From 495d6d9f7e3caaca68b560948d6bc903d2793536 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?D=C4=81vis=20Mos=C4=81ns?= <davispuh@gmail.com>
Date: Sat, 4 Jul 2026 05:15:58 +0300
Subject: [PATCH] Fix comment to be after `extern (C):`

Currently code like this
```c
 #define G1

 #ifdef  G1  // Guard1
 #define A 1
 #else
 #define A 2
 #endif

 #ifdef  G2  // Guard2
 #define B 3
 #else
 #define B 4
 #endif
```

Produces:
```d
extern (C): // Guard1
enum A = 1;

// Guard2

enum B = 4;
```

Notice how `Guard1` comment is in same line as `extern (C):` which looks wrong.
This commit fixes this issue so that it's on a new line like `Guard2`.
---
 dstep/translator/Output.d     | 20 +++++++++++++++++---
 tests/unit/CommentUnitTests.d | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+), 3 deletions(-)

diff --git a/dstep/translator/Output.d b/dstep/translator/Output.d
index 0fb36bfd..c1f8d591 100644
--- a/dstep/translator/Output.d
+++ b/dstep/translator/Output.d
@@ -218,6 +218,7 @@ class Output
 
     private uint lastestOffset = 0;
     private uint lastestLine = 0;
+    private uint lastContentLine = 0;
     private uint headerEndOffset = 0;
 
     this(Output parent)
@@ -231,6 +232,7 @@ class Output
         commentIndex = parent.commentIndex;
         lastestOffset = parent.lastestOffset;
         lastestLine = parent.lastestLine;
+        lastContentLine = parent.lastContentLine;
     }
 
     this(
@@ -268,6 +270,7 @@ class Output
 
         lastestOffset = 0;
         lastestLine = 0;
+        lastContentLine = 0;
         headerEndOffset = 0;
     }
 
@@ -325,6 +328,7 @@ class Output
 
             lastestOffset = max(lastestOffset, output.lastestOffset);
             lastestLine = max(lastestLine, output.lastestLine);
+            lastContentLine = max(lastContentLine, output.lastContentLine);
         }
     }
 
@@ -348,6 +352,7 @@ class Output
         indent();
         formattedWrite(buffer, fmt, args);
         stack.back = Entity.singleLine;
+        lastContentLine = lastestLine;
 
         if (first == Entity.bottom)
             first = Entity.singleLine;
@@ -469,6 +474,8 @@ class Output
         if (first == Entity.bottom)
             first = Entity.adaptiveLine;
 
+        lastContentLine = lastestLine;
+
         auto parts = adaptiveLineParts(fmt, args);
 
         chunks.put(Chunk(ChunkType.opening, parts[0], parts[1]));
@@ -715,13 +722,17 @@ D"[0 .. $ - 1]);
                 }
             }
         }
+
+        lastContentLine = comment.extent.end.line;
     }
 
     private void comment(in CommentIndex.Comment comment)
     {
-        if (lastestLine == comment.line)
+        auto wasInline = false;
+        if (lastContentLine == comment.line)
         {
             buffer.put(" ");
+            wasInline = true;
         }
         else if (stack.back != Entity.bottom)
         {
@@ -736,11 +747,14 @@ D"[0 .. $ - 1]);
 
         writeComment(comment);
 
-        stack.back = Entity.comment;
-
         if (first == Entity.bottom)
             first = Entity.comment;
 
+        if (!wasInline && lastestLine == comment.extent.end.line)
+            stack.back = Entity.separator;
+        else
+            stack.back = Entity.comment;
+
         lastestLine = comment.extent.end.line;
         lastestOffset = comment.extent.end.offset;
     }
diff --git a/tests/unit/CommentUnitTests.d b/tests/unit/CommentUnitTests.d
index d7ec906d..df1ed360 100644
--- a/tests/unit/CommentUnitTests.d
+++ b/tests/unit/CommentUnitTests.d
@@ -339,3 +339,35 @@ struct Foo
 D");
 
 }
+
+// Comment inside taken #ifdef branch must not join extern (C): line.
+unittest
+{
+    assertTranslates(
+q"C
+#define G1
+
+#ifdef  G1  // Guard1
+#define A 1
+#else
+#define A 2
+#endif
+
+#ifdef  G2  // Guard2
+#define B 3
+#else
+#define B 4
+#endif
+C",
+q"D
+extern (C):
+
+// Guard1
+
+enum A = 1;
+
+// Guard2
+
+enum B = 4;
+D", true);
+}