[ASTImporter] Make ODR error handling configurable

[gamesh411]

Summary

ODR errors are not necessarily true errors during the import of ASTs.
ASTMerge and CrossTU should use the warning equivalent of every CTU error,
while Sema should emit errors as before.

[gamesh411]

This revision is the alternative of the abandoned D55646.
Now Sema uses the old behavior of emitting ODR errors while merging and importing is done in a more lenient way.

[martong]

Ping

[a_sidorin]

Hi Gabor,
This patch LGTM mostly, but there is a comment inline.

include/clang/AST/ASTStructuralEquivalence.h

81

I see the argument order change but I don't see any callers changed. Do we really need this order change?

[gamesh411]

• Revert member order to original

include/clang/AST/ASTStructuralEquivalence.h

81

Strictly speaking, there is no need for this change, the constructor param order does not match the initialization, but that is just a nit. I have updated the diff. Cheers :)

[gamesh411]

ping @a_sidorin

include/clang/AST/ASTStructuralEquivalence.h

struct StructuralEquivalenceContext {
   llvm::DenseSet<std::pair<Decl *, Decl *>> &NonEquivalentDecls;
 
   StructuralEquivalenceKind EqKind;
 
   /// Whether we're being strict about the spelling of types when
   /// unifying two types.
   bool StrictTypeSpelling;
 
-  /// Whether warn or error on tag type mismatches.
-  bool ErrorOnTagTypeMismatch;
-
   /// Whether to complain about failures.
   bool Complain;
 
+  /// Whether warn or error on tag type mismatches.
+  bool ErrorOnTagTypeMismatch;
+
   /// \c true if the last diagnostic came from ToCtx.
   bool LastDiagFromC2 = false;
 
   StructuralEquivalenceContext(
       ASTContext &FromCtx, ASTContext &ToCtx,
       llvm::DenseSet<std::pair<Decl *, Decl *>> &NonEquivalentDecls,
       StructuralEquivalenceKind EqKind,
       bool StrictTypeSpelling = false, bool Complain = true,
       bool ErrorOnTagTypeMismatch = false)
       : FromCtx(FromCtx), ToCtx(ToCtx), NonEquivalentDecls(NonEquivalentDecls),
         EqKind(EqKind), StrictTypeSpelling(StrictTypeSpelling),
-        ErrorOnTagTypeMismatch(ErrorOnTagTypeMismatch), Complain(Complain) {}
+        Complain(Complain), ErrorOnTagTypeMismatch(ErrorOnTagTypeMismatch) {}
 
   DiagnosticBuilder Diag1(SourceLocation Loc, unsigned DiagID);
   DiagnosticBuilder Diag2(SourceLocation Loc, unsigned DiagID);
 
   /// Determine whether the two declarations are structurally
   /// equivalent.
   /// Implementation functions (all static functions in
   /// ASTStructuralEquivalence.cpp) must never call this function because that
struct StructuralEquivalenceContext {
   /// empty option if the context is not a record, i.e.. if the anonymous
   /// struct/union is at namespace or block scope.
   ///
   /// FIXME: This is needed by ASTImporter and ASTStructureEquivalence. It
   /// probably makes more sense in some other common place then here.
   static llvm::Optional<unsigned>
   findUntaggedStructOrUnionIndex(RecordDecl *Anon);
 
+  // If ErrorOnTagTypeMismatch is set, return the the error, otherwise get the
+  // relevant warning for the input error diagnostic.
+  unsigned getApplicableDiagnostic(unsigned ErrorDiagnostic);
+
 private:
   /// Finish checking all of the structural equivalences.
   ///
   /// \returns true if the equivalence check failed (non-equivalence detected),
   /// false if equivalence was detected.
   bool Finish();
 
   /// Check for common properties at Finish.

include/clang/Basic/DiagnosticASTKinds.td

let CategoryName = "VTable ABI Issue" in {
   def note_covariant_thunk : Note<
     "covariant thunk required by %0">;
 }
 
