Fix panic and incorrectly suggested examples in format_args macro.

compiler/rustc_builtin_macros/src/format.rs

@@ -569,6 +569,7 @@ fn make_format_args(
             detect_foreign_fmt,
             str_style,
             fmt_str,
+            uncooked_fmt_str.1.as_str(),
             fmt_span,
         );
     }
@@ -650,6 +651,7 @@ fn report_missing_placeholders(
     detect_foreign_fmt: bool,
     str_style: Option<usize>,
     fmt_str: &str,
+    uncooked_fmt_str: &str,
     fmt_span: Span,
 ) {
     let mut diag = if let &[(span, named)] = &unused[..] {
@@ -773,16 +775,20 @@ fn report_missing_placeholders(
                 diag.note(format!("consider adding {} format specifiers", unused.len()));
             }
         } else {
-            let original_fmt_str =
-                if fmt_str.len() >= 1 { &fmt_str[..fmt_str.len() - 1] } else { "" };
-
             let msg = if unused.len() == 1 {
                 "a format specifier".to_string()
             } else {
                 format!("{} format specifiers", unused.len())
             };
 
-            let sugg = format!("\"{}{}\"", original_fmt_str, "{}".repeat(unused.len()));
+            let sugg = match str_style {
+                None => format!("\"{}{}\"", uncooked_fmt_str, "{}".repeat(unused.len())),
+                Some(n_hashes) => format!(
+                    "r{hashes}\"{uncooked_fmt_str}{fmt_specifiers}\"{hashes}",
+                    hashes = "#".repeat(n_hashes),
+                    fmt_specifiers = "{}".repeat(unused.len())
+                ),
+            };
             let msg = format!("format specifiers use curly braces, consider adding {msg}");
 
             diag.span_suggestion_verbose(fmt_span, msg, sugg, Applicability::MaybeIncorrect);

tests/ui/suggestions/missing-format-specifiers-issue-68293.rs

@@ -32,4 +32,33 @@ fn missing_format_specifiers_multiple_unused_args() {
     //~| NOTE consider adding 2 format specifiers
 }
 
+fn unicode_unused_args() {
+    panic!("👆", "👆", 1);
+    //~^ ERROR multiple unused formatting arguments
+    //~| NOTE multiple missing formatting specifiers
+    //~| NOTE argument never used
+    //~| NOTE argument never used
+    //~| HELP format specifiers use curly braces, consider adding 2 format specifiers
+}
+
+fn raw_str_unused_arg() {
+    format_args!(r##"lJ𐏿Æ�.𐏿�"##, r#"r}J𐏿Æ" {}"#, 1);
+    //~^ ERROR multiple unused formatting arguments
+    //~| NOTE multiple missing formatting specifiers
+    //~| NOTE argument never used
+    //~| NOTE argument never used
+    //~| HELP format specifiers use curly braces, consider adding 2 format specifiers
+}
+
+fn valid_new_lines_unused_args() {
+    panic!("Expect 2 newlines
+
+", "👆", 1);
+    //~^ ERROR multiple unused formatting arguments
+    //~| NOTE argument never used
+    //~| NOTE argument never used
+    //~^^^^^^ NOTE multiple missing formatting specifiers
+    //~| HELP format specifiers use curly braces, consider adding 2 format specifiers
+}
+
 fn main() { }

tests/ui/suggestions/missing-format-specifiers-issue-68293.stderr

@@ -45,5 +45,52 @@ LL |     println!("list: {}", 1, 2, 3);
    |
    = note: consider adding 2 format specifiers
 
-error: aborting due to 4 previous errors
+error: multiple unused formatting arguments
+  --> $DIR/missing-format-specifiers-issue-68293.rs:36:17
+   |
+LL |     panic!("👆", "👆", 1);
+   |            ----  ^^^^  ^ argument never used
+   |            |     |
+   |            |     argument never used
+   |            multiple missing formatting specifiers
+   |
+help: format specifiers use curly braces, consider adding 2 format specifiers
+   |
+LL |     panic!("👆{}{}", "👆", 1);
+   |               ++++
+
+error: multiple unused formatting arguments
+  --> $DIR/missing-format-specifiers-issue-68293.rs:45:35
+   |
+LL |     format_args!(r##"lJ𐏿Æ�.𐏿�"##, r#"r}J𐏿Æ" {}"#, 1);
+   |                  ---------------  ^^^^^^^^^^^^^^  ^ argument never used
+   |                  |                |
+   |                  |                argument never used
+   |                  multiple missing formatting specifiers
+   |
+help: format specifiers use curly braces, consider adding 2 format specifiers
+   |
+LL |     format_args!(r##"lJ𐏿Æ�.𐏿�{}{}"##, r#"r}J𐏿Æ" {}"#, 1);
+   |                              ++++
+
+error: multiple unused formatting arguments
+  --> $DIR/missing-format-specifiers-issue-68293.rs:56:4
+   |
+LL |       panic!("Expect 2 newlines
+   |  ____________-
+LL | |
+LL | | ", "👆", 1);
+   | | -  ^^^^  ^ argument never used
+   | | |  |
+   | |_|  argument never used
+   |   multiple missing formatting specifiers
+   |
+help: format specifiers use curly braces, consider adding 2 format specifiers
+   |
+LL |     panic!("Expect 2 newlines
+LL |
+LL ~ {}{}", "👆", 1);
+   |
+
+error: aborting due to 7 previous errors