Simplify require, prefer.

1 files changed, 10 insertions, 11 deletions

diff --git a/c/common.h b/c/common.h
index 24c98c8..01083b8 100644
--- a/c/common.h
+++ b/c/common.h
@@ -55,24 +55,23 @@ std::optional<T> maybe_make(U... xs)
 }
 
 /* Call Windows API function, throwing error on NULL. */
-template <auto F, typename... T>
-inline auto require(T... xs)
+template <typename T>
+inline T require(T x)
 {
-	if (auto r = F(xs...)) return r;
-	else throw Win32Error();
+	if (!x) throw Win32Error();
+	return x;
 }
 
 /* Call Windows API function, showing a warning on NULL. */
-template <auto F, typename... T>
-inline auto prefer(T... xs)
+template <typename T>
+inline T prefer(T x)
 {
-	if (auto r = F(xs...))
-		return r;
-	else {
+	if (!x) {
 		EBMessageBox(Win32Error().what<TCHAR>(),
-			TEXT("System Error"), MB_ICONWARNING);
-		return (decltype(F(std::declval<T>()...)))NULL;
+		    TEXT("System Error"), MB_ICONWARNING);
+		return (T)NULL;
 	}
+	return x;
 }
 
 /* Return integer scaled for current DPI. */