make fallible_semantic_parent do ffi call

Author: malisas

src/clang.rs

@@ -110,7 +110,9 @@ impl Cursor {
     /// See documentation for `lexical_parent` for details on semantic vs
     /// lexical parents.
     pub fn fallible_semantic_parent(&self) -> Option<Cursor> {
-        let sp = self.semantic_parent();
+        let sp = unsafe {
+            Cursor { x: clang_getCursorSemanticParent(self.x) }
+        };
         if sp == *self || !sp.is_valid() {
             return None;
         }
@@ -122,9 +124,7 @@ impl Cursor {
     /// See documentation for `lexical_parent` for details on semantic vs
     /// lexical parents.
     pub fn semantic_parent(&self) -> Cursor {
-        unsafe {
-            Cursor { x: clang_getCursorSemanticParent(self.x) }
-        }
+        self.fallible_semantic_parent().unwrap()
     }
 
     /// Return the number of template arguments used by this cursor's referent,