This commit represents an attempt to address changes requested in the process of reviewing PR #2790.

The changes reflected in this commit are as follows:

- Revised `IndexingSlicingPass` struct name to IndexingSlicing for consistency with the rest of the code base.
- Revised match arm condition to use `(..)` shorthand in favor of `(_, _, _)`.
- Restored a couple telling variable names.
- Calls to `cx.span_lint` were revised to use `utils::span_help_and_lint`.
- Took a stab at refactoring some generalizable calls to `utils::span_help_and_lint` to minimize duplicate code.
- Revised INDEXING_SLICING declaration to pedantic rather than restriction.
- Added `&x[0..].get(..3)` to the test cases.

clippy_lints/src/lib.rs

@@ -431,7 +431,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
     reg.register_late_lint_pass(box unwrap::Pass);
     reg.register_late_lint_pass(box duration_subsec::DurationSubsec);
     reg.register_late_lint_pass(box default_trait_access::DefaultTraitAccess);
-    reg.register_late_lint_pass(box indexing_slicing::IndexingSlicingPass);
+    reg.register_late_lint_pass(box indexing_slicing::IndexingSlicing);
 
     reg.register_lint_group("clippy_restriction", vec![
         arithmetic::FLOAT_ARITHMETIC,