Tweak output for 'add line' suggestion

compiler/rustc_errors/src/emitter.rs

@@ -1832,6 +1832,12 @@ impl EmitterWriter {
             }
             let show_code_change = if has_deletion && !is_multiline {
                 DisplaySuggestion::Diff
+            } else if let [part] = &parts[..]
+                && part.snippet.ends_with('\n')
+                && part.snippet.trim() == complete.trim()
+            {
+                // We are adding a line(s) of code before code that was already there.
+                DisplaySuggestion::Add
             } else if (parts.len() != 1 || parts[0].snippet.trim() != complete.trim())
                 && !is_multiline
             {
@@ -1879,14 +1885,23 @@ impl EmitterWriter {
                 row_num += line_end - line_start;
             }
             let mut unhighlighted_lines = Vec::new();
+            let mut last_pos = 0;
+            let mut is_item_attribute = false;
             for (line_pos, (line, highlight_parts)) in lines.by_ref().zip(highlights).enumerate() {
+                last_pos = line_pos;
                 debug!(%line_pos, %line, ?highlight_parts);
 
                 // Remember lines that are not highlighted to hide them if needed
                 if highlight_parts.is_empty() {
                     unhighlighted_lines.push((line_pos, line));
                     continue;
                 }
+                if highlight_parts.len() == 1
+                    && line.trim().starts_with("#[")
+                    && line.trim().ends_with(']')
+                {
+                    is_item_attribute = true;
+                }
 
                 match unhighlighted_lines.len() {
                     0 => (),
@@ -1963,13 +1978,41 @@ impl EmitterWriter {
                     is_multiline,
                 )
             }
+            if let DisplaySuggestion::Add = show_code_change && is_item_attribute {
+                // The suggestion adds an entire line of code, ending on a newline, so we'll also
+                // print the *following* line, to provide context of what we're advicing people to
+                // do. Otherwise you would only see contextless code that can be confused for
+                // already existing code, despite the colors and UI elements.
+                // We special case `#[derive(_)]\n` and other attribute suggestions, because those
+                // are the ones where context is most useful.
+                let file_lines = sm
+                    .span_to_lines(span.primary_span().unwrap().shrink_to_hi())
+                    .expect("span_to_lines failed when emitting suggestion");
+                let line_num = sm.lookup_char_pos(parts[0].span.lo()).line;
+                if let Some(line) = file_lines.file.get_line(line_num - 1) {
+                    let line = normalize_whitespace(&line);
+                    self.draw_code_line(
+                        &mut buffer,
+                        &mut row_num,
+                        &[],
+                        line_num + last_pos + 1,
+                        &line,
+                        DisplaySuggestion::None,
+                        max_line_num_len,
+                        &file_lines,
+                        is_multiline,
+                    )
+                }
+            }
 
             // This offset and the ones below need to be signed to account for replacement code
             // that is shorter than the original code.
             let mut offsets: Vec<(usize, isize)> = Vec::new();
             // Only show an underline in the suggestions if the suggestion is not the
             // entirety of the code being shown and the displayed code is not multiline.
-            if let DisplaySuggestion::Diff | DisplaySuggestion::Underline = show_code_change {
+            if let DisplaySuggestion::Diff | DisplaySuggestion::Underline | DisplaySuggestion::Add =
+                show_code_change
+            {
                 draw_col_separator_no_space(&mut buffer, row_num, max_line_num_len + 1);
                 for part in parts {
                     let span_start_pos = sm.lookup_char_pos(part.span.lo()).col_display;
@@ -2247,6 +2290,10 @@ impl EmitterWriter {
                 }
             }
             buffer.append(*row_num, &normalize_whitespace(line_to_add), Style::NoStyle);
+        } else if let DisplaySuggestion::Add = show_code_change {
+            buffer.puts(*row_num, 0, &self.maybe_anonymized(line_num), Style::LineNumber);
+            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);
             draw_col_separator(buffer, *row_num, max_line_num_len + 1);
@@ -2281,6 +2328,7 @@ enum DisplaySuggestion {
     Underline,
     Diff,
     None,
+    Add,
 }
 
