =
-                                crate_graph.add_dep(from, CrateName::new(name).unwrap(), to)
+                            if crate_graph.add_dep(from, CrateName::new(name).unwrap(), to).is_err()
                             {
                                 log::error!("cyclic dependency between sysroot crates")
                             }
@@ -279,11 +279,14 @@ impl ProjectWorkspace {
                             }
                             if tgt.is_proc_macro(&cargo) {
                                 if let Some(proc_macro) = libproc_macro {
-                                    if let Err(_) = crate_graph.add_dep(
-                                        crate_id,
-                                        CrateName::new("proc_macro").unwrap(),
-                                        proc_macro,
-                                    ) {
+                                    if crate_graph
+                                        .add_dep(
+                                            crate_id,
+                                            CrateName::new("proc_macro").unwrap(),
+                                            proc_macro,
+                                        )
+                                        .is_err()
+                                    {
                                         log::error!(
                                             "cyclic dependency on proc_macro for {}",
                                             pkg.name(&cargo)
@@ -299,15 +302,19 @@ impl ProjectWorkspace {
                     // Set deps to the core, std and to the lib target of the current package
                     for &from in pkg_crates.get(&pkg).into_iter().flatten() {
                         if let Some(to) = lib_tgt {
-                            if to != from {
-                                if let Err(_) = crate_graph.add_dep(
-                                    from,
-                                    // For root projects with dashes in their name,
-                                    // cargo metadata does not do any normalization,
-                                    // so we do it ourselves currently
-                                    CrateName::normalize_dashes(pkg.name(&cargo)),
-                                    to,
-                                ) {
+                            if to != from
+                                && crate_graph
+                                    .add_dep(
+                                        from,
+                                        // For root projects with dashes in their name,
+                                        // cargo metadata does not do any normalization,
+                                        // so we do it ourselves currently
+                                        CrateName::normalize_dashes(pkg.name(&cargo)),
+                                        to,
+                                    )
+                                    .is_err()
+                            {
+                                {
                                     log::error!(
                                         "cyclic dependency between targets of {}",
                                         pkg.name(&cargo)
@@ -318,22 +325,25 @@ impl ProjectWorkspace {
                         // core is added as a dependency before std in order to
                         // mimic rustcs dependency order
                         if let Some(core) = libcore {
-                            if let Err(_) =
-                                crate_graph.add_dep(from, CrateName::new("core").unwrap(), core)
+                            if crate_graph
+                                .add_dep(from, CrateName::new("core").unwrap(), core)
+                                .is_err()
                             {
                                 log::error!("cyclic dependency on core for {}", pkg.name(&cargo))
                             }
                         }
                         if let Some(alloc) = liballoc {
-                            if let Err(_) =
-                                crate_graph.add_dep(from, CrateName::new("alloc").unwrap(), alloc)
+                            if crate_graph
+                                .add_dep(from, CrateName::new("alloc").unwrap(), alloc)
+                                .is_err()
                             {
                                 log::error!("cyclic dependency on alloc for {}", pkg.name(&cargo))
                             }
                         }
                         if let Some(std) = libstd {
-                            if let Err(_) =
-                                crate_graph.add_dep(from, CrateName::new("std").unwrap(), std)
+                            if crate_graph
+                                .add_dep(from, CrateName::new("std").unwrap(), std)
+                                .is_err()
                             {
                                 log::error!("cyclic dependency on std for {}", pkg.name(&cargo))
                             }
@@ -347,11 +357,10 @@ impl ProjectWorkspace {
                     for dep in pkg.dependencies(&cargo) {
                         if let Some(&to) = pkg_to_lib_crate.get(&dep.pkg) {
                             for &from in pkg_crates.get(&pkg).into_iter().flatten() {
-                                if let Err(_) = crate_graph.add_dep(
-                                    from,
-                                    CrateName::new(&dep.name).unwrap(),
-                                    to,
-                                ) {
+                                if crate_graph
+                                    .add_dep(from, CrateName::new(&dep.name).unwrap(), to)
+                                    .is_err()
+                                {
                                     log::error!(
                                         "cyclic dependency {} -> {}",
                                         pkg.name(&cargo),