Auto merge of #126597 - estebank:unicode-output, r=fmease

Add Unicode block-drawing compiler output support

Add nightly-only theming support to rustc output using Unicode box
drawing characters instead of ASCII-art to draw the terminal UI.

In order to enable, the flags `-Zunstable-options=yes --error-format=human-unicode` must be passed in.

After:

```
error: foo
  ╭▸ test.rs:3:3
  │
3 │       X0 Y0 Z0
  │   ┌───╿──│──┘
  │  ┌│───│──┘
  │ ┏││━━━┙
  │ ┃││
4 │ ┃││   X1 Y1 Z1
5 │ ┃││   X2 Y2 Z2
  │ ┃│└────╿──│──┘ `Z` label
  │ ┃└─────│──┤
  │ ┗━━━━━━┥  `Y` is a good letter too
  │        `X` is a good letter
  ╰╴
note: bar
  ╭▸ test.rs:4:3
  │
4 │ ┏   X1 Y1 Z1
5 │ ┃   X2 Y2 Z2
6 │ ┃   X3 Y3 Z3
  │ ┗━━━━━━━━━━┛
  ├ note: bar
  ╰ note: baz
note: qux
  ╭▸ test.rs:4:3
  │
4 │   X1 Y1 Z1
  ╰╴  ━━━━━━━━
```

Before:

```
error: foo
 --> test.rs:3:3
  |
3 |       X0 Y0 Z0
  |    ___^__-__-
  |   |___|__|
  |  ||___|
  | |||
4 | |||   X1 Y1 Z1
5 | |||   X2 Y2 Z2
  | |||____^__-__- `Z` label
  | ||_____|__|
  | |______|  `Y` is a good letter too
  |        `X` is a good letter
  |
note: bar
 --> test.rs:4:3
  |
4 | /   X1 Y1 Z1
5 | |   X2 Y2 Z2
6 | |   X3 Y3 Z3
  | |__________^
  = note: bar
  = note: baz
note: qux
 --> test.rs:4:3
  |
4 |   X1 Y1 Z1
  |   ^^^^^^^^
```

After:

![rustc output with unicode box drawing characters](https://github.com/rust-lang/rust/assets/1606434/d210b79a-6579-4407-9706-ba8edc6e9f25)

Before:
![current rustc output with ASCII art](https://github.com/rust-lang/rust/assets/1606434/5aecccf8-a6ee-4469-8b39-72fb0d979a9f)

8 files changed, 41 insertions, 29 deletions

diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index 7ba3cfb66bd..d5f6bfe415d 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -6,7 +6,9 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
 use rustc_data_structures::sync::Lrc;
 use rustc_data_structures::unord::UnordSet;
 use rustc_errors::codes::*;
-use rustc_errors::emitter::{DynEmitter, HumanEmitter, stderr_destination};
+use rustc_errors::emitter::{
+    DynEmitter, HumanEmitter, HumanReadableErrorType, OutputTheme, stderr_destination,
+};
 use rustc_errors::json::JsonEmitter;
 use rustc_errors::{ErrorGuaranteed, TerminalUrl};
 use rustc_feature::UnstableFeatures;
@@ -154,6 +156,11 @@ pub(crate) fn new_dcx(
                     .teach(unstable_opts.teach)
                     .diagnostic_width(diagnostic_width)
                     .track_diagnostics(unstable_opts.track_diagnostics)
+                    .theme(if let HumanReadableErrorType::Unicode = kind {
+                        OutputTheme::Unicode
+                    } else {
+                        OutputTheme::Ascii
+                    })
                     .ui_testing(unstable_opts.ui_testing),
             )
         }
diff --git a/src/librustdoc/doctest.rs b/src/librustdoc/doctest.rs
index 11d8f1947d6..25e576e9e63 100644
--- a/src/librustdoc/doctest.rs
+++ b/src/librustdoc/doctest.rs
@@ -15,6 +15,7 @@ pub(crate) use make::DocTestBuilder;
 pub(crate) use markdown::test as test_markdown;
 use rustc_ast as ast;
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap, FxIndexSet};
+use rustc_errors::emitter::HumanReadableErrorType;
 use rustc_errors::{ColorConfig, DiagCtxtHandle, ErrorGuaranteed, FatalError};
 use rustc_hir::CRATE_HIR_ID;
 use rustc_hir::def_id::LOCAL_CRATE;
@@ -520,10 +521,14 @@ fn run_test(
     });
     if let ErrorOutputType::HumanReadable(kind, color_config) = rustdoc_options.error_format {
         let short = kind.short();
+        let unicode = kind == HumanReadableErrorType::Unicode;
 
