Tweak multispan rendering to reduce output length

compiler/rustc_errors/src/emitter.rs

@@ -3048,19 +3048,28 @@ impl FileWithAnnotatedLines {
                 // working correctly.
                 let middle = min(ann.line_start + 4, ann.line_end);
                 // We'll show up to 4 lines past the beginning of the multispan start.
-                // We will *not* include the tail of lines that are only whitespace.
+                // We will *not* include the tail of lines that are only whitespace, a comment or
+                // a bare delimiter.
+                let filter = |s: &str| {
+                    let s = s.trim();
+                    // Consider comments as empty, but don't consider docstrings to be empty.
+                    !(s.starts_with("//") && !(s.starts_with("///") || s.starts_with("//!")))
+                        // Consider lines with nothing but whitespace, a single delimiter as empty.
+                        && !["", "{", "}", "(", ")", "[", "]"].contains(&s)
+                };
                 let until = (ann.line_start..middle)
                     .rev()
                     .filter_map(|line| file.get_line(line - 1).map(|s| (line + 1, s)))
-                    .find(|(_, s)| !s.trim().is_empty())
+                    .find(|(_, s)| filter(s))
                     .map(|(line, _)| line)
                     .unwrap_or(ann.line_start);
                 for line in ann.line_start + 1..until {
                     // Every `|` that joins the beginning of the span (`___^`) to the end (`|__^`).
                     add_annotation_to_file(&mut output, Lrc::clone(&file), line, ann.as_line());
                 }
                 let line_end = ann.line_end - 1;
-                if middle < line_end {
+                let end_is_empty = file.get_line(line_end - 1).map_or(false, |s| !filter(&s));
+                if middle < line_end && !end_is_empty {
                     add_annotation_to_file(&mut output, Lrc::clone(&file), line_end, ann.as_line());
                 }
             } else {

src/tools/clippy/tests/ui-toml/arbitrary_source_item_ordering/ordering_mixed.default.stderr

@@ -20,7 +20,6 @@ LL | |     fn clone_self(&self) -> Self {
 LL | |         Self {
 LL | |             a: true,
 ...  |
-LL | |     }
 LL | | }
    | |_^
    |
@@ -32,7 +31,6 @@ LL | |     fn default() -> Self {
 LL | |         Self {
 LL | |             a: true,
 ...  |
-LL | |     }
 LL | | }
    | |_^
 

src/tools/clippy/tests/ui-toml/excessive_nesting/excessive_nesting.stderr

@@ -66,8 +66,7 @@ error: this block is too nested
 LL |                   if true {
    |  _________________________^
 LL | |                     if true {
-LL | |
-LL | |                     }
+...  |
 LL | |                 }
    | |_________________^
    |

src/tools/clippy/tests/ui-toml/undocumented_unsafe_blocks/undocumented_unsafe_blocks.default.stderr

@@ -286,7 +286,6 @@ LL | |         if unsafe { true } {
 LL | |             todo!();
 LL | |         } else {
 ...  |
-LL | |         }
 LL | |     };
    | |______^
    |

src/tools/clippy/tests/ui-toml/undocumented_unsafe_blocks/undocumented_unsafe_blocks.disabled.stderr

@@ -294,7 +294,6 @@ LL | |         if unsafe { true } {
 LL | |             todo!();
 LL | |         } else {
 ...  |
-LL | |         }
 LL | |     };
    | |______^
    |

src/tools/clippy/tests/ui/async_yields_async.stderr

@@ -80,7 +80,6 @@ error: an async construct yields a type which is itself awaitable
 LL |       let _m = async || {
    |  _______________________-
 LL | |         println!("I'm bored");
-LL | |         // Some more stuff
 ...  |
 LL | |         CustomFutureType
    | |         ^^^^^^^^^^^^^^^^

src/tools/clippy/tests/ui/bind_instead_of_map_multipart.stderr

@@ -44,7 +44,6 @@ LL | |         if {
 LL | |             if s == "43" {
 LL | |                 return Some(43);
 ...  |
-LL | |         }
 LL | |     });
    | |______^
    |