 // Importing ASTs
 def err_odr_variable_type_inconsistent : Error<
   "external variable %0 declared with incompatible types in different "
   "translation units (%1 vs. %2)">;
+def warn_odr_variable_type_inconsistent : Warning<
+  "external variable %0 declared with incompatible types in different "
+  "translation units (%1 vs. %2)">,
+  InGroup<ODR>;
 def err_odr_variable_multiple_def : Error<
   "external variable %0 defined in multiple translation units">;
+def warn_odr_variable_multiple_def : Warning<
+  "external variable %0 defined in multiple translation units">,
+  InGroup<ODR>;
 def note_odr_value_here : Note<"declared here with type %0">;
 def note_odr_defined_here : Note<"also defined here">;
 def err_odr_function_type_inconsistent : Error<
   "external function %0 declared with incompatible types in different "
   "translation units (%1 vs. %2)">;
-def warn_odr_tag_type_inconsistent
-    : Warning<"type %0 has incompatible definitions in different translation "
-              "units">,
-      InGroup<DiagGroup<"odr">>;
+def warn_odr_function_type_inconsistent : Warning<
+  "external function %0 declared with incompatible types in different "
+  "translation units (%1 vs. %2)">,
+  InGroup<ODR>;
 def err_odr_tag_type_inconsistent
     : Error<"type %0 has incompatible definitions in different translation "
             "units">;
+def warn_odr_tag_type_inconsistent
+    : Warning<"type %0 has incompatible definitions in different translation "
+              "units">,
+      InGroup<ODR>;
 def note_odr_tag_kind_here: Note<
   "%0 is a %select{struct|interface|union|class|enum}1 here">;
 def note_odr_field : Note<"field %0 has type %1 here">;
 def note_odr_field_name : Note<"field has name %0 here">;
 def note_odr_missing_field : Note<"no corresponding field here">;
 def note_odr_bit_field : Note<"bit-field %0 with type %1 and length %2 here">;
 def note_odr_not_bit_field : Note<"field %0 is not a bit-field">;
 def note_odr_base : Note<"class has base type %0">;
 def note_odr_virtual_base : Note<
   "%select{non-virtual|virtual}0 derivation here">;
 def note_odr_missing_base : Note<"no corresponding base class here">;
 def note_odr_number_of_bases : Note<
   "class has %0 base %plural{1:class|:classes}0">;
 def note_odr_enumerator : Note<"enumerator %0 with value %1 here">;
 def note_odr_missing_enumerator : Note<"no corresponding enumerator here">;
-
 def err_odr_field_type_inconsistent : Error<
   "field %0 declared with incompatible types in different "
   "translation units (%1 vs. %2)">;
+def warn_odr_field_type_inconsistent : Warning<
+  "field %0 declared with incompatible types in different "
+  "translation units (%1 vs. %2)">,
+  InGroup<ODR>;
 
 // Importing Objective-C ASTs
 def err_odr_ivar_type_inconsistent : Error<
   "instance variable %0 declared with incompatible types in different "
   "translation units (%1 vs. %2)">;
+def warn_odr_ivar_type_inconsistent : Warning<
+  "instance variable %0 declared with incompatible types in different "
+  "translation units (%1 vs. %2)">,
+  InGroup<ODR>;
 def err_odr_objc_superclass_inconsistent : Error<
   "class %0 has incompatible superclasses">;
+def warn_odr_objc_superclass_inconsistent : Warning<
+  "class %0 has incompatible superclasses">,
+  InGroup<ODR>;
 def note_odr_objc_superclass : Note<"inherits from superclass %0 here">;
 def note_odr_objc_missing_superclass : Note<"no corresponding superclass here">;
 def err_odr_objc_method_result_type_inconsistent : Error<
   "%select{class|instance}0 method %1 has incompatible result types in "
   "different translation units (%2 vs. %3)">;
+def warn_odr_objc_method_result_type_inconsistent : Warning<
+  "%select{class|instance}0 method %1 has incompatible result types in "
+  "different translation units (%2 vs. %3)">,
+  InGroup<ODR>;
 def err_odr_objc_method_num_params_inconsistent : Error<
   "%select{class|instance}0 method %1 has a different number of parameters in "
   "different translation units (%2 vs. %3)">;
+def warn_odr_objc_method_num_params_inconsistent : Warning<
+  "%select{class|instance}0 method %1 has a different number of parameters in "
+  "different translation units (%2 vs. %3)">,
+  InGroup<ODR>;
 def err_odr_objc_method_param_type_inconsistent : Error<
   "%select{class|instance}0 method %1 has a parameter with a different types "
   "in different translation units (%2 vs. %3)">;
+def warn_odr_objc_method_param_type_inconsistent : Warning<
+  "%select{class|instance}0 method %1 has a parameter with a different types "
+  "in different translation units (%2 vs. %3)">,
+  InGroup<ODR>;
 def err_odr_objc_method_variadic_inconsistent : Error<
   "%select{class|instance}0 method %1 is variadic in one translation unit "
   "and not variadic in another">;
+def warn_odr_objc_method_variadic_inconsistent : Warning<
+  "%select{class|instance}0 method %1 is variadic in one translation unit "
+  "and not variadic in another">,
+  InGroup<ODR>;
 def note_odr_objc_method_here : Note<
   "%select{class|instance}0 method %1 also declared here">;
 def err_odr_objc_property_type_inconsistent : Error<
   "property %0 declared with incompatible types in different "
   "translation units (%1 vs. %2)">;
+def warn_odr_objc_property_type_inconsistent : Warning<
+  "property %0 declared with incompatible types in different "
+  "translation units (%1 vs. %2)">,
+  InGroup<ODR>;
 def err_odr_objc_property_impl_kind_inconsistent : Error<
   "property %0 is implemented with %select{@synthesize|@dynamic}1 in one "
   "translation but %select{@dynamic|@synthesize}1 in another translation unit">;
+def warn_odr_objc_property_impl_kind_inconsistent : Warning<
+  "property %0 is implemented with %select{@synthesize|@dynamic}1 in one "
+  "translation but %select{@dynamic|@synthesize}1 in another translation unit">,
+  InGroup<ODR>;
 def note_odr_objc_property_impl_kind : Note<
   "property %0 is implemented with %select{@synthesize|@dynamic}1 here">;
 def err_odr_objc_synthesize_ivar_inconsistent : Error<
   "property %0 is synthesized to different ivars in different translation "
   "units (%1 vs. %2)">;
+def warn_odr_objc_synthesize_ivar_inconsistent : Warning<
+  "property %0 is synthesized to different ivars in different translation "
+  "units (%1 vs. %2)">,
+  InGroup<ODR>;
 def note_odr_objc_synthesize_ivar_here : Note<
   "property is synthesized to ivar %0 here">;
 
