From 252381640be00b7f380052bba022e5bfae633696 Mon Sep 17 00:00:00 2001
From: Karsten Sperling <113487422+ksperling-apple@users.noreply.github.com>
Date: Wed, 15 Nov 2023 20:36:58 +1300
Subject: [PATCH] Make (Fixed)Span<T>::data_equals a plain method (not a
 template) (#30479)

This allows implicit conversion (e.g. from std::array) to take place.
---
 src/lib/support/Span.h             | 22 ++--------------------
 src/lib/support/tests/TestSpan.cpp |  9 +++++++++
 2 files changed, 11 insertions(+), 20 deletions(-)

diff --git a/src/lib/support/Span.h b/src/lib/support/Span.h
index 2554cd4a695219..a6f63c7c59f33e 100644
--- a/src/lib/support/Span.h
+++ b/src/lib/support/Span.h
@@ -130,13 +130,10 @@ class Span
     reference front() const { return (*this)[0]; }
     reference back() const { return (*this)[size() - 1]; }
 
-    template <class U, typename = std::enable_if_t<std::is_same<std::remove_const_t<T>, std::remove_const_t<U>>::value>>
-    bool data_equal(const Span<U> & other) const
+    bool data_equal(const Span<const T> & other) const
     {
         return (size() == other.size()) && (empty() || (memcmp(data(), other.data(), size() * sizeof(T)) == 0));
     }
-    template <class U, size_t N, typename = std::enable_if_t<std::is_same<std::remove_const_t<T>, std::remove_const_t<U>>::value>>
-    inline bool data_equal(const FixedSpan<U, N> & other) const;
 
     Span SubSpan(size_t offset, size_t length) const
     {
@@ -329,15 +326,7 @@ class FixedSpan
     reference front() const { return (*this)[0]; }
     reference back() const { return (*this)[size() - 1]; }
 
-    // Allow data_equal for spans that are over the same type up to const-ness.
-    template <class U, typename = std::enable_if_t<std::is_same<std::remove_const_t<T>, std::remove_const_t<U>>::value>>
-    bool data_equal(const FixedSpan<U, N> & other) const
-    {
-        return (memcmp(data(), other.data(), N * sizeof(T)) == 0);
-    }
-
-    template <class U, typename = std::enable_if_t<std::is_same<std::remove_const_t<T>, std::remove_const_t<U>>::value>>
-    bool data_equal(const Span<U> & other) const
+    bool data_equal(const Span<const T> & other) const
     {
         return (N == other.size() && memcmp(data(), other.data(), N * sizeof(T)) == 0);
     }
@@ -359,13 +348,6 @@ template <class U, size_t N, typename>
 constexpr Span<T>::Span(const FixedSpan<U, N> & other) : mDataBuf(other.data()), mDataLen(other.size())
 {}
 
-template <class T>
-template <class U, size_t N, typename>
-inline bool Span<T>::data_equal(const FixedSpan<U, N> & other) const
-{
-    return other.data_equal(*this);
-}
-
 template <typename T>
 [[deprecated("Use !empty()")]] inline bool IsSpanUsable(const Span<T> & span)
 {
diff --git a/src/lib/support/tests/TestSpan.cpp b/src/lib/support/tests/TestSpan.cpp
index e1ff254a35b0a0..37e8d97de3488c 100644
--- a/src/lib/support/tests/TestSpan.cpp
+++ b/src/lib/support/tests/TestSpan.cpp
@@ -345,6 +345,15 @@ static void TestConversionConstructors(nlTestSuite * inSuite, void * inContext)
     ([](FixedSpan<const Foo, 3> f) {})(constArray);
     ([](Span<const Foo> f) {})(constArray);
 
+    NL_TEST_ASSERT(inSuite, span10.data_equal(span10));
+    NL_TEST_ASSERT(inSuite, span10.data_equal(span9));
+    NL_TEST_ASSERT(inSuite, span10.data_equal(array));
+    NL_TEST_ASSERT(inSuite, span10.data_equal(constArray));
+    NL_TEST_ASSERT(inSuite, span9.data_equal(span9));
+    NL_TEST_ASSERT(inSuite, span9.data_equal(span10));
+    NL_TEST_ASSERT(inSuite, span9.data_equal(array));
+    NL_TEST_ASSERT(inSuite, span9.data_equal(constArray));
+
     // The following should not compile
     // Span<const Foo> error1 = std::array<Foo, 3>(); // Span would point into a temporary value
 }