fails:String#concat concatenates the given argument to self and returns self
fails:String#concat converts the given argument to a String using to_str
fails:String#concat raises a TypeError if the given argument can't be converted to a String
fails:String#concat raises a RuntimeError when self is frozen
fails:String#concat works when given a subclass instance
fails:String#concat taints self if other is tainted
fails:String#concat untrusts self if other is untrusted
fails:String#concat with Integer concatencates the argument interpreted as a codepoint
fails:String#concat with Integer returns a ASCII-8BIT string if self is US-ASCII and the argument is between 128-255 (inclusive)
fails:String#concat with Integer raises RangeError if the argument is an invalid codepoint for self's encoding
fails:String#concat with Integer raises RangeError if the argument is negative
fails:String#concat with Integer doesn't call to_int on its argument
fails:String#concat with Integer raises a RuntimeError when self is frozen
fails:String#concat when self is in an ASCII-incompatible encoding incompatible with the argument's encoding uses self's encoding if both are empty
fails:String#concat when self is in an ASCII-incompatible encoding incompatible with the argument's encoding uses self's encoding if the argument is empty
fails:String#concat when self is in an ASCII-incompatible encoding incompatible with the argument's encoding uses the argument's encoding if self is empty
fails:String#concat when self is in an ASCII-incompatible encoding incompatible with the argument's encoding raises Encoding::CompatibilityError if neither are empty
fails:String#concat when the argument is in an ASCII-incompatible encoding incompatible with self's encoding uses self's encoding if both are empty
fails:String#concat when the argument is in an ASCII-incompatible encoding incompatible with self's encoding uses self's encoding if the argument is empty
fails:String#concat when the argument is in an ASCII-incompatible encoding incompatible with self's encoding uses the argument's encoding if self is empty
fails:String#concat when the argument is in an ASCII-incompatible encoding incompatible with self's encoding raises Encoding::CompatibilityError if neither are empty
fails:String#concat when self and the argument are in different ASCII-compatible encodings uses self's encoding if both are ASCII-only
fails:String#concat when self and the argument are in different ASCII-compatible encodings uses self's encoding if the argument is ASCII-only
fails:String#concat when self and the argument are in different ASCII-compatible encodings uses the argument's encoding if self is ASCII-only
fails:String#concat when self and the argument are in different ASCII-compatible encodings raises Encoding::CompatibilityError if neither are ASCII-only
fails:String#concat when self is ASCII-8BIT and argument is US-ASCII uses ASCII-8BIT encoding