 // Importing C++ ASTs
 def note_odr_friend : Note<"friend declared here">;
 def note_odr_missing_friend : Note<"no corresponding friend here">;
 def err_odr_different_num_template_parameters : Error<
   "template parameter lists have a different number of parameters (%0 vs %1)">;
+def warn_odr_different_num_template_parameters : Warning<
+  "template parameter lists have a different number of parameters (%0 vs %1)">,
+  InGroup<ODR>;
 def note_odr_template_parameter_list : Note<
   "template parameter list also declared here">;
 def err_odr_different_template_parameter_kind : Error<
   "template parameter has different kinds in different translation units">;
+def warn_odr_different_template_parameter_kind : Warning<
+  "template parameter has different kinds in different translation units">,
+  InGroup<ODR>;
 def note_odr_template_parameter_here : Note<
   "template parameter declared here">;
 def err_odr_parameter_pack_non_pack : Error<
   "parameter kind mismatch; parameter is %select{not a|a}0 parameter pack">;
+def warn_odr_parameter_pack_non_pack : Warning<
+  "parameter kind mismatch; parameter is %select{not a|a}0 parameter pack">,
+  InGroup<ODR>;
 def note_odr_parameter_pack_non_pack : Note<
   "%select{parameter|parameter pack}0 declared here">;
 def err_odr_non_type_parameter_type_inconsistent : Error<
   "non-type template parameter declared with incompatible types in different "
   "translation units (%0 vs. %1)">;
+def warn_odr_non_type_parameter_type_inconsistent : Warning<
+  "non-type template parameter declared with incompatible types in different "
+  "translation units (%0 vs. %1)">,
+  InGroup<ODR>;
 def err_unsupported_ast_node: Error<"cannot import unsupported AST node %0">;
 
 def remark_sanitize_address_insert_extra_padding_accepted : Remark<
     "-fsanitize-address-field-padding applied to %0">, ShowInSystemHeader,
     InGroup<SanitizeAddressRemarks>;
 def remark_sanitize_address_insert_extra_padding_rejected : Remark<
     "-fsanitize-address-field-padding ignored for %0 because it "
     "%select{is not C++|is packed|is a union|is trivially copyable|"

include/clang/Basic/DiagnosticGroups.td

 
 // Aggregation warning settings.
 def Implicit : DiagGroup<"implicit", [
     ImplicitFunctionDeclare,
     ImplicitInt
 ]>;
 
 // Empty DiagGroups are recognized by clang but ignored.
+def ODR : DiagGroup<"odr">;
 def : DiagGroup<"abi">;
 def AbsoluteValue : DiagGroup<"absolute-value">;
 def AddressOfTemporary : DiagGroup<"address-of-temporary">;
 def : DiagGroup<"aggregate-return">;
 def GNUAlignofExpression : DiagGroup<"gnu-alignof-expression">;
 def AmbigMemberTemplate : DiagGroup<"ambiguous-member-template">;
 def GNUAnonymousStruct : DiagGroup<"gnu-anonymous-struct">;
 def GNUAutoType : DiagGroup<"gnu-auto-type">;

lib/AST/ASTStructuralEquivalence.cpp

if (Field1->isAnonymousStructOrUnion() &&
     return IsStructurallyEquivalent(Context, D1, D2);
   }
 
