New rule: If expressions should not be too complex

[fourls]

Prerequisites

• This rule has not already been suggested.
• This should be a new rule, not an improvement to an existing rule.
• This rule would be generally useful, not specific to my code or setup.

Suggested rule title

If expressions should not be too complex

Rule description

Similar to the existing RoutineNestingDepth and TooManyNestedRoutines rules, this rule would catch if expressions that are unclear due to their size. This could be measured in a few ways, e.g.:

• Sum length of the guard, then, or else expressions
• Number of lines the entire expression covers
• Number of nested if expressions
• Whether anonymous methods are present
• etc.

Rationale

Keeping ternary use limited makes code more readable and less prone to errors.