Alloc hir::Lit in an arena to remove the destructor from Expr

This allows allocating `Expr`s into a dropless arena, which is useful
for using length prefixed thing slices in HIR, since these can only be
allocated in the dropless arena and not in a typed arena. This is
something I'm working on.

Author: Noratrieb

clippy_lints/src/bool_assert_comparison.rs

@@ -41,7 +41,7 @@ fn extract_bool_lit(e: &Expr<'_>) -> Option<bool> {
     }) = e.kind
         && !e.span.from_expansion()
     {
-        Some(b)
+        Some(*b)
     } else {
         None
     }

clippy_lints/src/manual_strip.rs

@@ -159,7 +159,7 @@ fn eq_pattern_length<'tcx>(cx: &LateContext<'tcx>, pattern: &Expr<'_>, expr: &'t
         ..
     }) = expr.kind
     {
-        constant_length(cx, pattern).map_or(false, |length| length == n)
+        constant_length(cx, pattern).map_or(false, |length| length == *n)
     } else {
         len_arg(cx, expr).map_or(false, |arg| eq_expr_value(cx, pattern, arg))
     }

clippy_lints/src/matches/match_like_matches.rs

@@ -162,7 +162,7 @@ fn find_bool_lit(ex: &ExprKind<'_>) -> Option<bool> {
                 node: LitKind::Bool(b), ..
             }) = exp.kind
             {
-                Some(b)
+                Some(*b)
             } else {
                 None
             }

clippy_lints/src/methods/open_options.rs

@@ -48,7 +48,7 @@ fn get_open_options(cx: &LateContext<'_>, argument: &Expr<'_>, options: &mut Vec
                         ..
                     } = *span
                     {
-                        if lit { Argument::True } else { Argument::False }
+                        if *lit { Argument::True } else { Argument::False }
                     } else {
                         // The function is called with a literal which is not a boolean literal.
                         // This is theoretically possible, but not very likely.

clippy_lints/src/utils/author.rs

@@ -430,7 +430,7 @@ impl<'a, 'tcx> PrintVisitor<'a, 'tcx> {
                 kind!("Unary(UnOp::{op:?}, {inner})");
                 self.expr(inner);
             },
-            ExprKind::Lit(ref lit) => {
+            ExprKind::Lit(lit) => {
                 bind!(self, lit);
                 kind!("Lit(ref {lit})");
                 self.lit(lit);