Add ErrorGuaranteed to ast::LitKind::Err, token::LitKind::Err.

This mostly works well, and eliminates a couple of delayed bugs.

One annoying thing is that we should really also add an
`ErrorGuaranteed` to `proc_macro::bridge::LitKind::Err`. But that's
difficult because `proc_macro` doesn't have access to `ErrorGuaranteed`,
so we have to fake it.

compiler/rustc_ast/src/ast.rs

@@ -1846,7 +1846,7 @@ pub enum LitKind {
     /// A boolean literal (`true`, `false`).
     Bool(bool),
     /// Placeholder for a literal that wasn't well-formed in some way.
-    Err,
+    Err(ErrorGuaranteed),
 }
 
 impl LitKind {
@@ -1893,7 +1893,7 @@ impl LitKind {
             | LitKind::Int(_, LitIntType::Unsuffixed)
             | LitKind::Float(_, LitFloatType::Unsuffixed)
             | LitKind::Bool(..)
-            | LitKind::Err => false,
+            | LitKind::Err(_) => false,
         }
     }
 }

compiler/rustc_ast/src/token.rs

@@ -13,7 +13,7 @@ use rustc_macros::HashStable_Generic;
 use rustc_span::symbol::{kw, sym};
 #[allow(hidden_glob_reexports)]
 use rustc_span::symbol::{Ident, Symbol};
-use rustc_span::{edition::Edition, Span, DUMMY_SP};
+use rustc_span::{edition::Edition, ErrorGuaranteed, Span, DUMMY_SP};
 use std::borrow::Cow;
 use std::fmt;
 
@@ -75,7 +75,7 @@ pub enum LitKind {
     ByteStrRaw(u8), // raw byte string delimited by `n` hash symbols
     CStr,
     CStrRaw(u8),
-    Err,
+    Err(ErrorGuaranteed),
 }
 
 /// A literal token.
@@ -144,7 +144,7 @@ impl fmt::Display for Lit {
             CStrRaw(n) => {
                 write!(f, "cr{delim}\"{symbol}\"{delim}", delim = "#".repeat(n as usize))?
             }
-            Integer | Float | Bool | Err => write!(f, "{symbol}")?,
+            Integer | Float | Bool | Err(_) => write!(f, "{symbol}")?,
         }
 
         if let Some(suffix) = suffix {
@@ -159,7 +159,7 @@ impl LitKind {
     /// An English article for the literal token kind.
     pub fn article(self) -> &'static str {
         match self {
-            Integer | Err => "an",
+            Integer | Err(_) => "an",
             _ => "a",
         }
     }
@@ -174,12 +174,12 @@ impl LitKind {
             Str | StrRaw(..) => "string",
             ByteStr | ByteStrRaw(..) => "byte string",
             CStr | CStrRaw(..) => "C string",
-            Err => "error",
+            Err(_) => "error",
         }
     }
 
     pub(crate) fn may_have_suffix(self) -> bool {
-        matches!(self, Integer | Float | Err)
+        matches!(self, Integer | Float | Err(_))
     }
 }
 

compiler/rustc_ast/src/util/literal.rs

@@ -144,7 +144,7 @@ impl LitKind {
                 buf.push(0);
                 LitKind::CStr(buf.into(), StrStyle::Raw(n))
             }
-            token::Err => LitKind::Err,
+            token::Err(guar) => LitKind::Err(guar),
         })
     }
 }
@@ -201,7 +201,7 @@ impl fmt::Display for LitKind {
                 }
             }
             LitKind::Bool(b) => write!(f, "{}", if b { "true" } else { "false" })?,
-            LitKind::Err => {
+            LitKind::Err(_) => {
                 // This only shows up in places like `-Zunpretty=hir` output, so we
                 // don't bother to produce something useful.
                 write!(f, "<bad-literal>")?;
@@ -237,7 +237,7 @@ impl MetaItemLit {
             LitKind::Char(_) => token::Char,
             LitKind::Int(..) => token::Integer,
             LitKind::Float(..) => token::Float,
-            LitKind::Err => token::Err,
+            LitKind::Err(guar) => token::Err(guar),
         };
 
         token::Lit::new(kind, self.symbol, self.suffix)

