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, 5 insertions, 22 deletions

diff --git a/compiler/rustc_ast/src/util/literal.rs b/compiler/rustc_ast/src/util/literal.rs
index e267f8cd100..db2ac9626af 100644
--- a/compiler/rustc_ast/src/util/literal.rs
+++ b/compiler/rustc_ast/src/util/literal.rs
@@ -8,8 +8,8 @@ use rustc_span::symbol::{kw, sym, Symbol};
 use rustc_span::Span;
 use std::ascii;
 
+#[derive(Debug)]
 pub enum LitError {
-    NotLiteral,
     LexerError,
     InvalidSuffix,
     InvalidIntSuffix,
@@ -202,27 +202,10 @@ impl Lit {
         Ok(Lit { token_lit, kind: LitKind::from_token_lit(token_lit)?, span })
     }
 
-    /// Converts arbitrary token into an AST literal.
-    ///
-    /// Keep this in sync with `Token::can_begin_literal_or_bool` excluding unary negation.
-    pub fn from_token(token: &Token) -> Result<Lit, LitError> {
-        let lit = match token.uninterpolate().kind {
-            token::Ident(name, false) if name.is_bool_lit() => {
-                token::Lit::new(token::Bool, name, None)
-            }
-            token::Literal(lit) => lit,
-            token::Interpolated(ref nt) => {
-                if let token::NtExpr(expr) | token::NtLiteral(expr) = &**nt
-                    && let ast::ExprKind::Lit(lit) = &expr.kind
-                {
-                    return Ok(lit.clone());
-                }
-                return Err(LitError::NotLiteral);
-            }
-            _ => return Err(LitError::NotLiteral),
-        };
-
-        Lit::from_token_lit(lit, token.span)
+    /// Converts an arbitrary token into an AST literal.
+    pub fn from_token(token: &Token) -> Option<Lit> {
+        token::Lit::from_token(token)
+            .and_then(|token_lit| Lit::from_token_lit(token_lit, token.span).ok())
     }
 
     /// Attempts to recover an AST literal from semantic literal.