identity_conversion: make it use a rustfix test

tests/ui/identity_conversion.fixed

@@ -0,0 +1,58 @@
+// run-rustfix
+
+#![deny(clippy::identity_conversion)]
+
+fn test_generic<T: Copy>(val: T) -> T {
+    let _ = val;
+    val
+}
+
+fn test_generic2<T: Copy + Into<i32> + Into<U>, U: From<T>>(val: T) {
+    // ok
+    let _: i32 = val.into();
+    let _: U = val.into();
+    let _ = U::from(val);
+}
+
+fn test_questionmark() -> Result<(), ()> {
+    {
+        let _: i32 = 0i32;
+        Ok(Ok(()))
+    }??;
+    Ok(())
+}
+
+fn test_issue_3913() -> Result<(), std::io::Error> {
+    use std::fs;
+    use std::path::Path;
+
+    let path = Path::new(".");
+    for _ in fs::read_dir(path)? {}
+
+    Ok(())
+}
+
+fn main() {
+    test_generic(10i32);
+    test_generic2::<i32, i32>(10i32);
+    test_questionmark().unwrap();
+    test_issue_3913().unwrap();
+
+    let _: String = "foo".into();
+    let _: String = From::from("foo");
+    let _ = String::from("foo");
+    #[allow(clippy::identity_conversion)]
+    {
+        let _: String = "foo".into();
+        let _ = String::from("foo");
+        let _ = "".lines().into_iter();
+    }
+
+    let _: String = "foo".to_string();
+    let _: String = "foo".to_string();
+    let _ = "foo".to_string();
+    let _ = format!("A: {:04}", 123);
+    let _ = "".lines();
+    let _ = vec![1, 2, 3].into_iter();
+    let _: String = format!("Hello {}", "world");
+}

tests/ui/identity_conversion.rs

@@ -1,3 +1,5 @@
+// run-rustfix
+
 #![deny(clippy::identity_conversion)]
 
 fn test_generic<T: Copy>(val: T) -> T {

tests/ui/identity_conversion.stderr

@@ -1,65 +1,65 @@
 error: identical conversion
-  --> $DIR/identity_conversion.rs:4:13
+  --> $DIR/identity_conversion.rs:6:13
    |
 LL |     let _ = T::from(val);
    |             ^^^^^^^^^^^^ help: consider removing `T::from()`: `val`
    |
 note: lint level defined here
-  --> $DIR/identity_conversion.rs:1:9
+  --> $DIR/identity_conversion.rs:3:9
    |
 LL | #![deny(clippy::identity_conversion)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: identical conversion
-  --> $DIR/identity_conversion.rs:5:5
+  --> $DIR/identity_conversion.rs:7:5
    |
 LL |     val.into()
    |     ^^^^^^^^^^ help: consider removing `.into()`: `val`
 
 error: identical conversion
-  --> $DIR/identity_conversion.rs:17:22
+  --> $DIR/identity_conversion.rs:19:22
    |
 LL |         let _: i32 = 0i32.into();
    |                      ^^^^^^^^^^^ help: consider removing `.into()`: `0i32`
 
 error: identical conversion
-  --> $DIR/identity_conversion.rs:49:21
+  --> $DIR/identity_conversion.rs:51:21
    |
 LL |     let _: String = "foo".to_string().into();
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `.into()`: `"foo".to_string()`
 
 error: identical conversion
-  --> $DIR/identity_conversion.rs:50:21
+  --> $DIR/identity_conversion.rs:52:21
    |
 LL |     let _: String = From::from("foo".to_string());
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `From::from()`: `"foo".to_string()`
 
 error: identical conversion
-  --> $DIR/identity_conversion.rs:51:13
+  --> $DIR/identity_conversion.rs:53:13
    |
 LL |     let _ = String::from("foo".to_string());
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `String::from()`: `"foo".to_string()`
 
 error: identical conversion
-  --> $DIR/identity_conversion.rs:52:13
+  --> $DIR/identity_conversion.rs:54:13
    |
 LL |     let _ = String::from(format!("A: {:04}", 123));
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `String::from()`: `format!("A: {:04}", 123)`
 
 error: identical conversion
-  --> $DIR/identity_conversion.rs:53:13
+  --> $DIR/identity_conversion.rs:55:13
    |
 LL |     let _ = "".lines().into_iter();
    |             ^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `.into_iter()`: `"".lines()`
 
 error: identical conversion
-  --> $DIR/identity_conversion.rs:54:13
+  --> $DIR/identity_conversion.rs:56:13
    |
 LL |     let _ = vec![1, 2, 3].into_iter().into_iter();
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `.into_iter()`: `vec![1, 2, 3].into_iter()`
 
 error: identical conversion
-  --> $DIR/identity_conversion.rs:55:21
+  --> $DIR/identity_conversion.rs:57:21
    |
 LL |     let _: String = format!("Hello {}", "world").into();
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `.into()`: `format!("Hello {}", "world")`