Resolve needless_borrow clippy lints

    error: this expression borrows a reference (`&syn::Type`) that is immediately dereferenced by the compiler
       --> serde_derive/src/internals/check.rs:399:37
        |
    399 |     if let Type::Path(ty) = ungroup(&field.ty) {
        |                                     ^^^^^^^^^ help: change this to: `field.ty`
        |
    note: the lint level is defined here
       --> serde_derive/src/lib.rs:18:9
        |
    18  | #![deny(clippy::all, clippy::pedantic)]
        |         ^^^^^^^^^^^
        = note: `#[deny(clippy::needless_borrow)]` implied by `#[deny(clippy::all)]`
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_borrow

    error: this expression borrows a reference (`&str`) that is immediately dereferenced by the compiler
       --> serde_derive/src/de.rs:478:52
        |
    478 |         &type_path, params, fields, false, cattrs, &expecting,
        |                                                    ^^^^^^^^^^ help: change this to: `expecting`
        |
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_borrow

    error: this expression borrows a reference (`&str`) that is immediately dereferenced by the compiler
       --> serde_derive/src/de.rs:564:76
        |
    564 |     let visit_seq = Stmts(deserialize_seq_in_place(params, fields, cattrs, &expecting));
        |                                                                            ^^^^^^^^^^ help: change this to: `expecting`
        |
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_borrow

    error: this expression borrows a reference (`&str`) that is immediately dereferenced by the compiler
       --> serde_derive/src/de.rs:925:51
        |
    925 |         &type_path, params, fields, true, cattrs, &expecting,
        |                                                   ^^^^^^^^^^ help: change this to: `expecting`
        |
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_borrow

    error: this expression borrows a reference (`&str`) that is immediately dereferenced by the compiler
        --> serde_derive/src/de.rs:1066:76
         |
    1066 |     let visit_seq = Stmts(deserialize_seq_in_place(params, fields, cattrs, &expecting));
         |                                                                            ^^^^^^^^^^ help: change this to: `expecting`
         |
         = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_borrow

    error: this expression borrows a reference (`&proc_macro2::TokenStream`) that is immediately dereferenced by the compiler
        --> serde_derive/src/de.rs:2288:80
         |
    2288 |         let fallthrough_borrowed_arm = fallthrough_borrowed.as_ref().unwrap_or(&fallthrough_arm);
         |                                                                                ^^^^^^^^^^^^^^^^ help: change this to: `fallthrough_arm`
         |
         = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_borrow

    error: this expression borrows a reference (`&syn::Member`) that is immediately dereferenced by the compiler
        --> serde_derive/src/ser.rs:1102:43
         |
    1102 |                 get_member(params, field, &member)
         |                                           ^^^^^^^ help: change this to: `member`
         |
         = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_borrow

serde_derive/src/de.rs

@@ -475,7 +475,7 @@ fn deserialize_tuple(
     };
 
     let visit_seq = Stmts(deserialize_seq(
-        &type_path, params, fields, false, cattrs, &expecting,
+        &type_path, params, fields, false, cattrs, expecting,
     ));
 
     let visitor_expr = quote! {
@@ -561,7 +561,7 @@ fn deserialize_tuple_in_place(
         None
     };
 
-    let visit_seq = Stmts(deserialize_seq_in_place(params, fields, cattrs, &expecting));
+    let visit_seq = Stmts(deserialize_seq_in_place(params, fields, cattrs, expecting));
 
     let visitor_expr = quote! {
         __Visitor {
@@ -922,7 +922,7 @@ fn deserialize_struct(
     let expecting = cattrs.expecting().unwrap_or(&expecting);
 
     let visit_seq = Stmts(deserialize_seq(
-        &type_path, params, fields, true, cattrs, &expecting,
+        &type_path, params, fields, true, cattrs, expecting,
     ));
 
     let (field_visitor, fields_stmt, visit_map) = if cattrs.has_flatten() {
@@ -1063,7 +1063,7 @@ fn deserialize_struct_in_place(
     };
     let expecting = cattrs.expecting().unwrap_or(&expecting);
 
-    let visit_seq = Stmts(deserialize_seq_in_place(params, fields, cattrs, &expecting));
+    let visit_seq = Stmts(deserialize_seq_in_place(params, fields, cattrs, expecting));
 
     let (field_visitor, fields_stmt, visit_map) =
         deserialize_struct_as_struct_in_place_visitor(params, fields, cattrs);
@@ -2285,7 +2285,7 @@ fn deserialize_identifier(
     };
 
     let visit_borrowed = if fallthrough_borrowed.is_some() || collect_other_fields {
-        let fallthrough_borrowed_arm = fallthrough_borrowed.as_ref().unwrap_or(&fallthrough_arm);
+        let fallthrough_borrowed_arm = fallthrough_borrowed.as_ref().unwrap_or(fallthrough_arm);
         Some(quote! {
             fn visit_borrowed_str<__E>(self, __value: &'de str) -> _serde::__private::Result<Self::Value, __E>
             where

serde_derive/src/internals/check.rs

@@ -396,7 +396,7 @@ fn member_message(member: &Member) -> String {
 }
 
 fn allow_transparent(field: &Field, derive: Derive) -> bool {
-    if let Type::Path(ty) = ungroup(&field.ty) {
+    if let Type::Path(ty) = ungroup(field.ty) {
         if let Some(seg) = ty.path.segments.last() {
             if seg.ident == "PhantomData" {
                 return false;

serde_derive/src/ser.rs

@@ -1099,7 +1099,7 @@ fn serialize_struct_visitor(
             let mut field_expr = if is_enum {
                 quote!(#member)
             } else {
-                get_member(params, field, &member)
+                get_member(params, field, member)
             };
 
             let key_expr = field.attrs.name().serialize_name();