Fix invalid camel case suggestion involving unicode idents

Follow up to #77805.

Author: estebank

compiler/rustc_lint/src/nonstandard_style.rs

@@ -57,7 +57,7 @@ declare_lint! {
 declare_lint_pass!(NonCamelCaseTypes => [NON_CAMEL_CASE_TYPES]);
 
 fn char_has_case(c: char) -> bool {
-    c.is_lowercase() || c.is_uppercase()
+    c.to_lowercase().to_string() != c.to_uppercase().to_string()
 }
 
 fn is_camel_case(name: &str) -> bool {
@@ -138,6 +138,8 @@ impl NonCamelCaseTypes {
                         to_camel_case(name),
                         Applicability::MaybeIncorrect,
                     );
+                } else {
+                    err.span_label(ident.span, "should have an UpperCamelCase name");
                 }
 
                 err.emit();
@@ -299,6 +301,8 @@ impl NonSnakeCase {
                     } else {
                         err.help(&format!("convert the identifier to snake case: `{}`", sc));
                     }
+                } else {
+                    err.span_label(ident.span, "should have a snake_case name");
                 }
 
                 err.emit();
@@ -477,6 +481,8 @@ impl NonUpperCaseGlobals {
                         uc,
                         Applicability::MaybeIncorrect,
                     );
+                } else {
+                    err.span_label(ident.span, "should have an UPPER_CASE name");
                 }
 
                 err.emit();

src/test/ui/lint/special-upper-lower-cases.stderr

@@ -2,29 +2,29 @@ warning: type `𝕟𝕠𝕥𝕒𝕔𝕒𝕞𝕖𝕝` should have an upper camel
   --> $DIR/special-upper-lower-cases.rs:11:8
    |
 LL | struct 𝕟𝕠𝕥𝕒𝕔𝕒𝕞𝕖𝕝;
-   |        ^^^^^^^^^
+   |        ^^^^^^^^^ should have an UpperCamelCase name
    |
    = note: `#[warn(non_camel_case_types)]` on by default
 
 warning: type `𝕟𝕠𝕥_𝕒_𝕔𝕒𝕞𝕖𝕝` should have an upper camel case name
   --> $DIR/special-upper-lower-cases.rs:15:8
    |
 LL | struct 𝕟𝕠𝕥_𝕒_𝕔𝕒𝕞𝕖𝕝;
-   |        ^^^^^^^^^^^ help: convert the identifier to upper camel case: `𝕟𝕠𝕥𝕒𝕔𝕒𝕞𝕖𝕝`
+   |        ^^^^^^^^^^^ should have an UpperCamelCase name
 
 warning: static variable `𝗻𝗼𝗻𝘂𝗽𝗽𝗲𝗿𝗰𝗮𝘀𝗲` should have an upper case name
   --> $DIR/special-upper-lower-cases.rs:18:8
    |
 LL | static 𝗻𝗼𝗻𝘂𝗽𝗽𝗲𝗿𝗰𝗮𝘀𝗲: i32 = 1;
-   |        ^^^^^^^^^^^^
+   |        ^^^^^^^^^^^^ should have an UPPER_CASE name
    |
    = note: `#[warn(non_upper_case_globals)]` on by default
 
 warning: variable `𝓢𝓝𝓐𝓐𝓐𝓐𝓚𝓔𝓢` should have a snake case name
   --> $DIR/special-upper-lower-cases.rs:22:9
    |
 LL |     let 𝓢𝓝𝓐𝓐𝓐𝓐𝓚𝓔𝓢 = 1;
-   |         ^^^^^^^^^
+   |         ^^^^^^^^^ should have a snake_case name
    |
    = note: `#[warn(non_snake_case)]` on by default