Adding upstream version 115.8.0esr.upstream/115.8.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 73 insertions, 0 deletions

diff --git a/third_party/rust/darling/examples/automatic_bounds.rs b/third_party/rust/darling/examples/automatic_bounds.rs
new file mode 100644
index 0000000000..8312afed4c
--- /dev/null
+++ b/third_party/rust/darling/examples/automatic_bounds.rs
@@ -0,0 +1,73 @@
+use darling::{FromDeriveInput, FromMeta};
+
+#[derive(FromMeta, PartialEq, Eq, Debug)]
+enum Volume {
+    Whisper,
+    Talk,
+    Shout,
+}
+
+/// A more complex example showing the ability to skip at a field or struct
+/// level while still tracking which type parameters need to be bounded.
+/// This can be seen by expanding this example using `cargo expand`.
+#[derive(FromMeta)]
+#[allow(dead_code)]
+enum Emphasis<T> {
+    Constant(Volume),
+    Variable(darling::util::PathList),
+    #[darling(skip)]
+    PerPhoneme(Option<T>),
+    Strided {
+        #[darling(skip)]
+        step: Vec<T>,
+        #[darling(multiple)]
+        volume: Vec<Volume>,
+    },
+}
+
+#[derive(FromDeriveInput)]
+#[darling(attributes(speak))]
+struct SpeakingOptions<T, U> {
+    max_volume: U,
+    #[darling(skip, default)]
+    additional_data: Vec<T>,
+}
+
+#[derive(Default)]
+struct Phoneme {
+    #[allow(dead_code)]
+    first: String,
+}
+
+// This is probably the holy grail for `darling`'s own internal use-case:
+// Auto-apply `Default` bound to skipped *field* types in `where` clause.
+impl<T, U> Default for SpeakingOptions<T, U>
+where
+    Vec<T>: Default,
+    U: Default,
+{
+    fn default() -> Self {
+        Self {
+            max_volume: Default::default(),
+            additional_data: Default::default(),
+        }
+    }
+}
+
+fn main() {
+    let derive_input = syn::parse_str(
+        r#"
+        #[derive(Speak)]
+        #[speak(max_volume = "shout")]
+        enum HtmlElement {
+            Div(String)
+        }
+    "#,
+    )
+    .unwrap();
+
+    let parsed: SpeakingOptions<Phoneme, Volume> =
+        FromDeriveInput::from_derive_input(&derive_input).unwrap();
+    assert_eq!(parsed.max_volume, Volume::Shout);
+    assert_eq!(parsed.additional_data.len(), 0);
+}