Ensure arbitrary variables with data types are extracted correctly (#16986)

Closes #16983

This PR fixes an issue where the arbitrary variable machine did not
extract data type correctly.

## Test plan

- Added regression test

CHANGELOG.md

@@ -23,6 +23,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Ensure classes containing numbers followed by dash or underscore are extracted correctly ([#16980](https://github.com/tailwindlabs/tailwindcss/pull/16980))
 - Ensure arbitrary container queries are extracted correctly ([#16984](https://github.com/tailwindlabs/tailwindcss/pull/16984))
 - Ensure classes ending in `[` are extracted in Slim templating language ([#16985](https://github.com/tailwindlabs/tailwindcss/pull/16985))
+- Ensure arbitrary variables with data types are extracted correctly ([#16986](https://github.com/tailwindlabs/tailwindcss/pull/16986))
 
 ## [4.0.10] - 2025-03-05
 

crates/oxide/src/extractor/arbitrary_value_machine.rs

@@ -176,6 +176,8 @@ mod tests {
                 "[&>[data-slot=icon]:last-child]",
                 vec!["[&>[data-slot=icon]:last-child]"],
             ),
+            // With data types
+            ("[length:32rem]", vec!["[length:32rem]"]),
             // Spaces are not allowed
             ("[ #0088cc ]", vec![]),
             // Unbalanced brackets are not allowed

crates/oxide/src/extractor/arbitrary_variable_machine.rs

@@ -36,6 +36,14 @@ enum State {
     #[default]
     Idle,
 
+    /// Currently parsing the data type of the arbitrary variable
+    ///
+    /// ```text
+    /// (length:--my-opacity)
+    ///  ^^^^^^^
+    /// ```
+    ParsingDataType,
+
     /// Currently parsing the inside of the arbitrary variable
     ///
     /// ```text
@@ -81,6 +89,13 @@ impl Machine for ArbitraryVariableMachine {
                         self.next(cursor)
                     }
 
+                    Class::AlphaLower => {
+                        self.start_pos = cursor.pos;
+                        self.state = State::ParsingDataType;
+                        cursor.advance();
+                        self.next(cursor)
+                    }
+
                     _ => MachineState::Idle,
                 },
 
@@ -89,6 +104,38 @@ impl Machine for ArbitraryVariableMachine {
                 _ => MachineState::Idle,
             },
 
+            State::ParsingDataType => {
+                while cursor.pos < len {
+                    match cursor.curr.into() {
+                        // Valid data type characters
+                        //
+                        // E.g.: `(length:--my-length)`
+                        //         ^
+                        Class::AlphaLower | Class::Dash => {
+                            cursor.advance();
+                        }
+
+                        // End of the data type
+                        //
+                        // E.g.: `(length:--my-length)`
+                        //               ^
+                        Class::Colon => match cursor.next.into() {
+                            Class::Dash => {
+                                self.state = State::Parsing;
+                                cursor.advance();
+                                return self.next(cursor);
+                            }
+
+                            _ => return self.restart(),
+                        },
+
+                        // Anything else is not a valid character
+                        _ => return self.restart(),
+                    };
+                }
+                self.restart()
+            }
+
             State::Parsing => match self.css_variable_machine.next(cursor) {
                 MachineState::Idle => self.restart(),
                 MachineState::Done(_) => match cursor.next.into() {
@@ -286,6 +333,8 @@ mod tests {
                 "(--my-img,url('https://example.com?q=(][)'))",
                 vec!["(--my-img,url('https://example.com?q=(][)'))"],
             ),
+            // With a type hint
+            ("(length:--my-length)", vec!["(length:--my-length)"]),
             // --------------------------------------------------------
 
             // Exceptions:

crates/oxide/src/extractor/mod.rs

@@ -846,7 +846,7 @@ mod tests {
             ],
         );
     }
-  
+
     // https://github.com/tailwindlabs/tailwindcss/issues/16978
     #[test]
     fn test_classes_containing_number_followed_by_dash_or_underscore() {
@@ -856,6 +856,15 @@ mod tests {
         );
     }
 
+    // https://github.com/tailwindlabs/tailwindcss/issues/16983
+    #[test]
+    fn test_arbitrary_variable_with_data_type() {
+        assert_extract_sorted_candidates(
+            r#"<div class="bg-(length:--my-length) bg-[color:var(--my-color)]"></div>"#,
+            vec!["bg-(length:--my-length)", "bg-[color:var(--my-color)]"],
+        );
+    }
+
     #[test]
     fn test_extract_css_variables() {
         for (input, expected) in [