uncommon_codepoints: lint against 00B7 MIDDLE DOT in final position

compiler/rustc_lint/src/non_ascii_idents.rs

@@ -187,20 +187,31 @@ impl EarlyLintPass for NonAsciiIdents {
             }
             has_non_ascii_idents = true;
             cx.emit_span_lint(NON_ASCII_IDENTS, sp, IdentifierNonAsciiChar);
-            if check_uncommon_codepoints
-                && !symbol_str.chars().all(GeneralSecurityProfile::identifier_allowed)
-            {
-                let codepoints: Vec<_> = symbol_str
+            if check_uncommon_codepoints {
+                let mut 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, codepoints_len },
-                );
+                // 00B7 MIDDLE DOT '·' is considered by
+                // [UTS 39](https://unicode.org/reports/tr39/#Identifier_Status_and_Type)
+                // to be "Allowed - Inclusion" due to its presence in [UTR 31 Table 3a - Optional Characters for Medial]
+                // (https://www.unicode.org/reports/tr31/#Table_Optional_Medial);
+                // as such, it is unsuitable for appearing in the final position of identifiers.
+                if symbol_str.chars().last() == Some('·') {
+                    codepoints.push('·');
+                }
+
+                if !codepoints.is_empty() {
+                    cx.emit_span_lint(
+                        UNCOMMON_CODEPOINTS,
+                        sp,
+                        IdentifierUncommonCodepoints {
+                            codepoints_len: codepoints.len(),
+                            codepoints,
+                        },
+                    );
+                }
             }
         }
 

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

@@ -11,3 +11,9 @@ fn main() {
     // using the same identifier the second time won't trigger the lint.
     println!("{}", ㇻㇲㇳ);
 }
+
+// 00B7 MIDDLE DOT '·' is linted against only in final position.
+
+const FOO·: () = (); //~ ERROR identifier contains an uncommon Unicode codepoint
+
+const FOL·LY: () = ();

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

@@ -22,6 +22,12 @@ error: identifier contains uncommon Unicode codepoints: 'ㇻ', 'ㇲ', and 'ㇳ'
 LL |     let ㇻㇲㇳ = "rust";
    |         ^^^^^^
 
+error: identifier contains an uncommon Unicode codepoint: '·'
+  --> $DIR/lint-uncommon-codepoints.rs:17:7
+   |
+LL | const FOO·: () = ();
+   |       ^^^^
+
 warning: constant `µ` should have an upper case name
   --> $DIR/lint-uncommon-codepoints.rs:3:7
    |
@@ -30,5 +36,5 @@ LL | const µ: f64 = 0.000001;
    |
    = note: `#[warn(non_upper_case_globals)]` on by default
 
-error: aborting due to 3 previous errors; 1 warning emitted
+error: aborting due to 4 previous errors; 1 warning emitted