1 files changed, 72 insertions, 0 deletions
diff --git a/src/container_attributes.rs b/src/container_attributes.rs
new file mode 100644
index 0000000..9a91ac8
--- /dev/null
+++ b/src/container_attributes.rs
@@ -0,0 +1,72 @@
+use crate::ARBITRARY_ATTRIBUTE_NAME;
+use syn::{
+    parse::Error, punctuated::Punctuated, DeriveInput, Lit, Meta, MetaNameValue, NestedMeta, Token,
+    TypeParam,
+};
+
+pub struct ContainerAttributes {
+    /// Specify type bounds to be applied to the derived `Arbitrary` implementation instead of the
+    /// default inferred bounds.
+    ///
+    /// ```ignore
+    /// #[arbitrary(bound = "T: Default, U: Debug")]
+    /// ```
+    ///
+    /// Multiple attributes will be combined as long as they don't conflict, e.g.
+    ///
+    /// ```ignore
+    /// #[arbitrary(bound = "T: Default")]
+    /// #[arbitrary(bound = "U: Default")]
+    /// ```
+    pub bounds: Option<Vec<Punctuated<TypeParam, Token![,]>>>,
+}
+
+impl ContainerAttributes {
+    pub fn from_derive_input(derive_input: &DeriveInput) -> Result<Self, Error> {
+        let mut bounds = None;
+
+        for attr in &derive_input.attrs {
+            if !attr.path.is_ident(ARBITRARY_ATTRIBUTE_NAME) {
+                continue;
+            }
+
+            let meta_list = match attr.parse_meta()? {
+                Meta::List(l) => l,
+                _ => {
+                    return Err(Error::new_spanned(
+                        attr,
+                        format!(
+                            "invalid `{}` attribute. expected list",
+                            ARBITRARY_ATTRIBUTE_NAME
+                        ),
+                    ))
+                }
+            };
+
+            for nested_meta in meta_list.nested.iter() {
+                match nested_meta {
+                    NestedMeta::Meta(Meta::NameValue(MetaNameValue {
+                        path,
+                        lit: Lit::Str(bound_str_lit),
+                        ..
+                    })) if path.is_ident("bound") => {
+                        bounds
+                            .get_or_insert_with(Vec::new)
+                            .push(bound_str_lit.parse_with(Punctuated::parse_terminated)?);
+                    }
+                    _ => {
+                        return Err(Error::new_spanned(
+                            attr,
+                            format!(
+                                "invalid `{}` attribute. expected `bound = \"..\"`",
+                                ARBITRARY_ATTRIBUTE_NAME,
+                            ),
+                        ))
+                    }
+                }
+            }
+        }
+
+        Ok(Self { bounds })
+    }
+}