Rollup merge of #144609 - Muscraft:right-align, r=compiler-errors

feat: Right align line numbers

As part of my work on getting `annotate-snipptes` to be used as `rustc`'s renderer, I realized that `rustc` left-aligned line numbers, while `annotate-snippets` right-aligned them. This PR switches `rustc` to right-align the line numbers, matching `annotate-snippets`. In practice, this change isn't very noticeable in day-to-day output, as it only shows up when a diagnostic span contains line numbers with different lengths (9->10, 99->100, 999->1000, etc.).

`rustc`
```
error[E0412]: cannot find type `F` in this scope
  --> $DIR/ui-testing-optout.rs:92:10
   |
4  | type A = B;
   | ----------- similarly named type alias `A` defined here
...
92 | type E = F;
   |          ^ help: a type alias with a similar name exists: `A`
```
`annotate-snippets`
```
error[E0412]: cannot find type `F` in this scope
  --> $DIR/ui-testing-optout.rs:92:10
   |
 4 | type A = B;
   | ----------- similarly named type alias `A` defined here
...
92 | type E = F;
   |          ^ help: a type alias with a similar name exists: `A`
```

r? ``@compiler-errors``

2 files changed, 54 insertions, 44 deletions

diff --git a/compiler/rustc_errors/src/emitter.rs b/compiler/rustc_errors/src/emitter.rs
index 95400ac2ca3..46a4a186824 100644
--- a/compiler/rustc_errors/src/emitter.rs
+++ b/compiler/rustc_errors/src/emitter.rs
@@ -713,8 +713,7 @@ impl HumanEmitter {
                 Style::LineNumber,
             );
         }
-        buffer.puts(line_offset, 0, &self.maybe_anonymized(line_index), Style::LineNumber);
-
+        self.draw_line_num(buffer, line_index, line_offset, width_offset - 3);
         self.draw_col_separator_no_space(buffer, line_offset, width_offset - 2);
         left
     }
@@ -2128,11 +2127,11 @@ impl HumanEmitter {
                 // Account for a suggestion to completely remove a line(s) with whitespace (#94192).
                 let line_end = sm.lookup_char_pos(parts[0].span.hi()).line;
                 for line in line_start..=line_end {
-                    buffer.puts(
+                    self.draw_line_num(
+                        &mut buffer,
+                        line,
                         row_num - 1 + line - line_start,
-                        0,
-                        &self.maybe_anonymized(line),
-                        Style::LineNumber,
+                        max_line_num_len,
                     );
                     buffer.puts(
                         row_num - 1 + line - line_start,
@@ -2612,12 +2611,7 @@ impl HumanEmitter {
             // For more info: https://github.com/rust-lang/rust/issues/92741
             let lines_to_remove = file_lines.lines.iter().take(file_lines.lines.len() - 1);
             for (index, line_to_remove) in lines_to_remove.enumerate() {
-                buffer.puts(
-                    *row_num - 1,
-                    0,
-                    &self.maybe_anonymized(line_num + index),
-                    Style::LineNumber,
-                );
+                self.draw_line_num(buffer, line_num + index, *row_num - 1, max_line_num_len);
                 buffer.puts(*row_num - 1, max_line_num_len + 1, "- ", Style::Removal);
                 let line = normalize_whitespace(
                     &file_lines.file.get_line(line_to_remove.line_index).unwrap(),
@@ -2634,11 +2628,11 @@ impl HumanEmitter {
             let last_line_index = file_lines.lines[file_lines.lines.len() - 1].line_index;
             let last_line = &file_lines.file.get_line(last_line_index).unwrap();
             if last_line != line_to_add {
-                buffer.puts(
+                self.draw_line_num(
+                    buffer,
+                    line_num + file_lines.lines.len() - 1,
                     *row_num - 1,
-                    0,
-                    &self.maybe_anonymized(line_num + file_lines.lines.len() - 1),
-                    Style::LineNumber,
+                    max_line_num_len,
                 );
                 buffer.puts(*row_num - 1, max_line_num_len + 1, "- ", Style::Removal);
                 buffer.puts(
@@ -2661,7 +2655,7 @@ impl HumanEmitter {
                     // 2 -     .await
                     //   |
                     // *row_num -= 1;
-                    buffer.puts(*row_num, 0, &self.maybe_anonymized(line_num), Style::LineNumber);
+                    self.draw_line_num(buffer, line_num, *row_num, max_line_num_len);
                     buffer.puts(*row_num, max_line_num_len + 1, "+ ", Style::Addition);
                     buffer.append(*row_num, &normalize_whitespace(line_to_add), Style::NoStyle);
                 } else {
@@ -2671,7 +2665,7 @@ impl HumanEmitter {
                 *row_num -= 2;
             }
         } else if is_multiline {
-            buffer.puts(*row_num, 0, &self.maybe_anonymized(line_num), Style::LineNumber);
+            self.draw_line_num(buffer, line_num, *row_num, max_line_num_len);
             match &highlight_parts {
                 [SubstitutionHighlight { start: 0, end }] if *end == line_to_add.len() => {
                     buffer.puts(*row_num, max_line_num_len + 1, "+ ", Style::Addition);
@@ -2702,11 +2696,11 @@ impl HumanEmitter {
                 Style::NoStyle,
             );
         } else if let DisplaySuggestion::Add = show_code_change {
-            buffer.puts(*row_num, 0, &self.maybe_anonymized(line_num), Style::LineNumber);
+            self.draw_line_num(buffer, line_num, *row_num, max_line_num_len);
             buffer.puts(*row_num, max_line_num_len + 1, "+ ", Style::Addition);
             buffer.append(*row_num, &normalize_whitespace(line_to_add), Style::NoStyle);
         } else {
-            buffer.puts(*row_num, 0, &self.maybe_anonymized(line_num), Style::LineNumber);
+            self.draw_line_num(buffer, line_num, *row_num, max_line_num_len);
             self.draw_col_separator(buffer, *row_num, max_line_num_len + 1);
             buffer.append(*row_num, &normalize_whitespace(line_to_add), Style::NoStyle);
         }
@@ -3016,6 +3010,22 @@ impl HumanEmitter {
             OutputTheme::Unicode => "…",
         }
     }
+
+    fn draw_line_num(
+        &self,
+        buffer: &mut StyledBuffer,
+        line_num: usize,
+        line_offset: usize,
+        max_line_num_len: usize,
+    ) {
+        let line_num = self.maybe_anonymized(line_num);
+        buffer.puts(
+            line_offset,
+            max_line_num_len.saturating_sub(str_width(&line_num)),
+            &line_num,
+            Style::LineNumber,
+        );
+    }
 }
 
