[clang] 1ac592c - [clang] fix merging of UsingShadowDecl (#80245)

[via cfe-commits]

Author: Matheus Izvekov
Date: 2024-05-30T03:43:27-03:00
New Revision: 1ac592c4e7b4ba7c680af9286ad79ed27ad628f1

URL: https://github.com/llvm/llvm-project/commit/1ac592c4e7b4ba7c680af9286ad79ed27ad628f1
DIFF: https://github.com/llvm/llvm-project/commit/1ac592c4e7b4ba7c680af9286ad79ed27ad628f1.diff

LOG: [clang] fix merging of UsingShadowDecl (#80245)

[clang] fix merging of UsingShadowDecl

Previously, when deciding if two UsingShadowDecls where mergeable,
we would incorrectly only look for both pointing to the exact redecla
ration, whereas the correct thing is to look for declarations to the
same entity.

This problem has existed as far back as 2013, introduced in commit
fd8634a09de71.

This problem could manifest itself as ODR check false positives when
importing modules.

Fixes: #80252

Added: 
    

Modified: 
    clang/docs/ReleaseNotes.rst
    clang/lib/AST/ASTContext.cpp
    clang/test/Modules/cxx20-decls.cppm

Removed: 
    


################################################################################
diff  --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 44035f48cb3f9..9dc93f53fe716 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -813,6 +813,9 @@ Bug Fixes to C++ Support
 - Clang now allows ``@$``` in raw string literals. Fixes (#GH93130).
 - Fix an assertion failure when checking invalid ``this`` usage in the wrong context. (Fixes #GH91536).
 - Clang no longer models dependent NTTP arguments as ``TemplateParamObjectDecl`` s. Fixes (#GH84052).
+- Fix incorrect merging of modules which contain using declarations which shadow
+  other declarations. This could manifest as ODR checker false positives.
+  Fixes (`#80252 <https://github.com/llvm/llvm-project/issues/80252>`_)
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^

diff  --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 06780ceba4074..73d3b152c49f1 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -6794,7 +6794,7 @@ bool ASTContext::isSameEntity(const NamedDecl *X, const NamedDecl *Y) const {
   // Using shadow declarations with the same target match.
   if (const auto *USX = dyn_cast<UsingShadowDecl>(X)) {
     const auto *USY = cast<UsingShadowDecl>(Y);
-    return USX->getTargetDecl() == USY->getTargetDecl();
+    return declaresSameEntity(USX->getTargetDecl(), USY->getTargetDecl());
   }
 
   // Using declarations with the same qualifier match. (We already know that

diff  --git a/clang/test/Modules/cxx20-decls.cppm b/clang/test/Modules/cxx20-decls.cppm
index 9f0c40685b68f..0e8b59708ab4c 100644
--- a/clang/test/Modules/cxx20-decls.cppm
+++ b/clang/test/Modules/cxx20-decls.cppm
@@ -28,8 +28,8 @@ using xxx = baz::foo;
 // CHECK-NEXT: NamespaceDecl 0x[[BAZ_REDECL_ADDR:[^ ]*]] prev 0x[[BAZ_ADDR:[^ ]*]]
 // CHECK:      TypeAliasDecl 0x[[ALIAS_REDECL_ADDR:[^ ]*]] prev 0x[[ALIAS_ADDR:[^ ]*]]
 // FIXME: UsingShadowDecl should have been merged
-// CHECK:      UsingShadowDecl 0x{{[^ ]*}} <{{.*}}> col:{{.*}} imported in A.<global> hidden implicit TypeAlias 0x[[ALIAS_REDECL_ADDR]] 'foo'
+// CHECK:      UsingShadowDecl 0x{{[^ ]*}} prev 0x[[SHADOW_ADDR:[^ ]*]] {{.*}} imported in A.<global> {{.*}} 'foo'
 
 // CHECK-LABEL: Dumping baz:
 // CHECK-NEXT: NamespaceDecl 0x[[BAZ_ADDR]] <{{.*}}> line:{{.*}} baz
-// CHECK:      UsingShadowDecl 0x[[SHADOW_ADDR:[^ ]*]] <{{.*}}> col:{{.*}} implicit TypeAlias 0x[[ALIAS_ADDR]] 'foo'
+// CHECK:      UsingShadowDecl 0x[[SHADOW_ADDR]] {{.*}} 'foo'