C backend: fix enough that zig test works

 * test_functions: properly add dependencies of the array on test
   functions and test names so that the order comes out correctly.
 * fix lowering of struct literals to add parentheses around the type
   name.
 * omit const qualifier in slices because otherwise slices cannot be
   reassigned even when they are local variables.
 * special case pointer to functions and double pointer to functions in
   renderTypeAndName. This code will need to be cleaned up but for now
   it helps us make progress on other C backend stuff.
 * fix slice element access to lower to `.ptr[` instead of `[`.
 * airSliceElemVal: respect volatile slices

1 files changed, 8 insertions, 0 deletions

diff --git a/src/type.zig b/src/type.zig
index e1a407011b..a43c80cb2e 100644
--- a/src/type.zig
+++ b/src/type.zig
@@ -252,6 +252,14 @@ pub const Type = extern union {
         };
     }
 
+    /// If it is a function pointer, returns the function type. Otherwise returns null.
+    pub fn castPtrToFn(ty: Type) ?Type {
+        if (ty.zigTypeTag() != .Pointer) return null;
+        const elem_ty = ty.childType();
+        if (elem_ty.zigTypeTag() != .Fn) return null;
+        return elem_ty;
+    }
+
     pub fn ptrIsMutable(ty: Type) bool {
         return switch (ty.tag()) {
             .single_const_pointer_to_comptime_int,