don't lint external macro expansions

Author: Jarcho

clippy_lints/src/redundant_slicing.rs

@@ -2,7 +2,7 @@ use if_chain::if_chain;
 use rustc_errors::Applicability;
 use rustc_hir::{Expr, ExprKind, LangItem};
 use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::ty::TyS;
+use rustc_middle::{lint::in_external_macro, ty::TyS};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 
 use crate::utils::{is_type_lang_item, snippet_with_applicability, span_lint_and_sugg};
@@ -39,6 +39,10 @@ declare_lint_pass!(RedundantSlicing => [REDUNDANT_SLICING]);
 
 impl LateLintPass<'_> for RedundantSlicing {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+        if in_external_macro(cx.sess, expr.span) {
+            return;
+        }
+
         if_chain! {
             if let ExprKind::AddrOf(_, _, addressee) = expr.kind;
             if let ExprKind::Index(indexed, range) = addressee.kind;