Improve Unclear error FS3204 Multicase union struct

src/Compiler/Checking/CheckDeclarations.fs

@@ -3162,8 +3162,21 @@ module EstablishTypeDefinitionCores =
                     if not ctorArgNames.IsEmpty then errorR (Error(FSComp.SR.parsOnlyClassCanTakeValueArguments(), m))
 
             let envinner = AddDeclaredTypars CheckForDuplicateTypars (tycon.Typars m) envinner
-            let envinner = MakeInnerEnvForTyconRef envinner thisTyconRef false 
+            let envinner = MakeInnerEnvForTyconRef envinner thisTyconRef false
+
+            let multiCaseUnionStructCheck (unionCases: UnionCase list) =
+                if tycon.IsStructRecordOrUnionTycon && unionCases.Length > 1 then 
+                    let fieldNames = [ for uc in unionCases do for ft in uc.FieldTable.TrueInstanceFieldsAsList do yield ft ]
+                    let fieldNames = fieldNames |> List.map(fun x -> (x.LogicalName, x.rfield_name_generated, x.Range))
+
+                    if fieldNames |> List.distinctBy(fun (name, _, _) -> name) |> List.length <> fieldNames.Length then
+                        let fieldRanges =
+                            fieldNames
+                            |> List.filter(fun (name, isGenerated, _) -> (not isGenerated || name = "Item") || isGenerated)
+                            |> List.map(fun (_, _, m) -> m)
 
+                        for m in fieldRanges do
+                            errorR(Error(FSComp.SR.tcStructUnionMultiCaseDistinctFields(), m))
 
             // Notify the Language Service about field names in record/class declaration
             let ad = envinner.AccessRights
@@ -3255,10 +3268,7 @@ module EstablishTypeDefinitionCores =
 
                     let hasRQAAttribute = HasFSharpAttribute cenv.g cenv.g.attrib_RequireQualifiedAccessAttribute tycon.Attribs
                     let unionCases = TcRecdUnionAndEnumDeclarations.TcUnionCaseDecls cenv envinner innerParent thisTy thisTyInst hasRQAAttribute tpenv unionCases
-                    if tycon.IsStructRecordOrUnionTycon && unionCases.Length > 1 then 
-                      let fieldNames = [ for uc in unionCases do for ft in uc.FieldTable.TrueInstanceFieldsAsList do yield ft.LogicalName ]
-                      if fieldNames |> List.distinct |> List.length <> fieldNames.Length then 
-                          errorR(Error(FSComp.SR.tcStructUnionMultiCaseDistinctFields(), m))
+                    multiCaseUnionStructCheck unionCases
 
                     writeFakeUnionCtorsToSink unionCases
                     let repr = Construct.MakeUnionRepr unionCases

src/Compiler/FSComp.txt

@@ -1372,7 +1372,7 @@ tcTupleStructMismatch,"One tuple type is a struct tuple, the other is a referenc
 3201,tcModuleAbbrevFirstInMutRec,"In a recursive declaration group, module abbreviations must come after all 'open' declarations and before other declarations"
 3202,tcUnsupportedMutRecDecl,"This declaration is not supported in recursive declaration groups"
 3203,parsInvalidUseOfRec,"Invalid use of 'rec' keyword"
-3204,tcStructUnionMultiCaseDistinctFields,"If a union type has more than one case and is a struct, then all fields within the union type must be given unique names."
+3204,tcStructUnionMultiCaseDistinctFields,"If a union type has more than one case and is a struct, then all fields within the union type must be given unique field names. For example: 'type A = B of b: int | C of c: int' (unique field names 'b' and 'c' assigned)."
 3206,CallerMemberNameIsOverriden,"The CallerMemberNameAttribute applied to parameter '%s' will have no effect. It is overridden by the CallerFilePathAttribute."
 3207,tcFixedNotAllowed,"Invalid use of 'fixed'. 'fixed' may only be used in a declaration of the form 'use x = fixed expr' where the expression is an array, the address of a field, the address of an array element or a string'"
 3208,tcCouldNotFindOffsetToStringData,"Could not find method System.Runtime.CompilerServices.OffsetToStringData in references when building 'fixed' expression."

src/Compiler/xlf/FSComp.txt.cs.xlf

@@ -7513,8 +7513,8 @@
         <note />
       </trans-unit>
       <trans-unit id="tcStructUnionMultiCaseDistinctFields">
-        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique names.</source>
-        <target state="translated">Pokud je typ sjednocení struktura a obsahuje více než jeden případ, všem polím v tomto typu sjednocení se musí přiřadit jedinečný název.</target>
+        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique field names. For example: 'type A = B of b: int | C of c: int' (unique field names 'b' and 'c' assigned).</source>
+        <target state="needs-review-translation">Pokud je typ sjednocení struktura a obsahuje více než jeden případ, všem polím v tomto typu sjednocení se musí přiřadit jedinečný název.</target>
         <note />
       </trans-unit>
       <trans-unit id="CallerMemberNameIsOverriden">

