Avoid underflow in render_source_line
While testing rust-lang/rust#47655 I was able to make the compiler panic when it's compiled with debug assertions:
```shell
> rustc /dev/null --crate-type proc-macro
error: internal compiler error: unexpected panic
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports
note: rustc 1.25.0-dev running on x86_64-apple-darwin
note: run with `RUST_BACKTRACE=1` for a backtrace
thread 'rustc' panicked at 'attempt to subtract with overflow', librustc_errors/emitter.rs:287:49
```
Without debug assertions the following warning is emitted:
```shell
> rustc /dev/null --crate-type proc-macro
warning: unused variable: `registrar`
--> /dev/null:0:1
|
|
= note: #[warn(unused_variables)] on by default
= note: to avoid this warning, consider using `_registrar` instead
```
The panic is due to the unused variable warning being spanned to `/dev/null:0:1`. When `render_source_line` subtracts 1 from the line number to look up the source line it panics due to underflow. Without debug assertions this would wrap and cause us to return a blank string instead.
Fix by explicitly testing for 0 and exiting early. I'm unsure how to automatically test this now that rust-lang/rust#46655 has been approved.
Add line numbers and columns to error messages spanning multiple files
If an error message is emitted that spans several files, only the
primary file currently has line and column data attached. This is
useful information, even in files other than the one in which the error
occurs. We can often work out which line and column the error
corresponds to in other files — in this case it is helpful to add them
(in the case of ambiguity, the first relevant line/column is picked,
which is still helpful than none).
If an error message is emitted that spans several files, only the
primary file currently has line and column data attached. This is
useful information, even in files other than the one in which the error
occurs. We can often work out which line and column the error
corresponds to in other files — in this case it is helpful to add them
(in the case of ambiguity, the first relevant line/column is picked,
which is still helpful than none).
While testing rust-lang/rust#47655 I was able to make the compiler panic
when it's compiled with debug assertions:
```shell
> rustc /dev/null --crate-type proc-macro
error: internal compiler error: unexpected panic
note: the compiler unexpectedly panicked. this is a bug.
note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports
note: rustc 1.25.0-dev running on x86_64-apple-darwin
note: run with `RUST_BACKTRACE=1` for a backtrace
thread 'rustc' panicked at 'attempt to subtract with overflow', librustc_errors/emitter.rs:287:49
```
Without debug assertions the following warning is emitted:
```shell
> rustc /dev/null --crate-type proc-macro
warning: unused variable: `registrar`
--> /dev/null:0:1
|
|
= note: #[warn(unused_variables)] on by default
= note: to avoid this warning, consider using `_registrar` instead
```
The panic is due to the unused variable warning being spanned to
`/dev/null:0:1`. When `render_source_line` subtracts 1 from the line
number to look up the source line it panics due to underflow. Without
debug assertions this would wrap and cause us to return a blank string
instead.
Fix by explicitly testing for 0 and exiting early. I'm unsure how to
automatically test this now that rust-lang/rust#46655 has been approved.
fix mispositioned span
This fixes#47377
The output now looks like this
```
error[E0369]: binary operation `+` cannot be applied to type `&str`
--> h.rs:3:11
|
3 | let _a = b + ", World!";
| ^^^^^^^^^^^^^^ `+` can't be used to concatenate two `&str` strings
help: `to_owned()` can be used to create an owned `String` from a string reference. String concatenation appends the string on the right to the string on the left and may require reallocation. This requires ownership of the string on the left
|
3 | let _a = b.to_owned() + ", World!";
| ^^^^^^^^^
error: aborting due to previous error
```
For the case when emojis are involved, it gives the new output for proper indentation.
But for an indentation as follows,
```
fn main() {
let b = "hello";
let _a = b + ", World!";
}
```
it still mispositions the span
```
3 | println!("🦀🦀🦀🦀🦀"); let _a = b + ", World!";
| ^^^^^^^^^^^^^^ `+` can't be used to concatenate two `&str` strings
|
3 | println!("🦀🦀🦀🦀🦀"); let _a = b.to_owned() + ", World!";
| ^^^^^^^
error: aborting due to previous erro
```
cc @estebank @est31
Refactor internal suggestion API
~~The only functional change is that whitespace, which is suggested to be added, also gets `^^^^` under it. An example is shown in the tests (the only test that changed).~~
Continuation of #41876
r? @nagisa
the changes are probably best viewed [without whitespace](https://github.com/rust-lang/rust/pull/45741/files?w=1)
Fixes#44078. Fixes#44023.
The start_col member is given in chars,
while the code previously assumed it was given in bytes.
The more basic issue #44080 doesn't get fixed.
Point at `:` when using it instead of `;`
When triggering type ascription in such a way that we can infer a
statement end was intended, add a suggestion for the change. Always
point out the reason for the expectation of a type is due to type
ascription.
Fix#42057, #41928.
Now there's a way to add suggestions that hide the suggested code when
presented inline, to avoid weird wording when short code snippets are
added at the end.
