[parse.tentative.html]
  [Parsing an invalid string throws SyntaxError]
    expected: FAIL

  [Parsing a string with a non numeric token throws SyntaxError]
    expected: FAIL

  [Parsing a string with left over numeric tokens throws SyntaxError]
    expected: FAIL

  [Parsing a calc with incompatible units throws a SyntaxError]
    expected: FAIL

  [Parsing ignores surrounding spaces]
    expected: FAIL

