From 4e841c405554d019814cae8927cc87fde8f4e44f Mon Sep 17 00:00:00 2001
From: dawe <dawedawe@posteo.de>
Date: Wed, 10 Nov 2021 15:42:22 +0100
Subject: [PATCH 1/2] Fix 1954: val mutable in signature loses 'mutable'

---
 src/Fantomas.Tests/SignatureTests.fs | 18 ++++++++++++++++++
 src/Fantomas/CodePrinter.fs          |  5 +++--
 src/Fantomas/SourceParser.fs         |  4 ++--
 3 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/src/Fantomas.Tests/SignatureTests.fs b/src/Fantomas.Tests/SignatureTests.fs
index b9eed23bc2..5c683b1eab 100644
--- a/src/Fantomas.Tests/SignatureTests.fs
+++ b/src/Fantomas.Tests/SignatureTests.fs
@@ -171,6 +171,24 @@ module Tainted
 val GetHashCodeTainted: (Tainted<'T> -> int) when 'T: equality
 """
 
+[<Test>]
+let ``should keep mutable in type signature, 1954`` () =
+    formatSourceString
+        true
+        """
+module Tainted
+val mutable showParserStackOnParseError: bool
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+module Tainted
+
+val mutable showParserStackOnParseError: bool
+"""
+
 [<Test>]
 let ``should keep access modifiers in signatures seperated`` () =
     formatSourceString
diff --git a/src/Fantomas/CodePrinter.fs b/src/Fantomas/CodePrinter.fs
index b7870f753f..a11012a516 100644
--- a/src/Fantomas/CodePrinter.fs
+++ b/src/Fantomas/CodePrinter.fs
@@ -867,7 +867,7 @@ and genMemberFlagsForMemberBinding astContext (mf: MemberFlags) (rangeOfBindingA
             |> Option.defaultValue (!- "override ")
         <| ctx
 
-and genVal astContext (Val (ats, px, ao, s, identRange, t, vi, isInline, _, eo) as node) =
+and genVal astContext (Val (ats, px, ao, s, identRange, t, vi, isInline, isMutable, _, eo) as node) =
     let range, synValTyparDecls =
         match node with
         | ValSpfn (_, _, synValTyparDecls, _, _, _, _, _, _, _, range) -> range, synValTyparDecls
@@ -883,6 +883,7 @@ and genVal astContext (Val (ats, px, ao, s, identRange, t, vi, isInline, _, eo)
     +> genAttributes astContext ats
     +> (!- "val "
         +> onlyIf isInline (!- "inline ")
+        +> onlyIf isMutable (!- "mutable ")
         +> opt sepSpace ao genAccess
         -- s
         +> genericParams
@@ -4045,7 +4046,7 @@ and genMemberSig astContext node =
         | SynMemberSig.NestedType (_, r) -> r, SynMemberSig_NestedType
 
     match node with
-    | MSMember (Val (ats, px, ao, s, _, t, vi, isInline, ValTyparDecls (tds, _, tcs), eo), mf) ->
+    | MSMember (Val (ats, px, ao, s, _, t, vi, isInline, _, ValTyparDecls (tds, _, tcs), eo), mf) ->
         let (FunType namedArgs) = (t, vi)
 
         let isFunctionProperty =
diff --git a/src/Fantomas/SourceParser.fs b/src/Fantomas/SourceParser.fs
index 3a29e4af27..1be8c46c95 100644
--- a/src/Fantomas/SourceParser.fs
+++ b/src/Fantomas/SourceParser.fs
@@ -1510,9 +1510,9 @@ let (|MSMember|MSInterface|MSInherit|MSValField|MSNestedType|) =
     | SynMemberSig.NestedType (tds, _) -> MSNestedType tds
 
 let (|Val|)
-    (ValSpfn (ats, (IdentOrKeyword (OpNameFullInPattern (s, _)) as ident), tds, t, vi, isInline, _, px, ao, eo, _))
+    (ValSpfn (ats, (IdentOrKeyword (OpNameFullInPattern (s, _)) as ident), tds, t, vi, isInline, isMutable, px, ao, eo, _))
     =
-    (ats, px, ao, s, ident.idRange, t, vi, isInline, tds, eo)
+    (ats, px, ao, s, ident.idRange, t, vi, isInline, isMutable, tds, eo)
 
 // Misc
 

From 2eb43b91564914283db50a742fd8ddb505fd2838 Mon Sep 17 00:00:00 2001
From: dawe <dawedawe@posteo.de>
Date: Wed, 10 Nov 2021 15:52:15 +0100
Subject: [PATCH 2/2] Fix formatting of (|Val|)

---
 src/Fantomas/SourceParser.fs | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/Fantomas/SourceParser.fs b/src/Fantomas/SourceParser.fs
index 1be8c46c95..6fd51bee08 100644
--- a/src/Fantomas/SourceParser.fs
+++ b/src/Fantomas/SourceParser.fs
@@ -1510,7 +1510,17 @@ let (|MSMember|MSInterface|MSInherit|MSValField|MSNestedType|) =
     | SynMemberSig.NestedType (tds, _) -> MSNestedType tds
 
 let (|Val|)
-    (ValSpfn (ats, (IdentOrKeyword (OpNameFullInPattern (s, _)) as ident), tds, t, vi, isInline, isMutable, px, ao, eo, _))
+    (ValSpfn (ats,
+              (IdentOrKeyword (OpNameFullInPattern (s, _)) as ident),
+              tds,
+              t,
+              vi,
+              isInline,
+              isMutable,
+              px,
+              ao,
+              eo,
+              _))
     =
     (ats, px, ao, s, ident.idRange, t, vi, isInline, isMutable, tds, eo)