Fix S1168: FP with local function

[andrei-epure-sonarsource]

Description

csharpsquid:S1168 (Empty arrays and collections should be returned instead of null) raises an issue when the returned type is not a collection/array, but the roslyn IArrayTypeSymbol.

Repro steps

1. Create a method that returns IEnumerable and returns a not-null result
2. Inside this method, create a local function that returns a non-enumerable type
3. Return null inside the local function

private IEnumerable<Instruction> Foo()
{
  var instructions = new List<Instruction>();
  // some logic
  return instructions;

  IArrayTypeSymbol LocalBar(SyntaxNode parent)
  {
    return null; // FP
  }
}

Expected behavior

Should not raise issue.

Actual behavior

csharpsquid:S1168 "Return an empty collection instead of null."

Related information

• SonarC# Version "7.9 (build 7566)"