Internal lint for usage of ty::TyKind

[flip1995]

cc #2077 (comment)
cc rust-lang/rust#49509

[oli-obk]

Can you add this lint to rustc? We might need to put it behind a -Z flag so that we don't expose it to users (allow(usage_of_ty_kind) should complain about an unknown lint without the -Z flag).

[flip1995]

Yes can do. While doing this should I also move the DEFAULT_HASH_TYPES lint to rustc, since it is also on the list in rust-lang/rust#49509?

rust-clippy/clippy_lints/src/utils/internal_lints.rs

Lines 68 to 77 in 3f24cdf

	/// **What it does:** Checks for the presence of the default hash types "HashMap" or "HashSet"
	/// and recommends the FxHash* variants.
	///
	/// **Why is this bad?** The FxHash variants have better performance
	/// and we don't need any collision prevention in clippy.
	declare_clippy_lint! {
	pub DEFAULT_HASH_TYPES,
	internal,
	"forbid HashMap and HashSet and suggest the FxHash* variants"
	}

[oli-obk]

good idea!

[flip1995]

Fixing done in #3495. Closing this in favor of a rustc implementation.