Don't let trivia content before make a member definition multiline

src/Fantomas.Tests/ClassTests.fs

@@ -109,7 +109,6 @@ type Shape2D(x0: float, y0: float) =
         and set yval = y <- yval
 
     abstract Area: float
-
     abstract Perimeter: float
     abstract Name: string
 
@@ -118,7 +117,6 @@ type Shape2D(x0: float, y0: float) =
         y <- y + dy
 
     abstract Rotate: float -> unit
-
     default this.Rotate(angle) = rotAngle <- rotAngle + angle
 """
 

src/Fantomas.Tests/TypeDeclarationTests.fs

@@ -95,7 +95,6 @@ type Test() =
     member this.Function1<'a>(x, y) = printfn "%A, %A" x y
 
     abstract AbstractMethod<'a, 'b> : 'a * 'b -> unit
-
     override this.AbstractMethod<'a, 'b>(x: 'a, y: 'b) = printfn "%A, %A" x y
 """
 
@@ -1033,4 +1032,23 @@ type FormattingSpecs() =
 
     [<Fact>]
     let ``false is false`` () = test <@ false = false @>
+"""
+
+[<Test>]
+let ``line comment above single line abstract slot should not make it multiline, 757`` () =
+    formatSourceString false """[<AllowNullLiteral>]
+type Graph2dOptions =
+    abstract zoomMin: float option with get, set
+    // abstract moment: MomentConstructor option with get, set
+    abstract maxHeight: HeightWidthType option with get, set
+    abstract zIndex: float option with get, set
+"""  config
+    |> prepend newline
+    |> should equal """
+[<AllowNullLiteral>]
+type Graph2dOptions =
+    abstract zoomMin: float option with get, set
+    // abstract moment: MomentConstructor option with get, set
+    abstract maxHeight: HeightWidthType option with get, set
+    abstract zIndex: float option with get, set
 """

src/Fantomas/CodePrinter.fs

@@ -2330,10 +2330,14 @@ and genMemberDefnList astContext node =
 
     | m::rest ->
         let attrs = getRangesFromAttributesFromSynMemberDefinition m
-        sepNlnConsideringTriviaContentBeforeWithAttributes m.Range attrs +>
-        (expressionFitsOnRestOfLine
-            (genMemberDefn astContext m)
-            (sepNlnBeforeMultilineConstruct m.Range attrs +> genMemberDefn astContext m +> onlyIf (List.isNotEmpty rest) sepNln))
+
+        sepNlnConsideringTriviaContentBeforeWithAttributes m.Range attrs
+        +> enterNode m.Range
+        +> (expressionFitsOnRestOfLine
+              (genMemberDefn astContext m)
+              (sepNlnBeforeMultilineConstruct m.Range attrs
+               +> genMemberDefn astContext m
+               +> onlyIf (List.isNotEmpty rest) sepNln))
 
         +> genMemberDefnList astContext rest