Fix 2024 edition doctest panic output
Fixes#137970.
The problem was that the output was actually displayed by rustc itself because we're exiting with `Result<(), String>`, and the display is really not great. So instead, we get the output, we print it and then we return an `ExitCode`.
r? ````@aDotInTheVoid````
Greatly simplify doctest parsing and information extraction
The original process was pretty terrible, as it tried to extract information such as attributes by performing matches over tokens like `#!`, which doesn't work very well considering you can have `# ! [`, which is valid.
Also, it now does it in one pass: if the parser is happy, then we try to extract information, otherwise we return early.
r? `@fmease`
This prevents the included test case from getting at nightly-only
features when run on stable. The harness builds with
RUSTC_BOOTSTRAP, but the bundle doesn't.
rustdoc: make doctest span tweak a 2024 edition change
Fixes#132203
This is a compatibility hack, because I think the new behavior is better. When an A `include_str!` B, and B `include_str!` C, the path to C should be resolved relative to B, not A. That's how `include!` itself works, so that's how `include_str!` with should work.
rustdoc: Remove usage of `allow(unused)` attribute on `no_run` merged doctests
Fixes [#130681](https://github.com/rust-lang/rust/issues/130681).
It fixes the behaviour difference with the current doctests.
r? ``@notriddle``
Fixes#132203
This is a compatibility hack, because I think the new behavior is better.
When an A `include_str!` B, and B `include_str!` C, the path to C should
be resolved relative to B, not A. That's how `include!` itself works,
so that's how `include_str!` with should work.
No longer track "zero-width" chars in `SourceMap`, read directly from the line when calculating the `display_col` of a `BytePos`. Move `char_width` to `rustc_span` and use it from the emitter.
This change allows the following to properly align in terminals (depending on the font, the replaced control codepoints are rendered as 1 or 2 width, on my terminal they are rendered as 1, on VSCode text they are rendered as 2):
```
error: this file contains an unclosed delimiter
--> $DIR/issue-68629.rs:5:17
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LL | ␜␟ts␀