Optimize union case fields enumeration (#7840)

Author: auduchinok

src/fsharp/PatternMatchCompilation.fs

@@ -1031,7 +1031,7 @@ let CompilePatternBasic
                                                           (isNil origInputValTypars &&
                                                            not origInputVal.IsMemberOrModuleBinding &&
                                                            not ucref.Tycon.IsStructRecordOrUnionTycon  &&
-                                                           ucref.UnionCase.RecdFields.Length >= 1 &&
+                                                           ucref.UnionCase.RecdFieldsArray.Length >= 1 &&
                                                            ucref.Tycon.UnionCasesArray.Length > 1) ->
 
                        let v, vExpr = mkCompGenLocal m "unionCase" (mkProvenUnionCaseTy ucref tinst)

src/fsharp/SignatureConformance.fs

@@ -346,8 +346,8 @@ type Checker(g, amap, denv, remapInfo: SignatureRepackageInfo, checkingSig) =
             sigUnionCase.OtherRangeOpt <- Some (implUnionCase.Range, true)
             implUnionCase.OtherRangeOpt <- Some (sigUnionCase.Range, false)
             if implUnionCase.Id.idText <> sigUnionCase.Id.idText then  err FSComp.SR.ModuleContainsConstructorButNamesDiffer
-            elif implUnionCase.RecdFields.Length <> sigUnionCase.RecdFields.Length then err FSComp.SR.ModuleContainsConstructorButDataFieldsDiffer
-            elif not (List.forall2 (checkField aenv) implUnionCase.RecdFields sigUnionCase.RecdFields) then err FSComp.SR.ModuleContainsConstructorButTypesOfFieldsDiffer
+            elif implUnionCase.RecdFieldsArray.Length <> sigUnionCase.RecdFieldsArray.Length then err FSComp.SR.ModuleContainsConstructorButDataFieldsDiffer
+            elif not (Array.forall2 (checkField aenv) implUnionCase.RecdFieldsArray sigUnionCase.RecdFieldsArray) then err FSComp.SR.ModuleContainsConstructorButTypesOfFieldsDiffer
             elif isLessAccessible implUnionCase.Accessibility sigUnionCase.Accessibility then err FSComp.SR.ModuleContainsConstructorButAccessibilityDiffers
             else checkAttribs aenv implUnionCase.Attribs sigUnionCase.Attribs (fun attribs -> implUnionCase.Attribs <- attribs)