Make reflection.h types C++20 compatible.

As of C++20, it is malformed to have an unnamed class used in typedef with a base class. In the generated reflection code for a struct, we were using the following construct to create a reflectable entry for each field in a struct. ``` struct var { typedef struct /* no name */ : ::bond::reflection::FieldTemplate<...> {} field_name; } ``` Now, instead of using an unnamed class, we generate a named class and refer to that: ``` struct var { typedef struct field_name_type : ::bond::reflection::FieldTemplate<...> {} field_name; } ``` Since the "field_name_type" struct now has a name in the `var` struct, it may conflict with user-defined field names in the struct. (E.g., if there is another field with the name "field_name_type") To avoid this problem, we ensure that the generated type name is unique. This means that the name of the type may change as fields are add/removed from structs. Only the member for each field in the `var` struct is part of the interface, not the name of the type providing its implementation, so we're free to change the names of these types now and at any time in the future. See also, [C++ proposal P1766R1][1], which make the code we had malformed. Fixes microsoft#1027 [1]: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1766r1.html
chwarr · Apr 29, 2020 · f1cb707 · f1cb707
1 parent 802438e
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -22,6 +22,10 @@ different versioning scheme, following the Haskell community's
   for MSVC 2013, which is no longer a supported compiler.
 * Fixed MSVC warning for deprecation of `std::result_of_t` in `/std:c++17`.
   ([Issue #1007](https://github.com/microsoft/bond/issues/1007))
+* Fixed MSVC warning C5208: unnamed class used in typedef name cannot
+  declare members other than non-static data members, member enumerations,
+  or member classes. ([Issue
+  #1027](https://github.com/microsoft/bond/issues/1027))
 
 ### C# ###
 

diff --git a/compiler/src/Language/Bond/Codegen/Cpp/Reflection_h.hs b/compiler/src/Language/Bond/Codegen/Cpp/Reflection_h.hs
@@ -31,7 +31,7 @@ reflection_h export_attribute cpp file imports declarations = ("_reflection.h",
 #{CPP.closeNamespace cpp}
 |])
   where
-    idl = MappingContext idlTypeMapping [] [] []  
+    idl = MappingContext idlTypeMapping [] [] []
 
     -- C++ type
     cppType = getTypeName cpp
@@ -51,7 +51,7 @@ reflection_h export_attribute cpp file imports declarations = ("_reflection.h",
         #{newlineBeginSep 2 fieldMetadata structFields}
 
         public: struct var
-        {#{fieldTemplates structFields}};
+        {#{fieldTemplates (zip structFields uniqueFieldTemplateStructNames)}};
 
         private: typedef boost::mpl::list<> fields0;
         #{newlineSep 2 pushField indexedFields}
@@ -92,7 +92,7 @@ reflection_h export_attribute cpp file imports declarations = ("_reflection.h",
         }|]
           where
             static Field {..} = [lt|(void)s_#{fieldName}_metadata;|]
-        
+
         -- reversed list of field names zipped with indexes
         indexedFields :: [(String, Int)]
         indexedFields = zipWith ((,) . fieldName) (reverse structFields) [0..]
@@ -106,16 +106,25 @@ reflection_h export_attribute cpp file imports declarations = ("_reflection.h",
         fieldMetadata Field {..} =
             [lt|private: #{export_attr}static const ::bond::Metadata s_#{fieldName}_metadata;|]
 
-        fieldTemplates = F.foldMap $ \ f@Field {..} -> [lt|
+        -- fieldTemplateReservedNames are names used in ::bond::reflection::FieldTemplate<>
+        fieldTemplateReservedNames = ["FieldTemplate", "struct_type", "field_pointer", "field_type", "value_type", "field_modifier", "metadata", "field", "id", "GetVariable"]
+
+        fieldNames = map (\f -> fieldName f) structFields
+
+        fieldTemplateStructReservedNames = fieldTemplateReservedNames ++ fieldNames
+
+        uniqueFieldTemplateStructNames = uniqueNames (map (\n -> n ++ "_type") fieldNames) fieldTemplateStructReservedNames
+
+        fieldTemplates = F.foldMap $ \ (f@Field {..}, sn) -> [lt|
             // #{fieldName}
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct #{sn} : ::bond::reflection::FieldTemplate<
                 #{fieldOrdinal},
                 #{CPP.modifierTag f},
                 #{className},
                 #{cppType fieldType},
                 &#{className}::#{fieldName},
                 &s_#{fieldName}_metadata
-            > {}  #{fieldName};
+            > {} #{fieldName};
         |]
 