 #[derive(Debug, Clone, Copy)]
diff --git a/compiler/rustc_parse/src/parser/tests.rs b/compiler/rustc_parse/src/parser/tests.rs
index 15679d23bc5..43a1d779a75 100644
--- a/compiler/rustc_parse/src/parser/tests.rs
+++ b/compiler/rustc_parse/src/parser/tests.rs
@@ -2114,15 +2114,15 @@ fn foo() {
 error: foo
   --> test.rs:3:6
    |
-3  |      X0 Y0 Z0
+ 3 |      X0 Y0 Z0
    |  _______^
-4  | |    X1 Y1 Z1
+ 4 | |    X1 Y1 Z1
    | | ____^____-
    | ||____|
    |  |    `X` is a good letter
-5  |  | 1
-6  |  | 2
-7  |  | 3
+ 5 |  | 1
+ 6 |  | 2
+ 7 |  | 3
 ...   |
 15 |  |   X2 Y2 Z2
 16 |  |   X3 Y3 Z3
@@ -2133,15 +2133,15 @@ error: foo
 error: foo
    ╭▸ test.rs:3:6
    │
-3  │      X0 Y0 Z0
+ 3 │      X0 Y0 Z0
    │ ┏━━━━━━━┛
-4  │ ┃    X1 Y1 Z1
+ 4 │ ┃    X1 Y1 Z1
    │ ┃┌────╿────┘
    │ ┗│━━━━┥
    │  │    `X` is a good letter
-5  │  │ 1
-6  │  │ 2
-7  │  │ 3
+ 5 │  │ 1
+ 6 │  │ 2
+ 7 │  │ 3
    ‡  │
 15 │  │   X2 Y2 Z2
 16 │  │   X3 Y3 Z3
@@ -2189,15 +2189,15 @@ fn foo() {
 error: foo
   --> test.rs:3:6
    |
-3  |      X0 Y0 Z0
+ 3 |      X0 Y0 Z0
    |  _______^
-4  | |  1
-5  | |  2
-6  | |  3
-7  | |    X1 Y1 Z1
+ 4 | |  1
+ 5 | |  2
+ 6 | |  3
+ 7 | |    X1 Y1 Z1
    | | _________-
-8  | || 4
-9  | || 5
+ 8 | || 4
+ 9 | || 5
 10 | || 6
 11 | ||   X2 Y2 Z2
    | ||__________- `Z` is a good letter too
@@ -2211,15 +2211,15 @@ error: foo
 error: foo
    ╭▸ test.rs:3:6
    │
-3  │      X0 Y0 Z0
+ 3 │      X0 Y0 Z0
    │ ┏━━━━━━━┛
-4  │ ┃  1
-5  │ ┃  2
-6  │ ┃  3
-7  │ ┃    X1 Y1 Z1
+ 4 │ ┃  1
+ 5 │ ┃  2
+ 6 │ ┃  3
+ 7 │ ┃    X1 Y1 Z1
    │ ┃┌─────────┘
-8  │ ┃│ 4
-9  │ ┃│ 5
+ 8 │ ┃│ 4
+ 9 │ ┃│ 5
 10 │ ┃│ 6
 11 │ ┃│   X2 Y2 Z2
    │ ┃└──────────┘ `Z` is a good letter too