 impl FileWithAnnotatedLines {

src/tools/clippy/tests/ui/crashes/ice-6252.stderr

@@ -6,11 +6,11 @@ LL |     _n: PhantomData,
    |
 help: consider importing one of these items
    |
-LL | use core::marker::PhantomData;
+LL + use core::marker::PhantomData;
    |
-LL | use serde::__private::PhantomData;
+LL + use serde::__private::PhantomData;
    |
-LL | use std::marker::PhantomData;
+LL + use std::marker::PhantomData;
    |
 
 error[E0412]: cannot find type `VAL` in this scope

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

@@ -14,7 +14,8 @@ LL | | }
    = help: remove the manual implementation...
 help: ...and instead derive it
    |
-LL | #[derive(Default)]
+LL + #[derive(Default)]
+LL | struct FooDefault<'a> {
    |
 
 error: this `impl` can be derived
@@ -30,7 +31,8 @@ LL | | }
    = help: remove the manual implementation...
 help: ...and instead derive it
    |
-LL | #[derive(Default)]
+LL + #[derive(Default)]
+LL | struct TupleDefault(bool, i32, u64);
    |
 
 error: this `impl` can be derived
@@ -46,7 +48,8 @@ LL | | }
    = help: remove the manual implementation...
 help: ...and instead derive it
    |
-LL | #[derive(Default)]
+LL + #[derive(Default)]
+LL | struct StrDefault<'a>(&'a str);
    |
 
 error: this `impl` can be derived
@@ -62,7 +65,8 @@ LL | | }
    = help: remove the manual implementation...
 help: ...and instead derive it
    |
-LL | #[derive(Default)]
+LL + #[derive(Default)]
+LL | struct Y(u32);
    |
 
 error: this `impl` can be derived
@@ -78,7 +82,8 @@ LL | | }
    = help: remove the manual implementation...
 help: ...and instead derive it
    |
-LL | #[derive(Default)]
+LL + #[derive(Default)]
+LL | struct WithoutSelfCurly {
    |
 
 error: this `impl` can be derived
@@ -94,7 +99,8 @@ LL | | }
    = help: remove the manual implementation...
 help: ...and instead derive it
    |
-LL | #[derive(Default)]
+LL + #[derive(Default)]
+LL | struct WithoutSelfParan(bool);
    |
 
 error: this `impl` can be derived
@@ -110,7 +116,8 @@ LL | | }
    = help: remove the manual implementation...
 help: ...and instead derive it
    |
-LL | #[derive(Default)]
+LL + #[derive(Default)]
+LL | pub struct RepeatDefault1 {
    |
 
 error: this `impl` can be derived
@@ -126,7 +133,8 @@ LL | | }
    = help: remove the manual implementation...
 help: ...and instead derive it...
    |
-LL | #[derive(Default)]
+LL + #[derive(Default)]
+LL | pub enum SimpleEnum {
    |
 help: ...and mark the default variant
    |

tests/ui/array-slice-vec/repeat_empty_ok.stderr

@@ -7,7 +7,8 @@ LL |     let headers = [Header{value: &[]}; 128];
    = note: the `Copy` trait is required because this value will be copied for each element of the array
 help: consider annotating `Header<'_>` with `#[derive(Copy)]`
    |
-LL | #[derive(Copy)]
+LL + #[derive(Copy)]
+LL | pub struct Header<'a> {
    |
 
 error[E0277]: the trait bound `Header<'_>: Copy` is not satisfied
@@ -19,7 +20,8 @@ LL |     let headers = [Header{value: &[0]}; 128];
    = note: the `Copy` trait is required because this value will be copied for each element of the array
 help: consider annotating `Header<'_>` with `#[derive(Copy)]`
    |
-LL | #[derive(Copy)]
+LL + #[derive(Copy)]
+LL | pub struct Header<'a> {
    |
 
