Fix msg for verbose suggestions with confusable capitalization

compiler/rustc_errors/src/emitter.rs

@@ -1742,9 +1742,17 @@ impl HumanEmitter {
         buffer.append(0, level.to_str(), Style::Level(*level));
         buffer.append(0, ": ", Style::HeaderMsg);
 
+        let mut msg = vec![(suggestion.msg.to_owned(), Style::NoStyle)];
+        if suggestions
+            .iter()
+            .take(MAX_SUGGESTIONS)
+            .any(|(_, _, _, only_capitalization)| *only_capitalization)
+        {
+            msg.push((" (notice the capitalization difference)".into(), Style::NoStyle));
+        }
         self.msgs_to_buffer(
             &mut buffer,
-            &[(suggestion.msg.to_owned(), Style::NoStyle)],
+            &msg,
             args,
             max_line_num_len,
             "suggestion",
@@ -1753,12 +1761,8 @@ impl HumanEmitter {
 
         let mut row_num = 2;
         draw_col_separator_no_space(&mut buffer, 1, max_line_num_len + 1);
-        let mut notice_capitalization = false;
-        for (complete, parts, highlights, only_capitalization) in
-            suggestions.iter().take(MAX_SUGGESTIONS)
-        {
+        for (complete, parts, highlights, _) in suggestions.iter().take(MAX_SUGGESTIONS) {
             debug!(?complete, ?parts, ?highlights);
-            notice_capitalization |= only_capitalization;
 
             let has_deletion = parts.iter().any(|p| p.is_deletion(sm));
             let is_multiline = complete.lines().count() > 1;
@@ -2057,9 +2061,6 @@ impl HumanEmitter {
             let others = suggestions.len() - MAX_SUGGESTIONS;
             let msg = format!("and {} other candidate{}", others, pluralize!(others));
             buffer.puts(row_num, max_line_num_len + 3, &msg, Style::NoStyle);
-        } else if notice_capitalization {
-            let msg = "notice the capitalization difference";
-            buffer.puts(row_num, max_line_num_len + 3, msg, Style::NoStyle);
         }
         emit_to_destination(&buffer.render(), level, &mut self.dst, self.short_message)?;
         Ok(())

compiler/rustc_errors/src/lib.rs

@@ -319,7 +319,9 @@ impl CodeSuggestion {
                 // We need to keep track of the difference between the existing code and the added
                 // or deleted code in order to point at the correct column *after* substitution.
                 let mut acc = 0;
+                let mut only_capitalization = false;
                 for part in &substitution.parts {
+                    only_capitalization |= is_case_difference(sm, &part.snippet, part.span);
                     let cur_lo = sm.lookup_char_pos(part.span.lo());
                     if prev_hi.line == cur_lo.line {
                         let mut count =
@@ -392,7 +394,6 @@ impl CodeSuggestion {
                     }
                 }
                 highlights.push(std::mem::take(&mut line_highlight));
-                let only_capitalization = is_case_difference(sm, &buf, bounding_span);
                 // if the replacement already ends with a newline, don't print the next line
                 if !buf.ends_with('\n') {
                     push_trailing(&mut buf, prev_line.as_ref(), &prev_hi, None);

src/tools/clippy/tests/ui/match_str_case_mismatch.stderr

@@ -17,7 +17,7 @@ error: this `match` arm has a differing case than its expression
 LL |         "~!@#$%^&*()-_=+Foo" => {},
    |         ^^^^^^^^^^^^^^^^^^^^
    |
-help: consider changing the case of this arm to respect `to_ascii_lowercase`
+help: consider changing the case of this arm to respect `to_ascii_lowercase` (notice the capitalization difference)
    |
 LL |         "~!@#$%^&*()-_=+foo" => {},
    |         ~~~~~~~~~~~~~~~~~~~~

tests/ui/error-codes/E0423.stderr

@@ -53,7 +53,7 @@ help: use struct literal syntax instead
    |
 LL |     let f = Foo { a: val };
    |             ~~~~~~~~~~~~~~
-help: a function with a similar name exists
+help: a function with a similar name exists (notice the capitalization difference)
    |
 LL |     let f = foo();
    |             ~~~

