Rollup merge of rust-lang#83916 - Amanieu:asm_anonconst, r=petrochenkov

Use AnonConst for asm! constants

This replaces the old system which used explicit promotion. See rust-lang#83169 for more background.

The syntax for `const` operands is still the same as before: `const <expr>`.

Fixes rust-lang#83169

Because the implementation is heavily based on inline consts, we suffer from the same issues:
- We lose the ability to use expressions derived from generics. See the deleted tests in `src/test/ui/asm/const.rs`.
- We are hitting the same ICEs as inline consts, for example rust-lang#78174. It is unlikely that we will be able to stabilize this before inline consts are stabilized.

clippy_lints/src/loops/never_loop.rs

@@ -142,12 +142,12 @@ fn never_loop_expr(expr: &Expr<'_>, main_loop_id: HirId) -> NeverLoopResult {
             .map(|(o, _)| match o {
                 InlineAsmOperand::In { expr, .. }
                 | InlineAsmOperand::InOut { expr, .. }
-                | InlineAsmOperand::Const { expr }
                 | InlineAsmOperand::Sym { expr } => never_loop_expr(expr, main_loop_id),
                 InlineAsmOperand::Out { expr, .. } => never_loop_expr_all(&mut expr.iter(), main_loop_id),
                 InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => {
                     never_loop_expr_all(&mut once(in_expr).chain(out_expr.iter()), main_loop_id)
                 },
+                InlineAsmOperand::Const { .. } => NeverLoopResult::Otherwise,
             })
             .fold(NeverLoopResult::Otherwise, combine_both),
         ExprKind::Struct(_, _, None)

clippy_lints/src/utils/inspector.rs

@@ -306,7 +306,6 @@ fn print_expr(cx: &LateContext<'_>, expr: &hir::Expr<'_>, indent: usize) {
                 match op {
                     hir::InlineAsmOperand::In { expr, .. }
                     | hir::InlineAsmOperand::InOut { expr, .. }
-                    | hir::InlineAsmOperand::Const { expr }
                     | hir::InlineAsmOperand::Sym { expr } => print_expr(cx, expr, indent + 1),
                     hir::InlineAsmOperand::Out { expr, .. } => {
                         if let Some(expr) = expr {
@@ -319,6 +318,10 @@ fn print_expr(cx: &LateContext<'_>, expr: &hir::Expr<'_>, indent: usize) {
                             print_expr(cx, out_expr, indent + 1);
                         }
                     },
+                    hir::InlineAsmOperand::Const { anon_const } => {
+                        println!("{}anon_const:", ind);
+                        print_expr(cx, &cx.tcx.hir().body(anon_const.body).value, indent + 1);
+                    }
                 }
             }
         },

clippy_utils/src/hir_utils.rs

@@ -663,7 +663,8 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
                                 self.hash_expr(out_expr);
                             }
                         },
-                        InlineAsmOperand::Const { expr } | InlineAsmOperand::Sym { expr } => self.hash_expr(expr),
+                        InlineAsmOperand::Const { anon_const } => self.hash_body(anon_const.body),
+                        InlineAsmOperand::Sym { expr } => self.hash_expr(expr),
                     }
                 }
             },