misc improvements

- avoid needless pass by value in
  `DeclarativeMacroExpander::expand{,_unhygienic}`, thus avoiding the
  need to clone

crates/hir-expand/src/db.rs

diff --git a/crates/hir-expand/src/db.rs b/crates/hir-expand/src/db.rs
index 69bacad..92be93a 100644
--- a/crates/hir-expand/src/db.rs
+++ b/crates/hir-expand/src/db.rs
@@ -275,7 +275,7 @@
         }
         MacroDefKind::Declarative(it, _) => db
             .decl_macro_expander(loc.krate, it)
-            .expand_unhygienic(db, tt, loc.kind.call_style(), span),
+            .expand_unhygienic(db, &tt, loc.kind.call_style(), span),
         MacroDefKind::BuiltIn(_, it) => {
             it.expand(db, actual_macro_call, &tt, span).map_err(Into::into)
         }
@@ -547,9 +547,9 @@
 
             let arg = macro_arg;
             let res = match loc.def.kind {
-                MacroDefKind::Declarative(id, _) => db
-                    .decl_macro_expander(loc.def.krate, id)
-                    .expand(db, arg.clone(), macro_call_id, span),
+                MacroDefKind::Declarative(id, _) => {
+                    db.decl_macro_expander(loc.def.krate, id).expand(db, arg, macro_call_id, span)
+                }
                 MacroDefKind::BuiltIn(_, it) => {
                     it.expand(db, macro_call_id, arg, span).map_err(Into::into).zip_val(None)
                 }
@@ -589,7 +589,7 @@
                 }
                 MacroDefKind::ProcMacro(_, _, _) => unreachable!(),
             };
-            (ExpandResult { value: res.value, err: res.err }, span)
+            (res, span)
         }
     };
 

crates/hir-expand/src/declarative.rs

diff --git a/crates/hir-expand/src/declarative.rs b/crates/hir-expand/src/declarative.rs
index 99db0db..e6374b6 100644
--- a/crates/hir-expand/src/declarative.rs
+++ b/crates/hir-expand/src/declarative.rs
@@ -32,7 +32,7 @@
     pub fn expand(
         &self,
         db: &dyn ExpandDatabase,
-        tt: tt::TopSubtree,
+        tt: &tt::TopSubtree,
         call_id: MacroCallId,
         span: Span,
     ) -> ExpandResult<(tt::TopSubtree, Option<u32>)> {
@@ -46,7 +46,7 @@
                 .mac
                 .expand(
                     db,
-                    &tt,
+                    tt,
                     |s| {
                         s.ctx =
                             apply_mark(db, s.ctx, call_id.into(), self.transparency, self.edition)
@@ -61,7 +61,7 @@
     pub fn expand_unhygienic(
         &self,
         db: &dyn ExpandDatabase,
-        tt: tt::TopSubtree,
+        tt: &tt::TopSubtree,
         call_style: MacroCallStyle,
         call_site: Span,
     ) -> ExpandResult<tt::TopSubtree> {
@@ -72,7 +72,7 @@
             ),
             None => self
                 .mac
-                .expand(db, &tt, |_| (), call_style, call_site)
+                .expand(db, tt, |_| (), call_style, call_site)
                 .map(TupleExt::head)
                 .map_err(Into::into),
         }

crates/load-cargo/src/lib.rs

diff --git a/crates/load-cargo/src/lib.rs b/crates/load-cargo/src/lib.rs
index fd90bc4..96c95ec 100644
--- a/crates/load-cargo/src/lib.rs
+++ b/crates/load-cargo/src/lib.rs
@@ -171,7 +171,7 @@
             .map(|(crate_id, path)| {
                 (
                     crate_id,
-                    path.map_or_else(Err, |(_, path)| {
+                    path.and_then(|(_, path)| {
                         proc_macro_server.as_ref().map_err(Clone::clone).and_then(
                             |proc_macro_server| load_proc_macro(proc_macro_server, &path, &[]),
                         )