src/Compiler/xlf/FSComp.txt.de.xlf

@@ -7513,8 +7513,8 @@
         <note />
       </trans-unit>
       <trans-unit id="tcStructUnionMultiCaseDistinctFields">
-        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique names.</source>
-        <target state="translated">Wenn ein Union-Typ mehrere case-Anweisungen aufweist und eine Struktur ist, müssen für alle Felder im Union-Typ eindeutige Namen angegeben werden.</target>
+        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique field names. For example: 'type A = B of b: int | C of c: int' (unique field names 'b' and 'c' assigned).</source>
+        <target state="needs-review-translation">Wenn ein Union-Typ mehrere case-Anweisungen aufweist und eine Struktur ist, müssen für alle Felder im Union-Typ eindeutige Namen angegeben werden.</target>
         <note />
       </trans-unit>
       <trans-unit id="CallerMemberNameIsOverriden">

src/Compiler/xlf/FSComp.txt.es.xlf

@@ -7513,8 +7513,8 @@
         <note />
       </trans-unit>
       <trans-unit id="tcStructUnionMultiCaseDistinctFields">
-        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique names.</source>
-        <target state="translated">Si un tipo de unión tiene más de un caso y un struct, a todos los campos dentro del tipo de unión se les deben dar nombres únicos.</target>
+        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique field names. For example: 'type A = B of b: int | C of c: int' (unique field names 'b' and 'c' assigned).</source>
+        <target state="needs-review-translation">Si un tipo de unión tiene más de un caso y un struct, a todos los campos dentro del tipo de unión se les deben dar nombres únicos.</target>
         <note />
       </trans-unit>
       <trans-unit id="CallerMemberNameIsOverriden">

src/Compiler/xlf/FSComp.txt.fr.xlf

@@ -7513,8 +7513,8 @@
         <note />
       </trans-unit>
       <trans-unit id="tcStructUnionMultiCaseDistinctFields">
-        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique names.</source>
-        <target state="translated">Si un type union a plusieurs étiquettes case, et s'il s'agit d'un struct, tous les champs du type union doivent avoir des noms uniques.</target>
+        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique field names. For example: 'type A = B of b: int | C of c: int' (unique field names 'b' and 'c' assigned).</source>
+        <target state="needs-review-translation">Si un type union a plusieurs étiquettes case, et s'il s'agit d'un struct, tous les champs du type union doivent avoir des noms uniques.</target>
         <note />
       </trans-unit>
       <trans-unit id="CallerMemberNameIsOverriden">

src/Compiler/xlf/FSComp.txt.it.xlf

@@ -7513,8 +7513,8 @@
         <note />
       </trans-unit>
       <trans-unit id="tcStructUnionMultiCaseDistinctFields">
-        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique names.</source>
-        <target state="translated">Se un tipo di unione contiene più di un case ed è una struttura, è necessario assegnare nomi univoci a tutti i campi all'interno del tipo di unione.</target>
+        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique field names. For example: 'type A = B of b: int | C of c: int' (unique field names 'b' and 'c' assigned).</source>
+        <target state="needs-review-translation">Se un tipo di unione contiene più di un case ed è una struttura, è necessario assegnare nomi univoci a tutti i campi all'interno del tipo di unione.</target>
         <note />
       </trans-unit>
       <trans-unit id="CallerMemberNameIsOverriden">

src/Compiler/xlf/FSComp.txt.ja.xlf

@@ -7513,8 +7513,8 @@
         <note />
       </trans-unit>
       <trans-unit id="tcStructUnionMultiCaseDistinctFields">
-        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique names.</source>
-        <target state="translated">共用体型が複数のケースを持つ 1 つの構造体である場合は、共用体型内のすべてのフィールドに一意の名前を付ける必要があります。</target>
+        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique field names. For example: 'type A = B of b: int | C of c: int' (unique field names 'b' and 'c' assigned).</source>
+        <target state="needs-review-translation">共用体型が複数のケースを持つ 1 つの構造体である場合は、共用体型内のすべてのフィールドに一意の名前を付ける必要があります。</target>
         <note />
       </trans-unit>
       <trans-unit id="CallerMemberNameIsOverriden">

src/Compiler/xlf/FSComp.txt.ko.xlf

@@ -7513,8 +7513,8 @@
         <note />
       </trans-unit>
       <trans-unit id="tcStructUnionMultiCaseDistinctFields">
-        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique names.</source>
-        <target state="translated">공용 구조체 형식이 둘 이상의 case를 포함하고 구조체인 경우 공용 구조체 형식 내의 모든 필드에 고유한 이름을 지정해야 합니다.</target>
+        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique field names. For example: 'type A = B of b: int | C of c: int' (unique field names 'b' and 'c' assigned).</source>
+        <target state="needs-review-translation">공용 구조체 형식이 둘 이상의 case를 포함하고 구조체인 경우 공용 구조체 형식 내의 모든 필드에 고유한 이름을 지정해야 합니다.</target>
         <note />
       </trans-unit>
       <trans-unit id="CallerMemberNameIsOverriden">

