Improve code and apply suggestions

Author: GuillaumeGomez

clippy_lints/src/useless_concat.rs

@@ -82,12 +82,14 @@ impl LateLintPass<'_> for UselessConcat {
                 }
             }
             let literal = match literal {
-                Some(lit) => {
+                Some(original_lit) => {
                     // Literals can also be number, so we need to check this case too.
+                    let lit = original_lit.strip_prefix("r").unwrap_or(original_lit);
+                    let lit = lit.trim_start_matches('#');
                     if lit.starts_with('"') {
-                        lit.to_string()
+                        original_lit.to_string()
                     } else {
-                        format!("\"{lit}\"")
+                        format!("\"{original_lit}\"")
                     }
                 },
                 None => "\"\"".to_string(),

clippy_lints_internal/src/invalid_paths.rs

@@ -63,10 +63,6 @@ pub fn check_path(cx: &LateContext<'_>, path: &[&str]) -> bool {
     if !def_path_res(cx.tcx, path).is_empty() {
         return true;
     }
-    // `builtin` macros don't seem to be found in `def_path_res`...
-    if path == ["core", "macros", "builtin", "concat"] {
-        return true;
-    }
 
     // Some implementations can't be found by `path_to_res`, particularly inherent
     // implementations of native types. Check lang items.

clippy_utils/src/paths.rs

@@ -27,11 +27,7 @@ pub const SYM_MODULE: [&str; 3] = ["rustc_span", "symbol", "sym"];
 pub const SYNTAX_CONTEXT: [&str; 3] = ["rustc_span", "hygiene", "SyntaxContext"];
 
 // Paths in `core`/`alloc`/`std`. This should be avoided and cleaned up by adding diagnostic items.
-pub const ABORT: [&str; 3] = ["std", "process", "abort"];
-pub const CHILD: [&str; 3] = ["std", "process", "Child"];
-pub const CHILD_ID: [&str; 4] = ["std", "process", "Child", "id"];
-pub const CHILD_KILL: [&str; 4] = ["std", "process", "Child", "kill"];
-pub const PANIC_ANY: [&str; 3] = ["std", "panic", "panic_any"];
+#[expect(clippy::invalid_paths)]
 pub const CONCAT: [&str; 4] = ["core", "macros", "builtin", "concat"];
 pub const CHAR_IS_ASCII: [&str; 5] = ["core", "char", "methods", "<impl char>", "is_ascii"];
 pub const IO_ERROR_NEW: [&str; 5] = ["std", "io", "error", "Error", "new"];

tests/ui/useless_concat.fixed

@@ -1,6 +1,11 @@
+//@aux-build:proc_macros.rs
+
 #![warn(clippy::useless_concat)]
 #![allow(clippy::print_literal)]
 
+extern crate proc_macros;
+use proc_macros::{external, with_span};
+
 macro_rules! my_concat {
     ($fmt:literal $(, $e:expr)*) => {
         println!(concat!("ERROR: ", $fmt), $($e,)*);
@@ -10,11 +15,18 @@ macro_rules! my_concat {
 fn main() {
     let x = ""; //~ useless_concat
     let x = "a"; //~ useless_concat
+    let x = r##"a"##; //~ useless_concat
     let x = "1"; //~ useless_concat
     println!("b: {}", "a"); //~ useless_concat
     // Should not lint.
     let x = concat!("a", "b");
     let local_i32 = 1;
     my_concat!("{}", local_i32);
     let x = concat!(file!(), "#L", line!());
+
+    external! { concat!(); }
+    with_span! {
+        span
+        concat!();
+    }
 }

tests/ui/useless_concat.rs

@@ -1,6 +1,11 @@
+//@aux-build:proc_macros.rs
+
 #![warn(clippy::useless_concat)]
 #![allow(clippy::print_literal)]
 
+extern crate proc_macros;
+use proc_macros::{external, with_span};
+
 macro_rules! my_concat {
     ($fmt:literal $(, $e:expr)*) => {
         println!(concat!("ERROR: ", $fmt), $($e,)*);
@@ -10,11 +15,18 @@ macro_rules! my_concat {
 fn main() {
     let x = concat!(); //~ useless_concat
     let x = concat!("a"); //~ useless_concat
+    let x = concat!(r##"a"##); //~ useless_concat
     let x = concat!(1); //~ useless_concat
     println!("b: {}", concat!("a")); //~ useless_concat
     // Should not lint.
     let x = concat!("a", "b");
     let local_i32 = 1;
     my_concat!("{}", local_i32);
     let x = concat!(file!(), "#L", line!());
+
+    external! { concat!(); }
+    with_span! {
+        span
+        concat!();
+    }
 }

tests/ui/useless_concat.stderr

@@ -1,5 +1,5 @@
 error: unneeded use of `concat!` macro
-  --> tests/ui/useless_concat.rs:11:13
+  --> tests/ui/useless_concat.rs:16:13
    |
 LL |     let x = concat!();
    |             ^^^^^^^^^ help: replace with: `""`
@@ -8,22 +8,28 @@ LL |     let x = concat!();
    = help: to override `-D warnings` add `#[allow(clippy::useless_concat)]`
 
 error: unneeded use of `concat!` macro
-  --> tests/ui/useless_concat.rs:12:13
+  --> tests/ui/useless_concat.rs:17:13
    |
 LL |     let x = concat!("a");
    |             ^^^^^^^^^^^^ help: replace with: `"a"`
 
 error: unneeded use of `concat!` macro
-  --> tests/ui/useless_concat.rs:13:13
+  --> tests/ui/useless_concat.rs:18:13
+   |
+LL |     let x = concat!(r##"a"##);
+   |             ^^^^^^^^^^^^^^^^^ help: replace with: `r##"a"##`
+
+error: unneeded use of `concat!` macro
+  --> tests/ui/useless_concat.rs:19:13
    |
 LL |     let x = concat!(1);
    |             ^^^^^^^^^^ help: replace with: `"1"`
 
 error: unneeded use of `concat!` macro
-  --> tests/ui/useless_concat.rs:14:23
+  --> tests/ui/useless_concat.rs:20:23
    |
 LL |     println!("b: {}", concat!("a"));
    |                       ^^^^^^^^^^^^ help: replace with: `"a"`
 
-error: aborting due to 4 previous errors
+error: aborting due to 5 previous errors