add checking type

Author: kyoto7250

clippy_lints/src/bytes_count_to_len.rs

@@ -1,8 +1,13 @@
-use clippy_utils::diagnostics::span_lint_and_note;
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::source::snippet_with_applicability;
+use clippy_utils::ty::is_type_diagnostic_item;
 use if_chain::if_chain;
+use rustc_errors::Applicability;
 use rustc_hir as hir;
 use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::ty;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::sym;
 
 declare_clippy_lint! {
     /// ### What it does
@@ -16,37 +21,45 @@ declare_clippy_lint! {
     /// ### Example
     /// ```rust
     /// "hello".bytes().count();
+    /// String::from("hello").bytes().count();
     /// ```
     /// Use instead:
     /// ```rust
-    /// "hello".len();
+    /// "hello".len()
+    /// String::from("hello").len();
     /// ```
-    #[clippy::version = "1.60.0"]
+    #[clippy::version = "1.62.0"]
     pub BYTES_COUNT_TO_LEN,
     complexity,
-    "Using bytest().count() when len() performs the same functionality"
+    "Using bytes().count() when len() performs the same functionality"
 }
 
 declare_lint_pass!(BytesCountToLen => [BYTES_COUNT_TO_LEN]);
 
 impl<'tcx> LateLintPass<'tcx> for BytesCountToLen {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
         if_chain! {
-            //check for method call called "count"
-            if let hir::ExprKind::MethodCall(count_path, count_args, _) = &expr.kind;
-            if count_path.ident.name == rustc_span::sym::count;
-            if let [bytes_expr] = &**count_args;
-            //check for method call called "bytes" that was linked to "count"
-            if let hir::ExprKind::MethodCall(bytes_path, _, _) = &bytes_expr.kind;
-            if bytes_path.ident.name.as_str() == "bytes";
+            if let hir::ExprKind::MethodCall(expr_method, expr_args, _) = &expr.kind;
+            if expr_method.ident.name == rustc_span::sym::count;
+
+            if let [bytes_expr] = &**expr_args;
+            if let hir::ExprKind::MethodCall(bytes_method, bytes_args, _) = &bytes_expr.kind;
+            if bytes_method.ident.name.as_str() == "bytes";
+
+            if let [str_expr] = &**bytes_args;
+            let ty = cx.typeck_results().expr_ty(str_expr).peel_refs();
+
+            if is_type_diagnostic_item(cx, ty, sym::String) || ty.kind() == &ty::Str;
             then {
-                span_lint_and_note(
+                let mut applicability = Applicability::MachineApplicable;
+                span_lint_and_sugg(
                     cx,
                     BYTES_COUNT_TO_LEN,
                     expr.span,
                     "using long and hard to read `.bytes().count()`",
-                    None,
-                    "`.len()` achieves same functionality"
+                    "consider calling `.len` instead:",
+                    format!("{}.len()", snippet_with_applicability(cx, str_expr.span, "..", &mut applicability)),
+                    applicability
                 );
             }
         };