Vk: rvalue overloads for MeshLayout setters.

So it's possible to do

    Vk::Mesh mesh{Vk::MeshLayout{}
        .addBinding(...)
        .addAttribute(...)
    };

Without this, the above will result in a dangling layout reference.

src/Magnum/Vk/MeshLayout.cpp

@@ -172,7 +172,7 @@ bool MeshLayout::operator==(const MeshLayout& other) const {
     #undef _c
 }
 
-MeshLayout& MeshLayout::addBinding(const UnsignedInt binding, const UnsignedInt stride) {
+MeshLayout& MeshLayout::addBinding(const UnsignedInt binding, const UnsignedInt stride) & {
     if(!_state) _state.emplace();
 
     /* Ensure order for efficient comparisons */
@@ -190,7 +190,11 @@ MeshLayout& MeshLayout::addBinding(const UnsignedInt binding, const UnsignedInt
     return *this;
 }
 
-MeshLayout& MeshLayout::addInstancedBinding(const UnsignedInt binding, const UnsignedInt stride, const UnsignedInt divisor) {
+MeshLayout&& MeshLayout::addBinding(const UnsignedInt binding, const UnsignedInt stride) && {
+    return std::move(addBinding(binding, stride));
+}
+
+MeshLayout& MeshLayout::addInstancedBinding(const UnsignedInt binding, const UnsignedInt stride, const UnsignedInt divisor) & {
     if(!_state) _state.emplace();
 
     /* Ensure order for efficient comparisons */
@@ -221,7 +225,11 @@ MeshLayout& MeshLayout::addInstancedBinding(const UnsignedInt binding, const Uns
     return *this;
 }
 
-MeshLayout& MeshLayout::addAttribute(const UnsignedInt location, const UnsignedInt binding, const VertexFormat format, const UnsignedInt offset) {
+MeshLayout&& MeshLayout::addInstancedBinding(const UnsignedInt binding, const UnsignedInt stride, const UnsignedInt divisor) && {
+    return std::move(addInstancedBinding(binding, stride, divisor));
+}
+
+MeshLayout& MeshLayout::addAttribute(const UnsignedInt location, const UnsignedInt binding, const VertexFormat format, const UnsignedInt offset) & {
     if(!_state) _state.emplace();
 
     /* Ensure order for efficient comparisons */
@@ -240,10 +248,18 @@ MeshLayout& MeshLayout::addAttribute(const UnsignedInt location, const UnsignedI
     return *this;
 }
 
-MeshLayout& MeshLayout::addAttribute(const UnsignedInt location, const UnsignedInt binding, const Magnum::VertexFormat format, const UnsignedInt offset) {
+MeshLayout&& MeshLayout::addAttribute(const UnsignedInt location, const UnsignedInt binding, const VertexFormat format, const UnsignedInt offset) && {
+    return std::move(addAttribute(location, binding, format, offset));
+}
+
+MeshLayout& MeshLayout::addAttribute(const UnsignedInt location, const UnsignedInt binding, const Magnum::VertexFormat format, const UnsignedInt offset) & {
     return addAttribute(location, binding, vertexFormat(format), offset);
 }
 
+MeshLayout&& MeshLayout::addAttribute(const UnsignedInt location, const UnsignedInt binding, const Magnum::VertexFormat format, const UnsignedInt offset) && {
+    return std::move(addAttribute(location, binding, format, offset));
+}
+
 Debug& operator<<(Debug& debug, const MeshPrimitive value) {
     debug << "Vk::MeshPrimitive" << Debug::nospace;
 

src/Magnum/Vk/MeshLayout.h

@@ -307,7 +307,9 @@ class MAGNUM_VK_EXPORT MeshLayout {
          *
          * @see @ref addInstancedBinding()
          */
-        MeshLayout& addBinding(UnsignedInt binding, UnsignedInt stride);
+        MeshLayout& addBinding(UnsignedInt binding, UnsignedInt stride) &;
+        /** @overload */
+        MeshLayout&& addBinding(UnsignedInt binding, UnsignedInt stride) &&;
 