 

diff --git a/compiler/tests/TestMain.hs b/compiler/tests/TestMain.hs
@@ -76,6 +76,7 @@ tests = testGroup "Compiler tests"
             , verifyCppCodegen "aliases"
             , verifyCppCodegen "alias_key"
             , verifyCppCodegen "maybe_blob"
+            , verifyCppCodegen "metadata_edge_cases"
             , verifyCodegen
                 [ "c++"
                 , "--enum-header"

diff --git a/compiler/tests/generated/alias_key_reflection.h b/compiler/tests/generated/alias_key_reflection.h
@@ -21,24 +21,24 @@ namespace test
         public: struct var
         {
             // m
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct m_type : ::bond::reflection::FieldTemplate<
                 0,
                 ::bond::reflection::optional_field_modifier,
                 foo,
                 std::map<std::string, int32_t>,
                 &foo::m,
                 &s_m_metadata
-            > {}  m;
+            > {} m;
 
             // s
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct s_type : ::bond::reflection::FieldTemplate<
                 1,
                 ::bond::reflection::optional_field_modifier,
                 foo,
                 std::set<int32_t>,
                 &foo::s,
                 &s_s_metadata
-            > {}  s;
+            > {} s;
         };
 
         private: typedef boost::mpl::list<> fields0;

diff --git a/compiler/tests/generated/alias_with_allocator_reflection.h b/compiler/tests/generated/alias_with_allocator_reflection.h
@@ -31,124 +31,124 @@ namespace test
         public: struct var
         {
             // l
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct l_type : ::bond::reflection::FieldTemplate<
                 0,
                 ::bond::reflection::optional_field_modifier,
                 foo,
                 std::list<bool, typename std::allocator_traits<arena>::template rebind_alloc<bool> >,
                 &foo::l,
                 &s_l_metadata
-            > {}  l;
+            > {} l;
 
             // v
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct v_type : ::bond::reflection::FieldTemplate<
                 1,
                 ::bond::reflection::optional_field_modifier,
                 foo,
                 std::vector<bool, typename std::allocator_traits<arena>::template rebind_alloc<bool> >,
                 &foo::v,
                 &s_v_metadata
-            > {}  v;
+            > {} v;
 
             // s
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct s_type : ::bond::reflection::FieldTemplate<
                 2,
                 ::bond::reflection::optional_field_modifier,
                 foo,
                 std::set<bool, std::less<bool>, typename std::allocator_traits<arena>::template rebind_alloc<bool> >,
                 &foo::s,
                 &s_s_metadata
-            > {}  s;
+            > {} s;
 
             // m
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct m_type : ::bond::reflection::FieldTemplate<
                 3,
                 ::bond::reflection::optional_field_modifier,
                 foo,
                 std::map<std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> >, bool, std::less<std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> > >, typename std::allocator_traits<arena>::template rebind_alloc<std::pair<const std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> >, bool> > >,
                 &foo::m,
                 &s_m_metadata
-            > {}  m;
+            > {} m;
 
             // st
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct st_type : ::bond::reflection::FieldTemplate<
                 4,
                 ::bond::reflection::optional_field_modifier,
                 foo,
                 std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> >,
                 &foo::st,
                 &s_st_metadata
-            > {}  st;
+            > {} st;
 
             // d
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct d_type : ::bond::reflection::FieldTemplate<
                 5,
                 ::bond::reflection::optional_field_modifier,
                 foo,
                 std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> >,
                 &foo::d,
                 &s_d_metadata
-            > {}  d;
+            > {} d;
 
             // l1
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct l1_type : ::bond::reflection::FieldTemplate<
                 10,
                 ::bond::reflection::optional_field_modifier,
                 foo,
                 ::bond::maybe<std::list<bool, typename std::allocator_traits<arena>::template rebind_alloc<bool> > >,
                 &foo::l1,
                 &s_l1_metadata
-            > {}  l1;
+            > {} l1;
 