         if short {
             compiler.arg("--error-format").arg("short");
         }
+        if unicode {
+            compiler.arg("--error-format").arg("human-unicode");
+        }
 
         match color_config {
             ColorConfig::Never => {
diff --git a/src/tools/clippy/tests/ui/empty_line_after/doc_comments.stderr b/src/tools/clippy/tests/ui/empty_line_after/doc_comments.stderr
index c238b4c9a17..2852e26680f 100644
--- a/src/tools/clippy/tests/ui/empty_line_after/doc_comments.stderr
+++ b/src/tools/clippy/tests/ui/empty_line_after/doc_comments.stderr
@@ -3,7 +3,7 @@ error: empty line after doc comment
    |
 LL | / /// for the crate
 LL | |
-   | |_
+   | |_^
 LL |   fn first_in_crate() {}
    |   ------------------- the comment documents this function
    |
@@ -22,7 +22,7 @@ error: empty line after doc comment
    |
 LL | /     /// for the module
 LL | |
-   | |_
+   | |_^
 LL |       fn first_in_module() {}
    |       -------------------- the comment documents this function
    |
@@ -39,7 +39,7 @@ error: empty line after doc comment
    |
 LL | /     /// # Indented
 LL | |
-   | |_
+   | |_^
 LL |       /// Blank line
 LL |       fn indented() {}
    |       ------------- the comment documents this function
@@ -55,7 +55,7 @@ error: empty line after doc comment
    |
 LL | / /// This should produce a warning
 LL | |
-   | |_
+   | |_^
 LL |   fn with_doc_and_newline() {}
    |   ------------------------- the comment documents this function
    |
@@ -69,7 +69,7 @@ LL | |
 LL | | /** This is also a doc comment and is part of the warning
 LL | |  */
 LL | |
-   | |_
+   | |_^
 ...
 LL |   fn three_attributes() {}
    |   --------------------- the comment documents this function
@@ -82,7 +82,7 @@ error: empty line after doc comment
 LL | /     /// docs for `old_code`
 LL | |     // fn old_code() {}
 LL | |
-   | |_
+   | |_^
 LL |       fn new_code() {}
    |       ------------- the comment documents this function
    |
@@ -102,7 +102,7 @@ LL | |     /// Docs
 LL | |     /// for OldB
 LL | |     // struct OldB;
 LL | |
-   | |_
+   | |_^
 ...
 LL |       struct Multiple;
    |       --------------- the comment documents this struct
@@ -125,7 +125,7 @@ LL | /     /**
 LL | |      * Meant to be inner doc comment
 LL | |      */
 LL | |
-   | |_
+   | |_^
 LL |       fn first_in_module() {}
    |       -------------------- the comment documents this function
    |
@@ -143,7 +143,7 @@ LL | |      * Docs for `old_code`
 LL | |      */
 LL | |     /* fn old_code() {} */
 LL | |
-   | |_
+   | |_^
 ...
 LL |       fn new_code() {}
    |       ------------- the comment documents this function
@@ -161,7 +161,7 @@ error: empty line after doc comment
 LL | /     /// Docs for `old_code2`
 LL | |     /* fn old_code2() {} */
 LL | |
-   | |_
+   | |_^
 LL |       /// Docs for `new_code2`
 LL |       fn new_code2() {}
    |       -------------- the comment documents this function
diff --git a/src/tools/clippy/tests/ui/empty_line_after/outer_attribute.stderr b/src/tools/clippy/tests/ui/empty_line_after/outer_attribute.stderr
index 958b40424a9..75fc23e9e7e 100644