   // Check for equivalent field names.
   IdentifierInfo *Name1 = Field1->getIdentifier();
   IdentifierInfo *Name2 = Field2->getIdentifier();
   if (!::IsStructurallyEquivalent(Name1, Name2)) {
     if (Context.Complain) {
-      Context.Diag2(Owner2->getLocation(),
-                    Context.ErrorOnTagTypeMismatch
-                        ? diag::err_odr_tag_type_inconsistent
-                        : diag::warn_odr_tag_type_inconsistent)
+      Context.Diag2(
+          Owner2->getLocation(),
+          Context.getApplicableDiagnostic(diag::err_odr_tag_type_inconsistent))
           << Context.ToCtx.getTypeDeclType(Owner2);
       Context.Diag2(Field2->getLocation(), diag::note_odr_field_name)
           << Field2->getDeclName();
       Context.Diag1(Field1->getLocation(), diag::note_odr_field_name)
           << Field1->getDeclName();
     }
     return false;
   }
 
   if (!IsStructurallyEquivalent(Context, Field1->getType(),
                                 Field2->getType())) {
     if (Context.Complain) {
-      Context.Diag2(Owner2->getLocation(),
-                    Context.ErrorOnTagTypeMismatch
-                        ? diag::err_odr_tag_type_inconsistent
-                        : diag::warn_odr_tag_type_inconsistent)
+      Context.Diag2(
+          Owner2->getLocation(),
+          Context.getApplicableDiagnostic(diag::err_odr_tag_type_inconsistent))
           << Context.ToCtx.getTypeDeclType(Owner2);
       Context.Diag2(Field2->getLocation(), diag::note_odr_field)
           << Field2->getDeclName() << Field2->getType();
       Context.Diag1(Field1->getLocation(), diag::note_odr_field)
           << Field1->getDeclName() << Field1->getType();
     }
     return false;
   }
 
   if (Field1->isBitField() != Field2->isBitField()) {
     if (Context.Complain) {
-      Context.Diag2(Owner2->getLocation(),
-                    Context.ErrorOnTagTypeMismatch
-                        ? diag::err_odr_tag_type_inconsistent
-                        : diag::warn_odr_tag_type_inconsistent)
+      Context.Diag2(
+          Owner2->getLocation(),
+          Context.getApplicableDiagnostic(diag::err_odr_tag_type_inconsistent))
           << Context.ToCtx.getTypeDeclType(Owner2);
       if (Field1->isBitField()) {
         Context.Diag1(Field1->getLocation(), diag::note_odr_bit_field)
             << Field1->getDeclName() << Field1->getType()
             << Field1->getBitWidthValue(Context.FromCtx);
         Context.Diag2(Field2->getLocation(), diag::note_odr_not_bit_field)
             << Field2->getDeclName();
       } else {
static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
   if (Field1->isBitField()) {
     // Make sure that the bit-fields are the same length.
     unsigned Bits1 = Field1->getBitWidthValue(Context.FromCtx);
     unsigned Bits2 = Field2->getBitWidthValue(Context.ToCtx);
 
     if (Bits1 != Bits2) {
       if (Context.Complain) {
         Context.Diag2(Owner2->getLocation(),
-                      Context.ErrorOnTagTypeMismatch
-                          ? diag::err_odr_tag_type_inconsistent
-                          : diag::warn_odr_tag_type_inconsistent)
+                      Context.getApplicableDiagnostic(
+                          diag::err_odr_tag_type_inconsistent))
             << Context.ToCtx.getTypeDeclType(Owner2);
         Context.Diag2(Field2->getLocation(), diag::note_odr_bit_field)
             << Field2->getDeclName() << Field2->getType() << Bits2;
         Context.Diag1(Field1->getLocation(), diag::note_odr_bit_field)
             << Field1->getDeclName() << Field1->getType() << Bits1;
       }
       return false;
     }
static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
   return true;
 }
 