             // v1
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct v1_type : ::bond::reflection::FieldTemplate<
                 11,
                 ::bond::reflection::optional_field_modifier,
                 foo,
                 ::bond::maybe<std::vector<bool, typename std::allocator_traits<arena>::template rebind_alloc<bool> > >,
                 &foo::v1,
                 &s_v1_metadata
-            > {}  v1;
+            > {} v1;
 
             // s1
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct s1_type : ::bond::reflection::FieldTemplate<
                 12,
                 ::bond::reflection::optional_field_modifier,
                 foo,
                 ::bond::maybe<std::set<bool, std::less<bool>, typename std::allocator_traits<arena>::template rebind_alloc<bool> > >,
                 &foo::s1,
                 &s_s1_metadata
-            > {}  s1;
+            > {} s1;
 
             // m1
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct m1_type : ::bond::reflection::FieldTemplate<
                 13,
                 ::bond::reflection::optional_field_modifier,
                 foo,
                 ::bond::maybe<std::map<std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> >, bool, std::less<std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> > >, typename std::allocator_traits<arena>::template rebind_alloc<std::pair<const std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> >, bool> > > >,
                 &foo::m1,
                 &s_m1_metadata
-            > {}  m1;
+            > {} m1;
 
             // st1
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct st1_type : ::bond::reflection::FieldTemplate<
                 14,
                 ::bond::reflection::optional_field_modifier,
                 foo,
                 ::bond::maybe<std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> > >,
                 &foo::st1,
                 &s_st1_metadata
-            > {}  st1;
+            > {} st1;
 
             // na
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct na_type : ::bond::reflection::FieldTemplate<
                 15,
                 ::bond::reflection::optional_field_modifier,
                 foo,
                 std::set<std::list<std::map<int32_t, std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> >, std::less<int32_t>, typename std::allocator_traits<arena>::template rebind_alloc<std::pair<const int32_t, std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> > > > >, typename std::allocator_traits<arena>::template rebind_alloc<std::map<int32_t, std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> >, std::less<int32_t>, typename std::allocator_traits<arena>::template rebind_alloc<std::pair<const int32_t, std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> > > > > > >, std::less<std::list<std::map<int32_t, std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> >, std::less<int32_t>, typename std::allocator_traits<arena>::template rebind_alloc<std::pair<const int32_t, std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> > > > >, typename std::allocator_traits<arena>::template rebind_alloc<std::map<int32_t, std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> >, std::less<int32_t>, typename std::allocator_traits<arena>::template rebind_alloc<std::pair<const int32_t, std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> > > > > > > >, typename std::allocator_traits<arena>::template rebind_alloc<std::list<std::map<int32_t, std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> >, std::less<int32_t>, typename std::allocator_traits<arena>::template rebind_alloc<std::pair<const int32_t, std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> > > > >, typename std::allocator_traits<arena>::template rebind_alloc<std::map<int32_t, std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> >, std::less<int32_t>, typename std::allocator_traits<arena>::template rebind_alloc<std::pair<const int32_t, std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> > > > > > > > >,
                 &foo::na,
                 &s_na_metadata
-            > {}  na;
+            > {} na;
         };
 
         private: typedef boost::mpl::list<> fields0;
@@ -192,24 +192,24 @@ namespace test
         public: struct var
         {
             // f
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct f_type : ::bond::reflection::FieldTemplate<
                 0,
                 ::bond::reflection::optional_field_modifier,
                 withFoo,
                 ::test::foo,
                 &withFoo::f,
                 &s_f_metadata
-            > {}  f;
+            > {} f;
 
