During my ongoing work on DotNetAnalyzers/StyleCopAnalyzers#261, I noticed a potential problem with CommonFormattingHelpers.IsFirstTokenOnLine.

Consider the following code:

int x = Foo(a
, b);

In this case, IsFirstTokenOnLine returns true for the , token. However, if the input is modified to the following:

int x = Foo(a // a comment
, b);

The code returns false for the , token. This occurs because non-whitespace characters appear between the , token and the preceding token a.