more clippy fixes:

clippy::match_like_matches_macro
clippy::to_string_in_format_args
clippy::single_char_add_str
clippy::filter_map_identity
clippy::clone_on_copy
clippy::useless_format
clippy::unused_unit

crates/hir/src/lib.rs

@@ -1812,14 +1812,12 @@ impl Macro {
 
     pub fn is_builtin_derive(&self, db: &dyn HirDatabase) -> bool {
         match self.id {
-            MacroId::Macro2Id(it) => match it.lookup(db.upcast()).expander {
-                MacroExpander::BuiltInDerive(_) => true,
-                _ => false,
-            },
-            MacroId::MacroRulesId(it) => match it.lookup(db.upcast()).expander {
-                MacroExpander::BuiltInDerive(_) => true,
-                _ => false,
-            },
+            MacroId::Macro2Id(it) => {
+                matches!(it.lookup(db.upcast()).expander, MacroExpander::BuiltInDerive(_))
+            }
+            MacroId::MacroRulesId(it) => {
+                matches!(it.lookup(db.upcast()).expander, MacroExpander::BuiltInDerive(_))
+            }
             MacroId::ProcMacroId(_) => false,
         }
     }

crates/hir_def/src/nameres/collector.rs

@@ -504,10 +504,8 @@ impl DefCollector<'_> {
         } else {
             PathKind::Abs
         };
-        let path = ModPath::from_segments(
-            path_kind.clone(),
-            [krate.clone(), name![prelude], edition].into_iter(),
-        );
+        let path =
+            ModPath::from_segments(path_kind, [krate.clone(), name![prelude], edition].into_iter());
         // Fall back to the older `std::prelude::v1` for compatibility with Rust <1.52.0
         // FIXME remove this fallback
         let fallback_path =

crates/hir_def/src/path.rs

@@ -120,7 +120,7 @@ impl Path {
         let res = Path {
             type_anchor: self.type_anchor.clone(),
             mod_path: Interned::new(ModPath::from_segments(
-                self.mod_path.kind.clone(),
+                self.mod_path.kind,
                 self.mod_path.segments()[..self.mod_path.segments().len() - 1].iter().cloned(),
             )),
             generic_args: self.generic_args[..self.generic_args.len() - 1].to_vec().into(),

crates/hir_expand/src/fixup.rs

@@ -176,7 +176,7 @@ mod tests {
         );
 
         let mut actual = tt.to_string();
-        actual.push_str("\n");
+        actual.push('\n');
 
         expect.indent(false);
         expect.assert_eq(&actual);

crates/ide/src/annotations.rs

@@ -79,7 +79,7 @@ pub(crate) fn annotations(
                             .map(|variant| {
                                 variant.source(db).and_then(|node| name_range(db, node, file_id))
                             })
-                            .filter_map(std::convert::identity)
+                            .flatten()
                             .for_each(|range| {
                                 annotations.push(Annotation {
                                     range,

crates/ide/src/file_structure.rs

@@ -138,7 +138,7 @@ fn structure_node(node: &SyntaxNode) -> Option<StructureNode> {
                     collapse_ws(param_list.syntax(), &mut detail);
                 }
                 if let Some(ret_type) = it.ret_type() {
-                    detail.push_str(" ");
+                    detail.push(' ');
                     collapse_ws(ret_type.syntax(), &mut detail);
                 }
 

crates/ide_assists/src/handlers/generate_delegate_methods.rs

@@ -156,7 +156,7 @@ pub(crate) fn generate_delegate_methods(acc: &mut Assists, ctx: &AssistContext)
                             }
                             None => {
                                 let offset = strukt.syntax().text_range().end();
-                                let snippet = format!("\n\n{}", impl_def.syntax().to_string());
+                                let snippet = format!("\n\n{}", impl_def.syntax());
                                 builder.insert(offset, snippet);
                             }
                         }

crates/ide_assists/src/handlers/merge_match_arms.rs

@@ -103,10 +103,7 @@ fn are_same_types(
     for (other_arm_type_name, other_arm_type) in arm_types {
         match (current_arm_types.get(&other_arm_type_name), other_arm_type) {
             (Some(Some(current_arm_type)), Some(other_arm_type))
-                if other_arm_type.original == current_arm_type.original =>
-            {
-                ()
-            }
+                if other_arm_type.original == current_arm_type.original => {}
             _ => return false,
         }
     }

crates/ide_assists/src/utils/gen_trait_fn_body.rs

@@ -206,7 +206,7 @@ fn gen_debug_impl(adt: &ast::Adt, func: &ast::Fn) -> Option<()> {
 
                             // => <expr>.field(field)
                             let method_name = make::name_ref("field");
-                            let field_path = &format!("{}", name);
+                            let field_path = &name.to_string();
                             let field_path = make::expr_path(make::ext::ident_path(field_path));
                             let args = make::arg_list(vec![field_path]);
                             expr = make::expr_method_call(expr, method_name, args);

crates/ide_db/src/famous_defs.rs

@@ -108,7 +108,7 @@ impl FamousDefs<'_, '_> {
             self.test(),
             self.proc_macro(),
         ])
-        .filter_map(|it| it)
+        .flatten()
     }
 
     fn find_trait(&self, path: &str) -> Option<Trait> {

crates/rust-analyzer/tests/slow-tests/main.rs

@@ -533,7 +533,7 @@ mod bar;
 
 fn main() {{}}
 "#,
-        PROJECT = project.to_string(),
+        PROJECT = project,
     );
 
     let server =

crates/text_edit/src/lib.rs

@@ -94,7 +94,7 @@ impl TextEdit {
 
         let text_size = TextSize::of(&*text);
         let mut total_len = text_size;
-        let mut max_total_len = text_size.clone();
+        let mut max_total_len = text_size;
         for indel in &self.indels {
             total_len += TextSize::of(&indel.insert);
             total_len -= indel.delete.len();