tsmt: return error code instead of panic

src/merkle/tiered_smt/error.rs

@@ -0,0 +1,49 @@
+use core::fmt::Display;
+
+#[derive(Debug, PartialEq, Eq)]
+pub enum TieredSmtProofError {
+    EntriesEmpty,
+    PathTooLong,
+    NotATierPath(u8),
+    MultipleEntriesOutsideLastTier,
+    EmptyValueNotAllowed,
+    UnmatchingPrefixes(u64, u64),
+}
+
+impl Display for TieredSmtProofError {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        match self {
+            TieredSmtProofError::EntriesEmpty => {
+                write!(f, "Missing entries for tiered sparse merkle tree proof")
+            }
+            TieredSmtProofError::PathTooLong => {
+                write!(
+                    f,
+                    "Path longer than maximum depth of 64 for tiered sparse merkle tree proof"
+                )
+            }
+            TieredSmtProofError::NotATierPath(got) => {
+                write!(
+                    f,
+                    "Path length does not correspond to a tier. Got {} Expected one of 16,32,48,64",
+                    got
+                )
+            }
+            TieredSmtProofError::MultipleEntriesOutsideLastTier => {
+                write!(f, "Multiple entries are only allowed for the last tier (depth 64)")
+            }
+            TieredSmtProofError::EmptyValueNotAllowed => {
+                write!(
+                    f,
+                    "The empty value [0,0,0,0] is not allowed inside a tiered sparse merkle tree"
+                )
+            }
+            TieredSmtProofError::UnmatchingPrefixes(first, second) => {
+                write!(f, "Not all leaves have the same prefix. First {} second {}", first, second)
+            }
+        }
+    }
+}
+
+#[cfg(feature = "std")]
+impl std::error::Error for TieredSmtProofError {}