             // f1
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct f1_type : ::bond::reflection::FieldTemplate<
                 1,
                 ::bond::reflection::optional_field_modifier,
                 withFoo,
                 ::test::foo,
                 &withFoo::f1,
                 &s_f1_metadata
-            > {}  f1;
+            > {} f1;
         };
 
         private: typedef boost::mpl::list<> fields0;

diff --git a/compiler/tests/generated/aliases_reflection.h b/compiler/tests/generated/aliases_reflection.h
@@ -21,14 +21,14 @@ namespace tests
         public: struct var
         {
             // aa
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct aa_type : ::bond::reflection::FieldTemplate<
                 0,
                 ::bond::reflection::optional_field_modifier,
                 Foo<T>,
                 std::vector<std::vector<T> >,
                 &Foo<T>::aa,
                 &s_aa_metadata
-            > {}  aa;
+            > {} aa;
         };
 
         private: typedef boost::mpl::list<> fields0;
@@ -73,14 +73,14 @@ namespace tests
         public: struct var
         {
             // aWrappedEnum
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct aWrappedEnum_type : ::bond::reflection::FieldTemplate<
                 0,
                 ::bond::reflection::optional_field_modifier,
                 WrappingAnEnum,
                 ::tests::EnumToWrap,
                 &WrappingAnEnum::aWrappedEnum,
                 &s_aWrappedEnum_metadata
-            > {}  aWrappedEnum;
+            > {} aWrappedEnum;
         };
 
         private: typedef boost::mpl::list<> fields0;

diff --git a/compiler/tests/generated/alloc_ctors/alias_key_reflection.h b/compiler/tests/generated/alloc_ctors/alias_key_reflection.h
@@ -21,24 +21,24 @@ namespace test
         public: struct var
         {
             // m
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct m_type : ::bond::reflection::FieldTemplate<
                 0,
                 ::bond::reflection::optional_field_modifier,
                 foo,
                 std::map<std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> >, int32_t, std::less<std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> > >, typename std::allocator_traits<arena>::template rebind_alloc<std::pair<const std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> >, int32_t> > >,
                 &foo::m,
                 &s_m_metadata
-            > {}  m;
+            > {} m;
 
             // s
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct s_type : ::bond::reflection::FieldTemplate<
                 1,
                 ::bond::reflection::optional_field_modifier,
                 foo,
                 std::set<int32_t, std::less<int32_t>, typename std::allocator_traits<arena>::template rebind_alloc<int32_t> >,
                 &foo::s,
                 &s_s_metadata
-            > {}  s;
+            > {} s;
         };
 
         private: typedef boost::mpl::list<> fields0;

diff --git a/compiler/tests/generated/alloc_ctors/aliases_reflection.h b/compiler/tests/generated/alloc_ctors/aliases_reflection.h
@@ -21,14 +21,14 @@ namespace tests
         public: struct var
         {
             // aa
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct aa_type : ::bond::reflection::FieldTemplate<
                 0,
                 ::bond::reflection::optional_field_modifier,
                 Foo<T>,
                 std::vector<std::vector<T, typename std::allocator_traits<arena>::template rebind_alloc<T> >, typename std::allocator_traits<arena>::template rebind_alloc<std::vector<T, typename std::allocator_traits<arena>::template rebind_alloc<T> > > >,
                 &Foo<T>::aa,
                 &s_aa_metadata
-            > {}  aa;
+            > {} aa;
         };
 
         private: typedef boost::mpl::list<> fields0;
@@ -73,14 +73,14 @@ namespace tests
         public: struct var
         {
             // aWrappedEnum
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct aWrappedEnum_type : ::bond::reflection::FieldTemplate<
                 0,
                 ::bond::reflection::optional_field_modifier,
                 WrappingAnEnum,
                 ::tests::EnumToWrap,
                 &WrappingAnEnum::aWrappedEnum,
                 &s_aWrappedEnum_metadata
-            > {}  aWrappedEnum;
+            > {} aWrappedEnum;
         };
 
         private: typedef boost::mpl::list<> fields0;

diff --git a/compiler/tests/generated/alloc_ctors/attributes_reflection.h b/compiler/tests/generated/alloc_ctors/attributes_reflection.h
@@ -20,14 +20,14 @@ namespace tests
         public: struct var
         {
             // f
-            typedef struct : ::bond::reflection::FieldTemplate<
+            typedef struct f_type : ::bond::reflection::FieldTemplate<
                 0,
                 ::bond::reflection::optional_field_modifier,
                 Foo,
                 std::basic_string<char, std::char_traits<char>, typename std::allocator_traits<arena>::template rebind_alloc<char> >,
                 &Foo::f,
                 &s_f_metadata
-            > {}  f;
+            > {} f;
         };
 
         private: typedef boost::mpl::list<> fields0;