1 files changed, 97 insertions, 0 deletions
diff --git a/src/syn_utils.rs b/src/syn_utils.rs
new file mode 100644
index 0000000..4588186
--- /dev/null
+++ b/src/syn_utils.rs
@@ -0,0 +1,97 @@
+use syn::{
+    punctuated::Punctuated, GenericArgument, Path, PathArguments, ReturnType, TraitBound, Type,
+    TypeParamBound,
+};
+
+pub trait TypeMatcher<T> {
+    fn match_type<'a>(&self, t: &'a Type) -> Option<&'a T> {
+        None
+    }
+    fn match_path<'a>(&self, path: &'a Path) -> Option<&'a T> {
+        None
+    }
+}
+
+pub fn trait_bounds<T>(
+    bounds: &Punctuated<TypeParamBound, T>,
+) -> impl Iterator<Item = &TraitBound> {
+    bounds.iter().filter_map(|b| match b {
+        TypeParamBound::Trait(t) => Some(t),
+        TypeParamBound::Lifetime(_) => None,
+    })
+}
+
+pub fn find_in_type<'a, T>(t: &'a Type, matcher: &dyn TypeMatcher<T>) -> Option<&'a T> {
+    if let Some(ret) = matcher.match_type(t) {
+        return Some(ret);
+    }
+    match t {
+        Type::Array(array) => find_in_type(&array.elem, matcher),
+        Type::BareFn(fun) => {
+            for input in &fun.inputs {
+                if let Some(ret) = find_in_type(&input.ty, matcher) {
+                    return Some(ret);
+                }
+            }
+            if let ReturnType::Type(_, t) = &fun.output {
+                return find_in_type(t, matcher);
+            }
+            None
+        }
+        Type::Group(group) => find_in_type(&group.elem, matcher),
+        Type::ImplTrait(impltrait) => {
+            for bound in &impltrait.bounds {
+                if let TypeParamBound::Trait(bound) = bound {
+                    if let Some(ret) = find_in_path(&bound.path, matcher) {
+                        return Some(ret);
+                    }
+                }
+            }
+            None
+        }
+        Type::Infer(_) => None,
+        Type::Macro(_) => None,
+        Type::Paren(paren) => find_in_type(&paren.elem, matcher),
+        Type::Path(path) => find_in_path(&path.path, matcher),
+        Type::Ptr(ptr) => find_in_type(&ptr.elem, matcher),
+        Type::Reference(reference) => find_in_type(&reference.elem, matcher),
+        Type::Slice(slice) => find_in_type(&slice.elem, matcher),
+        Type::TraitObject(traitobj) => {
+            for bound in &traitobj.bounds {
+                if let TypeParamBound::Trait(bound) = bound {
+                    if let Some(ret) = find_in_path(&bound.path, matcher) {
+                        return Some(ret);
+                    }
+                }
+            }
+            None
+        }
+        Type::Tuple(tuple) => {
+            for elem in &tuple.elems {
+                if let Some(ret) = find_in_type(elem, matcher) {
+                    return Some(ret);
+                }
+            }
+            None
+        }
+        _other => None,
+    }
+}
+
+pub fn find_in_path<'a, T>(path: &'a Path, matcher: &dyn TypeMatcher<T>) -> Option<&'a T> {
+    if let Some(ret) = matcher.match_path(path) {
+        return Some(ret);
+    }
+    for segment in &path.segments {
+        if let PathArguments::AngleBracketed(args) = &segment.arguments {
+            for arg in &args.args {
+                if let GenericArgument::Type(t) = arg {
+                    if let Some(ret) = find_in_type(t, matcher) {
+                        return Some(ret);
+                    }
+                }
+            }
+        }
+    }
+    None
+}