chore: add blocknumber convenience impls (#1368)

ethers-core/src/types/block.rs

@@ -533,6 +533,26 @@ impl BlockNumber {
             _ => None,
         }
     }
+
+    /// Returns `true` if a numeric block number is set
+    pub fn is_number(&self) -> bool {
+        matches!(self, BlockNumber::Number(_))
+    }
+
+    /// Returns `true` if it's "latest"
+    pub fn is_latest(&self) -> bool {
+        matches!(self, BlockNumber::Latest)
+    }
+
+    /// Returns `true` if it's "pending"
+    pub fn is_pending(&self) -> bool {
+        matches!(self, BlockNumber::Pending)
+    }
+
+    /// Returns `true` if it's "earliest"
+    pub fn is_earliest(&self) -> bool {
+        matches!(self, BlockNumber::Earliest)
+    }
 }
 
 impl<T: Into<U64>> From<T> for BlockNumber {
@@ -590,6 +610,12 @@ impl fmt::Display for BlockNumber {
     }
 }
 
+impl Default for BlockNumber {
+    fn default() -> Self {
+        BlockNumber::Latest
+    }
+}
+
 #[cfg(test)]
 #[cfg(not(feature = "celo"))]
 mod tests {