Fix missing union keyword highlighting in source pages

crates/bin/docs_rs_web/assets/syntaxes/Packages/Rust/Rust.sublime-syntax

@@ -136,6 +136,9 @@ contexts:
     - match: \b(crate|extern|use|where)\b
       scope: keyword.other.rust
 
+    - match: \bunion(?=\s+[[:alpha:]_][[:alnum:]_]*\s*\{)\b
+      scope: keyword.other.rust
+
     - match: \b(break|else|for|if|loop|match|while|continue)\b
       scope: keyword.control.rust
 

crates/bin/docs_rs_web/assets/syntaxes/Packages/Rust/syntax_test_rust.rs

@@ -1148,3 +1148,12 @@ let p_imm: *const u32 = &i as *const u32;
 type ExampleRawPointer = HashMap<*const i32, Option<i32>, BuildHasherDefault<FnvHasher>>;
 //                               ^^^^^^ storage.modifier - invalid
 //                                      ^^^ storage.type
+
+
+union MyUnion {
+// <- keyword.other
+    f1: u32,
+}
+
+let union = 1;
+//  ^^^^^ - keyword.other

crates/bin/docs_rs_web/src/utils/highlight.rs

@@ -135,4 +135,30 @@ mod tests {
         let highlighted = with_lang(Some("toml"), &text, None);
         assert!(highlighted.starts_with("<p>\n"));
     }
+
+    #[test]
+    fn rust_union_is_highlighted_as_keyword() {
+        let highlighted = with_lang(Some("rust"), "union Foo { field: u8 }\n", None);
+        assert!(highlighted.contains("<span class=\"syntax-keyword\">union</span> Foo"));
+    }
+
+    #[test]
+    fn rust_union_identifier_is_not_highlighted_as_keyword() {
+        let highlighted = with_lang(
+            Some("rust"),
+            "struct X { union: u32 }\nlet x = X { union: 0 };\nprintln!(\"{}\", x.union);\n",
+            None,
+        );
+        assert!(highlighted.contains("union:"));
+        assert!(highlighted.contains("x.union"));
+        assert!(!highlighted.contains("<span class=\"syntax-keyword\">union</span>:"));
+        assert!(!highlighted.contains(".<span class=\"syntax-keyword\">union</span>"));
+    }
+
+    #[test]
+    fn rust_union_macro_name_is_not_highlighted_as_keyword() {
+        let highlighted = with_lang(Some("rust"), "macro_rules! union { () => {} }\nunion!();\n", None);
+        assert!(highlighted.contains("macro_rules! union"));
+        assert!(!highlighted.contains("<span class=\"syntax-keyword\">union</span>!"));
+    }
 }