uucore: remove unneccessary closues

This adresses only those where the fix has less letters than the
original and is "trivial" (There are possibly a lot of std::string::ToString::to_string
and those may only be shortened with additional imports).

Found with clippy::redundant-closure-for-method-calls

src/uu/numfmt/src/format.rs

@@ -53,11 +53,7 @@ impl<'a> Iterator for WhitespaceSplitter<'a> {
                 .unwrap_or(haystack.len()),
         );
 
-        let (field, rest) = field.split_at(
+        let (field, rest) = field.split_at(field.find(char::is_whitespace).unwrap_or(field.len()));
-            field
-                .find(|c: char| c.is_whitespace())
-                .unwrap_or(field.len()),
-        );
 
         self.s = if rest.is_empty() { None } else { Some(rest) };
 
@@ -107,7 +103,7 @@ fn parse_implicit_precision(s: &str) -> usize {
     match s.split_once('.') {
         Some((_, decimal_part)) => decimal_part
             .chars()
-            .take_while(|c| c.is_ascii_digit())
+            .take_while(char::is_ascii_digit)
             .count(),
         None => 0,
     }

src/uu/sort/src/numeric_str_cmp.rs

@@ -221,8 +221,8 @@ pub fn numeric_str_cmp((a, a_info): (&str, &NumInfo), (b, b_info): (&str, &NumIn
         a_info.exponent.cmp(&b_info.exponent)
     } else {
         // walk the characters from the front until we find a difference
-        let mut a_chars = a.chars().filter(|c| c.is_ascii_digit());
+        let mut a_chars = a.chars().filter(char::is_ascii_digit);
-        let mut b_chars = b.chars().filter(|c| c.is_ascii_digit());
+        let mut b_chars = b.chars().filter(char::is_ascii_digit);
         loop {
             let a_next = a_chars.next();
             let b_next = b_chars.next();

src/uu/sort/src/sort.rs

@@ -985,7 +985,7 @@ impl FieldSelector {
                 let mut range = match to {
                     Some(Resolution::StartOfChar(mut to)) => {
                         // We need to include the character at `to`.
-                        to += line[to..].chars().next().map_or(1, |c| c.len_utf8());
+                        to += line[to..].chars().next().map_or(1, char::len_utf8);
                         from..to
                     }
                     Some(Resolution::EndOfChar(to)) => from..to,

src/uu/uniq/src/uniq.rs

@@ -160,7 +160,7 @@ impl Uniq {
 
             // fast path: avoid skipping
             if self.ignore_case && slice_start == 0 && slice_stop == len {
-                return closure(&mut fields_to_check.chars().flat_map(|c| c.to_uppercase()));
+                return closure(&mut fields_to_check.chars().flat_map(char::to_uppercase));
             }
 
             // fast path: we can avoid mapping chars to upper-case, if we don't want to ignore the case
@@ -173,7 +173,7 @@ impl Uniq {
                     .chars()
                     .skip(slice_start)
                     .take(slice_stop)
-                    .flat_map(|c| c.to_uppercase()),
+                    .flat_map(char::to_uppercase),
             )
         } else {
             closure(&mut fields_to_check.chars())

src/uu/wc/src/wc.rs

@@ -190,7 +190,7 @@ impl<'a> Inputs<'a> {
 
         // The 1-based index of each yielded item must be tracked for error reporting.
         let mut with_idx = base.enumerate().map(|(i, v)| (i + 1, v));
-        let files0_from_path = settings.files0_from.as_ref().map(|p| p.as_borrowed());
+        let files0_from_path = settings.files0_from.as_ref().map(Input::as_borrowed);
 
         let iter = iter::from_fn(move || {
             let (idx, next) = with_idx.next()?;

src/uucore/src/lib/parser/parse_size.rs

@@ -90,9 +90,9 @@ impl<'parser> Parser<'parser> {
             NumberSystem::Hexadecimal => size
                 .chars()
                 .take(2)
-                .chain(size.chars().skip(2).take_while(|c| c.is_ascii_hexdigit()))
+                .chain(size.chars().skip(2).take_while(char::is_ascii_hexdigit))
                 .collect(),
-            _ => size.chars().take_while(|c| c.is_ascii_digit()).collect(),
+            _ => size.chars().take_while(char::is_ascii_digit).collect(),
         };
         let mut unit: &str = &size[numeric_string.len()..];
 
@@ -243,7 +243,7 @@ impl<'parser> Parser<'parser> {
 
         let num_digits: usize = size
             .chars()
-            .take_while(|c| c.is_ascii_digit())
+            .take_while(char::is_ascii_digit)
             .collect::<String>()
             .len();
         let all_zeros = size.chars().all(|c| c == '0');