better type assertion ergonomic

fix-vm/src/boxing.rs

@@ -160,6 +160,22 @@ enum TagVal {
 pub(crate) struct RawTag(TagVal);
 
 impl RawTag {
+    pub(crate) const P1: RawTag = RawTag(TagVal::_P1);
+    pub(crate) const P2: RawTag = RawTag(TagVal::_P2);
+    pub(crate) const P3: RawTag = RawTag(TagVal::_P3);
+    pub(crate) const P4: RawTag = RawTag(TagVal::_P4);
+    pub(crate) const P5: RawTag = RawTag(TagVal::_P5);
+    pub(crate) const P6: RawTag = RawTag(TagVal::_P6);
+    pub(crate) const P7: RawTag = RawTag(TagVal::_P7);
+
+    pub(crate) const N1: RawTag = RawTag(TagVal::_N1);
+    pub(crate) const N2: RawTag = RawTag(TagVal::_N2);
+    pub(crate) const N3: RawTag = RawTag(TagVal::_N3);
+    pub(crate) const N4: RawTag = RawTag(TagVal::_N4);
+    pub(crate) const N5: RawTag = RawTag(TagVal::_N5);
+    pub(crate) const N6: RawTag = RawTag(TagVal::_N6);
+    pub(crate) const N7: RawTag = RawTag(TagVal::_N7);
+
     #[inline]
     #[must_use]
     pub(crate) fn new(neg: bool, val: NonZeroU8) -> RawTag {
@@ -195,7 +211,7 @@ impl RawTag {
     /// `val` must be in the range `1..8`
     #[inline]
     #[must_use]
-    pub(crate) unsafe fn new_unchecked(neg: bool, val: u8) -> RawTag {
+    pub(crate) const unsafe fn new_unchecked(neg: bool, val: u8) -> RawTag {
         RawTag(match (neg, val) {
             (false, 1) => TagVal::_P1,
             (false, 2) => TagVal::_P2,
@@ -244,7 +260,7 @@ impl RawTag {
 
     #[inline]
     #[must_use]
-    pub(crate) fn neg_val(self) -> (bool, u8) {
+    pub(crate) const fn neg_val(self) -> (bool, u8) {
         match self.0 {
             TagVal::_P1 => (false, 1),
             TagVal::_P2 => (false, 2),
@@ -285,17 +301,17 @@ impl Header {
     }
 
     #[inline]
-    fn tag(self) -> RawTag {
+    const fn tag(self) -> RawTag {
         unsafe { RawTag::new_unchecked(self.get_sign(), self.get_tag()) }
     }
 
     #[inline]
-    fn get_sign(self) -> bool {
+    const fn get_sign(self) -> bool {
         self.0 & 0x8000 != 0
     }
 
     #[inline]
-    fn get_tag(self) -> u8 {
+    const fn get_tag(self) -> u8 {
         (self.0 & 0x0007) as u8
     }
 
@@ -341,7 +357,7 @@ impl Value {
 
     #[inline]
     #[must_use]
-    pub(crate) fn tag(&self) -> RawTag {
+    pub(crate) const fn tag(&self) -> RawTag {
         self.header.tag()
     }
 
@@ -417,7 +433,7 @@ impl RawBox {
 
     #[inline]
     #[must_use]
-    pub(crate) fn tag(&self) -> Option<RawTag> {
+    pub(crate) const fn tag(&self) -> Option<RawTag> {
         if self.is_value() {
             Some(unsafe { self.value.tag() })
         } else {
@@ -433,7 +449,7 @@ impl RawBox {
 
     #[inline]
     #[must_use]
-    pub(crate) fn is_value(&self) -> bool {
+    pub(crate) const fn is_value(&self) -> bool {
         (unsafe { self.float.is_nan() } && unsafe { self.bits & SIGN_MASK != QUIET_NAN })
     }