 /// Determine structural equivalence of two records.
 static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
                                      RecordDecl *D1, RecordDecl *D2) {
   if (D1->isUnion() != D2->isUnion()) {
     if (Context.Complain) {
-      Context.Diag2(D2->getLocation(),
-                    Context.ErrorOnTagTypeMismatch
-                        ? diag::err_odr_tag_type_inconsistent
-                        : diag::warn_odr_tag_type_inconsistent)
+      Context.Diag2(D2->getLocation(), Context.getApplicableDiagnostic(
+                                           diag::err_odr_tag_type_inconsistent))
           << Context.ToCtx.getTypeDeclType(D2);
       Context.Diag1(D1->getLocation(), diag::note_odr_tag_kind_here)
           << D1->getDeclName() << (unsigned)D1->getTagKind();
     }
     return false;
   }
 
   if (!D1->getDeclName() && !D2->getDeclName()) {
if (auto *D1CXX = dyn_cast<CXXRecordDecl>(D1)) {
     if (auto *D2CXX = dyn_cast<CXXRecordDecl>(D2)) {
       if (D1CXX->hasExternalLexicalStorage() &&
           !D1CXX->isCompleteDefinition()) {
         D1CXX->getASTContext().getExternalSource()->CompleteType(D1CXX);
       }
 
       if (D1CXX->getNumBases() != D2CXX->getNumBases()) {
         if (Context.Complain) {
-          Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
+          Context.Diag2(D2->getLocation(),
+                        Context.getApplicableDiagnostic(
+                            diag::err_odr_tag_type_inconsistent))
               << Context.ToCtx.getTypeDeclType(D2);
           Context.Diag2(D2->getLocation(), diag::note_odr_number_of_bases)
               << D2CXX->getNumBases();
           Context.Diag1(D1->getLocation(), diag::note_odr_number_of_bases)
               << D1CXX->getNumBases();
         }
         return false;
       }
 
       // Check the base classes.
       for (CXXRecordDecl::base_class_iterator Base1 = D1CXX->bases_begin(),
                                               BaseEnd1 = D1CXX->bases_end(),
                                               Base2 = D2CXX->bases_begin();
            Base1 != BaseEnd1; ++Base1, ++Base2) {
         if (!IsStructurallyEquivalent(Context, Base1->getType(),
                                       Base2->getType())) {
           if (Context.Complain) {
             Context.Diag2(D2->getLocation(),
-                          diag::warn_odr_tag_type_inconsistent)
+                          Context.getApplicableDiagnostic(
+                              diag::err_odr_tag_type_inconsistent))
                 << Context.ToCtx.getTypeDeclType(D2);
             Context.Diag2(Base2->getBeginLoc(), diag::note_odr_base)
                 << Base2->getType() << Base2->getSourceRange();
             Context.Diag1(Base1->getBeginLoc(), diag::note_odr_base)
                 << Base1->getType() << Base1->getSourceRange();
           }
           return false;
         }
 
         // Check virtual vs. non-virtual inheritance mismatch.
         if (Base1->isVirtual() != Base2->isVirtual()) {
           if (Context.Complain) {
             Context.Diag2(D2->getLocation(),
-                          diag::warn_odr_tag_type_inconsistent)
+                          Context.getApplicableDiagnostic(
+                              diag::err_odr_tag_type_inconsistent))
                 << Context.ToCtx.getTypeDeclType(D2);
             Context.Diag2(Base2->getBeginLoc(), diag::note_odr_virtual_base)
                 << Base2->isVirtual() << Base2->getSourceRange();
             Context.Diag1(Base1->getBeginLoc(), diag::note_odr_base)
                 << Base1->isVirtual() << Base1->getSourceRange();
           }
           return false;
         }
       }
 
       // Check the friends for consistency.
       CXXRecordDecl::friend_iterator Friend2 = D2CXX->friend_begin(),
                                      Friend2End = D2CXX->friend_end();
       for (CXXRecordDecl::friend_iterator Friend1 = D1CXX->friend_begin(),
                                           Friend1End = D1CXX->friend_end();
            Friend1 != Friend1End; ++Friend1, ++Friend2) {
         if (Friend2 == Friend2End) {
           if (Context.Complain) {
             Context.Diag2(D2->getLocation(),
-                          diag::warn_odr_tag_type_inconsistent)
-                    << Context.ToCtx.getTypeDeclType(D2CXX);
+                          Context.getApplicableDiagnostic(
+                              diag::err_odr_tag_type_inconsistent))
             Context.Diag1((*Friend1)->getFriendLoc(), diag::note_odr_friend);
             Context.Diag2(D2->getLocation(), diag::note_odr_missing_friend);
           }
           return false;
         }
 