compiler/rustc_ast_lowering/src/expr.rs

@@ -124,8 +124,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     let lit_kind = match LitKind::from_token_lit(*token_lit) {
                         Ok(lit_kind) => lit_kind,
                         Err(err) => {
-                            report_lit_error(&self.tcx.sess.parse_sess, err, *token_lit, e.span);
-                            LitKind::Err
+                            let guar = report_lit_error(
+                                &self.tcx.sess.parse_sess,
+                                err,
+                                *token_lit,
+                                e.span,
+                            );
+                            LitKind::Err(guar)
                         }
                     };
                     let lit = self.arena.alloc(respan(self.lower_span(e.span), lit_kind));

compiler/rustc_ast_lowering/src/lib.rs

@@ -966,10 +966,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 {
                     lit
                 } else {
+                    let guar = self.dcx().has_errors().unwrap();
                     MetaItemLit {
                         symbol: kw::Empty,
                         suffix: None,
-                        kind: LitKind::Err,
+                        kind: LitKind::Err(guar),
                         span: DUMMY_SP,
                     }
                 };

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -254,7 +254,7 @@ fn literal_to_string(lit: token::Lit) -> String {
         token::CStrRaw(n) => {
             format!("cr{delim}\"{symbol}\"{delim}", delim = "#".repeat(n as usize))
         }
-        token::Integer | token::Float | token::Bool | token::Err => symbol.to_string(),
+        token::Integer | token::Float | token::Bool | token::Err(_) => symbol.to_string(),
     };
 
     if let Some(suffix) = suffix {

compiler/rustc_builtin_macros/src/concat.rs

@@ -40,7 +40,7 @@ pub fn expand_concat(
                     cx.dcx().emit_err(errors::ConcatBytestr { span: e.span });
                     has_errors = true;
                 }
-                Ok(ast::LitKind::Err) => {
+                Ok(ast::LitKind::Err(_)) => {
                     has_errors = true;
                 }
                 Err(err) => {

compiler/rustc_builtin_macros/src/concat_bytes.rs

@@ -44,7 +44,7 @@ fn invalid_type_err(
         Ok(ast::LitKind::Bool(_)) => {
             dcx.emit_err(ConcatBytesInvalid { span, lit_kind: "boolean", sugg: None });
         }
-        Ok(ast::LitKind::Err) => {}
+        Ok(ast::LitKind::Err(_)) => {}
         Ok(ast::LitKind::Int(_, _)) if !is_nested => {
             let sugg =
                 snippet.map(|snippet| ConcatBytesInvalidSuggestion::IntLit { span: span, snippet });

compiler/rustc_expand/src/base.rs

@@ -1266,7 +1266,7 @@ pub fn expr_to_spanned_string<'a>(
                 );
                 Some((err, true))
             }
-            Ok(ast::LitKind::Err) => None,
+            Ok(ast::LitKind::Err(_)) => None,
             Err(err) => {
                 report_lit_error(&cx.sess.parse_sess, err, token_lit, expr.span);
                 None

compiler/rustc_expand/src/proc_macro_server.rs

@@ -10,7 +10,7 @@ use rustc_ast::util::literal::escape_byte_str_symbol;
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::Lrc;
-use rustc_errors::{MultiSpan, PResult};
+use rustc_errors::{ErrorGuaranteed, MultiSpan, PResult};
 use rustc_parse::lexer::nfc_normalize;
 use rustc_parse::parse_stream_from_source_str;
 use rustc_session::parse::ParseSess;
@@ -63,7 +63,12 @@ impl FromInternal<token::LitKind> for LitKind {
             token::ByteStrRaw(n) => LitKind::ByteStrRaw(n),
             token::CStr => LitKind::CStr,
             token::CStrRaw(n) => LitKind::CStrRaw(n),
-            token::Err => LitKind::Err,
+            token::Err(_guar) => {
+                // This is the only place a `pm::bridge::LitKind::ErrWithGuar`
+                // is constructed. Note that an `ErrorGuaranteed` is available,
+                // as required. See the comment in `to_internal`.
+                LitKind::ErrWithGuar
+            }
             token::Bool => unreachable!(),
         }
     }
@@ -82,7 +87,16 @@ impl ToInternal<token::LitKind> for LitKind {
             LitKind::ByteStrRaw(n) => token::ByteStrRaw(n),
             LitKind::CStr => token::CStr,
             LitKind::CStrRaw(n) => token::CStrRaw(n),
-            LitKind::Err => token::Err,
+            LitKind::ErrWithGuar => {
+                // This is annoying but valid. `LitKind::ErrWithGuar` would
+                // have an `ErrorGuaranteed` except that type isn't available
+                // in that crate. So we have to fake one. And we don't want to
+                // use a delayed bug because there might be lots of these,
+                // which would be expensive.
+                #[allow(deprecated)]
+                let guar = ErrorGuaranteed::unchecked_error_guaranteed();
+                token::Err(guar)
+            }
         }
     }
 }
@@ -477,7 +491,7 @@ impl server::FreeFunctions for Rustc<'_, '_> {
                 | token::LitKind::ByteStrRaw(_)
                 | token::LitKind::CStr
                 | token::LitKind::CStrRaw(_)
-                | token::LitKind::Err => return Err(()),
+                | token::LitKind::Err(_) => return Err(()),
                 token::LitKind::Integer | token::LitKind::Float => {}
             }
 

compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

@@ -1319,7 +1319,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 tcx.type_of(tcx.require_lang_item(hir::LangItem::CStr, Some(lit.span)))
                     .skip_binder(),
             ),
-            ast::LitKind::Err => Ty::new_misc_error(tcx),
+            ast::LitKind::Err(guar) => Ty::new_error(tcx, guar),
         }
     }
 

compiler/rustc_mir_build/src/build/expr/as_constant.rs

@@ -164,11 +164,7 @@ fn lit_to_mir_constant<'tcx>(
             })?,
         (ast::LitKind::Bool(b), ty::Bool) => ConstValue::Scalar(Scalar::from_bool(*b)),
         (ast::LitKind::Char(c), ty::Char) => ConstValue::Scalar(Scalar::from_char(*c)),
-        (ast::LitKind::Err, _) => {
-            return Err(LitToConstError::Reported(
-                tcx.dcx().delayed_bug("encountered LitKind::Err during mir build"),
-            ));
-        }
+        (ast::LitKind::Err(guar), _) => return Err(LitToConstError::Reported(*guar)),
         _ => return Err(LitToConstError::TypeError),
     };
 

compiler/rustc_mir_build/src/thir/constant.rs

@@ -71,11 +71,7 @@ pub(crate) fn lit_to_const<'tcx>(
             ty::ValTree::from_scalar_int(bits)
         }
         (ast::LitKind::Char(c), ty::Char) => ty::ValTree::from_scalar_int((*c).into()),
-        (ast::LitKind::Err, _) => {
-            return Err(LitToConstError::Reported(
-                tcx.dcx().delayed_bug("encountered LitKind::Err during mir build"),
-            ));
-        }
+        (ast::LitKind::Err(guar), _) => return Err(LitToConstError::Reported(*guar)),
         _ => return Err(LitToConstError::TypeError),
     };
 

compiler/rustc_mir_build/src/thir/cx/expr.rs

@@ -897,12 +897,14 @@ impl<'tcx> Cx<'tcx> {
                 let hir_id = self.tcx.local_def_id_to_hir_id(def_id.expect_local());
                 let generics = self.tcx.generics_of(hir_id.owner);
                 let Some(&index) = generics.param_def_id_to_index.get(&def_id) else {
-                    self.tcx.dcx().has_errors().unwrap();
+                    let guar = self.tcx.dcx().has_errors().unwrap();
                     // We already errored about a late bound const
-                    return ExprKind::Literal {
-                        lit: &Spanned { span: DUMMY_SP, node: LitKind::Err },
-                        neg: false,
-                    };
+
+                    let lit = self
+                        .tcx
+                        .hir_arena
+                        .alloc(Spanned { span: DUMMY_SP, node: LitKind::Err(guar) });
+                    return ExprKind::Literal { lit, neg: false };
                 };
                 let name = self.tcx.hir().name(hir_id);
                 let param = ty::ParamConst::new(index, name);

compiler/rustc_parse/src/lexer/mod.rs

@@ -481,8 +481,8 @@ impl<'sess, 'src> StringReader<'sess, 'src> {
                 let mut kind = token::Integer;
                 if empty_int {
                     let span = self.mk_sp(start, end);
-                    self.dcx().emit_err(errors::NoDigitsLiteral { span });
-                    kind = token::Err;
+                    let guar = self.dcx().emit_err(errors::NoDigitsLiteral { span });
+                    kind = token::Err(guar);
                 } else if matches!(base, Base::Binary | Base::Octal) {
                     let base = base as u32;
                     let s = self.str_from_to(start + BytePos(2), end);
@@ -492,8 +492,9 @@ impl<'sess, 'src> StringReader<'sess, 'src> {
                             start + BytePos::from_usize(2 + idx + c.len_utf8()),
                         );
                         if c != '_' && c.to_digit(base).is_none() {
+                            let guar =
                                 self.dcx().emit_err(errors::InvalidDigitLiteral { span, base });
-                            kind = token::Err;
+                            kind = token::Err(guar);
                         }
                     }
                 }
@@ -711,7 +712,7 @@ impl<'sess, 'src> StringReader<'sess, 'src> {
                 let hi = lo + BytePos(end - start);
                 let span = self.mk_sp(lo, hi);
                 let is_fatal = err.is_fatal();
-                if let Some(_guar) = emit_unescape_error(
+                if let Some(guar) = emit_unescape_error(
                     self.dcx(),
                     lit_content,
                     span_with_quotes,
@@ -721,18 +722,19 @@ impl<'sess, 'src> StringReader<'sess, 'src> {
                     err,
                 ) {
                     assert!(is_fatal);
-                    kind = token::Err;
+                    kind = token::Err(guar);
                 }
             }
         });
 
