made children not to return null and reorder children in evaluation o… (#22726)

* made children not to return null and reorder children in evaluation order

* added some verification

* fixed formatting

* fixed ordering

* removed temp variable.

src/Compilers/CSharp/Portable/Operations/CSharpOperationFactory.cs

@@ -423,7 +423,7 @@ private IEventReferenceExpression CreateBoundEventAccessOperation(BoundEventAcce
             ITypeSymbol type = boundEventAccess.Type;
             Optional<object> constantValue = ConvertToOptional(boundEventAccess.ConstantValue);
             bool isImplicit = boundEventAccess.WasCompilerGenerated;
-            return new LazyEventReferenceExpression(@event, instance,  _semanticModel, syntax, type, constantValue, isImplicit);
+            return new LazyEventReferenceExpression(@event, instance, _semanticModel, syntax, type, constantValue, isImplicit);
         }
 
         private IEventAssignmentExpression CreateBoundEventAssignmentOperatorOperation(BoundEventAssignmentOperator boundEventAssignmentOperator)
@@ -996,7 +996,7 @@ private IIncrementOrDecrementExpression CreateBoundIncrementOperatorOperation(Bo
 
         private IInvalidExpression CreateBoundBadExpressionOperation(BoundBadExpression boundBadExpression)
         {
-            Lazy<ImmutableArray<IOperation>> children = new Lazy<ImmutableArray<IOperation>>(() => boundBadExpression.ChildBoundNodes.SelectAsArray(n => Create(n)));
+            Lazy<ImmutableArray<IOperation>> children = new Lazy<ImmutableArray<IOperation>>(() => boundBadExpression.ChildBoundNodes.Select(n => Create(n)).WhereNotNull().ToImmutableArray());
             SyntaxNode syntax = boundBadExpression.Syntax;
             // We match semantic model here: if the expression IsMissing, we have a null type, rather than the ErrorType of the bound node.
             ITypeSymbol type = syntax.IsMissing ? null : boundBadExpression.Type;
@@ -1490,7 +1490,7 @@ private ILockStatement CreateBoundLockStatementOperation(BoundLockStatement boun
 
         private IInvalidStatement CreateBoundBadStatementOperation(BoundBadStatement boundBadStatement)
         {
-            Lazy<ImmutableArray<IOperation>> children = new Lazy<ImmutableArray<IOperation>>(() => boundBadStatement.ChildBoundNodes.SelectAsArray(n => Create(n)));
+            Lazy<ImmutableArray<IOperation>> children = new Lazy<ImmutableArray<IOperation>>(() => boundBadStatement.ChildBoundNodes.Select(n => Create(n)).WhereNotNull().ToImmutableArray());
             SyntaxNode syntax = boundBadStatement.Syntax;
             ITypeSymbol type = null;
             Optional<object> constantValue = default(Optional<object>);

src/Compilers/VisualBasic/Portable/Operations/VisualBasicOperationFactory.vb

@@ -502,7 +502,8 @@ Namespace Microsoft.CodeAnalysis.Semantics
         End Function
 
         Private Function CreateBoundBadExpressionOperation(boundBadExpression As BoundBadExpression) As IInvalidExpression
-            Dim children As Lazy(Of ImmutableArray(Of IOperation)) = New Lazy(Of ImmutableArray(Of IOperation))(Function() boundBadExpression.ChildBoundNodes.SelectAsArray(Function(n) Create(n)))
+            Dim children As Lazy(Of ImmutableArray(Of IOperation)) = New Lazy(Of ImmutableArray(Of IOperation))(
+                Function() boundBadExpression.ChildBoundNodes.Select(Function(n) Create(n)).WhereNotNull().ToImmutableArray())
             Dim syntax As SyntaxNode = boundBadExpression.Syntax
             ' We match semantic model here: If the Then expression IsMissing, we have a null type, rather than the ErrorType Of the bound node.
             Dim type As ITypeSymbol = If(syntax.IsMissing, Nothing, boundBadExpression.Type)

src/Test/Utilities/Portable/Compilation/OperationTreeVerifier.cs

@@ -326,7 +326,9 @@ internal void VisitRefKindArrayElement(RefKind element)
 
         private void VisitChildren(IOperation operation)
         {
-            var children = operation.Children.WhereNotNull().ToImmutableArray();
+            Debug.Assert(operation.Children.All(o => o != null));
+
+            var children = operation.Children.ToImmutableArray();
             if (!children.IsEmpty || operation.Kind != OperationKind.None)
             {
                 VisitArray(children, "Children", logElementCount: true);
@@ -1315,7 +1317,7 @@ public override void VisitDynamicMemberReferenceExpression(IDynamicMemberReferen
             LogString(")");
             LogCommonPropertiesAndNewLine(operation);
 
-            VisitArrayCommon(operation.TypeArguments, "Type Arguments", logElementCount: true,logNullForDefault: false, arrayElementVisitor: VisitSymbolArrayElement);
+            VisitArrayCommon(operation.TypeArguments, "Type Arguments", logElementCount: true, logNullForDefault: false, arrayElementVisitor: VisitSymbolArrayElement);
 
             VisitInstanceExpression(operation.Instance);
         }