--- a/src/tools/clippy/tests/ui/empty_line_after/outer_attribute.stderr
+++ b/src/tools/clippy/tests/ui/empty_line_after/outer_attribute.stderr
@@ -3,7 +3,7 @@ error: empty line after outer attribute
    |
 LL | / #[crate_type = "lib"]
 LL | |
-   | |_
+   | |_^
 LL |   fn first_in_crate() {}
    |   ------------------- the attribute applies to this function
    |
@@ -20,7 +20,7 @@ error: empty line after outer attribute
    |
 LL | / #[inline]
 LL | |
-   | |_
+   | |_^
 LL |   /// some comment
 LL |   fn with_one_newline_and_comment() {}
    |   --------------------------------- the attribute applies to this function
@@ -32,7 +32,7 @@ error: empty line after outer attribute
    |
 LL | / #[inline]
 LL | |
-   | |_
+   | |_^
 LL |   fn with_one_newline() {}
    |   --------------------- the attribute applies to this function
    |
@@ -44,7 +44,7 @@ error: empty lines after outer attribute
 LL | /     #[crate_type = "lib"]
 LL | |
 LL | |
-   | |_
+   | |_^
 LL |       fn with_two_newlines() {}
    |       ---------------------- the attribute applies to this function
    |
@@ -59,7 +59,7 @@ error: empty line after outer attribute
    |
 LL | / #[doc = "doc attributes should be considered attributes"]
 LL | |
-   | |_
+   | |_^
 LL |   enum Baz {
    |   -------- the attribute applies to this enum
    |
@@ -70,7 +70,7 @@ error: empty line after outer attribute
    |
 LL | / #[repr(C)]
 LL | |
-   | |_
+   | |_^
 LL |   struct Foo {
    |   ---------- the attribute applies to this struct
    |
@@ -81,7 +81,7 @@ error: empty line after outer attribute
    |
 LL | / #[allow(dead_code)]
 LL | |
-   | |_
+   | |_^
 LL |   mod foo {}
    |   ------- the attribute applies to this module
    |
@@ -93,7 +93,7 @@ error: empty line after outer attribute
 LL | / #[inline]
 LL | | // Still lint cases where the empty line does not immediately follow the attribute
 LL | |
-   | |_
+   | |_^
 LL |   fn comment_before_empty_line() {}
    |   ------------------------------ the attribute applies to this function
    |
@@ -106,7 +106,7 @@ LL | / #[allow(unused)]
 LL | |
 LL | | // This comment is isolated
 LL | |
-   | |_
+   | |_^
 LL |   pub fn isolated_comment() {}
    |   ------------------------- the attribute applies to this function
    |
diff --git a/src/tools/clippy/tests/ui/four_forward_slashes.stderr b/src/tools/clippy/tests/ui/four_forward_slashes.stderr
index a2218ea4d10..3606a2227a0 100644
--- a/src/tools/clippy/tests/ui/four_forward_slashes.stderr
+++ b/src/tools/clippy/tests/ui/four_forward_slashes.stderr
@@ -3,7 +3,7 @@ error: this item has comments with 4 forward slashes (`////`). These look like d
    |
 LL | / //// whoops
 LL | | fn a() {}
-   | |_
+   | |_^
    |
    = note: `-D clippy::four-forward-slashes` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::four_forward_slashes)]`
@@ -18,7 +18,7 @@ error: this item has comments with 4 forward slashes (`////`). These look like d
 LL | / //// whoops
 LL | | #[allow(dead_code)]
 LL | | fn b() {}
-   | |_
+   | |_^
    |
 help: make this a doc comment by removing one `/`
    |
@@ -32,7 +32,7 @@ LL | / //// whoops
 LL | | //// two borked comments!
 LL | | #[track_caller]