src/tools/clippy/tests/ui/branches_sharing_code/shared_at_bottom.stderr

@@ -115,8 +115,7 @@ error: all if blocks contain the same code at the end
   --> tests/ui/branches_sharing_code/shared_at_bottom.rs:183:5
    |
 LL | /         x << 2
-LL | |
-LL | |
+...  |
 LL | |     };
    | |_____^
    |
@@ -131,8 +130,7 @@ error: all if blocks contain the same code at the end
   --> tests/ui/branches_sharing_code/shared_at_bottom.rs:192:5
    |
 LL | /         x * 4
-LL | |
-LL | |
+...  |
 LL | |     }
    | |_____^
    |

src/tools/clippy/tests/ui/collapsible_else_if.stderr

@@ -43,9 +43,7 @@ LL |       } else {
    |  ____________^
 LL | |         if y == "world" {
 LL | |             println!("world")
-LL | |         }
 ...  |
-LL | |         }
 LL | |     }
    | |_____^
    |
@@ -66,9 +64,7 @@ LL |       } else {
    |  ____________^
 LL | |         if let Some(42) = Some(42) {
 LL | |             println!("world")
-LL | |         }
 ...  |
-LL | |         }
 LL | |     }
    | |_____^
    |
@@ -89,9 +85,7 @@ LL |       } else {
    |  ____________^
 LL | |         if let Some(42) = Some(42) {
 LL | |             println!("world")
-LL | |         }
 ...  |
-LL | |         }
 LL | |     }
    | |_____^
    |
@@ -112,9 +106,7 @@ LL |       } else {
    |  ____________^
 LL | |         if x == "hello" {
 LL | |             println!("world")
-LL | |         }
 ...  |
-LL | |         }
 LL | |     }
    | |_____^
    |
@@ -135,9 +127,7 @@ LL |       } else {
    |  ____________^
 LL | |         if let Some(42) = Some(42) {
 LL | |             println!("world")
-LL | |         }
 ...  |
-LL | |         }
 LL | |     }
    | |_____^
    |

src/tools/clippy/tests/ui/copy_iterator.stderr

@@ -6,7 +6,6 @@ LL | |
 LL | |
 LL | |     type Item = u8;
 ...  |
-LL | |     }
 LL | | }
    | |_^
    |

src/tools/clippy/tests/ui/crashes/ice-360.stderr

@@ -2,11 +2,7 @@ error: this loop never actually loops
   --> tests/ui/crashes/ice-360.rs:5:5
    |
 LL | /     loop {
-LL | |
-LL | |
-LL | |
 ...  |
-LL | |
 LL | |     }
    | |_____^
    |
@@ -16,11 +12,7 @@ error: this loop could be written as a `while let` loop
   --> tests/ui/crashes/ice-360.rs:5:5
    |
 LL | /     loop {
-LL | |
-LL | |
-LL | |
 ...  |
-LL | |
 LL | |     }
    | |_____^ help: try: `while let Some(ele) = iter.next() { .. }`
    |

src/tools/clippy/tests/ui/crate_level_checks/no_std_swap.stderr

@@ -2,8 +2,7 @@ error: this looks like you are trying to swap `a` and `b`
   --> tests/ui/crate_level_checks/no_std_swap.rs:12:5
    |
 LL | /     a = b;
-LL | |
-LL | |
+...  |
 LL | |     b = a;
    | |_________^ help: try: `core::mem::swap(&mut a, &mut b)`
    |

src/tools/clippy/tests/ui/derivable_impls.stderr

@@ -6,7 +6,6 @@ LL | |     fn default() -> Self {
 LL | |         Self {
 LL | |             a: false,
 ...  |
-LL | |     }
 LL | | }
    | |_^
    |

src/tools/clippy/tests/ui/empty_line_after/doc_comments.stderr

@@ -99,8 +99,7 @@ LL | /     /// for OldA
 LL | |     // struct OldA;
 LL | |
 LL | |     /// Docs
-LL | |     /// for OldB
-LL | |     // struct OldB;
+...  |
 LL | |
    | |_^
 ...

