Re: [PATCH] [RFC] span-v2: using concepts, constraints and ranges:: instead of enable_if

[Jonathan Wakely]

On 05/12/19 13:49 +0000, Jonathan Wakely wrote:

This also causes two new FAILs in 23_containers/span/lwg3255.cc but
that turns out to be a bug in the test, which fails now t hat you've
fixed a bug in span. I'll fix that as well.

Here's that fix for the buggy test.

Tested powerpc64le-linux, committed to trunk as attached.



commit 2a392014c8f474492be34f73fb0f1a6efb56aa70
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Thu Dec 5 13:37:54 2019 +0000

    libstdc++: Fix bug in std::span test
    
    The previous commit fixed the std::span constructors from const arrays,
    revealing a bug in this test.
    
            * testsuite/23_containers/span/lwg3255.cc: Fix test. Constructing a
            span of non-const elements should not be possible from a const array
            or an array of const elements.

diff --git a/libstdc++-v3/testsuite/23_containers/span/lwg3255.cc b/libstdc++-v3/testsuite/23_containers/span/lwg3255.cc
index bab7da3bf19..eec686b4ea2 100644
--- a/libstdc++-v3/testsuite/23_containers/span/lwg3255.cc
+++ b/libstdc++-v3/testsuite/23_containers/span/lwg3255.cc
@@ -39,7 +39,6 @@ static_assert( is_constructible_v<span<int, 1>, array<int, 1>&> );
 static_assert( is_constructible_v<span<const int, 1>, array<int, 1>&> );
 static_assert( is_constructible_v<span<const int, 1>, array<const int, 1>&> );
 
-static_assert( is_constructible_v<span<int, 1>, const array<int, 1>&> );
 static_assert( is_constructible_v<span<const int, 1>, const array<int, 1>&> );
 static_assert( is_constructible_v<span<const int, 1>, const array<const int, 1>&> );
 
@@ -63,6 +62,12 @@ static_assert( is_constructible_v<span<int>, array<int, 2>&> );
 static_assert( is_constructible_v<span<const int>, array<int, 2>&> );
 static_assert( is_constructible_v<span<const int>, array<const int, 2>&> );
 
-static_assert( is_constructible_v<span<int>, const array<int, 2>&> );
 static_assert( is_constructible_v<span<const int>, const array<int, 2>&> );
 static_assert( is_constructible_v<span<const int>, const array<const int, 2>&> );
+
+static_assert( ! is_constructible_v<span<int, 1>, array<const int, 1>&> );
+static_assert( ! is_constructible_v<span<int, 1>, const array<int, 1>&> );
+static_assert( ! is_constructible_v<span<int, 1>, const array<const int, 1>&> );
+static_assert( ! is_constructible_v<span<int>, array<const int, 2>&> );
+static_assert( ! is_constructible_v<span<int>, const array<int, 2>&> );
+static_assert( ! is_constructible_v<span<int>, const array<const int, 2>&> );