Auto merge of #103693 - HKalbasi:master, r=oli-obk

Make rustc_target usable outside of rustc

I'm working on showing type size in rust-analyzer (https://github.com/rust-lang/rust-analyzer/pull/13490) and I currently copied rustc code inside rust-analyzer, which works, but is bad. With this change, I would become able to use `rustc_target` and `rustc_index` directly in r-a, reducing the amount of copy needed.

This PR contains some feature flag to put nightly features behind them to make crates buildable on the stable compiler + makes layout related types generic over index type + removes interning of nested layouts.

clippy_lints/src/casts/cast_possible_truncation.rs

@@ -2,12 +2,11 @@ use clippy_utils::consts::{constant, Constant};
 use clippy_utils::diagnostics::span_lint;
 use clippy_utils::expr_or_init;
 use clippy_utils::ty::{get_discriminant_value, is_isize_or_usize};
-use rustc_ast::ast;
-use rustc_attr::IntType;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::{BinOpKind, Expr, ExprKind};
 use rustc_lint::LateContext;
 use rustc_middle::ty::{self, FloatTy, Ty};
+use rustc_target::abi::IntegerType;
 
 use super::{utils, CAST_ENUM_TRUNCATION, CAST_POSSIBLE_TRUNCATION};
 
@@ -122,7 +121,7 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_expr: &Expr<'_>,
             let cast_from_ptr_size = def.repr().int.map_or(true, |ty| {
                 matches!(
                     ty,
-                    IntType::SignedInt(ast::IntTy::Isize) | IntType::UnsignedInt(ast::UintTy::Usize)
+                    IntegerType::Pointer(_),
                 )
             });
             let suffix = match (cast_from_ptr_size, is_isize_or_usize(cast_to)) {

clippy_lints/src/lib.rs

@@ -26,7 +26,6 @@
 extern crate rustc_arena;
 extern crate rustc_ast;
 extern crate rustc_ast_pretty;
-extern crate rustc_attr;
 extern crate rustc_data_structures;
 extern crate rustc_driver;
 extern crate rustc_errors;