+pub type ExpandResult<T> = ValueResult<T, ExpandError>;
+
+#[derive(Debug, PartialEq, Eq, Clone)]
+pub enum ExpandError {
+ UnresolvedProcMacro,
+ Mbe(mbe::ExpandError),
+ Other(Box<str>),
+}
+
+impl From<mbe::ExpandError> for ExpandError {
+ fn from(mbe: mbe::ExpandError) -> Self {
+ Self::Mbe(mbe)
+ }
+}
+
+impl fmt::Display for ExpandError {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ match self {
+ ExpandError::UnresolvedProcMacro => f.write_str("unresolved proc-macro"),
+ ExpandError::Mbe(it) => it.fmt(f),
+ ExpandError::Other(it) => f.write_str(it),
+ }
+ }
+}
+