         if (!IsStructurallyEquivalent(Context, *Friend1, *Friend2)) {
           if (Context.Complain) {
-            Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
+            Context.Diag2(D2->getLocation(),
+                          Context.getApplicableDiagnostic(
+                              diag::err_odr_tag_type_inconsistent))
                 << Context.ToCtx.getTypeDeclType(D2CXX);
             Context.Diag1((*Friend1)->getFriendLoc(), diag::note_odr_friend);
             Context.Diag2((*Friend2)->getFriendLoc(), diag::note_odr_friend);
           }
           return false;
         }
       }
 
       if (Friend2 != Friend2End) {
         if (Context.Complain) {
-          Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
-                  << Context.ToCtx.getTypeDeclType(D2);
+          Context.Diag2(D2->getLocation(),
+                        Context.getApplicableDiagnostic(
+                            diag::err_odr_tag_type_inconsistent))
           Context.Diag2((*Friend2)->getFriendLoc(), diag::note_odr_friend);
           Context.Diag1(D1->getLocation(), diag::note_odr_missing_friend);
         }
         return false;
       }
     } else if (D1CXX->getNumBases() > 0) {
       if (Context.Complain) {
-        Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
+        Context.Diag2(D2->getLocation(),
+                      Context.getApplicableDiagnostic(
+                          diag::err_odr_tag_type_inconsistent))
             << Context.ToCtx.getTypeDeclType(D2);
         const CXXBaseSpecifier *Base1 = D1CXX->bases_begin();
         Context.Diag1(Base1->getBeginLoc(), diag::note_odr_base)
             << Base1->getType() << Base1->getSourceRange();
         Context.Diag2(D2->getLocation(), diag::note_odr_missing_base);
       }
       return false;
     }
   }
 
   // Check the fields for consistency.
   RecordDecl::field_iterator Field2 = D2->field_begin(),
                              Field2End = D2->field_end();
   for (RecordDecl::field_iterator Field1 = D1->field_begin(),
                                   Field1End = D1->field_end();
        Field1 != Field1End; ++Field1, ++Field2) {
     if (Field2 == Field2End) {
       if (Context.Complain) {
         Context.Diag2(D2->getLocation(),
-                      Context.ErrorOnTagTypeMismatch
-                          ? diag::err_odr_tag_type_inconsistent
-                          : diag::warn_odr_tag_type_inconsistent)
+                      Context.getApplicableDiagnostic(
+                          diag::err_odr_tag_type_inconsistent))
             << Context.ToCtx.getTypeDeclType(D2);
         Context.Diag1(Field1->getLocation(), diag::note_odr_field)
             << Field1->getDeclName() << Field1->getType();
         Context.Diag2(D2->getLocation(), diag::note_odr_missing_field);
       }
       return false;
     }
 
     if (!IsStructurallyEquivalent(Context, *Field1, *Field2))
       return false;
   }
 
   if (Field2 != Field2End) {
     if (Context.Complain) {
-      Context.Diag2(D2->getLocation(),
-                    Context.ErrorOnTagTypeMismatch
-                        ? diag::err_odr_tag_type_inconsistent
-                        : diag::warn_odr_tag_type_inconsistent)
+      Context.Diag2(D2->getLocation(), Context.getApplicableDiagnostic(
+                                           diag::err_odr_tag_type_inconsistent))
           << Context.ToCtx.getTypeDeclType(D2);
       Context.Diag2(Field2->getLocation(), diag::note_odr_field)
           << Field2->getDeclName() << Field2->getType();
       Context.Diag1(D1->getLocation(), diag::note_odr_missing_field);
     }
     return false;
   }
 
static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
   EnumDecl::enumerator_iterator EC2 = D2->enumerator_begin(),
                                 EC2End = D2->enumerator_end();
   for (EnumDecl::enumerator_iterator EC1 = D1->enumerator_begin(),
                                      EC1End = D1->enumerator_end();
        EC1 != EC1End; ++EC1, ++EC2) {
     if (EC2 == EC2End) {
       if (Context.Complain) {
         Context.Diag2(D2->getLocation(),
-                      Context.ErrorOnTagTypeMismatch
-                          ? diag::err_odr_tag_type_inconsistent
-                          : diag::warn_odr_tag_type_inconsistent)
+                      Context.getApplicableDiagnostic(
+                          diag::err_odr_tag_type_inconsistent))
             << Context.ToCtx.getTypeDeclType(D2);
         Context.Diag1(EC1->getLocation(), diag::note_odr_enumerator)
             << EC1->getDeclName() << EC1->getInitVal().toString(10);
         Context.Diag2(D2->getLocation(), diag::note_odr_missing_enumerator);
       }
       return false;
     }
 