 error: aborting due to 2 previous errors

tests/ui/associated-types/defaults-suitability.stderr

@@ -11,7 +11,8 @@ LL |     type Ty: Clone = NotClone;
    |              ^^^^^ required by this bound in `Tr::Ty`
 help: consider annotating `NotClone` with `#[derive(Clone)]`
    |
-LL | #[derive(Clone)]
+LL + #[derive(Clone)]
+LL | struct NotClone;
    |
 
 error[E0277]: the trait bound `NotClone: Clone` is not satisfied
@@ -30,7 +31,8 @@ LL |     type Ty = NotClone;
    |          -- required by a bound in this associated type
 help: consider annotating `NotClone` with `#[derive(Clone)]`
    |
-LL | #[derive(Clone)]
+LL + #[derive(Clone)]
+LL | struct NotClone;
    |
 
 error[E0277]: the trait bound `T: Clone` is not satisfied

tests/ui/binop/issue-28837.stderr

@@ -157,7 +157,8 @@ LL | struct A;
    | ^^^^^^^^ must implement `PartialEq<_>`
 help: consider annotating `A` with `#[derive(PartialEq)]`
    |
-LL | #[derive(PartialEq)]
+LL + #[derive(PartialEq)]
+LL | struct A;
    |
 
 error[E0369]: binary operation `!=` cannot be applied to type `A`
@@ -175,7 +176,8 @@ LL | struct A;
    | ^^^^^^^^ must implement `PartialEq<_>`
 help: consider annotating `A` with `#[derive(PartialEq)]`
    |
-LL | #[derive(PartialEq)]
+LL + #[derive(PartialEq)]
+LL | struct A;
    |
 
 error[E0369]: binary operation `<` cannot be applied to type `A`
@@ -193,7 +195,8 @@ LL | struct A;
    | ^^^^^^^^ must implement `PartialOrd<_>`
 help: consider annotating `A` with `#[derive(PartialEq, PartialOrd)]`
    |
-LL | #[derive(PartialEq, PartialOrd)]
+LL + #[derive(PartialEq, PartialOrd)]
+LL | struct A;
    |
 
 error[E0369]: binary operation `<=` cannot be applied to type `A`
@@ -211,7 +214,8 @@ LL | struct A;
    | ^^^^^^^^ must implement `PartialOrd<_>`
 help: consider annotating `A` with `#[derive(PartialEq, PartialOrd)]`
    |
-LL | #[derive(PartialEq, PartialOrd)]
+LL + #[derive(PartialEq, PartialOrd)]
+LL | struct A;
    |
 
 error[E0369]: binary operation `>` cannot be applied to type `A`
@@ -229,7 +233,8 @@ LL | struct A;
    | ^^^^^^^^ must implement `PartialOrd<_>`
 help: consider annotating `A` with `#[derive(PartialEq, PartialOrd)]`
    |
-LL | #[derive(PartialEq, PartialOrd)]
+LL + #[derive(PartialEq, PartialOrd)]
+LL | struct A;
    |
 
 error[E0369]: binary operation `>=` cannot be applied to type `A`
@@ -247,7 +252,8 @@ LL | struct A;
    | ^^^^^^^^ must implement `PartialOrd<_>`
 help: consider annotating `A` with `#[derive(PartialEq, PartialOrd)]`
    |
-LL | #[derive(PartialEq, PartialOrd)]
+LL + #[derive(PartialEq, PartialOrd)]
+LL | struct A;
    |
 
 error: aborting due to 15 previous errors

tests/ui/box/unit/unique-pinned-nocopy.stderr

@@ -19,7 +19,8 @@ LL |       let _j = i.clone();
            candidate #1: `Clone`
 help: consider annotating `R` with `#[derive(Clone)]`
    |
-LL | #[derive(Clone)]
+LL + #[derive(Clone)]
+LL | struct R {
    |
 
 error: aborting due to previous error

tests/ui/coherence/coherence_inherent.stderr

@@ -7,7 +7,7 @@ LL |         s.the_fn();
    = help: items from traits can only be used if the trait is in scope
 help: the following trait is implemented but not in scope; perhaps add a `use` for it:
    |
-LL |     use Lib::TheTrait;
+LL +     use Lib::TheTrait;
    |
 
