Support ForEachVariableStatement in stackalloc analyzer

src/NetAnalyzers/CSharp/Microsoft.NetCore.Analyzers/Runtime/CSharpDoNotUseStackallocInLoops.cs

@@ -38,7 +38,8 @@ public sealed override void Initialize(AnalysisContext context)
                         // foreach loops are special, in that as with other loops we don't want stackallocs
                         // in the body of the loop, but in the expression of a foreach is ok.
                         case SyntaxKind.ForEachStatement:
-                            ForEachStatementSyntax foreachStatement = (ForEachStatementSyntax)node;
+                        case SyntaxKind.ForEachVariableStatement:
+                            var foreachStatement = (CommonForEachStatementSyntax)node;
                             if (foreachStatement.Expression.Contains(ctx.Node))
                             {
                                 continue;
@@ -71,7 +72,7 @@ static bool ShouldWarn(IOperation? op, SyntaxNode node)
                                         foreach (IOperation child in block.Operations)
                                         {
                                             if (child.Syntax.SpanStart > node.SpanStart &&
-                                                (child is IReturnOperation || (child is IBranchOperation branch && branch.BranchKind == BranchKind.Break)))
+                                                (child is IReturnOperation or IBranchOperation { BranchKind: BranchKind.Break }))
                                             {
                                                 // Err on the side of false negatives / caution and say this stackalloc is ok.
                                                 // Note, too, it's possible we're breaking out of a nested loop, and the outer loop
@@ -88,7 +89,7 @@ static bool ShouldWarn(IOperation? op, SyntaxNode node)
                             }
 
                             // Warn as needed.
-                            if (ShouldWarn(ctx.SemanticModel.GetOperationWalkingUpParentChain(ctx.Node, default), ctx.Node))
+                            if (ShouldWarn(ctx.SemanticModel.GetOperationWalkingUpParentChain(ctx.Node, ctx.CancellationToken), ctx.Node))
                             {
                                 ctx.ReportDiagnostic(ctx.Node.CreateDiagnostic(Rule));
                             }

src/NetAnalyzers/UnitTests/Microsoft.NetCore.Analyzers/Runtime/DoNotUseStackallocInLoopsTests.cs

@@ -285,5 +285,26 @@ private static void SourceOfForeachLoopInAnotherLoop() {
                 }"
             }.RunAsync();
         }
+
+        [Fact]
+        public async Task Diagnostics_StackallocAsSourceOfForeachVariableLoop()
+        {
+            await new VerifyCS.Test
+            {
+                LanguageVersion = LanguageVersion.CSharp8,
+                TestCode = @"
+                using System;
+                public class C
+                {
+                    public static void Foo()
+                    {
+                        foreach (var (x, y) in stackalloc (double, double)[] { (0, 0) })
+                        {
+                            Span<byte> span = {|CA2014:stackalloc byte[1024]|};
+                        }
+                    }
+                }"
+            }.RunAsync();
+        }
     }
 }