Fallible masp epoch conversion

crates/core/src/masp.rs

@@ -61,13 +61,15 @@ impl FromStr for MaspEpoch {
 impl MaspEpoch {
     /// Converts and `Epoch` into a `MaspEpoch` based on the provided conversion
     /// rate
-    pub fn from_epoch(epoch: Epoch, masp_epoch_multiplier: u64) -> Self {
-        Self(
+    pub fn try_from_epoch(
+        epoch: Epoch,
+        masp_epoch_multiplier: u64,
+    ) -> Result<Self, &'static str> {
+        Ok(Self(
             epoch
                 .checked_div(masp_epoch_multiplier)
-                // FIXME: error here
-                .expect("Masp epoch multiplier should not be 0"),
-        )
+                .ok_or("Masp epoch multiplier cannot be 0")?,
+        ))
     }
 
     /// Returns a 0 masp epoch
@@ -82,13 +84,16 @@ impl MaspEpoch {
 
     /// Check if the given epoch is also a new masp epoch based on the
     /// multiplier provided
-    pub fn is_masp_new_epoch(epoch: Epoch, masp_epoch_multiplier: u64) -> bool {
-        matches!(
-            Self::from_epoch(epoch, masp_epoch_multiplier)
+    pub fn is_masp_new_epoch(
+        epoch: Epoch,
+        masp_epoch_multiplier: u64,
+    ) -> Result<bool, &'static str> {
+        Ok(matches!(
+            Self::try_from_epoch(epoch, masp_epoch_multiplier)?
                 .0
                 .checked_rem(masp_epoch_multiplier),
             Some(Epoch(0))
-        )
+        ))
     }
 
     /// Initialize a new masp epoch from the provided one

crates/namada/src/ledger/native_vp/masp.rs

@@ -358,10 +358,13 @@ where
                     "Missing expected masp epoch multiplier parameter",
                 ))
             })?;
-        let masp_epoch = MaspEpoch::from_epoch(
+        let masp_epoch = MaspEpoch::try_from_epoch(
             self.ctx.get_block_epoch()?,
             masp_epoch_multiplier,
-        );
+        )
+        .map_err(|msg| {
+            Error::NativeVpError(native_vp::Error::new_const(msg))
+        })?;
         let conversion_state = self.ctx.state.in_mem().get_conversion_state();
         let shielded_tx = self.ctx.get_shielded_action(tx_data)?;
 

crates/sdk/src/queries/shell.rs

@@ -342,7 +342,8 @@ where
                 "Missing expected masp epoch multiplier parameter",
             )
         })?;
-    Ok(MaspEpoch::from_epoch(epoch, masp_epoch_multiplier))
+    MaspEpoch::try_from_epoch(epoch, masp_epoch_multiplier)
+        .map_err(namada_storage::Error::new_const)
 }
 
 fn native_token<D, H, V, T>(

crates/shielded_token/src/conversion.rs

@@ -331,10 +331,11 @@ where
     let masp_epoch_multiplier = storage
         .read::<u64>(&parameters::storage::get_masp_epoch_multiplier_key())?
         .expect("masp epoch multiplier should properly decode");
-    let masp_epoch = MaspEpoch::from_epoch(
+    let masp_epoch = MaspEpoch::try_from_epoch(
         storage.get_block_epoch()?,
         masp_epoch_multiplier,
-    );
+    )
+    .map_err(namada_storage::Error::new_const)?;
     let prev_masp_epoch = match masp_epoch.prev() {
         Some(epoch) => epoch,
         None => return Ok(()),

crates/state/src/wl_state.rs

@@ -205,13 +205,15 @@ where
             && MaspEpoch::is_masp_new_epoch(
                 self.in_mem.block.epoch,
                 masp_epoch_multiplier,
-            );
+            )
+            .map_err(namada_storage::Error::new_const)?;
 
         if masp_new_epoch {
-            let masp_epoch = MaspEpoch::from_epoch(
+            let masp_epoch = MaspEpoch::try_from_epoch(
                 self.in_mem.block.epoch,
                 masp_epoch_multiplier,
-            );
+            )
+            .map_err(namada_storage::Error::new_const)?;
             tracing::info!("Began a new masp epoch {masp_epoch}");
         }