     llvm::APSInt Val1 = EC1->getInitVal();
     llvm::APSInt Val2 = EC2->getInitVal();
     if (!llvm::APSInt::isSameValue(Val1, Val2) ||
         !IsStructurallyEquivalent(EC1->getIdentifier(), EC2->getIdentifier())) {
       if (Context.Complain) {
         Context.Diag2(D2->getLocation(),
-                      Context.ErrorOnTagTypeMismatch
-                          ? diag::err_odr_tag_type_inconsistent
-                          : diag::warn_odr_tag_type_inconsistent)
+                      Context.getApplicableDiagnostic(
+                          diag::err_odr_tag_type_inconsistent))
             << Context.ToCtx.getTypeDeclType(D2);
         Context.Diag2(EC2->getLocation(), diag::note_odr_enumerator)
             << EC2->getDeclName() << EC2->getInitVal().toString(10);
         Context.Diag1(EC1->getLocation(), diag::note_odr_enumerator)
             << EC1->getDeclName() << EC1->getInitVal().toString(10);
       }
       return false;
     }
   }
 
   if (EC2 != EC2End) {
     if (Context.Complain) {
-      Context.Diag2(D2->getLocation(),
-                    Context.ErrorOnTagTypeMismatch
-                        ? diag::err_odr_tag_type_inconsistent
-                        : diag::warn_odr_tag_type_inconsistent)
+      Context.Diag2(D2->getLocation(), Context.getApplicableDiagnostic(
+                                           diag::err_odr_tag_type_inconsistent))
           << Context.ToCtx.getTypeDeclType(D2);
       Context.Diag2(EC2->getLocation(), diag::note_odr_enumerator)
           << EC2->getDeclName() << EC2->getInitVal().toString(10);
       Context.Diag1(D1->getLocation(), diag::note_odr_missing_enumerator);
     }
     return false;
   }
 
   return true;
 }
 
 static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
                                      TemplateParameterList *Params1,
                                      TemplateParameterList *Params2) {
   if (Params1->size() != Params2->size()) {
     if (Context.Complain) {
       Context.Diag2(Params2->getTemplateLoc(),
-                    diag::err_odr_different_num_template_parameters)
+                    Context.getApplicableDiagnostic(
+                        diag::err_odr_different_num_template_parameters))
           << Params1->size() << Params2->size();
       Context.Diag1(Params1->getTemplateLoc(),
                     diag::note_odr_template_parameter_list);
     }
     return false;
   }
 
   for (unsigned I = 0, N = Params1->size(); I != N; ++I) {
     if (Params1->getParam(I)->getKind() != Params2->getParam(I)->getKind()) {
       if (Context.Complain) {
         Context.Diag2(Params2->getParam(I)->getLocation(),
-                      diag::err_odr_different_template_parameter_kind);
+                      Context.getApplicableDiagnostic(
+                          diag::err_odr_different_template_parameter_kind));
         Context.Diag1(Params1->getParam(I)->getLocation(),
                       diag::note_odr_template_parameter_here);
       }
       return false;
     }
 
     if (!IsStructurallyEquivalent(Context, Params1->getParam(I),
                                   Params2->getParam(I)))
       return false;
   }
 
   return true;
 }
 
 static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
                                      TemplateTypeParmDecl *D1,
                                      TemplateTypeParmDecl *D2) {
   if (D1->isParameterPack() != D2->isParameterPack()) {
     if (Context.Complain) {
-      Context.Diag2(D2->getLocation(), diag::err_odr_parameter_pack_non_pack)
+      Context.Diag2(D2->getLocation(),
+                    Context.getApplicableDiagnostic(
+                        diag::err_odr_parameter_pack_non_pack))
           << D2->isParameterPack();
       Context.Diag1(D1->getLocation(), diag::note_odr_parameter_pack_non_pack)
           << D1->isParameterPack();
     }
     return false;
   }
 
   return true;
 }
 
 static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
                                      NonTypeTemplateParmDecl *D1,
                                      NonTypeTemplateParmDecl *D2) {
   if (D1->isParameterPack() != D2->isParameterPack()) {
     if (Context.Complain) {
-      Context.Diag2(D2->getLocation(), diag::err_odr_parameter_pack_non_pack)
+      Context.Diag2(D2->getLocation(),
+                    Context.getApplicableDiagnostic(
+                        diag::err_odr_parameter_pack_non_pack))
           << D2->isParameterPack();
       Context.Diag1(D1->getLocation(), diag::note_odr_parameter_pack_non_pack)
           << D1->isParameterPack();
     }
     return false;
   }
 
