CalculationsShouldNotOverflow.SyntaxKindWalker reduce allocations and evaluations in the hot path

[martin-strecker-sonarsource]

There are two things wrong with the walker:

sonar-dotnet/analyzers/src/SonarAnalyzer.CSharp/SymbolicExecution/Roslyn/CalculationsShouldNotOverflow.cs

Lines 50 to 65 in ba33020

	if (!IsUnchecked && !HasOverflow)
	{
	IsUnchecked = node.IsAnyKind(SyntaxKind.UncheckedStatement, SyntaxKind.UncheckedExpression);
	HasOverflow = node.IsAnyKind(
	SyntaxKind.AddExpression,
	SyntaxKind.AddAssignmentExpression,
	SyntaxKind.MultiplyExpression,
	SyntaxKind.MultiplyAssignmentExpression,
	SyntaxKind.SubtractExpression,
	SyntaxKind.SubtractAssignmentExpression,
	SyntaxKind.PostDecrementExpression,
	SyntaxKind.PostIncrementExpression,
	SyntaxKind.PreDecrementExpression,
	SyntaxKind.PreIncrementExpression);
	base.Visit(node);
	}

Flawed logic

IsUnchecked is reset too early here/at the wrong position or the IsUnchecked field is not needed at all. It should be reset after the unchecked block more like so:

        public override void Visit(SyntaxNode node)
        {
            if (!IsUnchecked && !HasOverflow)
            {
                HasOverflow = node.IsAnyKind(
                    SyntaxKind.AddExpression,
                    SyntaxKind.AddAssignmentExpression,
                    SyntaxKind.MultiplyExpression,
                    SyntaxKind.MultiplyAssignmentExpression,
                    SyntaxKind.SubtractExpression,
                    SyntaxKind.SubtractAssignmentExpression,
                    SyntaxKind.PostDecrementExpression,
                    SyntaxKind.PostIncrementExpression,
                    SyntaxKind.PreDecrementExpression,
                    SyntaxKind.PreIncrementExpression);
                base.Visit(node);
            }
        }

        public override void VisitCheckedExpression(CheckedExpressionSyntax node) // same for VisitCheckedStatement
        {
            IsUnchecked = node.IsKind(SyntaxKind.UncheckedExpression); // or dont' call base.VisitCheckedExpression
            base.VisitCheckedExpression(node);
            IsUnchecked = false; // this should actually be [CompilationOptions.CheckOverflow](https://learn.microsoft.com/en-us/dotnet/api/microsoft.codeanalysis.compilationoptions.checkoverflow?view=roslyn-dotnet-4.6.0)
        }

Nested checked/unchecked blocks are potentially wrong (for this to work, IsUnchecked must be a counter).

Array allocation in the hot path

Visit is performance-sensitive and allocates a params array on each invocation. The IsAnyKind should be replaced by a node.Kind() is SyntaxKind.AddExpression or SyntaxKind.AddAssignmentExpression or ... expression:

Also affected:

• SonarAnalyzer.SymbolicExecution.Roslyn.RuleChecks.CSharp.ConditionEvaluatesToConstant+SyntaxKindWalker.Visit
•  SonarAnalyzer.SymbolicExecution.Roslyn.RuleChecks.CSharp.NullPointerDereference+SyntaxKindWalker.Visit