Auto merge of #163 - catdesk:master, r=KiChjang

Change clang::Type::num_elements to return Option

Fixes #139.

Author: bors-servo

src/clang.rs

@@ -678,9 +678,12 @@ impl Type {
 
     /// Given that this type is an array or vector type, return its number of
     /// elements.
-    pub fn num_elements(&self) -> usize {
-        unsafe {
-            clang_getNumElements(self.x) as usize
+    pub fn num_elements(&self) -> Option<usize> {
+        let num_elements_returned = unsafe { clang_getNumElements(self.x) };
+        if num_elements_returned != -1 {
+            Some(num_elements_returned as usize)
+        } else {
+            None
         }
     }
 

src/ir/ty.rs

@@ -681,7 +681,7 @@ impl Type {
             CXType_ConstantArray => {
                 let inner = Item::from_ty(&ty.elem_type(), location, parent_id, ctx)
                                 .expect("Not able to resolve array element?");
-                TypeKind::Array(inner, ty.num_elements())
+                TypeKind::Array(inner, ty.num_elements().unwrap())
             }
             // A complex number is always a real and an imaginary part, so
             // represent that as a two-item array.