   // Check types.
   if (!IsStructurallyEquivalent(Context, D1->getType(), D2->getType())) {
     if (Context.Complain) {
       Context.Diag2(D2->getLocation(),
-                    diag::err_odr_non_type_parameter_type_inconsistent)
+                    Context.getApplicableDiagnostic(
+                        diag::err_odr_non_type_parameter_type_inconsistent))
           << D2->getType() << D1->getType();
       Context.Diag1(D1->getLocation(), diag::note_odr_value_here)
           << D1->getType();
     }
     return false;
   }
 
   return true;
 }
 
 static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
                                      TemplateTemplateParmDecl *D1,
                                      TemplateTemplateParmDecl *D2) {
   if (D1->isParameterPack() != D2->isParameterPack()) {
     if (Context.Complain) {
-      Context.Diag2(D2->getLocation(), diag::err_odr_parameter_pack_non_pack)
+      Context.Diag2(D2->getLocation(),
+                    Context.getApplicableDiagnostic(
+                        diag::err_odr_parameter_pack_non_pack))
           << D2->isParameterPack();
       Context.Diag1(D1->getLocation(), diag::note_odr_parameter_pack_non_pack)
           << D1->isParameterPack();
     }
     return false;
   }
 
   // Check template parameter lists.
if (const auto *RecType = dyn_cast<RecordType>(FieldType)) {
         continue;
       }
     }
   }
 
   return Index;
 }
 
+unsigned StructuralEquivalenceContext::getApplicableDiagnostic(
+    unsigned ErrorDiagnostic) {
+  if (ErrorOnTagTypeMismatch)
+    return ErrorDiagnostic;
+
+  switch (ErrorDiagnostic) {
+  case diag::err_odr_variable_type_inconsistent:
+    return diag::warn_odr_variable_type_inconsistent;
+  case diag::err_odr_variable_multiple_def:
+    return diag::warn_odr_variable_multiple_def;
+  case diag::err_odr_function_type_inconsistent:
+    return diag::warn_odr_function_type_inconsistent;
+  case diag::err_odr_tag_type_inconsistent:
+    return diag::warn_odr_tag_type_inconsistent;
+  case diag::err_odr_field_type_inconsistent:
+    return diag::warn_odr_field_type_inconsistent;
+  case diag::err_odr_ivar_type_inconsistent:
+    return diag::warn_odr_ivar_type_inconsistent;
+  case diag::err_odr_objc_superclass_inconsistent:
+    return diag::warn_odr_objc_superclass_inconsistent;
+  case diag::err_odr_objc_method_result_type_inconsistent:
+    return diag::warn_odr_objc_method_result_type_inconsistent;
+  case diag::err_odr_objc_method_num_params_inconsistent:
+    return diag::warn_odr_objc_method_num_params_inconsistent;
+  case diag::err_odr_objc_method_param_type_inconsistent:
+    return diag::warn_odr_objc_method_param_type_inconsistent;
+  case diag::err_odr_objc_method_variadic_inconsistent:
+    return diag::warn_odr_objc_method_variadic_inconsistent;
+  case diag::err_odr_objc_property_type_inconsistent:
+    return diag::warn_odr_objc_property_type_inconsistent;
+  case diag::err_odr_objc_property_impl_kind_inconsistent:
+    return diag::warn_odr_objc_property_impl_kind_inconsistent;
+  case diag::err_odr_objc_synthesize_ivar_inconsistent:
+    return diag::warn_odr_objc_synthesize_ivar_inconsistent;
+  case diag::err_odr_different_num_template_parameters:
+    return diag::warn_odr_different_num_template_parameters;
+  case diag::err_odr_different_template_parameter_kind:
+    return diag::warn_odr_different_template_parameter_kind;
+  case diag::err_odr_parameter_pack_non_pack:
+    return diag::warn_odr_parameter_pack_non_pack;
+  case diag::err_odr_non_type_parameter_type_inconsistent:
+    return diag::warn_odr_non_type_parameter_type_inconsistent;
+  }
+}
+
 bool StructuralEquivalenceContext::IsEquivalent(Decl *D1, Decl *D2) {
 
   // Ensure that the implementation functions (all static functions in this TU)
   // never call the public ASTStructuralEquivalence::IsEquivalent() functions,
   // because that will wreak havoc the internal state (DeclsToCheck and
   // TentativeEquivalences members) and can cause faulty behaviour. For
   // instance, some leaf declarations can be stated and cached as inequivalent
   // as a side effect of one inequivalent element in the DeclsToCheck list.