only call sepSpaceBeforeClassConstructor if we are generating a class (…

…#2284)

* only call sepSpaceBeforeClassConstructor if we are generating a class, fixes 2226

* Use Option.isNone

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## [Unreleased]
 
 ### Fixed
+* Explicit interface with SpaceBeforeClassConstructor. [#2226](https://github.com/fsprojects/fantomas/issues/2226)
 * Spaces around binary operators in units of measure. [#2207](https://github.com/fsprojects/fantomas/issues/2207)
 
 ## [5.0.0-alpha-008] - 2022-05-28

src/Fantomas.Core.Tests/InterfaceTests.fs

@@ -591,3 +591,38 @@ and Bar =
         [<SomeAttribute>]
         member this.SomeFunctionWithReturnType(a: int) : int = a + 5
 """
+
+[<Test>]
+let ``explicit interface with SpaceBeforeClassConstructor, 2226`` () =
+    formatSourceString
+        false
+        """
+type IInterface =
+    interface
+    end
+
+type IInterface2 =
+    interface
+        abstract member X: unit -> unit
+    end
+
+type IInterface3 =
+    abstract member X: unit -> unit
+"""
+        { config with SpaceBeforeClassConstructor = true }
+    |> prepend newline
+    |> should
+        equal
+        """
+type IInterface =
+    interface
+    end
+
+type IInterface2 =
+    interface
+        abstract member X: unit -> unit
+    end
+
+type IInterface3 =
+    abstract member X: unit -> unit
+"""

src/Fantomas.Core/CodePrinter.fs

@@ -3722,10 +3722,12 @@ and genTypeDefn
             | TCSimple TCInterface -> Some range
             | _ -> None
 
+        let isClass = Option.isNone interfaceRange
+
         let astContext = { astContext with InterfaceRange = interfaceRange }
 
         typeName
-        +> sepSpaceBeforeClassConstructor
+        +> onlyIf isClass sepSpaceBeforeClassConstructor
         +> leadingExpressionIsMultiline (opt sepNone impCtor (genMemberDefn astContext)) (fun isMulti ctx ->
             if isMulti
                && ctx.Config.AlternativeLongMemberDefinitions then