 error: aborting due to previous error

tests/ui/coherence/coherence_inherent_cc.stderr

@@ -7,7 +7,7 @@ LL |         s.the_fn();
    = help: items from traits can only be used if the trait is in scope
 help: the following trait is implemented but not in scope; perhaps add a `use` for it:
    |
-LL |     use coherence_inherent_cc_lib::TheTrait;
+LL +     use coherence_inherent_cc_lib::TheTrait;
    |
 
 error: aborting due to previous error

tests/ui/const-generics/generic_const_exprs/issue-94287.stderr

@@ -8,7 +8,7 @@ LL |     If<{ FRAC <= 32 }>: True,
 help: consider enabling this feature
   --> $DIR/issue-94287.rs:1:1
    |
-LL | #![feature(generic_const_exprs)]
+LL + #![feature(generic_const_exprs)]
    |
 
 error: aborting due to previous error

tests/ui/const-generics/issues/issue-82956.stderr

@@ -6,13 +6,13 @@ LL |         let mut iter = IntoIter::new(self);
    |
 help: consider importing one of these items
    |
-LL | use std::array::IntoIter;
+LL + use std::array::IntoIter;
    |
-LL | use std::collections::binary_heap::IntoIter;
+LL + use std::collections::binary_heap::IntoIter;
    |
-LL | use std::collections::btree_map::IntoIter;
+LL + use std::collections::btree_map::IntoIter;
    |
-LL | use std::collections::btree_set::IntoIter;
+LL + use std::collections::btree_set::IntoIter;
    |
      and 8 other candidates
 

tests/ui/consts/const-blocks/fn-call-in-non-const.stderr

@@ -10,7 +10,8 @@ LL |     let _: [Option<Bar>; 2] = [no_copy(); 2];
    = help: create an inline `const` block, see RFC #2920 <https://github.com/rust-lang/rfcs/pull/2920> for more information
 help: consider annotating `Bar` with `#[derive(Copy)]`
    |
-LL | #[derive(Copy)]
+LL + #[derive(Copy)]
+LL | struct Bar;
    |
 
 error: aborting due to previous error

tests/ui/consts/const-blocks/migrate-fail.stderr

@@ -8,7 +8,8 @@ LL |         let arr: [Option<Bar>; 2] = [x; 2];
    = note: the `Copy` trait is required because this value will be copied for each element of the array
 help: consider annotating `Bar` with `#[derive(Copy)]`
    |
-LL | #[derive(Copy)]
+LL + #[derive(Copy)]
+LL | struct Bar;
    |
 
 error[E0277]: the trait bound `Bar: Copy` is not satisfied
@@ -21,7 +22,8 @@ LL |         let arr: [Option<Bar>; 2] = [x; 2];
    = note: the `Copy` trait is required because this value will be copied for each element of the array
 help: consider annotating `Bar` with `#[derive(Copy)]`
    |
-LL | #[derive(Copy)]
+LL + #[derive(Copy)]
+LL | struct Bar;
    |
 
 error: aborting due to 2 previous errors

tests/ui/consts/const-blocks/nll-fail.stderr

@@ -8,7 +8,8 @@ LL |         let arr: [Option<Bar>; 2] = [x; 2];
    = note: the `Copy` trait is required because this value will be copied for each element of the array
 help: consider annotating `Bar` with `#[derive(Copy)]`
    |
-LL | #[derive(Copy)]
+LL + #[derive(Copy)]
+LL | struct Bar;
    |
 
 error[E0277]: the trait bound `Bar: Copy` is not satisfied
@@ -21,7 +22,8 @@ LL |         let arr: [Option<Bar>; 2] = [x; 2];
    = note: the `Copy` trait is required because this value will be copied for each element of the array
 help: consider annotating `Bar` with `#[derive(Copy)]`
    |
-LL | #[derive(Copy)]
+LL + #[derive(Copy)]
+LL | struct Bar;
    |
 
 error: aborting due to 2 previous errors