[clang] Inject IndirectFieldDecl even if name conflicts. (#153140)

This modifies InjectAnonymousStructOrUnionMembers to inject an
IndirectFieldDecl and mark it invalid even if its name conflicts with
another name in the scope.

This resolves a crash on a further diagnostic
diag::err_multiple_mem_union_initialization which via
findDefaultInitializer relies on these declarations being present.

Fixes #149985

1 files changed, 41 insertions, 35 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 6581d4c..5001e08 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -5503,48 +5503,54 @@ InjectAnonymousStructOrUnionMembers(Sema &SemaRef, Scope *S, DeclContext *Owner,
     if ((isa<FieldDecl>(D) || isa<IndirectFieldDecl>(D)) &&
         cast<NamedDecl>(D)->getDeclName()) {
       ValueDecl *VD = cast<ValueDecl>(D);
-      if (CheckAnonMemberRedeclaration(SemaRef, S, Owner, VD->getDeclName(),
-                                       VD->getLocation(), AnonRecord->isUnion(),
-                                       SC)) {
-        // C++ [class.union]p2:
-        //   The names of the members of an anonymous union shall be
-        //   distinct from the names of any other entity in the
-        //   scope in which the anonymous union is declared.
+      // C++ [class.union]p2:
+      //   The names of the members of an anonymous union shall be
+      //   distinct from the names of any other entity in the
+      //   scope in which the anonymous union is declared.
+
+      bool FieldInvalid = CheckAnonMemberRedeclaration(
+          SemaRef, S, Owner, VD->getDeclName(), VD->getLocation(),
+          AnonRecord->isUnion(), SC);
+      if (FieldInvalid)
         Invalid = true;
-      } else {
-        // C++ [class.union]p2:
-        //   For the purpose of name lookup, after the anonymous union
-        //   definition, the members of the anonymous union are
-        //   considered to have been defined in the scope in which the
-        //   anonymous union is declared.
-        unsigned OldChainingSize = Chaining.size();
-        if (IndirectFieldDecl *IF = dyn_cast<IndirectFieldDecl>(VD))
-          Chaining.append(IF->chain_begin(), IF->chain_end());
-        else
-          Chaining.push_back(VD);
 
-        assert(Chaining.size() >= 2);
-        NamedDecl **NamedChain =
-          new (SemaRef.Context)NamedDecl*[Chaining.size()];
-        for (unsigned i = 0; i < Chaining.size(); i++)
-          NamedChain[i] = Chaining[i];
+      // Inject the IndirectFieldDecl even if invalid, because later
+      // diagnostics may depend on it being present, see findDefaultInitializer.
+
+      // C++ [class.union]p2:
+      //   For the purpose of name lookup, after the anonymous union
+      //   definition, the members of the anonymous union are
+      //   considered to have been defined in the scope in which the
+      //   anonymous union is declared.
+      unsigned OldChainingSize = Chaining.size();
+      if (IndirectFieldDecl *IF = dyn_cast<IndirectFieldDecl>(VD))
+        Chaining.append(IF->chain_begin(), IF->chain_end());
+      else
+        Chaining.push_back(VD);
 
-        IndirectFieldDecl *IndirectField = IndirectFieldDecl::Create(
-            SemaRef.Context, Owner, VD->getLocation(), VD->getIdentifier(),
-            VD->getType(), {NamedChain, Chaining.size()});
+      assert(Chaining.size() >= 2);
+      NamedDecl **NamedChain =
+          new (SemaRef.Context) NamedDecl *[Chaining.size()];
+      for (unsigned i = 0; i < Chaining.size(); i++)
+        NamedChain[i] = Chaining[i];
 
-        for (const auto *Attr : VD->attrs())
-          IndirectField->addAttr(Attr->clone(SemaRef.Context));
+      IndirectFieldDecl *IndirectField = IndirectFieldDecl::Create(
+          SemaRef.Context, Owner, VD->getLocation(), VD->getIdentifier(),
+          VD->getType(), {NamedChain, Chaining.size()});
 
-        IndirectField->setAccess(AS);
-        IndirectField->setImplicit();
-        SemaRef.PushOnScopeChains(IndirectField, S);
+      for (const auto *Attr : VD->attrs())
+        IndirectField->addAttr(Attr->clone(SemaRef.Context));
 
-        // That includes picking up the appropriate access specifier.
-        if (AS != AS_none) IndirectField->setAccess(AS);
+      IndirectField->setAccess(AS);
+      IndirectField->setImplicit();
+      IndirectField->setInvalidDecl(FieldInvalid);
+      SemaRef.PushOnScopeChains(IndirectField, S);
 
-        Chaining.resize(OldChainingSize);
-      }
+      // That includes picking up the appropriate access specifier.
+      if (AS != AS_none)
+        IndirectField->setAccess(AS);
+
+      Chaining.resize(OldChainingSize);
     }
   }