 LL | | fn c() {}
-   | |_
+   | |_^
    |
 help: turn these into doc comments by removing one `/`
    |
@@ -46,7 +46,7 @@ error: this item has comments with 4 forward slashes (`////`). These look like d
 LL | / //// between attributes
 LL | | #[allow(dead_code)]
 LL | | fn g() {}
-   | |_
+   | |_^
    |
 help: make this a doc comment by removing one `/`
    |
@@ -58,7 +58,7 @@ error: this item has comments with 4 forward slashes (`////`). These look like d
    |
 LL | /     //// not very start of contents
 LL | | fn h() {}
-   | |_
+   | |_^
    |
 help: make this a doc comment by removing one `/`
    |
diff --git a/src/tools/clippy/tests/ui/four_forward_slashes_first_line.stderr b/src/tools/clippy/tests/ui/four_forward_slashes_first_line.stderr
index 23937034b7e..81732346412 100644
--- a/src/tools/clippy/tests/ui/four_forward_slashes_first_line.stderr
+++ b/src/tools/clippy/tests/ui/four_forward_slashes_first_line.stderr
@@ -3,7 +3,7 @@ error: this item has comments with 4 forward slashes (`////`). These look like d
    |
 LL | / //// borked doc comment on the first line. doesn't combust!
 LL | | fn a() {}
-   | |_
+   | |_^
    |
    = note: `-D clippy::four-forward-slashes` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::four_forward_slashes)]`
diff --git a/src/tools/clippy/tests/ui/too_long_first_doc_paragraph-fix.stderr b/src/tools/clippy/tests/ui/too_long_first_doc_paragraph-fix.stderr
index 6403265a39c..6ef333f0cfd 100644
--- a/src/tools/clippy/tests/ui/too_long_first_doc_paragraph-fix.stderr
+++ b/src/tools/clippy/tests/ui/too_long_first_doc_paragraph-fix.stderr
@@ -6,7 +6,7 @@ LL | | /// A much longer explanation that goes into a lot more detail about
 LL | | /// how the thing works, possibly with doclinks and so one,
 LL | | /// and probably spanning a many rows. Blablabla, it needs to be over
 LL | | /// 200 characters so I needed to write something longeeeeeeer.
-   | |_
+   | |_^
    |
    = note: `-D clippy::too-long-first-doc-paragraph` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::too_long_first_doc_paragraph)]`
diff --git a/src/tools/clippy/tests/ui/too_long_first_doc_paragraph.stderr b/src/tools/clippy/tests/ui/too_long_first_doc_paragraph.stderr
index 39926647f54..95f42349b9b 100644
--- a/src/tools/clippy/tests/ui/too_long_first_doc_paragraph.stderr
+++ b/src/tools/clippy/tests/ui/too_long_first_doc_paragraph.stderr
@@ -23,7 +23,7 @@ error: first doc comment paragraph is too long
 LL | / /// Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nunc turpis nunc, lacinia
 LL | | /// a dolor in, pellentesque aliquet enim. Cras nec maximus sem. Mauris arcu libero,
 LL | | /// gravida non lacinia at, rhoncus eu lacus.
-   | |_
+   | |_^
 
 error: first doc comment paragraph is too long
   --> tests/ui/too_long_first_doc_paragraph.rs:36:1
@@ -32,7 +32,7 @@ LL | / /// Lorem
 LL | | /// ipsum dolor sit amet, consectetur adipiscing elit. Nunc turpis nunc, lacinia
 LL | | /// a dolor in, pellentesque aliquet enim. Cras nec maximus sem. Mauris arcu libero,
 LL | | /// gravida non lacinia at, rhoncus eu lacus.
-   | |_
+   | |_^
 
 error: aborting due to 3 previous errors