runtime: make ValueVariant lifetime-generic and add TryFrom<Value> conversions

fix-runtime/src/forced.rs

@@ -50,7 +50,7 @@ impl<'gc> Forced<'gc> for StrictValue<'gc> {
 macro_rules! impl_forced {
     ($($ty:ty),* $(,)?) => {
         $(
-        impl<'gc> Forced<'gc> for <$ty as ValueVariant>::Ty<'gc> {
+        impl<'gc> Forced<'gc> for <$ty as ValueVariant<'gc>>::Ty {
             const WIDTH: usize = 1;
 
             #[inline(always)]

fix-runtime/src/value.rs

@@ -21,12 +21,12 @@ mod private {
     pub trait Cealed {}
 }
 
-pub trait ValueVariant: private::Cealed {
+pub trait ValueVariant<'gc>: private::Cealed {
     #[expect(
         private_bounds,
         reason = "Storable is a sealed implementation detail of the value system"
     )]
-    type Ty<'gc>: Storable + 'gc;
+    type Ty: Storable + 'gc;
     const TYPE: NixType;
 }
 
@@ -64,10 +64,20 @@ macro_rules! define_value_types {
             }
         }
         impl private::Cealed for $itype {}
-        impl ValueVariant for $itype {
+        impl<'gc> ValueVariant<'gc> for $itype {
-            type Ty<'gc> = $itype;
+            type Ty = $itype;
             const TYPE: NixType = $ity;
         }
+        impl<'gc> TryFrom<Value<'gc>> for $itype {
+            type Error = ();
+            fn try_from(val: Value<'gc>) -> Result<Self, Self::Error> {
+                <Self as Storable>::is(&val.raw)
+                    // SAFETY: `is` returned true, so `val.raw` represents a
+                    // valid `Self` of this GC type.
+                    .then(|| unsafe { <Self as Storable>::from_raw_box(val.raw) })
+                    .ok_or(())
+            }
+        }
         )*
         $(
         impl Storable for Gc<'_, $gtype> {
@@ -88,10 +98,20 @@ macro_rules! define_value_types {
                 unsafe { Gc::from_ptr(<*mut $gtype as RawStore>::from_val(raw.value().unwrap_unchecked())) }
             }
         }
+        impl<'gc> TryFrom<Value<'gc>> for Gc<'gc, unelide_lifetimes!('gc; $gtype)> {
+            type Error = ();
+            fn try_from(val: Value<'gc>) -> Result<Self, Self::Error> {
+                <Self as Storable>::is(&val.raw)
+                    // SAFETY: `is` returned true, so `val.raw` represents a
+                    // valid `Self` of this GC type.
+                    .then(|| unsafe { <Self as Storable>::from_raw_box(val.raw) })
+                    .ok_or(())
+            }
+        }
         impl private::Cealed for Gc<'_, $gtype> {}
         impl private::Cealed for $gtype {}
-        impl ValueVariant for $gtype {
+        impl<'gc> ValueVariant<'gc> for unelide_lifetimes!('gc; $gtype) {
-            type Ty<'gc> = Gc<'gc, unelide_lifetimes!('gc; $gtype)>;
+            type Ty = Gc<'gc, unelide_lifetimes!('gc; $gtype)>;
             const TYPE: NixType = $gty;
         }
         )*
@@ -199,8 +219,8 @@ impl Storable for f64 {
     }
 }
 
-impl ValueVariant for f64 {
+impl<'gc> ValueVariant<'gc> for f64 {
-    type Ty<'gc> = f64;
+    type Ty = f64;
     const TYPE: NixType = NixType::Float;
 }
 
@@ -257,12 +277,12 @@ impl<'gc> Value<'gc> {
     }
 
     #[inline]
-    pub fn is<T: ValueVariant>(self) -> bool {
+    pub fn is<T: ValueVariant<'gc>>(self) -> bool {
         T::Ty::is(&self.raw)
     }
 
     #[inline]
-    pub fn downcast<T: ValueVariant>(self) -> Option<T::Ty<'gc>> {
+    pub fn downcast<T: ValueVariant<'gc>>(self) -> Option<T::Ty> {
         self.is::<T>()
             // SAFETY: `is::<T>()` returned true, so `self.raw` represents a
             // valid `T::Ty`.
@@ -332,7 +352,7 @@ impl<'gc> Value<'gc> {
     }
 
     #[inline]
-    pub fn expect<T: ValueVariant>(self) -> Result<T::Ty<'gc>, NixType> {
+    pub fn expect<T: ValueVariant<'gc>>(self) -> Result<T::Ty, NixType> {
         self.downcast::<T>().ok_or_else(|| self.ty())
     }
 
@@ -365,12 +385,12 @@ impl StaticValue {
     }
 
     #[inline]
-    pub fn is<T: ValueVariant>(self) -> bool {
+    pub fn is<T: ValueVariant<'static>>(self) -> bool {
         self.0.is::<T>()
     }
 
     #[inline]
-    pub fn downcast<T: ValueVariant>(self) -> Option<T::Ty<'static>> {
+    pub fn downcast<T: ValueVariant<'static>>(self) -> Option<T::Ty> {
         self.0.downcast::<T>()
     }
 
@@ -696,6 +716,12 @@ impl<'gc> Deref for StrictValue<'gc> {
     }
 }
 
+impl<'gc> From<StrictValue<'gc>> for Value<'gc> {
+    fn from(value: StrictValue<'gc>) -> Self {
+        value.0
+    }
+}
+
 impl fmt::Debug for StrictValue<'_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt::Debug::fmt(&self.0, f)