Move concat macro path into clippy_utils::paths

Author: GuillaumeGomez

clippy_lints/src/useless_concat.rs

@@ -1,5 +1,6 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::macros::macro_backtrace;
+use clippy_utils::paths::CONCAT;
 use clippy_utils::source::snippet_opt;
 use clippy_utils::{match_def_path, tokenize_with_text};
 use rustc_ast::LitKind;
@@ -42,7 +43,7 @@ impl LateLintPass<'_> for UselessConcat {
             // Get the direct parent of the expression.
             && let Some(macro_call) = macro_backtrace(expr.span).next()
             // Check if the `concat` macro from the `core` library.
-            && match_def_path(cx, macro_call.def_id, &["core", "macros", "builtin", "concat"])
+            && match_def_path(cx, macro_call.def_id, &CONCAT)
             // We get the original code to parse it.
             && let Some(original_code) = snippet_opt(cx, macro_call.span)
             // This check allows us to ensure that the code snippet:

clippy_utils/src/paths.rs

@@ -129,6 +129,7 @@ path_macros! {
 // Paths in `core`/`alloc`/`std`. This should be avoided and cleaned up by adding diagnostic items.
 pub static ALIGN_OF: PathLookup = value_path!(core::mem::align_of);
 pub static CHAR_TO_DIGIT: PathLookup = value_path!(char::to_digit);
+pub static CONCAT: PathLookup = value_path!(core::macros::builtin::concat);
 pub static IO_ERROR_NEW: PathLookup = value_path!(std::io::Error::new);
 pub static IO_ERRORKIND_OTHER_CTOR: PathLookup = value_path!(std::io::ErrorKind::Other);
 pub static ITER_STEP: PathLookup = type_path!(core::iter::Step);