src/Compiler/xlf/FSComp.txt.pl.xlf

@@ -7513,8 +7513,8 @@
         <note />
       </trans-unit>
       <trans-unit id="tcStructUnionMultiCaseDistinctFields">
-        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique names.</source>
-        <target state="translated">Jeśli typ unii ma więcej niż jeden przypadek i jest strukturą, wszystkim polom w typie unii należy nadać unikatowe nazwy.</target>
+        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique field names. For example: 'type A = B of b: int | C of c: int' (unique field names 'b' and 'c' assigned).</source>
+        <target state="needs-review-translation">Jeśli typ unii ma więcej niż jeden przypadek i jest strukturą, wszystkim polom w typie unii należy nadać unikatowe nazwy.</target>
         <note />
       </trans-unit>
       <trans-unit id="CallerMemberNameIsOverriden">

src/Compiler/xlf/FSComp.txt.pt-BR.xlf

@@ -7513,8 +7513,8 @@
         <note />
       </trans-unit>
       <trans-unit id="tcStructUnionMultiCaseDistinctFields">
-        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique names.</source>
-        <target state="translated">Se um tipo de união tiver mais de um caso e for struct, então todos os campos dentro do tipo de união deverão ter nomes exclusivos.</target>
+        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique field names. For example: 'type A = B of b: int | C of c: int' (unique field names 'b' and 'c' assigned).</source>
+        <target state="needs-review-translation">Se um tipo de união tiver mais de um caso e for struct, então todos os campos dentro do tipo de união deverão ter nomes exclusivos.</target>
         <note />
       </trans-unit>
       <trans-unit id="CallerMemberNameIsOverriden">

src/Compiler/xlf/FSComp.txt.ru.xlf

@@ -7513,8 +7513,8 @@
         <note />
       </trans-unit>
       <trans-unit id="tcStructUnionMultiCaseDistinctFields">
-        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique names.</source>
-        <target state="translated">Если тип объединения имеет более одного варианта и является структурой, всем полям в типе объединения необходимо присвоить уникальные имена.</target>
+        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique field names. For example: 'type A = B of b: int | C of c: int' (unique field names 'b' and 'c' assigned).</source>
+        <target state="needs-review-translation">Если тип объединения имеет более одного варианта и является структурой, всем полям в типе объединения необходимо присвоить уникальные имена.</target>
         <note />
       </trans-unit>
       <trans-unit id="CallerMemberNameIsOverriden">

src/Compiler/xlf/FSComp.txt.tr.xlf

@@ -7513,8 +7513,8 @@
         <note />
       </trans-unit>
       <trans-unit id="tcStructUnionMultiCaseDistinctFields">
-        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique names.</source>
-        <target state="translated">Bir birleşim türü büyük ve küçük harfler içeriyorsa ve bir yapıysa, birleşim türü içindeki tüm alanlara benzersiz adlar verilmelidir.</target>
+        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique field names. For example: 'type A = B of b: int | C of c: int' (unique field names 'b' and 'c' assigned).</source>
+        <target state="needs-review-translation">Bir birleşim türü büyük ve küçük harfler içeriyorsa ve bir yapıysa, birleşim türü içindeki tüm alanlara benzersiz adlar verilmelidir.</target>
         <note />
       </trans-unit>
       <trans-unit id="CallerMemberNameIsOverriden">

src/Compiler/xlf/FSComp.txt.zh-Hans.xlf

@@ -7513,8 +7513,8 @@
         <note />
       </trans-unit>
       <trans-unit id="tcStructUnionMultiCaseDistinctFields">
-        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique names.</source>
-        <target state="translated">如果联合类型有多个用例且为结构，则必须赋予此联合类型中的所有字段唯一的名称。</target>
+        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique field names. For example: 'type A = B of b: int | C of c: int' (unique field names 'b' and 'c' assigned).</source>
+        <target state="needs-review-translation">如果联合类型有多个用例且为结构，则必须赋予此联合类型中的所有字段唯一的名称。</target>
         <note />
       </trans-unit>
       <trans-unit id="CallerMemberNameIsOverriden">

src/Compiler/xlf/FSComp.txt.zh-Hant.xlf

@@ -7513,8 +7513,8 @@
         <note />
       </trans-unit>
       <trans-unit id="tcStructUnionMultiCaseDistinctFields">
-        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique names.</source>
-        <target state="translated">如果等位型別有一個以上的案例並且為結構，等位型別內所有欄位的名稱就都不得重複。</target>
+        <source>If a union type has more than one case and is a struct, then all fields within the union type must be given unique field names. For example: 'type A = B of b: int | C of c: int' (unique field names 'b' and 'c' assigned).</source>
+        <target state="needs-review-translation">如果等位型別有一個以上的案例並且為結構，等位型別內所有欄位的名稱就都不得重複。</target>
         <note />
       </trans-unit>
       <trans-unit id="CallerMemberNameIsOverriden">