INDEXING_SLICING should probably be a restriction lint.

clippy_lints/src/array_indexing.rs

@@ -43,9 +43,8 @@ declare_lint! {
 /// x[2];
 /// &x[0..2];
 /// ```
-declare_lint! {
+declare_restriction_lint! {
     pub INDEXING_SLICING,
-    Allow,
     "indexing/slicing usage"
 }
 

clippy_lints/src/lib.rs

@@ -260,11 +260,11 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
     reg.register_lint_group("clippy_restrictions", vec![
         arithmetic::FLOAT_ARITHMETIC,
         arithmetic::INTEGER_ARITHMETIC,
+        array_indexing::INDEXING_SLICING,
         assign_ops::ASSIGN_OPS,
     ]);
 
     reg.register_lint_group("clippy_pedantic", vec![
-        array_indexing::INDEXING_SLICING,
         booleans::NONMINIMAL_BOOL,
         enum_glob_use::ENUM_GLOB_USE,
         enum_variants::STUTTER,