Fix multiple labels when some don't have message
The diagnostic emitter now accounts for labels with no text message, presenting the underline on its own, without drawing the line for the non existing message below it. Go from
```
error: foo
--> test.rs:3:6
|
3 | a { b { c } d }
| ----^^^^^^^----
| | |
| | `b` is a good letter
|
```
to
```
error: foo
--> test.rs:3:6
|
3 | a { b { c } d }
| ----^^^^^^^----
| |
| `b` is a good letter
```
from
```
error: foo
--> test.rs:3:6
|
3 | a { b { c } d }
| ^^^^-------^^^^
| | |
| |
| `a` is a good letter
```
to
```
error: foo
--> test.rs:3:6
|
3 | a { b { c } d }
| ^^^^-------^^^^ `a` is a good letter
```
and from
```
error: foo
--> test.rs:3:6
|
3 | a { b { c } d }
| ^^^^-------^^^^
| | |
| |
|
```
to
```
error: foo
--> test.rs:3:6
|
3 | a { b { c } d }
| ^^^^-------^^^^
```
r? @nikomatsakis
cc @jonathandturner, @GuillaumeGomez, @nrc
The diagnostic emitter now accounts for labels with no text message,
presenting the underline on its own, without drawing the line for the
non existing message below it. Go from
```
error: foo
--> test.rs:3:6
|
3 | a { b { c } d }
| ----^^^^^^^----
| | |
| | `b` is a good letter
|
```
to
```
error: foo
--> test.rs:3:6
|
3 | a { b { c } d }
| ----^^^^^^^----
| |
| `b` is a good letter
```
and from
```
error: foo
--> test.rs:3:6
|
3 | a { b { c } d }
| ^^^^-------^^^^
| | |
| |
| `a` is a good letter
```
to
```
error: foo
--> test.rs:3:6
|
3 | a { b { c } d }
| ^^^^-------^^^^ `a` is a good letter
```
When dealing with multiline spans that span few lines, show the complete
span instead of restricting to the first character of the first line.
For example, instead of:
```
% ./rustc foo.rs
error[E0277]: the trait bound `{integer}: std::ops::Add<()>` is not satisfied
--> foo.rs:13:9
|
13 | foo(1 + bar(x,
| ^ trait `{integer}: std::ops::Add<()>` not satisfied
|
```
show
```
% ./rustc foo.rs
error[E0277]: the trait bound `{integer}: std::ops::Add<()>` is not satisfied
--> foo.rs:13:9
|
13 | foo(1 + bar(x,
| ________^ starting here...
14 | | y),
| |_____________^ ...ending here: trait `{integer}: std::ops::Add<()>` not satisfied
|
```