tests/ui/parser/kw-in-trait-bounds.stderr

@@ -4,7 +4,7 @@ error: expected identifier, found keyword `fn`
 LL | fn _f<F: fn(), G>(_: impl fn(), _: &dyn fn())
    |          ^^
    |
-help: use `Fn` to refer to the trait
+help: use `Fn` to refer to the trait (notice the capitalization difference)
    |
 LL | fn _f<F: Fn(), G>(_: impl fn(), _: &dyn fn())
    |          ~~
@@ -15,7 +15,7 @@ error: expected identifier, found keyword `fn`
 LL | fn _f<F: fn(), G>(_: impl fn(), _: &dyn fn())
    |                           ^^
    |
-help: use `Fn` to refer to the trait
+help: use `Fn` to refer to the trait (notice the capitalization difference)
    |
 LL | fn _f<F: fn(), G>(_: impl Fn(), _: &dyn fn())
    |                           ~~
@@ -26,7 +26,7 @@ error: expected identifier, found keyword `fn`
 LL | fn _f<F: fn(), G>(_: impl fn(), _: &dyn fn())
    |                                         ^^
    |
-help: use `Fn` to refer to the trait
+help: use `Fn` to refer to the trait (notice the capitalization difference)
    |
 LL | fn _f<F: fn(), G>(_: impl fn(), _: &dyn Fn())
    |                                         ~~
@@ -37,7 +37,7 @@ error: expected identifier, found keyword `fn`
 LL | G: fn(),
    |    ^^
    |
-help: use `Fn` to refer to the trait
+help: use `Fn` to refer to the trait (notice the capitalization difference)
    |
 LL | G: Fn(),
    |    ~~

tests/ui/parser/recover/recover-fn-trait-from-fn-kw.stderr

@@ -4,7 +4,7 @@ error: expected identifier, found keyword `fn`
 LL | fn foo(_: impl fn() -> i32) {}
    |                ^^
    |
-help: use `Fn` to refer to the trait
+help: use `Fn` to refer to the trait (notice the capitalization difference)
    |
 LL | fn foo(_: impl Fn() -> i32) {}
    |                ~~
@@ -15,7 +15,7 @@ error: expected identifier, found keyword `fn`
 LL | fn foo2<T: fn(i32)>(_: T) {}
    |            ^^
    |
-help: use `Fn` to refer to the trait
+help: use `Fn` to refer to the trait (notice the capitalization difference)
    |
 LL | fn foo2<T: Fn(i32)>(_: T) {}
    |            ~~

tests/ui/parser/typod-const-in-const-param-def.stderr

@@ -4,7 +4,7 @@ error: `const` keyword was mistyped as `Const`
 LL | pub fn foo<Const N: u8>() {}
    |            ^^^^^
    |
-help: use the `const` keyword
+help: use the `const` keyword (notice the capitalization difference)
    |
 LL | pub fn foo<const N: u8>() {}
    |            ~~~~~
@@ -15,7 +15,7 @@ error: `const` keyword was mistyped as `Const`
 LL | pub fn baz<Const N: u8, T>() {}
    |            ^^^^^
    |
-help: use the `const` keyword
+help: use the `const` keyword (notice the capitalization difference)
    |
 LL | pub fn baz<const N: u8, T>() {}
    |            ~~~~~
@@ -26,7 +26,7 @@ error: `const` keyword was mistyped as `Const`
 LL | pub fn qux<T, Const N: u8>() {}
    |               ^^^^^
    |
-help: use the `const` keyword
+help: use the `const` keyword (notice the capitalization difference)
    |
 LL | pub fn qux<T, const N: u8>() {}
    |               ~~~~~
@@ -37,7 +37,7 @@ error: `const` keyword was mistyped as `Const`
 LL | pub fn quux<T, Const N: u8, U>() {}
    |                ^^^^^
    |
-help: use the `const` keyword
+help: use the `const` keyword (notice the capitalization difference)
    |
 LL | pub fn quux<T, const N: u8, U>() {}
    |                ~~~~~

tests/ui/suggestions/assoc-ct-for-assoc-method.stderr

@@ -8,7 +8,7 @@ LL |     let x: i32 = MyS::foo;
    |
    = note: expected type `i32`
            found fn item `fn() -> MyS {MyS::foo}`
-help: try referring to the associated const `FOO` instead
+help: try referring to the associated const `FOO` instead (notice the capitalization difference)
    |
 LL |     let x: i32 = MyS::FOO;
    |                       ~~~

tests/ui/suggestions/bool_typo_err_suggest.stderr

@@ -15,7 +15,7 @@ error[E0425]: cannot find value `False` in this scope
 LL |     let y = False;
    |             ^^^^^ not found in this scope
    |
-help: you may want to use a bool value instead
+help: you may want to use a bool value instead (notice the capitalization difference)
    |
 LL |     let y = false;
    |             ~~~~~