Fix some of the things current Clippy complains about (#2363)

Author: adamreichold

common/src/bitset.rs

@@ -1,5 +1,5 @@
 use std::io::Write;
-use std::{fmt, io, u64};
+use std::{fmt, io};
 
 use ownedbytes::OwnedBytes;
 

src/aggregation/bucket/mod.rs

@@ -28,6 +28,7 @@ mod term_agg;
 mod term_missing_agg;
 
 use std::collections::HashMap;
+use std::fmt;
 
 pub use histogram::*;
 pub use range::*;
@@ -72,12 +73,12 @@ impl From<&str> for OrderTarget {
     }
 }
 
-impl ToString for OrderTarget {
-    fn to_string(&self) -> String {
+impl fmt::Display for OrderTarget {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match self {
-            OrderTarget::Key => "_key".to_string(),
-            OrderTarget::Count => "_count".to_string(),
-            OrderTarget::SubAggregation(agg) => agg.to_string(),
+            OrderTarget::Key => f.write_str("_key"),
+            OrderTarget::Count => f.write_str("_count"),
+            OrderTarget::SubAggregation(agg) => agg.fmt(f),
         }
     }
 }

src/aggregation/mod.rs

@@ -159,10 +159,6 @@ use itertools::Itertools;
 use serde::de::{self, Visitor};
 use serde::{Deserialize, Deserializer, Serialize};
 
-pub(crate) fn invalid_agg_request(message: String) -> crate::TantivyError {
-    crate::TantivyError::AggregationError(AggregationError::InvalidRequest(message))
-}
-
 fn parse_str_into_f64<E: de::Error>(value: &str) -> Result<f64, E> {
     let parsed = value.parse::<f64>().map_err(|_err| {
         de::Error::custom(format!("Failed to parse f64 from string: {:?}", value))

src/collector/facet_collector.rs

@@ -1,7 +1,7 @@
 use std::cmp::Ordering;
 use std::collections::{btree_map, BTreeMap, BTreeSet, BinaryHeap};
+use std::io;
 use std::ops::Bound;
-use std::{io, u64, usize};
 
 use crate::collector::{Collector, SegmentCollector};
 use crate::fastfield::FacetReader;

src/lib.rs

@@ -255,7 +255,7 @@ pub struct Version {
 
 impl fmt::Debug for Version {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "{}", self.to_string())
+        fmt::Display::fmt(self, f)
     }
 }
 
@@ -266,9 +266,10 @@ static VERSION: Lazy<Version> = Lazy::new(|| Version {
     index_format_version: INDEX_FORMAT_VERSION,
 });
 
-impl ToString for Version {
-    fn to_string(&self) -> String {
-        format!(
+impl fmt::Display for Version {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(
+            f,
             "tantivy v{}.{}.{}, index_format v{}",
             self.major, self.minor, self.patch, self.index_format_version
         )

sstable/src/lib.rs

@@ -1,6 +1,5 @@
 use std::io::{self, Write};
 use std::ops::Range;
-use std::usize;
 
 use merge::ValueMerger;