1 files changed, 48 insertions, 0 deletions
diff --git a/third_party/rust/async-trait/src/bound.rs b/third_party/rust/async-trait/src/bound.rs
new file mode 100644
index 0000000000..50182f6db8
--- /dev/null
+++ b/third_party/rust/async-trait/src/bound.rs
@@ -0,0 +1,48 @@
+use proc_macro2::{Ident, Span, TokenStream};
+use quote::quote_spanned;
+use syn::punctuated::Punctuated;
+use syn::{Token, TypeParamBound};
+
+pub type Supertraits = Punctuated<TypeParamBound, Token![+]>;
+
+pub enum InferredBound {
+    Send,
+    Sync,
+}
+
+pub fn has_bound(supertraits: &Supertraits, bound: &InferredBound) -> bool {
+    for supertrait in supertraits {
+        if let TypeParamBound::Trait(supertrait) = supertrait {
+            if supertrait.path.is_ident(bound)
+                || supertrait.path.segments.len() == 3
+                    && (supertrait.path.segments[0].ident == "std"
+                        || supertrait.path.segments[0].ident == "core")
+                    && supertrait.path.segments[1].ident == "marker"
+                    && supertrait.path.segments[2].ident == *bound
+            {
+                return true;
+            }
+        }
+    }
+    false
+}
+
+impl InferredBound {
+    fn as_str(&self) -> &str {
+        match self {
+            InferredBound::Send => "Send",
+            InferredBound::Sync => "Sync",
+        }
+    }
+
+    pub fn spanned_path(&self, span: Span) -> TokenStream {
+        let ident = Ident::new(self.as_str(), span);
+        quote_spanned!(span=> ::core::marker::#ident)
+    }
+}
+
+impl PartialEq<InferredBound> for Ident {
+    fn eq(&self, bound: &InferredBound) -> bool {
+        self == bound.as_str()
+    }
+}