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

1 files changed, 6 insertions, 4 deletions

diff --git a/compiler/rustc_parse/src/validate_attr.rs b/compiler/rustc_parse/src/validate_attr.rs
index 47477898b24..8e7f8bfe0f5 100644
--- a/compiler/rustc_parse/src/validate_attr.rs
+++ b/compiler/rustc_parse/src/validate_attr.rs
@@ -49,10 +49,12 @@ pub fn parse_meta<'a>(sess: &'a ParseSess, attr: &Attribute) -> PResult<'a, Meta
                 MetaItemKind::List(nmis)
             }
             MacArgs::Eq(_, MacArgsEq::Ast(expr)) => {
-                if let ast::ExprKind::Lit(lit) = &expr.kind {
-                    if !lit.kind.is_unsuffixed() {
+                if let ast::ExprKind::Lit(token_lit) = expr.kind
+                    && let Ok(lit) = ast::Lit::from_token_lit(token_lit, expr.span)
+                {
+                    if token_lit.suffix.is_some() {
                         let mut err = sess.span_diagnostic.struct_span_err(
-                            lit.span,
+                            expr.span,
                             "suffixed literals are not allowed in attributes",
                         );
                         err.help(
@@ -61,7 +63,7 @@ pub fn parse_meta<'a>(sess: &'a ParseSess, attr: &Attribute) -> PResult<'a, Meta
                         );
                         return Err(err);
                     } else {
-                        MetaItemKind::NameValue(lit.clone())
+                        MetaItemKind::NameValue(lit)
                     }
                 } else {
                     // The non-error case can happen with e.g. `#[foo = 1+1]`. The error case can