         // We normally exclude the quotes for the symbol, but for errors we
         // include it because it results in clearer error messages.
-        if kind != token::Err {
-            (kind, Symbol::intern(lit_content))
+        let sym = if !matches!(kind, token::Err(_)) {
+            Symbol::intern(lit_content)
         } else {
-            (token::Err, self.symbol_from_to(start, end))
-        }
+            self.symbol_from_to(start, end)
+        };
+        (kind, sym)
     }
 
     fn cook_unicode(

compiler/rustc_parse/src/parser/expr.rs

@@ -2140,12 +2140,12 @@ impl<'a> Parser<'a> {
                     Err(err) => {
                         let span = token.uninterpolated_span();
                         self.bump();
-                        report_lit_error(self.sess, err, lit, span);
+                        let guar = report_lit_error(self.sess, err, lit, span);
                         // Pack possible quotes and prefixes from the original literal into
                         // the error literal's symbol so they can be pretty-printed faithfully.
                         let suffixless_lit = token::Lit::new(lit.kind, lit.symbol, None);
                         let symbol = Symbol::intern(&suffixless_lit.to_string());
-                        let lit = token::Lit::new(token::Err, symbol, lit.suffix);
+                        let lit = token::Lit::new(token::Err(guar), symbol, lit.suffix);
                         Some(
                             MetaItemLit::from_token_lit(lit, span)
                                 .unwrap_or_else(|_| unreachable!()),

compiler/rustc_parse/src/parser/mod.rs

@@ -1459,7 +1459,7 @@ impl<'a> Parser<'a> {
         match self.parse_str_lit() {
             Ok(str_lit) => Some(str_lit),
             Err(Some(lit)) => match lit.kind {
-                ast::LitKind::Err => None,
+                ast::LitKind::Err(_) => None,
                 _ => {
                     self.dcx().emit_err(NonStringAbiLiteral { span: lit.span });
                     None

compiler/rustc_parse/src/validate_attr.rs

@@ -70,11 +70,11 @@ pub fn parse_meta<'a>(sess: &'a ParseSess, attr: &Attribute) -> PResult<'a, Meta
                             }
                         }
                         Err(err) => {
-                            report_lit_error(sess, err, token_lit, expr.span);
+                            let guar = report_lit_error(sess, err, token_lit, expr.span);
                             let lit = ast::MetaItemLit {
                                 symbol: token_lit.symbol,
                                 suffix: token_lit.suffix,
-                                kind: ast::LitKind::Err,
+                                kind: ast::LitKind::Err(guar),
                                 span: expr.span,
                             };
                             MetaItemKind::NameValue(lit)

library/proc_macro/src/bridge/mod.rs

@@ -337,7 +337,11 @@ pub enum LitKind {
     ByteStrRaw(u8),
     CStr,
     CStrRaw(u8),
-    Err,
+    // This should have an `ErrorGuaranteed`, except that type isn't available
+    // in this crate. (Imagine it is there.) Hence the `WithGuar` suffix. Must
+    // only be constructed in `LitKind::from_internal`, where an
+    // `ErrorGuaranteed` is available.
+    ErrWithGuar,
 }
 
 rpc_encode_decode!(
@@ -352,7 +356,7 @@ rpc_encode_decode!(
         ByteStrRaw(n),
         CStr,
         CStrRaw(n),
-        Err,
+        ErrWithGuar,
     }
 );
 

library/proc_macro/src/lib.rs

@@ -1451,7 +1451,7 @@ impl Literal {
                 f(&["cr", hashes, "\"", symbol, "\"", hashes, suffix])
             }
 
