Add quotes to character in ASTTransformer (#3077)

* Add quotes to character in ASTTransformer

* Update changelog

Co-authored-by: Florian Verdonck <[email protected]>

---------

Co-authored-by: Florian Verdonck <[email protected]>

Author: ErikSchierboom

CHANGELOG.md

@@ -1,5 +1,10 @@
 # Changelog
 
+## 6.3.3 - 2024-04-12
+
+### Fixed
+* FormatASTAsync loses single quotes for characters. [#3076](https://github.com/fsprojects/fantomas/issues/3076)
+
 ## 6.3.2 - 2024-04-12
 
 ### Changed

src/Fantomas.Core.Tests/StringTests.fs

@@ -335,3 +335,7 @@ bbb\"\"\"
 let ``unicode null character should be recognized as a trivia item, 2050`` () =
     formatSourceString "let s = \"\\000\"" config
     |> should equal "let s = \"\\000\"\n"
+
+[<Test>]
+let ``character quotes should be preserved, 3076`` () =
+    formatAST false "let s = 'A'" config |> should equal "let s = 'A'\n"

src/Fantomas.Core/ASTTransformer.fs

@@ -139,7 +139,7 @@ let mkConstant (creationAide: CreationAide) c r : Constant =
             | '\\' -> @"'\\'"
             | '\b' -> @"'\b'"
             | '\f' -> @"'\f'"
-            | _ -> c.ToString()
+            | _ -> $"'%c{c}'"
 
         orElse escapedChar
     | SynConst.Bytes(bytes, _, r) ->