Add space before parameters passed to inherited class. Fixes #720 (#723)

src/Fantomas.Tests/ClassTests.fs

@@ -465,3 +465,36 @@ type A =
     [<Emit("b")>]
     abstract b: Unit -> string
 """
+
+[<Test>]
+let ``string parameter to inherited class, 720`` () =
+    formatSourceString false """type Child() =
+  inherit Parent ""
+"""  config
+    |> prepend newline
+    |> should equal """
+type Child() =
+    inherit Parent ""
+"""
+
+[<Test>]
+let ``float parameter to inherited class`` () =
+    formatSourceString false """type Child() =
+  inherit Parent 7.9
+"""  config
+    |> prepend newline
+    |> should equal """
+type Child() =
+    inherit Parent 7.9
+"""
+
+[<Test>]
+let ``unit parameter to inherited class`` () =
+    formatSourceString false """type Child() =
+  inherit Parent ()
+"""  config
+    |> prepend newline
+    |> should equal """
+type Child() =
+    inherit Parent()
+"""

src/Fantomas/CodePrinter.fs

@@ -2112,7 +2112,13 @@ and genMemberDefn astContext node =
     | MDNestedType _ -> invalidArg "md" "This is not implemented in F# compiler"
     | MDOpen(s) -> !- (sprintf "open %s" s)
     // What is the role of so
-    | MDImplicitInherit(t, e, _) -> !- "inherit " +> genType astContext false t +> genExpr astContext e
+    | MDImplicitInherit(t, e, _) ->
+        let addSpaceAfterType =
+            match e with
+            | SynExpr.Const(SynConst.Unit, _) -> false
+            | SynExpr.Const(_, _) -> true // string, numbers, ...
+            | _ -> false
+        !- "inherit " +> genType astContext false t +> ifElse addSpaceAfterType sepSpace sepNone +> genExpr astContext e
     | MDInherit(t, _) -> !- "inherit " +> genType astContext false t
     | MDValField f -> genField astContext "val " f
     | MDImplicitCtor(ats, ao, ps, so) ->