Properly handle removal suggestion rendering

Do not leave a `+ ` line with only whitespace. In reality, the user will want to remove the entire line.

compiler/rustc_errors/src/emitter.rs

@@ -2273,9 +2273,26 @@ impl HumanEmitter {
                     &normalize_whitespace(last_line),
                     Style::NoStyle,
                 );
+                if !line_to_add.trim().is_empty() {
+                    // Check if after the removal, the line is left with only whitespace. If so, we
+                    // will not show an "addition" line, as removing the whole line is what the user
+                    // would really want.
+                    // For example, for the following:
+                    //   |
+                    // 2 -     .await
+                    // 2 +     (note the left over whitepsace)
+                    //   |
+                    // We really want
+                    //   |
+                    // 2 -     .await
+                    //   |
+                    // *row_num -= 1;
                     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 {
+                    *row_num -= 1;
+                }
             } else {
                 *row_num -= 2;
             }

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

@@ -86,7 +86,6 @@ LL |     dbg!();
 help: remove the invocation before committing it to a version control system
    |
 LL -     dbg!();
-LL +     
    |
 
 error: the `dbg!` macro is intended as a debugging tool
@@ -146,7 +145,6 @@ LL |     expand_to_dbg!();
 help: remove the invocation before committing it to a version control system
    |
 LL -             dbg!();
-LL +             
    |
 
 error: the `dbg!` macro is intended as a debugging tool

src/tools/clippy/tests/ui/dbg_macro/dbg_macro_unfixable.stderr

@@ -9,7 +9,6 @@ LL |     dbg!();
 help: remove the invocation before committing it to a version control system
    |
 LL -     dbg!();
-LL +     
    |
 
 error: the `dbg!` macro is intended as a debugging tool

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

@@ -96,12 +96,10 @@ LL |     let (l, r) = "a.b.c".split_once('.').unwrap();
 help: remove the `iter` usages
    |
 LL -     let l = iter.next().unwrap();
-LL +     
    |
 help: remove the `iter` usages
    |
 LL -     let r = iter.next().unwrap();
-LL +     
    |
 
 error: manual implementation of `split_once`
@@ -121,12 +119,10 @@ LL |     let (l, r) = "a.b.c".split_once('.')?;
 help: remove the `iter` usages
    |
 LL -     let l = iter.next()?;
-LL +     
    |
 help: remove the `iter` usages
    |
 LL -     let r = iter.next()?;
-LL +     
    |
 
 error: manual implementation of `rsplit_once`
@@ -146,12 +142,10 @@ LL |     let (l, r) = "a.b.c".rsplit_once('.').unwrap();
 help: remove the `iter` usages
    |
 LL -     let r = iter.next().unwrap();
-LL +     
    |
 help: remove the `iter` usages
    |
 LL -     let l = iter.next().unwrap();
-LL +     
    |
 
 error: manual implementation of `rsplit_once`
@@ -171,12 +165,10 @@ LL |     let (l, r) = "a.b.c".rsplit_once('.')?;
 help: remove the `iter` usages
    |
 LL -     let r = iter.next()?;
-LL +     
    |
 help: remove the `iter` usages
    |
 LL -     let l = iter.next()?;
-LL +     
    |
 
 error: manual implementation of `split_once`
@@ -202,12 +194,10 @@ LL |     let (a, b) = "a.b.c".split_once('.').unwrap();
 help: remove the `iter` usages
    |
 LL -     let a = iter.next().unwrap();
-LL +     
    |
 help: remove the `iter` usages
    |
 LL -     let b = iter.next().unwrap();
-LL +     
    |
 
 error: aborting due to 19 previous errors

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

@@ -64,7 +64,6 @@ LL +         let rslt0 = mutex.lock().unwrap().abs();
 help: remove separated single usage
    |
 LL -         let rslt0 = lock.abs();
-LL +         
    |
 
 error: temporary with significant `Drop` can be early dropped
@@ -88,7 +87,6 @@ LL +         mutex.lock().unwrap().clear();
 help: remove separated single usage
    |
 LL -         lock.clear();
-LL +         
    |
 
 error: aborting due to 4 previous errors