From 0e66c9a9bd9d3efe5e1c1d134819ec23bd792d5d Mon Sep 17 00:00:00 2001
From: mutouyun <orz@orzz.org>
Date: Sat, 29 Oct 2022 19:32:51 +0800
Subject: [PATCH] fix: [imp] error C3259: 'constexpr' functions can only have
 one return statement

---
 include/libimp/span.h | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/include/libimp/span.h b/include/libimp/span.h
index 2e013a8..c686f8d 100644
--- a/include/libimp/span.h
+++ b/include/libimp/span.h
@@ -190,22 +190,21 @@ public:
     return reverse_iterator(this->begin());
   }
 
-  constexpr span<element_type> first(size_type count) const noexcept {
+  constexpr span first(size_type count) const noexcept {
     return span(begin(), count);
   }
 
-  constexpr span<element_type> last(size_type count) const noexcept {
+  constexpr span last(size_type count) const noexcept {
     return span(end() - count, count);
   }
 
-  constexpr span<element_type> subspan(size_type offset, size_type count = (std::numeric_limits<size_type>::max)()) const noexcept {
-    if (offset >= size()) {
-      return {};
-    }
-    return span(begin() + offset, (std::min)(size() - offset, count));
+  constexpr span subspan(size_type offset, size_type count = (std::numeric_limits<size_type>::max)()) const noexcept {
+    return (offset >= size()) ? span() : span(begin() + offset, (std::min)(size() - offset, count));
   }
 };
 
+/// @brief Support for span equals comparison.
+
 template <typename T, typename U, 
           typename = decltype(std::declval<T>() == std::declval<U>())>
 bool operator==(span<T> a, span<U> b) noexcept {