From e8fb02fff024fc385a07531ca3ae97b6b6552705 Mon Sep 17 00:00:00 2001
From: dawe <dawedawe@posteo.de>
Date: Tue, 19 Dec 2023 22:00:31 +0100
Subject: [PATCH 1/4] add test

---
 .../PatternMatchingTests.fs                   | 23 +++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/src/Fantomas.Core.Tests/PatternMatchingTests.fs b/src/Fantomas.Core.Tests/PatternMatchingTests.fs
index 5b1126345a..011c906f4f 100644
--- a/src/Fantomas.Core.Tests/PatternMatchingTests.fs
+++ b/src/Fantomas.Core.Tests/PatternMatchingTests.fs
@@ -2262,3 +2262,26 @@ match subcategory with
 // Just treat as an unknown-to-LanguageService error.
  -> false
 """
+
+[<Test>]
+let ``comment lost after named pat pair, 2953`` () =
+    formatSourceString
+        """
+match synExpr with
+| SynExpr.App(
+    argExpr = SynExpr.Match _ // CCC
+    )
+     ->
+Some ident.idRange
+| _ -> defaultTraverse synExpr
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+match synExpr with
+| SynExpr.App(argExpr = SynExpr.Match _) -> // CCC
+    Some ident.idRange
+| _ -> defaultTraverse synExpr
+"""

From d8f5d8f0e22f3e2e2fd2fd975314e4e084d701c6 Mon Sep 17 00:00:00 2001
From: dawe <dawedawe@posteo.de>
Date: Tue, 19 Dec 2023 22:00:46 +0100
Subject: [PATCH 2/4] add changelog entry

---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4681412e53..15e388ab33 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@
 
 ### Fixed
 * Unmatched '{' error when formatting the code. [#3017](https://github.com/fsprojects/fantomas/issues/3017)
+* Comment lost after named pat pair. [#2953](https://github.com/fsprojects/fantomas/issues/2953)
 
 ## 6.3.0-alpha-004 - 2023-12-06
 

From 09b0b5b46e04d46352054510850df433225c208c Mon Sep 17 00:00:00 2001
From: dawe <dawedawe@posteo.de>
Date: Tue, 19 Dec 2023 22:01:09 +0100
Subject: [PATCH 3/4] try fix which isn't idempotent

---
 src/Fantomas.Core/CodePrinter.fs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/Fantomas.Core/CodePrinter.fs b/src/Fantomas.Core/CodePrinter.fs
index 42f5474b19..f8b187173a 100644
--- a/src/Fantomas.Core/CodePrinter.fs
+++ b/src/Fantomas.Core/CodePrinter.fs
@@ -2594,6 +2594,7 @@ let genPat (p: Pattern) =
             +> genSingleTextNode node.Equals
             +> sepSpace
             +> genPat node.Pattern
+            |> genNode node
 
         let pats =
             expressionFitsOnRestOfLine

From cd04b16583acbda08d7652d7185884ec3ac65cf7 Mon Sep 17 00:00:00 2001
From: dawe <dawedawe@posteo.de>
Date: Wed, 20 Dec 2023 14:04:52 +0100
Subject: [PATCH 4/4] fix idempotency issue by adding a conditional newline
 after the pats

---
 src/Fantomas.Core.Tests/PatternMatchingTests.fs | 5 +++--
 src/Fantomas.Core/CodePrinter.fs                | 6 +++++-
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/src/Fantomas.Core.Tests/PatternMatchingTests.fs b/src/Fantomas.Core.Tests/PatternMatchingTests.fs
index 011c906f4f..74db05a604 100644
--- a/src/Fantomas.Core.Tests/PatternMatchingTests.fs
+++ b/src/Fantomas.Core.Tests/PatternMatchingTests.fs
@@ -2281,7 +2281,8 @@ Some ident.idRange
         equal
         """
 match synExpr with
-| SynExpr.App(argExpr = SynExpr.Match _) -> // CCC
-    Some ident.idRange
+| SynExpr.App(
+    argExpr = SynExpr.Match _ // CCC
+    ) -> Some ident.idRange
 | _ -> defaultTraverse synExpr
 """
diff --git a/src/Fantomas.Core/CodePrinter.fs b/src/Fantomas.Core/CodePrinter.fs
index f8b187173a..042cd9a7c8 100644
--- a/src/Fantomas.Core/CodePrinter.fs
+++ b/src/Fantomas.Core/CodePrinter.fs
@@ -2605,7 +2605,11 @@ let genPat (p: Pattern) =
         +> optSingle genTyparDecls node.TyparDecls
         +> addSpaceBeforeParenInPattern node.Identifier
         +> genSingleTextNode node.OpeningParen
-        +> autoIndentAndNlnIfExpressionExceedsPageWidth (sepNlnWhenWriteBeforeNewlineNotEmpty +> pats)
+        +> autoIndentAndNlnIfExpressionExceedsPageWidth (
+            sepNlnWhenWriteBeforeNewlineNotEmpty
+            +> pats
+            +> sepNlnWhenWriteBeforeNewlineNotEmpty
+        )
         +> genSingleTextNode node.ClosingParen
         |> genNode node