From 7036a9b6f7d7df230b060252cc56f5f9a09eb43b Mon Sep 17 00:00:00 2001
From: asynts <asynts@gmail.com>
Date: Sun, 26 Jul 2020 18:08:40 +0200
Subject: [PATCH] AK: Define conversion from Span<T> to Span<const T>
 correctly.

I accidently wrote `Span<RemoveConst<T>>` when I meant
`Span<RemoveConst<T>::Type>`.

Changing that wouldn't be enough though, this constructor can only be
defined if T is not const, otherwise it would redefine the copy
constructor.  This can be avoided by overloading the cast operator.
---
 AK/Span.h         | 10 +++++-----
 AK/Tests/Span.cpp |  8 ++++++++
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/AK/Span.h b/AK/Span.h
index bf46986cd0..e974ce8807 100644
--- a/AK/Span.h
+++ b/AK/Span.h
@@ -52,11 +52,6 @@ public:
         , m_size(other.m_size)
     {
     }
-    ALWAYS_INLINE Span(const Span<RemoveConst<T>>& other)
-        : m_values(other.m_values)
-        , m_size(other.m_size)
-    {
-    }
 
     ALWAYS_INLINE const T* data() const { return m_values; }
     ALWAYS_INLINE T* data() { return m_values; }
@@ -115,6 +110,11 @@ public:
         m_values = other.m_values;
     }
 
+    ALWAYS_INLINE operator Span<const T>() const
+    {
+        return { data(), size() };
+    }
+
 protected:
     T* m_values { nullptr };
     size_t m_size { 0 };
diff --git a/AK/Tests/Span.cpp b/AK/Tests/Span.cpp
index ef0c48a9b0..301a1f9c28 100644
--- a/AK/Tests/Span.cpp
+++ b/AK/Tests/Span.cpp
@@ -36,6 +36,14 @@ TEST_CASE(default_constructor_is_empty)
     EXPECT(span.is_empty());
 }
 
+TEST_CASE(implicit_converson_to_const)
+{
+    Bytes bytes0;
+    ReadonlyBytes bytes1 { bytes0 };
+    [[maybe_unused]] ReadonlyBytes bytes2 = bytes0;
+    [[maybe_unused]] ReadonlyBytes bytes3 = static_cast<ReadonlyBytes>(bytes2);
+}
+
 TEST_CASE(span_works_with_constant_types)
 {
     const u8 buffer[4] { 1, 2, 3, 4 };