Add NetworkValidationError

The `require_network` function can fail in one way only, add a specific
error for the failure.

bitcoin/src/address/error.rs

@@ -9,6 +9,26 @@ use crate::blockdata::script::{witness_program, witness_version};
 use crate::prelude::*;
 use crate::{base58, Network};
 
+/// Address's network differs from required one.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct NetworkValidationError {
+    /// Network that was required.
+    pub(crate) required: Network,
+    /// The address itself.
+    pub(crate) address: Address<NetworkUnchecked>,
+}
+
+impl fmt::Display for NetworkValidationError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "address ")?;
+        fmt::Display::fmt(&self.address.0, f)?;
+        write!(f, " is not valid on {}", self.required)
+    }
+}
+
+#[cfg(feature = "std")]
+impl std::error::Error for NetworkValidationError {}
+
 /// Address error.
 #[derive(Debug, Clone, PartialEq, Eq)]
 #[non_exhaustive]

bitcoin/src/address/mod.rs

@@ -55,7 +55,7 @@ use self::error::P2shError;
 #[rustfmt::skip]                // Keep public re-exports separate.
 #[doc(inline)]
 pub use self::{
-    error::{Error, ParseError, UnknownAddressTypeError, UnknownHrpError, FromScriptError},
+    error::{Error, NetworkValidationError, ParseError, UnknownAddressTypeError, UnknownHrpError, FromScriptError, },
 };
 
 /// The different types of addresses.
@@ -667,11 +667,11 @@ impl Address<NetworkUnchecked> {
     /// For details about this mechanism, see section [*Parsing addresses*](Address#parsing-addresses)
     /// on [`Address`].
     #[inline]
-    pub fn require_network(self, required: Network) -> Result<Address, Error> {
+    pub fn require_network(self, required: Network) -> Result<Address, NetworkValidationError> {
         if self.is_valid_for_network(required) {
             Ok(self.assume_checked())
         } else {
-            Err(Error::NetworkValidation { required, address: self })
+            Err(NetworkValidationError { required, address: self })
         }
     }