Add regression test for literal_string_with_formatting_arg

tests/ui/literal_string_with_formatting_arg.rs

@@ -0,0 +1,25 @@
+#![warn(clippy::literal_string_with_formatting_arg)]
+#![allow(clippy::unnecessary_literal_unwrap)]
+
+fn main() {
+    let x: Option<usize> = None;
+    let y = "hello";
+    x.expect("{y}"); //~ literal_string_with_formatting_arg
+    x.expect("{:?}"); //~ literal_string_with_formatting_arg
+    x.expect("{y:?}"); //~ literal_string_with_formatting_arg
+    x.expect(" {y:?} {y:?} "); //~ literal_string_with_formatting_arg
+    x.expect(" {y:..} {y:?} "); //~ literal_string_with_formatting_arg
+    x.expect(r" {y:?} {y:?} "); //~ literal_string_with_formatting_arg
+    x.expect(r"{y:?} y:?}"); //~ literal_string_with_formatting_arg
+    x.expect(r##" {y:?} {y:?} "##); //~ literal_string_with_formatting_arg
+    "\\.+*?()|[]{}^$#&-~".chars().any(|x| x == 'a');
+
+    // Should not lint!
+    format!("{y:?}");
+    println!("{y:?}");
+    x.expect("{{y} {x");
+    x.expect("{{y:?}");
+    x.expect("{y:...}");
+    // Unicode characters escape should not lint either.
+    "\u{0052}".to_string();
+}

tests/ui/literal_string_with_formatting_arg.stderr

@@ -0,0 +1,59 @@
+error: this is a formatting argument but it is not part of a formatting macro
+  --> tests/ui/literal_string_with_formatting_arg.rs:7:15
+   |
+LL |     x.expect("{y}");
+   |               ^^^
+   |
+   = note: `-D clippy::literal-string-with-formatting-arg` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::literal_string_with_formatting_arg)]`
+
+error: this is a formatting argument but it is not part of a formatting macro
+  --> tests/ui/literal_string_with_formatting_arg.rs:8:15
+   |
+LL |     x.expect("{:?}");
+   |               ^^^^
+
+error: this is a formatting argument but it is not part of a formatting macro
+  --> tests/ui/literal_string_with_formatting_arg.rs:9:15
+   |
+LL |     x.expect("{y:?}");
+   |               ^^^^^
+
+error: these are formatting arguments but are not part of a formatting macro
+  --> tests/ui/literal_string_with_formatting_arg.rs:10:16
+   |
+LL |     x.expect(" {y:?} {y:?} ");
+   |                ^^^^^ ^^^^^
+
+error: this is a formatting argument but it is not part of a formatting macro
+  --> tests/ui/literal_string_with_formatting_arg.rs:11:23
+   |
+LL |     x.expect(" {y:..} {y:?} ");
+   |                       ^^^^^
+
+error: these are formatting arguments but are not part of a formatting macro
+  --> tests/ui/literal_string_with_formatting_arg.rs:12:17
+   |
+LL |     x.expect(r" {y:?} {y:?} ");
+   |                 ^^^^^ ^^^^^
+
+error: this is a formatting argument but it is not part of a formatting macro
+  --> tests/ui/literal_string_with_formatting_arg.rs:13:16
+   |
+LL |     x.expect(r"{y:?} y:?}");
+   |                ^^^^^
+
+error: these are formatting arguments but are not part of a formatting macro
+  --> tests/ui/literal_string_with_formatting_arg.rs:14:19
+   |
+LL |     x.expect(r##" {y:?} {y:?} "##);
+   |                   ^^^^^ ^^^^^
+
+error: this is a formatting argument but it is not part of a formatting macro
+  --> tests/ui/literal_string_with_formatting_arg.rs:15:17
+   |
+LL |     "\\.+*?()|[]{}^$#&-~".chars().any(|x| x == 'a');
+   |                 ^^
+
+error: aborting due to 9 previous errors
+