impl Clone for Error

CHANGELOG.md

@@ -3,6 +3,9 @@
 ## Unreleased
 
 - Fix a bug where using a trait that accepts `#[darling(attributes(...))]` without specifying any attributes would emit code that did not compile. [#183](https://github.com/TedDriggs/darling/issues/183)
+- Impl `Clone` for `darling::Error` [#184](https://github.com/TedDriggs/darling/pull/184)
+- Impl `From<darling::Error> for syn::Error` [#184](https://github.com/TedDriggs/darling/pull/184)
+- Add `Error::span` and `Error::explicit_span` methods [#184](https://github.com/TedDriggs/darling/pull/184)
 
 ## v0.14.0 (April 13, 2022)
 

core/src/error/kind.rs

@@ -6,10 +6,10 @@ type DeriveInputShape = String;
 type FieldName = String;
 type MetaFormat = String;
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 // Don't want to publicly commit to ErrorKind supporting equality yet, but
 // not having it makes testing very difficult.
-#[cfg_attr(test, derive(Clone, PartialEq, Eq))]
+#[cfg_attr(test, derive(PartialEq, Eq))]
 pub(in crate::error) enum ErrorKind {
     /// An arbitrary error message.
     Custom(String),
@@ -104,10 +104,10 @@ impl From<ErrorUnknownField> for ErrorKind {
 
 /// An error for an unknown field, with a possible "did-you-mean" suggestion to get
 /// the user back on the right track.
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 // Don't want to publicly commit to ErrorKind supporting equality yet, but
 // not having it makes testing very difficult.
-#[cfg_attr(test, derive(Clone, PartialEq, Eq))]
+#[cfg_attr(test, derive(PartialEq, Eq))]
 pub(in crate::error) struct ErrorUnknownField {
     name: String,
     did_you_mean: Option<String>,

core/src/error/mod.rs

@@ -56,8 +56,7 @@ pub type Result<T> = ::std::result::Result<T, Error>;
 ///    to ensure those errors appear in the right place. Use `darling::util::SpannedValue` to keep
 ///    span information around on parsed fields so that custom diagnostics can point to the correct
 ///    parts of the input AST.
-#[derive(Debug)]
-#[cfg_attr(test, derive(Clone))]
+#[derive(Debug, Clone)]
 pub struct Error {
     kind: ErrorKind,
     locations: Vec<String>,
@@ -449,14 +448,16 @@ impl From<Error> for syn::Error {
         if e.len() == 1 {
             syn::Error::new(e.span(), e)
         } else {
-            e.flatten()
-                .into_iter()
-                .map(syn::Error::from)
-                .reduce(|mut accum, next| {
-                    accum.combine(next);
-                    accum
-                })
-                .expect("darling::Error can never be empty")
+            let mut syn_errors = e.flatten().into_iter().map(syn::Error::from);
+            let mut error = syn_errors
+                .next()
+                .expect("darling::Error can never be empty");
+
+            for next_error in syn_errors {
+                error.combine(next_error);
+            }
+
+            error
         }
     }
 }