Auto merge of #513 - emilio:const-fn-arg, r=fitzgen

Use the constness of the inner type when converting array function args.

Fixes #509

I'm actually surprised we had no tests for this.

Author: bors-servo

src/codegen/mod.rs

@@ -2828,7 +2828,7 @@ mod utils {
             // [1]: http://c0x.coding-guidelines.com/6.7.5.3.html
             let arg_ty = match *arg_ty.canonical_type(ctx).kind() {
                 TypeKind::Array(t, _) => {
-                    t.to_rust_ty(ctx).to_ptr(arg_ty.is_const(), ctx.span())
+                    t.to_rust_ty(ctx).to_ptr(ctx.resolve_type(t).is_const(), ctx.span())
                 },
                 TypeKind::Pointer(inner) => {
                     let inner = ctx.resolve_item(inner);

tests/expectations/tests/const_array_fn_arg.rs

@@ -0,0 +1,9 @@
+/* automatically generated by rust-bindgen */
+
+
+#![allow(non_snake_case)]
+
+
+extern "C" {
+    pub fn f(a: *const ::std::os::raw::c_int);
+}

tests/headers/const_array_fn_arg.h

@@ -0,0 +1 @@
+void f(const int a[]);