Use token::Lit in ast::ExprKind::Lit.

Instead of `ast::Lit`.

Literal lowering now happens at two different times. Expression literals
are lowered when HIR is crated. Attribute literals are lowered during
parsing.

This commit changes the language very slightly. Some programs that used
to not compile now will compile. This is because some invalid literals
that are removed by `cfg` or attribute macros will no longer trigger
errors. See this comment for more details:
https://github.com/rust-lang/rust/pull/102944#issuecomment-1277476773

compiler/rustc_lint/src/builtin.rs

@@ -98,9 +98,10 @@ fn pierce_parens(mut expr: &ast::Expr) -> &ast::Expr {
 impl EarlyLintPass for WhileTrue {
     fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
         if let ast::ExprKind::While(cond, _, label) = &e.kind
-            && let ast::ExprKind::Lit(ref lit) = pierce_parens(cond).kind
-            && let ast::LitKind::Bool(true) = lit.kind
-            && !lit.span.from_expansion()
+            && let cond = pierce_parens(cond)
+            && let ast::ExprKind::Lit(token_lit) = cond.kind
+            && let token::Lit { kind: token::Bool, symbol: kw::True, .. } = token_lit
+            && !cond.span.from_expansion()
         {
             let condition_span = e.span.with_hi(cond.span.hi());
             cx.struct_span_lint(