Enable iter_on_empty_collections

Author: nickdrozd

clippy_dev/src/utils.rs

@@ -488,7 +488,8 @@ impl<'txt> RustSearcher<'txt> {
 
     /// Consumes the next token if it matches the requested value and captures the value if
     /// requested. Returns true if a token was matched.
-    fn read_token(&mut self, token: Token<'_>, captures: &mut slice::IterMut<'_, &mut &'txt str>) -> bool {
+    fn read_token(&mut self, token: Token<'_>, captures: &mut [&mut &'txt str]) -> bool {
+        let mut captures = captures.iter_mut();
         loop {
             match (token, self.next_token.kind) {
                 (_, lexer::TokenKind::Whitespace)
@@ -552,8 +553,7 @@ impl<'txt> RustSearcher<'txt> {
 
     #[must_use]
     pub fn find_token(&mut self, token: Token<'_>) -> bool {
-        let mut capture = [].iter_mut();
-        while !self.read_token(token, &mut capture) {
+        while !self.read_token(token, &mut []) {
             self.step();
             if self.at_end() {
                 return false;
@@ -566,8 +566,8 @@ impl<'txt> RustSearcher<'txt> {
     pub fn find_capture_token(&mut self, token: Token<'_>) -> Option<&'txt str> {
         let mut res = "";
         let mut capture = &mut res;
-        let mut capture = slice::from_mut(&mut capture).iter_mut();
-        while !self.read_token(token, &mut capture) {
+        let capture = slice::from_mut(&mut capture);
+        while !self.read_token(token, capture) {
             self.step();
             if self.at_end() {
                 return None;
@@ -578,8 +578,7 @@ impl<'txt> RustSearcher<'txt> {
 
     #[must_use]
     pub fn match_tokens(&mut self, tokens: &[Token<'_>], captures: &mut [&mut &'txt str]) -> bool {
-        let mut captures = captures.iter_mut();
-        tokens.iter().all(|&t| self.read_token(t, &mut captures))
+        tokens.iter().all(|&t| self.read_token(t, captures))
     }
 }
 

tests/dogfood.rs

@@ -96,6 +96,8 @@ fn run_clippy_for_package(project: &str) -> bool {
         "-D",
         "clippy::derive_partial_eq_without_eq",
         "-D",
+        "clippy::iter_on_empty_collections",
+        "-D",
         "clippy::iter_on_single_items",
         "-D",
         "clippy::needless_pass_by_ref_mut",