Squashed 'third_party/GSL/' content from commit 0cebbd7

Change-Id: Iffb2e32f2f45297ac6d3e82168cd9df4ac5acc2f
git-subtree-dir: third_party/GSL
git-subtree-split: 0cebbd77bfc21acbf1cc05983ad626539eeeb8e0
diff --git a/GSL.natvis b/GSL.natvis
new file mode 100644
index 0000000..a467a17
--- /dev/null
+++ b/GSL.natvis
@@ -0,0 +1,98 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- 
+    This will make GitHub and some editors recognize this code as XML: 
+    vim: syntax=xml
+-->
+<AutoVisualizer xmlns="http://schemas.microsoft.com/vstudio/debugger/natvis/2010">
+    <!-- These types are from the gsl_assert header. -->
+    <Type Name="gsl::fail_fast">
+        <!-- na hides the address, otherwise it would appear as 0x.... "Message" -->
+        <DisplayString>{_Data._What,nasb}</DisplayString>
+    </Type>
+
+    <!-- These types are from the gsl_util header. -->
+    <Type Name="gsl::final_action&lt;*&gt;">
+        <DisplayString>{{ invoke = {invoke_}, action = {f_} }}</DisplayString>
+        <Expand>
+            <Item Name="[invoke]">invoke_</Item>
+            <Item Name="[callback]">f_</Item>
+        </Expand>
+    </Type>
+
+    <!-- These types are from the span header. -->
+    <!-- This is for dynamic_extent spans. -->
+    <Type Name="gsl::span&lt;*, -1&gt;">
+        <DisplayString>{{ extent = {storage_.size_} }}</DisplayString>
+        <Expand>
+            <ArrayItems>
+                <Size>storage_.size_</Size>
+                <ValuePointer>storage_.data_</ValuePointer>
+            </ArrayItems>
+        </Expand>
+    </Type>
+
+    <!-- This works for constexpr size spans. -->
+    <Type Name="gsl::span&lt;*, *&gt;">
+        <DisplayString>{{ extent = {extent} }}</DisplayString>
+        <Expand>
+            <ArrayItems>
+                <Size>extent</Size>
+                <ValuePointer>storage_.data_</ValuePointer>
+            </ArrayItems>
+        </Expand>
+    </Type>
+
+    <!-- This is for dynamic_extent string_spans. -->
+    <Type Name="gsl::basic_string_span&lt;*, -1&gt;">
+        <DisplayString>{span_.storage_.data_,[span_.storage_.size_]na}</DisplayString>
+        <Expand>
+            <Item Name="[size]">span_.storage_.size_</Item>
+            <ArrayItems>
+                <Size>span_.storage_.size_</Size>
+                <ValuePointer>span_.storage_.data_</ValuePointer>
+            </ArrayItems>
+        </Expand>
+    </Type>
+
+    <!-- This works for constexpr size string_spans. -->
+    <Type Name="gsl::basic_string_span&lt;*, *&gt;">
+        <DisplayString>{span_.storage_.data_,[span_.extent]na}</DisplayString>
+        <Expand>
+            <Item Name="[size]">span_.extent</Item>
+            <ArrayItems>
+                <Size>span_.extent</Size>
+                <ValuePointer>span_.storage_.data_</ValuePointer>
+            </ArrayItems>
+        </Expand>
+    </Type>
+
+    <!-- This is for dynamic_extent zstring_spans. -->
+    <Type Name="gsl::basic_zstring_span&lt;*, -1&gt;">
+        <DisplayString>{span_.storage_.data_,[span_.storage_.size_]na}</DisplayString>
+        <Expand>
+            <Item Name="[size]">span_.storage_.size_</Item>
+            <ArrayItems>
+                <Size>span_.storage_.size_</Size>
+                <ValuePointer>span_.storage_.data_</ValuePointer>
+            </ArrayItems>
+        </Expand>
+    </Type>
+    
+    <!-- This works for constexpr size string_spans. -->
+    <Type Name="gsl::basic_zstring_span&lt;*, *&gt;">
+        <DisplayString>{span_.storage_.data_,[span_.extent]na}</DisplayString>
+        <Expand>
+            <Item Name="[size]">span_.extent</Item>
+            <ArrayItems>
+                <Size>span_.extent</Size>
+                <ValuePointer>span_.storage_.data_</ValuePointer>
+            </ArrayItems>
+        </Expand>
+    </Type>
+    
+    <!-- These types are from the gsl header. -->
+    <Type Name="gsl::not_null&lt;*&gt;">
+        <!-- We can always dereference this since it's an invariant. -->
+        <DisplayString>value = {*ptr_}</DisplayString>
+    </Type>
+</AutoVisualizer>