-            bridge::LitKind::Integer | bridge::LitKind::Float | bridge::LitKind::Err => {
+            bridge::LitKind::Integer | bridge::LitKind::Float | bridge::LitKind::ErrWithGuar => {
                 f(&[symbol, suffix])
             }
         })

src/tools/clippy/clippy_lints/src/matches/match_same_arms.rs

@@ -295,7 +295,8 @@ impl<'a> NormalizedPat<'a> {
                     LitKind::Char(val) => Self::LitInt(val.into()),
                     LitKind::Int(val, _) => Self::LitInt(val.get()),
                     LitKind::Bool(val) => Self::LitBool(val),
-                    LitKind::Float(..) | LitKind::Err => Self::Wild,
+                    LitKind::Float(..) => Self::Wild,
+                    LitKind::Err(guar) => Self::Err(guar),
                 },
                 _ => Self::Wild,
             },

src/tools/clippy/clippy_lints/src/redundant_type_annotations.rs

@@ -200,7 +200,7 @@ impl LateLintPass<'_> for RedundantTypeAnnotations {
                                 span_lint(cx, REDUNDANT_TYPE_ANNOTATIONS, local.span, "redundant type annotation");
                             }
                         },
-                        LitKind::Err => (),
+                        LitKind::Err(_) => (),
                         LitKind::ByteStr(..) => {
                             // We only lint if the type annotation is an array type (e.g. &[u8; 4]).
                             // If instead it is a slice (e.g. &[u8]) it may not be redundant, so we

src/tools/clippy/clippy_lints/src/utils/author.rs

@@ -279,7 +279,7 @@ impl<'a, 'tcx> PrintVisitor<'a, 'tcx> {
         match lit.value.node {
             LitKind::Bool(val) => kind!("Bool({val:?})"),
             LitKind::Char(c) => kind!("Char({c:?})"),
-            LitKind::Err => kind!("Err"),
+            LitKind::Err(_) => kind!("Err"),
             LitKind::Byte(b) => kind!("Byte({b})"),
             LitKind::Int(i, suffix) => {
                 let int_ty = match suffix {

src/tools/clippy/clippy_utils/src/consts.rs

@@ -286,7 +286,7 @@ pub fn lit_to_mir_constant<'tcx>(lit: &LitKind, ty: Option<Ty<'tcx>>) -> Constan
             _ => bug!(),
         },
         LitKind::Bool(b) => Constant::Bool(b),
-        LitKind::Err => Constant::Err,
+        LitKind::Err(_) => Constant::Err,
     }
 }
 

src/tools/rust-analyzer/crates/proc-macro-srv/src/server/rust_analyzer_span.rs

@@ -72,7 +72,7 @@ impl server::FreeFunctions for RaSpanServer {
     ) -> Result<bridge::Literal<Self::Span, Self::Symbol>, ()> {
         // FIXME: keep track of LitKind and Suffix
         Ok(bridge::Literal {
-            kind: bridge::LitKind::Err,
+            kind: bridge::LitKind::Integer, // dummy
             symbol: Symbol::intern(self.interner, s),
             suffix: None,
             span: self.call_site,
@@ -202,7 +202,7 @@ impl server::TokenStream for RaSpanServer {
                 tt::TokenTree::Leaf(tt::Leaf::Literal(lit)) => {
                     bridge::TokenTree::Literal(bridge::Literal {
                         // FIXME: handle literal kinds
-                        kind: bridge::LitKind::Err,
+                        kind: bridge::LitKind::Integer, // dummy
                         symbol: Symbol::intern(self.interner, &lit.text),
                         // FIXME: handle suffixes
                         suffix: None,

src/tools/rust-analyzer/crates/proc-macro-srv/src/server/token_id.rs

@@ -64,7 +64,7 @@ impl server::FreeFunctions for TokenIdServer {
     ) -> Result<bridge::Literal<Self::Span, Self::Symbol>, ()> {
         // FIXME: keep track of LitKind and Suffix
         Ok(bridge::Literal {
-            kind: bridge::LitKind::Err,
+            kind: bridge::LitKind::Integer, // dummy
             symbol: Symbol::intern(self.interner, s),
             suffix: None,
             span: self.call_site,
@@ -187,7 +187,7 @@ impl server::TokenStream for TokenIdServer {
                 tt::TokenTree::Leaf(tt::Leaf::Literal(lit)) => {
                     bridge::TokenTree::Literal(bridge::Literal {
                         // FIXME: handle literal kinds
-                        kind: bridge::LitKind::Err,
+                        kind: bridge::LitKind::Integer, // dummy
                         symbol: Symbol::intern(self.interner, &lit.text),
                         // FIXME: handle suffixes
                         suffix: None,