1 files changed, 32 insertions, 13 deletions
diff --git a/src/tools/clippy/clippy_lints/src/indexing_slicing.rs b/src/tools/clippy/clippy_lints/src/indexing_slicing.rs
index 4cd7dff4c..eebfb753a 100644
--- a/src/tools/clippy/clippy_lints/src/indexing_slicing.rs
+++ b/src/tools/clippy/clippy_lints/src/indexing_slicing.rs
@@ -1,13 +1,13 @@
 //! lint on indexing and slicing operations
 
 use clippy_utils::consts::{constant, Constant};
-use clippy_utils::diagnostics::{span_lint, span_lint_and_help};
+use clippy_utils::diagnostics::{span_lint, span_lint_and_then};
 use clippy_utils::higher;
 use rustc_ast::ast::RangeLimits;
 use rustc_hir::{Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty;
-use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_session::{declare_tool_lint, impl_lint_pass};
 
 declare_clippy_lint! {
     /// ### What it does
@@ -82,15 +82,29 @@ declare_clippy_lint! {
     "indexing/slicing usage"
 }
 
-declare_lint_pass!(IndexingSlicing => [INDEXING_SLICING, OUT_OF_BOUNDS_INDEXING]);
+impl_lint_pass!(IndexingSlicing => [INDEXING_SLICING, OUT_OF_BOUNDS_INDEXING]);
+
+#[derive(Copy, Clone)]
+pub struct IndexingSlicing {
+    suppress_restriction_lint_in_const: bool,
+}
+
+impl IndexingSlicing {
+    pub fn new(suppress_restriction_lint_in_const: bool) -> Self {
+        Self {
+            suppress_restriction_lint_in_const,
+        }
+    }
+}
 
 impl<'tcx> LateLintPass<'tcx> for IndexingSlicing {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
-        if cx.tcx.hir().is_inside_const_context(expr.hir_id) {
+        if self.suppress_restriction_lint_in_const && cx.tcx.hir().is_inside_const_context(expr.hir_id) {
             return;
         }
 
         if let ExprKind::Index(array, index) = &expr.kind {
+            let note = "the suggestion might not be applicable in constant blocks";
             let ty = cx.typeck_results().expr_ty(array).peel_refs();
             if let Some(range) = higher::Range::hir(index) {
                 // Ranged indexes, i.e., &x[n..m], &x[n..], &x[..n] and &x[..]
@@ -141,7 +155,13 @@ impl<'tcx> LateLintPass<'tcx> for IndexingSlicing {
                     (None, None) => return, // [..] is ok.
                 };
 
-                span_lint_and_help(cx, INDEXING_SLICING, expr.span, "slicing may panic", None, help_msg);
+                span_lint_and_then(cx, INDEXING_SLICING, expr.span, "slicing may panic", |diag| {
+                    diag.help(help_msg);
+
+                    if cx.tcx.hir().is_inside_const_context(expr.hir_id) {
+                        diag.note(note);
+                    }
+                });
             } else {
                 // Catchall non-range index, i.e., [n] or [n << m]
                 if let ty::Array(..) = ty.kind() {
@@ -156,14 +176,13 @@ impl<'tcx> LateLintPass<'tcx> for IndexingSlicing {
                     }
                 }
 
-                span_lint_and_help(
-                    cx,
-                    INDEXING_SLICING,
-                    expr.span,
-                    "indexing may panic",
-                    None,
-                    "consider using `.get(n)` or `.get_mut(n)` instead",
-                );
+                span_lint_and_then(cx, INDEXING_SLICING, expr.span, "indexing may panic", |diag| {
+                    diag.help("consider using `.get(n)` or `.get_mut(n)` instead");
+
+                    if cx.tcx.hir().is_inside_const_context(expr.hir_id) {
+                        diag.note(note);
+                    }
+                });
             }
         }
     }