From 44f4f67f460a3b3c9bb34851d3d812fbdba81936 Mon Sep 17 00:00:00 2001
From: Peter Jaszkowiak <p.jaszkow@gmail.com>
Date: Mon, 25 Nov 2024 21:50:26 -0700
Subject: fix confusing diagnostic for reserved `##`

---
 compiler/rustc_parse/src/errors.rs    |  9 +++++++++
 compiler/rustc_parse/src/lexer/mod.rs | 16 ++++++++++------
 2 files changed, 19 insertions(+), 6 deletions(-)

(limited to 'compiler/rustc_parse/src')

diff --git a/compiler/rustc_parse/src/errors.rs b/compiler/rustc_parse/src/errors.rs
index 9bdb99dc000..a48725de54b 100644
--- a/compiler/rustc_parse/src/errors.rs
+++ b/compiler/rustc_parse/src/errors.rs
@@ -2151,6 +2151,15 @@ pub(crate) enum UnknownPrefixSugg {
     },
 }
 
+#[derive(Diagnostic)]
+#[diag(parse_reserved_multihash)]
+#[note]
+pub(crate) struct ReservedMultihash {
+    #[primary_span]
+    pub span: Span,
+    #[subdiagnostic]
+    pub sugg: Option<GuardedStringSugg>,
+}
 #[derive(Diagnostic)]
 #[diag(parse_reserved_string)]
 #[note]
diff --git a/compiler/rustc_parse/src/lexer/mod.rs b/compiler/rustc_parse/src/lexer/mod.rs
index 5023e83bd67..787b298c8e4 100644
--- a/compiler/rustc_parse/src/lexer/mod.rs
+++ b/compiler/rustc_parse/src/lexer/mod.rs
@@ -803,7 +803,7 @@ impl<'psess, 'src> StringReader<'psess, 'src> {
 
         let mut cursor = Cursor::new(str_before);
 
-        let (span, unterminated) = match cursor.guarded_double_quoted_string() {
+        let (is_string, span, unterminated) = match cursor.guarded_double_quoted_string() {
             Some(rustc_lexer::GuardedStr { n_hashes, terminated, token_len }) => {
                 let end = start + BytePos(token_len);
                 let span = self.mk_sp(start, end);
@@ -816,13 +816,13 @@ impl<'psess, 'src> StringReader<'psess, 'src> {
 
                 let unterminated = if terminated { None } else { Some(str_start) };
 
-                (span, unterminated)
+                (true, span, unterminated)
             }
-            _ => {
+            None => {
                 // We should only get here in the `##+` case.
                 debug_assert_eq!(self.str_from_to(start, start + BytePos(2)), "##");
 
-                (span, None)
+                (false, span, None)
             }
         };
         if edition2024 {
@@ -844,7 +844,11 @@ impl<'psess, 'src> StringReader<'psess, 'src> {
             };
 
             // In Edition 2024 and later, emit a hard error.
-            let err = self.dcx().emit_err(errors::ReservedString { span, sugg });
+            let err = if is_string {
+                self.dcx().emit_err(errors::ReservedString { span, sugg })
+            } else {
+                self.dcx().emit_err(errors::ReservedMultihash { span, sugg })
+            };
 
             token::Literal(token::Lit {
                 kind: token::Err(err),
@@ -857,7 +861,7 @@ impl<'psess, 'src> StringReader<'psess, 'src> {
                 RUST_2024_GUARDED_STRING_INCOMPATIBLE_SYNTAX,
                 span,
                 ast::CRATE_NODE_ID,
-                BuiltinLintDiag::ReservedString(space_span),
+                BuiltinLintDiag::ReservedString { is_string, suggestion: space_span },
             );
 
             // For backwards compatibility, roll back to after just the first `#`
-- 
cgit 1.4.1-3-g733a5