Code fix for IDE0059 "Remove unnecessary assignment" removes empty lines or reorders code

[Tragetaschen]

Version Used: 16.6.2

Steps to Reproduce:

public class Test
{
    public long M(bool flag)
    {
        long a = 0; // IDE0059
        long b = 0; // IDE0059
        long c = 0; // IDE0059

        if (flag)
        {
            a = 1;
            b = 1;
            c = 1;
        }
        else
        {
            a = 2;
            b = 2;
            c = 2;
        }

        return a + b + c;
    }
}

1. Run "Remove unnecessary assignment" for c
2. Run "Remove unnecessary assignment" for b

Expected Behavior:

In both steps, the = 0 characters should be removed

         long a = 0; // IDE0059
-        long b = 0; // IDE0059
-        long c = 0; // IDE0059
+        long b; // IDE0059
+        long c; // IDE0059

         if (flag)

Actual Behavior:

After running "Remove unnecessary assignment" for c, the empty line below the declaration and the comment is also removed:

         long a = 0; // IDE0059
         long b = 0; // IDE0059
-        long c = 0; // IDE0059
-
+        long c;
         if (flag)

After then running "Remove unnecessary assignment" for b , the b and c declarations are reordered and the comment is removed:

         long a = 0; // IDE0059
-        long b = 0; // IDE0059
-        long c = 0; // IDE0059
-
+        long c;
+        long b;
         if (flag)

[kendrahavens]

Design meeting notes

• Opened separate bug to fix trailing trivia being deleted with codefix. https://github.com/dotnet/roslyn/issues/45711
• Design guidance: Don't reorder variable declarations within same group of declarations.
  • Originally there was no reordering with this codefix, but over time we noticed the action was almost always followed by needing to move the declaration nearer the first necessary assignment block. We want to preserve this behavior only if the declaration is moving to a different block. If the codefix would only cause a reordering within the same block then it should not be applied.