Bug 1681691 - Create a NonNegativePercentage type in values:specified. r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D109285

servo/components/style/values/specified/mod.rs

@@ -71,7 +71,7 @@ pub use self::list::Quotes;
 pub use self::motion::{OffsetPath, OffsetRotate};
 pub use self::outline::OutlineStyle;
 pub use self::page::{Orientation, PageSize, PaperSize};
-pub use self::percentage::Percentage;
+pub use self::percentage::{Percentage, NonNegativePercentage};
 pub use self::position::AspectRatio;
 pub use self::position::{
     GridAutoFlow, GridTemplateAreas, MasonryAutoFlow, Position, PositionOrAuto,

servo/components/style/values/specified/percentage.rs

@@ -7,6 +7,7 @@
 use crate::parser::{Parse, ParserContext};
 use crate::values::computed::percentage::Percentage as ComputedPercentage;
 use crate::values::computed::{Context, ToComputedValue};
+use crate::values::generics::NonNegative;
 use crate::values::specified::calc::CalcNode;
 use crate::values::specified::Number;
 use crate::values::{serialize_percentage, CSSFloat};
@@ -172,3 +173,16 @@ impl ToComputedValue for Percentage {
 }
 
 impl SpecifiedValueInfo for Percentage {}
+
+/// A wrapper of Percentage, whose value must be >= 0.
+pub type NonNegativePercentage = NonNegative<Percentage>;
+
+impl Parse for NonNegativePercentage {
+    #[inline]
+    fn parse<'i, 't>(
+        context: &ParserContext,
+        input: &mut Parser<'i, 't>,
+    ) -> Result<Self, ParseError<'i>> {
+        Ok(NonNegative(Percentage::parse_non_negative(context, input)?))
+    }
+}