Don't reject out of bound calc() values at parsing-time

https://bugzilla.mozilla.org/show_bug.cgi?id=1355014

components/style_traits/values.rs

@@ -150,6 +150,7 @@ macro_rules! __define_css_keyword_enum__actual {
 /// Helper types for the handling of specified values.
 pub mod specified {
     use app_units::Au;
+    use std::cmp;
 
     /// Whether to allow negative lengths or not.
     #[repr(u8)]
@@ -175,13 +176,47 @@ pub mod specified {
         /// Clamp the value following the rules of this numeric type.
         #[inline]
         pub fn clamp(&self, val: Au) -> Au {
-            use std::cmp;
             match *self {
                 AllowedLengthType::All => val,
                 AllowedLengthType::NonNegative => cmp::max(Au(0), val),
             }
         }
     }
+
+    /// Whether to allow negative lengths or not.
+    #[repr(u8)]
+    #[cfg_attr(feature = "servo", derive(HeapSizeOf))]
+    #[derive(Clone, Copy, Debug, Eq, PartialEq, PartialOrd)]
+    pub enum AllowedNumericType {
+        /// Allow all kind of numeric values.
+        All,
+        /// Allow only non-negative numeric values.
+        NonNegative,
+        /// Allow only numeric values greater or equal to 1.0.
+        AtLeastOne,
+    }
+
+    impl AllowedNumericType {
+        /// Whether the value fits the rules of this numeric type.
+        #[inline]
+        pub fn is_ok(&self, val: f32) -> bool {
+            match *self {
+                AllowedNumericType::All => true,
+                AllowedNumericType::NonNegative => val >= 0.0,
+                AllowedNumericType::AtLeastOne => val >= 1.0,
+            }
+        }
+
+        /// Clamp the value following the rules of this numeric type.
+        #[inline]
+        pub fn clamp(&self, val: f32) -> f32 {
+            match *self {
+                AllowedNumericType::NonNegative if val < 0. => 0.,
+                AllowedNumericType::AtLeastOne if val < 1. => 1.,
+                _ => val,
+            }
+        }
+    }
 }