bors 76fbb35831 Auto merge of #21079 - huonw:chained-cmp-tweaks, r=pnkfelix
First commit is mindless groundwork for the second one, to make the spans (arguably) nicer.

### before

```
require-parens-for-chained-comparison.rs:14:20: 14:22 error: Chained comparison operators require parentheses
require-parens-for-chained-comparison.rs:14     false == false == false;
                                                               ^~
require-parens-for-chained-comparison.rs:17:16: 17:17 error: Chained comparison operators require parentheses
require-parens-for-chained-comparison.rs:17     false == 0 < 2;
                                                           ^
require-parens-for-chained-comparison.rs:20:8: 20:9 error: Chained comparison operators require parentheses
require-parens-for-chained-comparison.rs:20     f<X>();
                                                   ^
require-parens-for-chained-comparison.rs:20:8: 20:9 help: Use ::< instead of < if you meant to specify type arguments.
require-parens-for-chained-comparison.rs:20     f<X>();
                                                   ^
```

### after

```
require-parens-for-chained-comparison.rs:14:11: 14:22 error: chained comparison operators require parentheses
require-parens-for-chained-comparison.rs:14     false == false == false;
                                                      ^~~~~~~~~~~
require-parens-for-chained-comparison.rs:17:11: 17:17 error: chained comparison operators require parentheses
require-parens-for-chained-comparison.rs:17     false == 0 < 2;
                                                      ^~~~~~
require-parens-for-chained-comparison.rs:20:6: 20:9 error: chained comparison operators require parentheses
require-parens-for-chained-comparison.rs:20     f<X>();
                                                 ^~~
require-parens-for-chained-comparison.rs:20:6: 20:9 help: use `::<...>` instead of `<...>` if you meant to specify type arguments
require-parens-for-chained-comparison.rs:20     f<X>();
                                                 ^~~
```
2015-01-24 17:07:43 +00:00
..
2015-01-18 19:43:44 -08:00