Extend and improve initial test cases for collapsible_str_replace

Author: nahuakang

tests/ui/collapsible_str_replace.rs

@@ -1,44 +1,70 @@
 #![warn(clippy::collapsible_str_replace)]
 
+fn get_filter() -> &'static str {
+    "u"
+}
+
 fn main() {
     let misspelled = "hesuo worpd";
 
     let p = 'p';
     let s = 's';
     let u = 'u';
 
+    // LINT CASES
     // If the first argument to a single `str::replace` call is a slice and none of the chars
     // are variables, recommend `collapsible_str_replace`
     let replacement = misspelled.replace(&['s', 'u', 'p'], "l");
     println!("{replacement}");
 
-    // The first iteration of `collapsible_str_replace` will not create lint if the first argument to
-    // a single `str::replace` call is a slice and one or more of its chars are variables
-    let replacement = misspelled.replace(&['s', u, 'p'], "l");
-    println!("{replacement}");
-
-    let replacement = misspelled.replace(&[s, u, 'p'], "l");
+    // If there are consecutive calls to `str::replace` and none of the chars are variables,
+    // recommend `collapsible_str_replace`
+    let replacement = misspelled.replace('s', "l").replace('u', "l");
     println!("{replacement}");
 
-    let replacement = misspelled.replace(&[s, u, p], "l");
+    let replacement = misspelled.replace('s', "l").replace('u', "l").replace('p', "l");
     println!("{replacement}");
 
-    // If there is a single call to `str::replace` and the first argument is a char or a variable, don't
-    // not recommend `collapsible_str_replace`
+    // NO LINT CASES
+    // If there is a single call to `str::replace` and the first argument is a char or a variable,
+    // do not recommend `collapsible_str_replace`
     let replacement = misspelled.replace('s', "l");
     println!("{replacement}");
 
     let replacement = misspelled.replace(s, "l");
     println!("{replacement}");
 
-    // If there are consecutive calls to `str::replace` and none of the chars are variables,
-    // recommend `collapsible_str_replace`
-    let replacement = misspelled.replace('s', "l").replace('u', "l");
+    // If the `from` argument is of kind other than a slice or a char, do not lint
+    let replacement = misspelled.replace(&get_filter(), "l");
+
+    // NO LINT TIL IMPROVEMENT
+    // If multiple `str::replace` calls contain slices and none of the chars are variables,
+    // the first iteration does not recommend `collapsible_str_replace`
+    let replacement = misspelled.replace(&['s', 'u', 'p'], "l").replace(&['s', 'p'], "l");
     println!("{replacement}");
 
-    let replacement = misspelled.replace('s', "l").replace('u', "l").replace('p', "l");
+    // If a mixture of `str::replace` calls with slice and char arguments are used for `from` arg,
+    // the first iteration does not recommend `collapsible_str_replace`
+    let replacement = misspelled.replace(&['s', 'u'], "l").replace('p', "l");
+    println!("replacement");
+
+    let replacement = misspelled.replace('p', "l").replace(&['s', 'u'], "l");
+
+    // The first iteration of `collapsible_str_replace` will not create lint if the first argument to
+    // a single `str::replace` call is a slice and one or more of its chars are variables
+    let replacement = misspelled.replace(&['s', u, 'p'], "l");
+    println!("{replacement}");
+
+    let replacement = misspelled.replace(&[s, u, 'p'], "l");
+    println!("{replacement}");
+
+    let replacement = misspelled.replace(&[s, u, p], "l");
+    println!("{replacement}");
+
+    let replacement = misspelled.replace(&[s, u], "l").replace(&[u, p], "l");
     println!("{replacement}");
 
+    // FALLBACK CASES
     // If there are consecutive calls to `str::replace` and all or any chars are variables,
     // recommend the fallback `misspelled.replace(&[s, u, p], "l")`
     let replacement = misspelled.replace(s, "l").replace('u', "l");