lexer/parser: ensure deps use the same unicode version

Add a compile time check in rustc_lexer and rustc_parse ensuring that unicode-related dependencies within the crate use the same unicode version.
These checks are inspired by the examples privided by @clarfonthey.

compiler/rustc_lexer/src/lib.rs

@@ -34,9 +34,26 @@
 use TokenKind::*;
 use cursor::EOF_CHAR;
 pub use cursor::{Cursor, FrontmatterAllowed};
-pub use unicode_ident::UNICODE_VERSION as UNICODE_IDENT_VERSION;
+pub use unicode_ident::UNICODE_VERSION;
 use unicode_properties::UnicodeEmoji;
 
+// Make sure that the Unicode version of the dependencies is the same.
+const _: () = {
+    let properties = unicode_properties::UNICODE_VERSION;
+    let ident = unicode_ident::UNICODE_VERSION;
+
+    if properties.0 != ident.0 as u64
+        || properties.1 != ident.1 as u64
+        || properties.2 != ident.2 as u64
+    {
+        panic!(
+            "unicode-properties and unicode-ident must use the same Unicode version, \
+            `unicode_properties::UNICODE_VERSION` and `unicode_ident::UNICODE_VERSION` are \
+            different."
+        );
+    }
+};
+
 /// Parsed token.
 /// It doesn't contain information about data that has been parsed,
 /// only the type of the token and its size.

compiler/rustc_parse/src/lib.rs

@@ -22,10 +22,10 @@
 use rustc_ast::tokenstream::TokenStream;
 use rustc_ast_pretty::pprust;
 use rustc_errors::{Diag, EmissionGuarantee, FatalError, PResult, pluralize};
+pub use rustc_lexer::UNICODE_VERSION;
 use rustc_session::parse::ParseSess;
 use rustc_span::source_map::SourceMap;
 use rustc_span::{FileName, SourceFile, Span};
-pub use unicode_normalization::UNICODE_VERSION as UNICODE_NORMALIZATION_VERSION;
 
 pub const MACRO_ARGUMENTS: Option<&str> = Some("macro arguments");
 
@@ -39,6 +39,44 @@
 
 mod errors;
 
+// Make sure that the Unicode version of the dependencies is the same.
+const _: () = {
+    let rustc_lexer = rustc_lexer::UNICODE_VERSION;
+    let rustc_span = rustc_span::UNICODE_VERSION;
+    let normalization = unicode_normalization::UNICODE_VERSION;
+    let width = unicode_width::UNICODE_VERSION;
+
+    if rustc_lexer.0 != rustc_span.0
+        || rustc_lexer.1 != rustc_span.1
+        || rustc_lexer.2 != rustc_span.2
+    {
+        panic!(
+            "rustc_lexer and rustc_span must use the same Unicode version, \
+            `rustc_lexer::UNICODE_VERSION` and `rustc_span::UNICODE_VERSION` are \
+            different."
+        );
+    }
+
+    if rustc_lexer.0 != normalization.0
+        || rustc_lexer.1 != normalization.1
+        || rustc_lexer.2 != normalization.2
+    {
+        panic!(
+            "rustc_lexer and unicode-normalization must use the same Unicode version, \
+            `rustc_lexer::UNICODE_VERSION` and `unicode_normalization::UNICODE_VERSION` are \
+            different."
+        );
+    }
+
+    if rustc_lexer.0 != width.0 || rustc_lexer.1 != width.1 || rustc_lexer.2 != width.2 {
+        panic!(
+            "rustc_lexer and unicode-width must use the same Unicode version, \
+            `rustc_lexer::UNICODE_VERSION` and `unicode_width::UNICODE_VERSION` are \
+            different."
+        );
+    }
+};
+
 rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
 
 // Unwrap the result if `Ok`, otherwise emit the diagnostics and abort.

compiler/rustc_span/src/lib.rs

@@ -39,6 +39,7 @@
 use rustc_serialize::opaque::{FileEncoder, MemDecoder};
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use tracing::debug;
+pub use unicode_width::UNICODE_VERSION;
 
 mod caching_source_map_view;
 pub mod source_map;

tests/ui-fulldeps/lexer/unicode-version.rs

@@ -12,7 +12,6 @@
 #![feature(rustc_private)]
 
 extern crate rustc_driver;
-extern crate rustc_lexer;
 extern crate rustc_parse;
 
 fn main() {
@@ -22,9 +21,5 @@ fn main() {
          it should also be updated in the reference at \
          https://github.com/rust-lang/reference/blob/HEAD/src/identifiers.md."
     );
-    println!("Unicode version of unicode-ident is: {:?}", rustc_lexer::UNICODE_IDENT_VERSION);
-    println!(
-        "Unicode version of unicode-normalization is: {:?}",
-        rustc_parse::UNICODE_NORMALIZATION_VERSION
-    );
+    println!("Unicode version used in rustc_parse is: {:?}", rustc_parse::UNICODE_VERSION);
 }

tests/ui-fulldeps/lexer/unicode-version.run.stdout

@@ -1,4 +1,3 @@
 Checking if Unicode version changed.
 If the Unicode version changes are intentional, it should also be updated in the reference at https://github.com/rust-lang/reference/blob/HEAD/src/identifiers.md.
-Unicode version of unicode-ident is: (17, 0, 0)
-Unicode version of unicode-normalization is: (17, 0, 0)
+Unicode version used in rustc_parse is: (17, 0, 0)