Merge dev15.7-preview1 to dev15.7.x

src/EditorFeatures/CSharpTest/UsePatternMatching/CSharpAsAndNullCheckTests.cs

@@ -114,6 +114,20 @@ void M()
 }");
         }
 
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsInlineTypeCheck)]
+        [WorkItem(25237, "https://github.com/dotnet/roslyn/issues/25237")]
+        public async Task TestMissingOnReturnStatement()
+        {
+            await TestMissingInRegularAndScriptAsync(
+@"class C
+{
+    void M()
+    {
+        [|return;|]
+    }
+}");
+        }
+
         [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsInlineTypeCheck)]
         public async Task TestMissingOnIsExpression()
         {

src/Features/CSharp/Portable/UsePatternMatching/CSharpAsAndNullCheckDiagnosticAnalyzer.cs

@@ -413,6 +413,11 @@ private static SyntaxNode GetLeftmostCondition(SyntaxNode node)
         {
             while (true)
             {
+                if (node == null)
+                {
+                    return null;
+                }
+
                 switch (node.Kind())
                 {
                     case SyntaxKind.WhileStatement:
@@ -428,13 +433,7 @@ private static SyntaxNode GetLeftmostCondition(SyntaxNode node)
                         var declarators = ((LocalDeclarationStatementSyntax)node).Declaration.Variables;
                         // We require this to be the only declarator in the declaration statement
                         // to simplify definitive assignment check and the code fix for now
-                        var value = declarators.Count == 1 ? declarators[0].Initializer?.Value : null;
-                        if (value == null)
-                        {
-                            return null;
-                        }
-
-                        node = value;
+                        node = declarators.Count == 1 ? declarators[0].Initializer?.Value : null;
                         continue;
                     case SyntaxKind.ParenthesizedExpression:
                         node = ((ParenthesizedExpressionSyntax)node).Expression;