refactor string_extend_chars: return when obj type is not string

Author: TaKO8Ki

clippy_lints/src/methods/string_extend_chars.rs

@@ -12,34 +12,35 @@ use super::STRING_EXTEND_CHARS;
 
 pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<'_>]) {
     let obj_ty = cx.typeck_results().expr_ty(&args[0]).peel_refs();
-    if is_type_diagnostic_item(cx, obj_ty, sym::string_type) {
-        let arg = &args[1];
-        if let Some(arglists) = method_chain_args(arg, &["chars"]) {
-            let target = &arglists[0][0];
-            let self_ty = cx.typeck_results().expr_ty(target).peel_refs();
-            let ref_str = if *self_ty.kind() == ty::Str {
-                ""
-            } else if is_type_diagnostic_item(cx, self_ty, sym::string_type) {
-                "&"
-            } else {
-                return;
-            };
+    if !is_type_diagnostic_item(cx, obj_ty, sym::string_type) {
+        return;
+    }
+    let arg = &args[1];
+    if let Some(arglists) = method_chain_args(arg, &["chars"]) {
+        let target = &arglists[0][0];
+        let self_ty = cx.typeck_results().expr_ty(target).peel_refs();
+        let ref_str = if *self_ty.kind() == ty::Str {
+            ""
+        } else if is_type_diagnostic_item(cx, self_ty, sym::string_type) {
+            "&"
+        } else {
+            return;
+        };
 
-            let mut applicability = Applicability::MachineApplicable;
-            span_lint_and_sugg(
-                cx,
-                STRING_EXTEND_CHARS,
-                expr.span,
-                "calling `.extend(_.chars())`",
-                "try this",
-                format!(
-                    "{}.push_str({}{})",
-                    snippet_with_applicability(cx, args[0].span, "..", &mut applicability),
-                    ref_str,
-                    snippet_with_applicability(cx, target.span, "..", &mut applicability)
-                ),
-                applicability,
-            );
-        }
+        let mut applicability = Applicability::MachineApplicable;
+        span_lint_and_sugg(
+            cx,
+            STRING_EXTEND_CHARS,
+            expr.span,
+            "calling `.extend(_.chars())`",
+            "try this",
+            format!(
+                "{}.push_str({}{})",
+                snippet_with_applicability(cx, args[0].span, "..", &mut applicability),
+                ref_str,
+                snippet_with_applicability(cx, target.span, "..", &mut applicability)
+            ),
+            applicability,
+        );
     }
 }