initial expression implementation

Change-Id: I6a6a69640c133bce112891bba09033b08e7c0dec

1 files changed, 12 insertions, 5 deletions

diff --git a/crates/core/src/hive/skipfield.rs b/crates/core/src/hive/skipfield.rs
index 0fb2ab4..16a3dcb 100644
--- a/crates/core/src/hive/skipfield.rs
+++ b/crates/core/src/hive/skipfield.rs
@@ -4,7 +4,10 @@
 //! types may be used by implementing this trait on them; the trait is not
 //! sealed.
 
-use core::ops::{Add, AddAssign, Sub, SubAssign};
+use core::{
+    cmp,
+    ops::{Add, AddAssign, Sub, SubAssign},
+};
 
 /// Trait describing integral types in a generic way suitable for use as the
 /// element type of a skipfield.
@@ -21,9 +24,13 @@ pub trait SkipfieldType:
     const ONE: Self;
 
     /// Conversion method from `usize` using `as` or an equivalent
+    ///
+    /// Caps the value of the input by the maximum of `Self`.
     fn from_usize(u: usize) -> Self;
 
     /// Conversion method from `isize` using `as` or an equivalent
+    ///
+    /// Caps the value of the input by the maximum of `Self`.
     fn from_isize(i: isize) -> Self;
 }
 
@@ -34,12 +41,12 @@ impl SkipfieldType for u16 {
 
     #[inline(always)]
     fn from_usize(u: usize) -> Self {
-        u as u16
+        cmp::min(u, Self::MAXIMUM as usize) as u16
     }
 
     #[inline(always)]
     fn from_isize(i: isize) -> Self {
-        i as u16
+        cmp::min(i, Self::MAXIMUM as isize) as u16
     }
 }
 
@@ -50,11 +57,11 @@ impl SkipfieldType for u8 {
 
     #[inline(always)]
     fn from_usize(u: usize) -> Self {
-        u as u8
+        cmp::min(u, Self::MAXIMUM as usize) as u8
     }
 
     #[inline(always)]
     fn from_isize(i: isize) -> Self {
-        i as u8
+        cmp::min(i, Self::MAXIMUM as isize) as u8
     }
 }