Auto merge of #94789 - compiler-errors:fatal-never, r=eddyb

Make fatal DiagnosticBuilder yield `!`

Fatal errors should really be fatal, so emitting them should cause us to exit at the same time.

Fine with just throwing away these changes if they're not worthwhile. Also, maybe we want to use an uninhabited enum instead of `!`.

r? `@eddyb` who has been working on `DiagnosticBuilder` stuff, feel free to reassign.

2 files changed, 20 insertions, 12 deletions

diff --git a/compiler/rustc_parse/src/lexer/mod.rs b/compiler/rustc_parse/src/lexer/mod.rs
index 601a39e69ab..92c5d329f6e 100644
--- a/compiler/rustc_parse/src/lexer/mod.rs
+++ b/compiler/rustc_parse/src/lexer/mod.rs
@@ -3,9 +3,7 @@ use rustc_ast::ast::{self, AttrStyle};
 use rustc_ast::token::{self, CommentKind, Token, TokenKind};
 use rustc_ast::tokenstream::{Spacing, TokenStream};
 use rustc_ast::util::unicode::contains_text_flow_control_chars;
-use rustc_errors::{
-    error_code, Applicability, DiagnosticBuilder, ErrorGuaranteed, FatalError, PResult,
-};
+use rustc_errors::{error_code, Applicability, DiagnosticBuilder, ErrorGuaranteed, PResult};
 use rustc_lexer::unescape::{self, Mode};
 use rustc_lexer::{Base, DocStyle, RawStrError};
 use rustc_session::lint::builtin::{
@@ -104,7 +102,7 @@ impl<'a> StringReader<'a> {
     }
 
     /// Report a fatal lexical error with a given span.
-    fn fatal_span(&self, sp: Span, m: &str) -> FatalError {
+    fn fatal_span(&self, sp: Span, m: &str) -> ! {
         self.sess.span_diagnostic.span_fatal(sp, m)
     }
 
@@ -114,7 +112,7 @@ impl<'a> StringReader<'a> {
     }
 
     /// Report a fatal error spanning [`from_pos`, `to_pos`).
-    fn fatal_span_(&self, from_pos: BytePos, to_pos: BytePos, m: &str) -> FatalError {
+    fn fatal_span_(&self, from_pos: BytePos, to_pos: BytePos, m: &str) -> ! {
         self.fatal_span(self.mk_sp(from_pos, to_pos), m)
     }
 
@@ -129,12 +127,24 @@ impl<'a> StringReader<'a> {
         to_pos: BytePos,
         m: &str,
         c: char,
-    ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+    ) -> DiagnosticBuilder<'a, !> {
         self.sess
             .span_diagnostic
             .struct_span_fatal(self.mk_sp(from_pos, to_pos), &format!("{}: {}", m, escaped_char(c)))
     }
 
+    fn struct_err_span_char(
+        &self,
+        from_pos: BytePos,
+        to_pos: BytePos,
+        m: &str,
+        c: char,
+    ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
+        self.sess
+            .span_diagnostic
+            .struct_span_err(self.mk_sp(from_pos, to_pos), &format!("{}: {}", m, escaped_char(c)))
+    }
+
     /// Detect usages of Unicode codepoints changing the direction of the text on screen and loudly
     /// complain about it.
     fn lint_unicode_text_flow(&self, start: BytePos) {
@@ -311,7 +321,7 @@ impl<'a> StringReader<'a> {
             rustc_lexer::TokenKind::Unknown | rustc_lexer::TokenKind::InvalidIdent => {
                 let c = self.str_from(start).chars().next().unwrap();
                 let mut err =
-                    self.struct_fatal_span_char(start, self.pos, "unknown start of token", c);
+                    self.struct_err_span_char(start, self.pos, "unknown start of token", c);
                 // FIXME: the lexer could be used to turn the ASCII version of unicode homoglyphs,
                 // instead of keeping a table in `check_for_substitution`into the token. Ideally,
                 // this should be inside `rustc_lexer`. However, we should first remove compound
@@ -503,8 +513,7 @@ impl<'a> StringReader<'a> {
             "found invalid character; only `#` is allowed in raw string delimitation",
             bad_char,
         )
-        .emit();
-        FatalError.raise()
+        .emit()
     }
 
     fn report_unterminated_raw_string(
@@ -541,8 +550,7 @@ impl<'a> StringReader<'a> {
             );
         }
 
-        err.emit();
-        FatalError.raise()
+        err.emit()
     }
 
     // RFC 3101 introduced the idea of (reserved) prefixes. As of Rust 2021,
@@ -601,7 +609,6 @@ impl<'a> StringReader<'a> {
                 found
             ),
         )
-        .raise();
     }
 
     fn validate_literal_escape(
diff --git a/compiler/rustc_parse/src/lib.rs b/compiler/rustc_parse/src/lib.rs
index 0ce86a764f4..1118caf5075 100644
--- a/compiler/rustc_parse/src/lib.rs
+++ b/compiler/rustc_parse/src/lib.rs
@@ -6,6 +6,7 @@
 #![feature(if_let_guard)]
 #![feature(let_chains)]
 #![feature(let_else)]
+#![feature(never_type)]
 #![recursion_limit = "256"]
 
 #[macro_use]