Use stackalloc directly into Span (#24212)

* Use stackalloc directly into Span

We have a few places in corefx where we were stackalloc'ing into a temporary pointer and then creating a Span from that.  Now that we're using a C# compiler which supports stackalloc'ing directly into span, use that feature instead.

* Address PR feedback

1 files changed, 3 insertions, 2 deletions

diff --git a/dir.props b/dir.props
index 5c90cfc83c..b75dec9297 100644
--- a/dir.props
+++ b/dir.props
@@ -209,9 +209,10 @@
     <GenerateTargetFrameworkAttribute>false</GenerateTargetFrameworkAttribute>
     <CopyNuGetImplementations>false</CopyNuGetImplementations>
   </PropertyGroup>
-
-  <!-- Set up handling of build warnings -->
+  
+  <!-- Language configuration -->
   <PropertyGroup>
+    <LangVersion>latest</LangVersion> <!-- default to allowing all language features -->
     <WarningLevel>4</WarningLevel>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
   </PropertyGroup>