Add Copy and map_ref for SpannedValue

Author: TedDriggs

CHANGELOG.md

@@ -1,5 +1,12 @@
 # Changelog
 
+## v0.13.0 (May 20, 2021)
+
+- Update darling to 2018 edition [#129](https://github.com/TedDriggs/darling/pull/129)
+- Error on duplicate fields in `#[darling(...)]` attributes [#130](https://github.com/TedDriggs/darling/pull/130)
+- Impl `Copy` for `SpannedValue<T: Copy>`
+- Add `SpannedValue::map_ref`
+
 ## v0.13.0-beta (April 20, 2021)
 
 - Update darling to 2018 edition [#129](https://github.com/TedDriggs/darling/pull/129)

core/src/util/spanned_value.rs

@@ -19,7 +19,7 @@ use crate::{
 /// but the user may not always explicitly set those options in their source code.
 /// In this case, using `Default::default()` will create an instance which points
 /// to `Span::call_site()`.
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Copy)]
 pub struct SpannedValue<T> {
     value: T,
     span: Span,
@@ -34,6 +34,11 @@ impl<T> SpannedValue<T> {
     pub fn span(&self) -> Span {
         self.span
     }
+
+    /// Apply a mapping function to a reference to the spanned value.
+    pub fn map_ref<U>(&self, map_fn: impl FnOnce(&T) -> U) -> SpannedValue<U> {
+        SpannedValue::new(map_fn(&self.value), self.span)
+    }
 }
 
 impl<T: Default> Default for SpannedValue<T> {