address requested changes

compiler/rustc_lint/messages.ftl

@@ -240,7 +240,10 @@ lint_hidden_unicode_codepoints = unicode codepoint changing visible direction of
 
 lint_identifier_non_ascii_char = identifier contains non-ASCII characters
 
-lint_identifier_uncommon_codepoints = identifier contains uncommon Unicode codepoints: {$codepoints}
+lint_identifier_uncommon_codepoints = identifier contains {$codepoints_len -> 
+    [one] an uncommon Unicode codepoint
+    *[other] uncommon Unicode codepoints
+}: {$codepoints}
 
 lint_ignored_unless_crate_specified = {$level}({$name}) is ignored unless specified at crate level
 

compiler/rustc_lint/src/lints.rs

@@ -1109,6 +1109,7 @@ pub struct MultipleSupertraitUpcastable {
 #[diag(lint_identifier_uncommon_codepoints)]
 pub struct IdentifierUncommonCodepoints {
     pub codepoints: Vec<char>,
+    pub codepoints_len: usize,
 }
 
 #[derive(LintDiagnostic)]

compiler/rustc_lint/src/non_ascii_idents.rs

@@ -190,15 +190,16 @@ fn check_crate(&mut self, cx: &EarlyContext<'_>, _: &ast::Crate) {
             if check_uncommon_codepoints
                 && !symbol_str.chars().all(GeneralSecurityProfile::identifier_allowed)
             {
+                let codepoints: Vec<_> = symbol_str
+                    .chars()
+                    .filter(|c| !GeneralSecurityProfile::identifier_allowed(*c))
+                    .collect();
+                let codepoints_len = codepoints.len();
+
                 cx.emit_span_lint(
                     UNCOMMON_CODEPOINTS,
                     sp,
-                    IdentifierUncommonCodepoints {
-                        codepoints: symbol_str
-                            .chars()
-                            .filter(|c| !GeneralSecurityProfile::identifier_allowed(*c))
-                            .collect(),
-                    },
+                    IdentifierUncommonCodepoints { codepoints, codepoints_len },
                 );
             }
         }

tests/ui/lexer/lex-emoji-identifiers.rs

@@ -4,7 +4,7 @@ fn invalid_emoji_usages() {
     let wireless🛜 = "basic emoji"; //~ ERROR: identifiers cannot contain emoji
     // FIXME
     let key1️⃣ = "keycap sequence"; //~ ERROR: unknown start of token
-                                    //~^ WARN: identifier contains uncommon Unicode codepoints
+                                    //~^ WARN: identifier contains an uncommon Unicode codepoint
     let flag🇺🇳 = "flag sequence"; //~ ERROR: identifiers cannot contain emoji
     let wales🏴 = "tag sequence"; //~ ERROR: identifiers cannot contain emoji
     let folded🙏🏿 = "modifier sequence"; //~ ERROR: identifiers cannot contain emoji

tests/ui/lexer/lex-emoji-identifiers.stderr

@@ -40,7 +40,7 @@ error: identifiers cannot contain emoji: `folded🙏🏿`
 LL |     let folded🙏🏿 = "modifier sequence";
    |         ^^^^^^^^^^
 
-warning: identifier contains uncommon Unicode codepoints: '\u{fe0f}'
+warning: identifier contains an uncommon Unicode codepoint: '\u{fe0f}'
   --> $DIR/lex-emoji-identifiers.rs:6:9
    |
 LL |     let key1️⃣ = "keycap sequence";

tests/ui/lint/rfc-2457-non-ascii-idents/lint-uncommon-codepoints.rs

@@ -1,9 +1,9 @@
 #![deny(uncommon_codepoints)]
 
-const µ: f64 = 0.000001; //~ ERROR identifier contains uncommon Unicode codepoints
+const µ: f64 = 0.000001; //~ ERROR identifier contains an uncommon Unicode codepoint
 //~| WARNING should have an upper case name
 
-fn dijkstra() {} //~ ERROR identifier contains uncommon Unicode codepoints
+fn dijkstra() {} //~ ERROR identifier contains an uncommon Unicode codepoint
 
 fn main() {
     let ㇻㇲㇳ = "rust"; //~ ERROR identifier contains uncommon Unicode codepoints

tests/ui/lint/rfc-2457-non-ascii-idents/lint-uncommon-codepoints.stderr

@@ -1,4 +1,4 @@
-error: identifier contains uncommon Unicode codepoints: 'µ'
+error: identifier contains an uncommon Unicode codepoint: 'µ'
   --> $DIR/lint-uncommon-codepoints.rs:3:7
    |
 LL | const µ: f64 = 0.000001;
@@ -10,7 +10,7 @@ note: the lint level is defined here
 LL | #![deny(uncommon_codepoints)]
    |         ^^^^^^^^^^^^^^^^^^^
 
-error: identifier contains uncommon Unicode codepoints: 'ij'
+error: identifier contains an uncommon Unicode codepoint: 'ij'
   --> $DIR/lint-uncommon-codepoints.rs:6:4
    |
 LL | fn dijkstra() {}