867d39cdf6
Don't forget that the lifetime on hir types is `'tcx` This PR just tracks the `'tcx` lifetime to wherever the original objects actually have that lifetime. This code is needed for https://github.com/rust-lang/rust/pull/107606 (now #120131) so that `ast_ty_to_ty` can invoke `lit_to_const` on an argument passed to it. Currently the argument is `&hir::Ty<'_>`, but after this PR it is `&'tcx hir::Ty<'tcx>`.
For high-level intro to how type checking works in rustc, see the type checking chapter of the rustc dev guide.