Rollup merge of #22276 - ruud-v-a:map-clone, r=nikomatsakis

This resolves #22243 for the single-letter variables that I could grep. Some occurences could not be replaced.

Author: steveklabnik

src/libcollections/bit.rs

@@ -2282,7 +2282,7 @@ mod tests {
     #[test]
     fn test_from_bools() {
         let bools = vec![true, false, true, true];
-        let bitv: Bitv = bools.iter().map(|n| *n).collect();
+        let bitv: Bitv = bools.iter().cloned().collect();
         assert_eq!(format!("{:?}", bitv), "1011");
     }
 
@@ -2295,12 +2295,12 @@ mod tests {
     #[test]
     fn test_bitv_iterator() {
         let bools = vec![true, false, true, true];
-        let bitv: Bitv = bools.iter().map(|n| *n).collect();
+        let bitv: Bitv = bools.iter().cloned().collect();
 
         assert_eq!(bitv.iter().collect::<Vec<bool>>(), bools);
 
         let long: Vec<_> = (0i32..10000).map(|i| i % 2 == 0).collect();
-        let bitv: Bitv = long.iter().map(|n| *n).collect();
+        let bitv: Bitv = long.iter().cloned().collect();
         assert_eq!(bitv.iter().collect::<Vec<bool>>(), long)
     }
 

src/libcollections/dlist.rs

@@ -895,7 +895,7 @@ impl<A: Ord> Ord for DList<A> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<A: Clone> Clone for DList<A> {
     fn clone(&self) -> DList<A> {
-        self.iter().map(|x| x.clone()).collect()
+        self.iter().cloned().collect()
     }
 }
 
@@ -1013,7 +1013,7 @@ mod tests {
 
     #[cfg(test)]
     fn list_from<T: Clone>(v: &[T]) -> DList<T> {
-        v.iter().map(|x| (*x).clone()).collect()
+        v.iter().cloned().collect()
     }
 
     #[test]

src/libcore/iter.rs

@@ -325,7 +325,7 @@ pub trait IteratorExt: Iterator + Sized {
     ///
     /// ```
     /// let xs = [100, 200, 300];
-    /// let mut it = xs.iter().map(|x| *x).peekable();
+    /// let mut it = xs.iter().cloned().peekable();
     /// assert_eq!(*it.peek().unwrap(), 100);
     /// assert_eq!(it.next().unwrap(), 100);
     /// assert_eq!(it.next().unwrap(), 200);

src/libcoretest/iter.rs

@@ -713,7 +713,7 @@ fn test_random_access_inspect() {
 fn test_random_access_map() {
     let xs = [1, 2, 3, 4, 5];
 
-    let mut it = xs.iter().map(|x| *x);
+    let mut it = xs.iter().cloned();
     assert_eq!(xs.len(), it.indexable());
     for (i, elt) in xs.iter().enumerate() {
         assert_eq!(Some(*elt), it.idx(i));

src/librustc/metadata/cstore.rs

@@ -218,7 +218,7 @@ impl CStore {
 
     pub fn find_extern_mod_stmt_cnum(&self, emod_id: ast::NodeId)
                                      -> Option<ast::CrateNum> {
-        self.extern_mod_crate_map.borrow().get(&emod_id).map(|x| *x)
+        self.extern_mod_crate_map.borrow().get(&emod_id).cloned()
     }
 }
 

src/librustc/middle/check_match.rs

@@ -75,7 +75,7 @@ impl<'a> fmt::Debug for Matrix<'a> {
             pretty_printed_matrix.iter().map(|row| row[col].len()).max().unwrap_or(0)
         }).collect();
 
-        let total_width = column_widths.iter().map(|n| *n).sum() + column_count * 3 + 1;
+        let total_width = column_widths.iter().cloned().sum() + column_count * 3 + 1;
         let br = repeat('+').take(total_width).collect::<String>();
         try!(write!(f, "{}\n", br));
         for row in pretty_printed_matrix {

src/librustc/middle/const_eval.rs

@@ -600,7 +600,7 @@ pub fn lit_to_const(lit: &ast::Lit) -> const_val {
     match lit.node {
         ast::LitStr(ref s, _) => const_str((*s).clone()),
         ast::LitBinary(ref data) => {
-            const_binary(Rc::new(data.iter().map(|x| *x).collect()))
+            const_binary(Rc::new(data.iter().cloned().collect()))
         }
         ast::LitByte(n) => const_uint(n as u64),
         ast::LitChar(n) => const_uint(n as u64),

src/librustc/middle/dependency_format.rs

@@ -158,7 +158,7 @@ fn calculate_type(sess: &session::Session,
 
     // Collect what we've got so far in the return vector.
     let mut ret = (1..sess.cstore.next_crate_num()).map(|i| {
-        match formats.get(&i).map(|v| *v) {
+        match formats.get(&i).cloned() {
             v @ Some(cstore::RequireDynamic) => v,
             _ => None,
         }

src/librustc/middle/infer/error_reporting.rs

@@ -924,7 +924,7 @@ impl<'a, 'tcx> Rebuilder<'a, 'tcx> {
 
     fn rebuild(&self)
                -> (ast::FnDecl, Option<ast::ExplicitSelf_>, ast::Generics) {
-        let mut expl_self_opt = self.expl_self_opt.map(|x| x.clone());
+        let mut expl_self_opt = self.expl_self_opt.cloned();
         let mut inputs = self.fn_decl.inputs.clone();
         let mut output = self.fn_decl.output.clone();
         let mut ty_params = self.generics.ty_params.clone();

src/librustc/middle/lang_items.rs

@@ -149,7 +149,7 @@ impl<'a, 'v> Visitor<'v> for LanguageItemCollector<'a> {
     fn visit_item(&mut self, item: &ast::Item) {
         match extract(&item.attrs) {
             Some(value) => {
-                let item_index = self.item_refs.get(&value[]).map(|x| *x);
+                let item_index = self.item_refs.get(&value[]).cloned();
 
                 match item_index {
                     Some(item_index) => {