src/tools/clippy/tests/ui/empty_line_after/outer_attribute.stderr

@@ -103,8 +103,7 @@ error: empty lines after outer attribute
   --> tests/ui/empty_line_after/outer_attribute.rs:64:1
    |
 LL | / #[allow(unused)]
-LL | |
-LL | | // This comment is isolated
+...  |
 LL | |
    | |_^
 LL |   pub fn isolated_comment() {}

src/tools/clippy/tests/ui/entry.stderr

@@ -16,8 +16,7 @@ LL | /     if !m.contains_key(&k) {
 LL | |         if true {
 LL | |             m.insert(k, v);
 LL | |         } else {
-LL | |             m.insert(k, v2);
-LL | |         }
+...  |
 LL | |     }
    | |_____^
    |
@@ -63,7 +62,6 @@ LL | |         if true {
 LL | |             m.insert(k, v);
 LL | |         } else {
 ...  |
-LL | |         }
 LL | |     }
    | |_____^
    |
@@ -154,7 +152,6 @@ LL | |         foo();
 LL | |         match 0 {
 LL | |             0 if false => {
 ...  |
-LL | |         }
 LL | |     }
    | |_____^
    |

src/tools/clippy/tests/ui/enum_variants.stderr

@@ -13,7 +13,6 @@ error: all variants have the same prefix: `c`
 LL | / enum Foo {
 LL | |
 LL | |     cFoo,
-LL | |
 ...  |
 LL | |     cBaz,
 LL | | }
@@ -45,9 +44,7 @@ error: all variants have the same prefix: `Food`
 LL | / enum Food {
 LL | |
 LL | |     FoodGood,
-LL | |
 ...  |
-LL | |
 LL | | }
    | |_^
    |

src/tools/clippy/tests/ui/fallible_impl_from.stderr

@@ -29,7 +29,6 @@ LL | |
 LL | |     fn from(i: usize) -> Invalid {
 LL | |         if i != 42 {
 ...  |
-LL | |     }
 LL | | }
    | |_^
    |
@@ -49,7 +48,6 @@ LL | |
 LL | |     fn from(s: Option<String>) -> Invalid {
 LL | |         let s = s.unwrap();
 ...  |
-LL | |     }
 LL | | }
    | |_^
    |
@@ -76,7 +74,6 @@ LL | |
 LL | |     fn from(s: &'a mut <Box<u32> as ProjStrTrait>::ProjString) -> Invalid {
 LL | |         if s.parse::<u32>().ok().unwrap() != 42 {
 ...  |
-LL | |     }
 LL | | }
    | |_^
    |

src/tools/clippy/tests/ui/if_same_then_else2.stderr

@@ -7,7 +7,6 @@ LL | |         for _ in &[42] {
 LL | |             let foo: &Option<_> = &Some::<u8>(42);
 LL | |             if foo.is_some() {
 ...  |
-LL | |         }
 LL | |     } else {
    | |_____^
    |
@@ -20,7 +19,6 @@ LL | |         for _ in &[42] {
 LL | |             let bar: &Option<_> = &Some::<u8>(42);
 LL | |             if bar.is_some() {
 ...  |
-LL | |         }
 LL | |     }
    | |_____^
    = note: `-D clippy::if-same-then-else` implied by `-D warnings`

src/tools/clippy/tests/ui/infinite_loops.stderr

@@ -20,7 +20,6 @@ error: infinite loop detected
 LL | /     loop {
 LL | |
 LL | |         loop {
-LL | |
 ...  |
 LL | |         do_something();
 LL | |     }
@@ -37,9 +36,7 @@ error: infinite loop detected
 LL | /         loop {
 LL | |
 LL | |             loop {
-LL | |
-LL | |                 do_something();
-LL | |             }
+...  |
 LL | |         }
    | |_________^
    |
@@ -79,8 +76,7 @@ error: infinite loop detected
 LL | /     loop {
 LL | |         fn inner_fn() -> ! {
 LL | |             std::process::exit(0);
-LL | |         }
-LL | |         do_something();
+...  |
 LL | |     }
    | |_____^
    |
@@ -97,7 +93,6 @@ LL | |
 LL | |         loop {
 LL | |             if cond {
 ...  |
-LL | |         }
 LL | |     }
    | |_____^
    |
@@ -114,7 +109,6 @@ LL | |
 LL | |         'inner: loop {
 LL | |             loop {
 ...  |
-LL | |         }
 LL | |     }
    | |_____^
    |
@@ -145,7 +139,6 @@ LL | |
 LL | |             'inner: loop {
 LL | |                 loop {
 ...  |
-LL | |             }
 LL | |         }
    | |_________^
    |
@@ -162,7 +155,6 @@ LL | |
 LL | |         match opt {
 LL | |             Some(v) => {
 ...  |
-LL | |         }
 LL | |     }
    | |_____^
    |
@@ -279,7 +271,6 @@ LL | |
 LL | |         'inner: loop {
 LL | |             loop {
 ...  |
-LL | |         }
 LL | |     }
    | |_____^
    |