From d10ee0d07e40535e3a167a0a857d9e3a1b1d6a3a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Fri, 29 Jan 2021 11:07:14 -0800
Subject: [PATCH 1/2] Fix invalid camel case suggestion involving unicode
 idents

Follow up to #77805.
---
 compiler/rustc_lint/src/nonstandard_style.rs      | 8 +++++++-
 src/test/ui/lint/special-upper-lower-cases.stderr | 8 ++++----
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/compiler/rustc_lint/src/nonstandard_style.rs b/compiler/rustc_lint/src/nonstandard_style.rs
index ebd6190dc74cc..94fd0e0f097e3 100644
--- a/compiler/rustc_lint/src/nonstandard_style.rs
+++ b/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();
diff --git a/src/test/ui/lint/special-upper-lower-cases.stderr b/src/test/ui/lint/special-upper-lower-cases.stderr
index f32193a2e4a47..e3b451a15a2cc 100644
--- a/src/test/ui/lint/special-upper-lower-cases.stderr
+++ b/src/test/ui/lint/special-upper-lower-cases.stderr
@@ -2,7 +2,7 @@ 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
 
@@ -10,13 +10,13 @@ warning: type `𝕟𝕠𝕥_𝕒_𝕔𝕒𝕞𝕖𝕝` should have an upper came
   --> $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
 
@@ -24,7 +24,7 @@ warning: variable `𝓢𝓝𝓐𝓐𝓐𝓐𝓚𝓔𝓢` should have a snake cas
   --> $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
 

From fa9a99fefce9fbfc73f74732a03925106a3b6e0f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Sat, 30 Jan 2021 22:06:10 -0800
Subject: [PATCH 2/2] review comments

---
 compiler/rustc_lint/src/nonstandard_style.rs | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/compiler/rustc_lint/src/nonstandard_style.rs b/compiler/rustc_lint/src/nonstandard_style.rs
index 94fd0e0f097e3..121dde325f74b 100644
--- a/compiler/rustc_lint/src/nonstandard_style.rs
+++ b/compiler/rustc_lint/src/nonstandard_style.rs
@@ -56,8 +56,19 @@ declare_lint! {
 
 declare_lint_pass!(NonCamelCaseTypes => [NON_CAMEL_CASE_TYPES]);
 
+/// Some unicode characters *have* case, are considered upper case or lower case, but they *can't*
+/// be upper cased or lower cased. For the purposes of the lint suggestion, we care about being able
+/// to change the char's case.
 fn char_has_case(c: char) -> bool {
-    c.to_lowercase().to_string() != c.to_uppercase().to_string()
+    let mut l = c.to_lowercase();
+    let mut u = c.to_uppercase();
+    while let Some(l) = l.next() {
+        match u.next() {
+            Some(u) if l != u => return true,
+            _ => {}
+        }
+    }
+    u.next().is_some()
 }
 
 fn is_camel_case(name: &str) -> bool {