         /**
          * @brief Add an instanced buffer binding
@@ -344,7 +346,9 @@ class MAGNUM_VK_EXPORT MeshLayout {
          * @requires_vk_feature @ref DeviceFeature::VertexAttributeInstanceRateZeroDivisor
          *      if @p divisor is `0`
          */
-        MeshLayout& addInstancedBinding(UnsignedInt binding, UnsignedInt stride, UnsignedInt divisor = 1);
+        MeshLayout& addInstancedBinding(UnsignedInt binding, UnsignedInt stride, UnsignedInt divisor = 1) &;
+        /** @overload */
+        MeshLayout&& addInstancedBinding(UnsignedInt binding, UnsignedInt stride, UnsignedInt divisor = 1) &&;
 
         /**
          * @brief Add an attribute
@@ -368,9 +372,13 @@ class MAGNUM_VK_EXPORT MeshLayout {
          * -    `format`
          * -    `offset`
          */
-        MeshLayout& addAttribute(UnsignedInt location, UnsignedInt binding, VertexFormat format, UnsignedInt offset);
+        MeshLayout& addAttribute(UnsignedInt location, UnsignedInt binding, VertexFormat format, UnsignedInt offset) &;
+        /** @overload */
+        MeshLayout&& addAttribute(UnsignedInt location, UnsignedInt binding, VertexFormat format, UnsignedInt offset) &&;
+        /** @overload */
+        MeshLayout& addAttribute(UnsignedInt location, UnsignedInt binding, Magnum::VertexFormat format, UnsignedInt offset) &;
         /** @overload */
-        MeshLayout& addAttribute(UnsignedInt location, UnsignedInt binding, Magnum::VertexFormat format, UnsignedInt offset);
+        MeshLayout&& addAttribute(UnsignedInt location, UnsignedInt binding, Magnum::VertexFormat format, UnsignedInt offset) &&;
 
         /** @brief Underlying @type_vk{PipelineVertexInputStateCreateInfo} structure */
         VkPipelineVertexInputStateCreateInfo& vkPipelineVertexInputStateCreateInfo() {

src/Magnum/Vk/Test/MeshLayoutTest.cpp

@@ -57,6 +57,8 @@ struct MeshLayoutTest: TestSuite::Tester {
     template<class T> void addAttribute();
     void addAttributeWrongOrder();
 
+    void rvalue();
+
     void compare();
     void compareExternalPointers();
 
@@ -84,6 +86,8 @@ MeshLayoutTest::MeshLayoutTest() {
               &MeshLayoutTest::addAttribute<Magnum::VertexFormat>,
               &MeshLayoutTest::addAttributeWrongOrder,
 
+              &MeshLayoutTest::rvalue,
+
               &MeshLayoutTest::compare,
               &MeshLayoutTest::compareExternalPointers,
 
@@ -383,6 +387,19 @@ void MeshLayoutTest::addAttributeWrongOrder() {
         "Vk::MeshLayout::addAttribute(): location 5 can't be ordered after 5\n");
 }
 
+void MeshLayoutTest::rvalue() {
+    MeshLayout&& layout = MeshLayout{MeshPrimitive::TriangleFan}
+        .addBinding(0, 37)
+        .addInstancedBinding(1, 26)
+        .addAttribute(0, 0, VertexFormat{}, 0)
+        .addAttribute(1, 1, Magnum::VertexFormat::Vector2, 0);
+
+    /* Just to test something, main point is that the above compiles, links and
+       returns a &&. Can't test anything related to the contents because the
+       destructor gets called at the end of the expression. */
+    CORRADE_VERIFY(&layout);
+}
+
 void MeshLayoutTest::compare() {
     MeshLayout emptyTriangles1{MeshPrimitive::Triangles};
     MeshLayout emptyTriangles2{MeshPrimitive::Triangles};