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

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: None (keinflue)

<details>
<summary>Changes</summary>

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

---
Full diff: https://github.com/llvm/llvm-project/pull/153140.diff


4 Files Affected:

- (modified) clang/docs/ReleaseNotes.rst (+2) 
- (modified) clang/lib/Sema/SemaDecl.cpp (+32-28) 
- (modified) clang/test/CXX/class/class.mem/p13.cpp (+1-1) 
- (modified) clang/test/CXX/class/class.union/class.union.anon/p4.cpp (+10) 


``````````diff
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 0e9fcaa5fac6a..00b21471f3731 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -184,6 +184,8 @@ Bug Fixes to C++ Support
   (``[[assume(expr)]]``) creates temporary objects.
 - Fix the dynamic_cast to final class optimization to correctly handle
   casts that are guaranteed to fail (#GH137518).
+- Fix a crash if errors "member of anonymous [...] redeclares" and
+  "intializing multiple members of union" coincide (#GH149985).
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index b5eb825eb52cc..052e026fa3ee3 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -5463,40 +5463,44 @@ InjectAnonymousStructOrUnionMembers(Sema &SemaRef, Scope *S, DeclContext *Owner,
         //   distinct from the names of any other entity in the
         //   scope in which the anonymous union is declared.
         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);
+      }
+      // Inject the IndirectFieldDecl even if invalid, because later
+      // diagnostics may depend on it being present.
+
+      // 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];
+      assert(Chaining.size() >= 2);
+      NamedDecl **NamedChain =
+          new (SemaRef.Context) NamedDecl *[Chaining.size()];
+      for (unsigned i = 0; i < Chaining.size(); i++)
+        NamedChain[i] = Chaining[i];
 
-        IndirectFieldDecl *IndirectField = IndirectFieldDecl::Create(
-            SemaRef.Context, Owner, VD->getLocation(), VD->getIdentifier(),
-            VD->getType(), {NamedChain, Chaining.size()});
+      IndirectFieldDecl *IndirectField = IndirectFieldDecl::Create(
+          SemaRef.Context, Owner, VD->getLocation(), VD->getIdentifier(),
+          VD->getType(), {NamedChain, Chaining.size()});
 
-        for (const auto *Attr : VD->attrs())
-          IndirectField->addAttr(Attr->clone(SemaRef.Context));
+      for (const auto *Attr : VD->attrs())
+        IndirectField->addAttr(Attr->clone(SemaRef.Context));
 
-        IndirectField->setAccess(AS);
-        IndirectField->setImplicit();
-        SemaRef.PushOnScopeChains(IndirectField, S);
+      IndirectField->setAccess(AS);
+      IndirectField->setImplicit();
+      IndirectField->setInvalidDecl(Invalid);
+      SemaRef.PushOnScopeChains(IndirectField, S);
 
-        // That includes picking up the appropriate access specifier.
-        if (AS != AS_none) IndirectField->setAccess(AS);
+      // That includes picking up the appropriate access specifier.
+      if (AS != AS_none)
+        IndirectField->setAccess(AS);
 
-        Chaining.resize(OldChainingSize);
-      }
+      Chaining.resize(OldChainingSize);
     }
   }
 
diff --git a/clang/test/CXX/class/class.mem/p13.cpp b/clang/test/CXX/class/class.mem/p13.cpp
index d947586c41940..4dc959cd0beb8 100644
--- a/clang/test/CXX/class/class.mem/p13.cpp
+++ b/clang/test/CXX/class/class.mem/p13.cpp
@@ -63,7 +63,7 @@ struct X4 { // expected-note{{previous}}
     int X;
     union {
       float Y;
-      unsigned X4; // expected-error{{redeclares 'X4'}}
+      unsigned X4; // expected-error{{redeclares 'X4'}} expected-error {{'X4' has the same name as its class}}
     };
   };
 };
diff --git a/clang/test/CXX/class/class.union/class.union.anon/p4.cpp b/clang/test/CXX/class/class.union/class.union.anon/p4.cpp
index a12ec38503fa8..710636d2235db 100644
--- a/clang/test/CXX/class/class.union/class.union.anon/p4.cpp
+++ b/clang/test/CXX/class/class.union/class.union.anon/p4.cpp
@@ -8,3 +8,13 @@ union U {
     int y = 1; // expected-error {{initializing multiple members of union}}
   };
 };
+
+namespace GH149985 {
+  union U {
+    int x; // expected-note {{previous declaration is here}}
+    union {
+      int x = {}; // expected-error {{member of anonymous union redeclares}} expected-note {{previous initialization is here}}
+    };
+    int y = {}; // expected-error {{initializing multiple members of union}}
+  };
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/153140