Sema: add warning for c++ member variable shadowing

Add a warning for shadowed variables across records.  Referencing a
shadow'ed variable may not give the desired variable.  Add an optional
warning for the shadowing.

Patch by James Sun!

llvm-svn: 294401

1 files changed, 55 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index e3310b60a2d..f84d14cfa8c 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -2758,6 +2758,56 @@ static AttributeList *getMSPropertyAttr(AttributeList *list) {
   return nullptr;
 }
 
+// Check if there is a field shadowing.
+void Sema::CheckShadowInheritedFields(const SourceLocation &Loc,
+                                      DeclarationName FieldName,
+                                      const CXXRecordDecl *RD) {
+  if (Diags.isIgnored(diag::warn_shadow_field, Loc))
+    return;
+
+  // To record a shadowed field in a base
+  std::map<CXXRecordDecl*, NamedDecl*> Bases;
+  auto FieldShadowed = [&](const CXXBaseSpecifier *Specifier,
+                           CXXBasePath &Path) {
+    const auto Base = Specifier->getType()->getAsCXXRecordDecl();
+    // Record an ambiguous path directly
+    if (Bases.find(Base) != Bases.end())
+      return true;
+    for (const auto Field : Base->lookup(FieldName)) {
+      if ((isa<FieldDecl>(Field) || isa<IndirectFieldDecl>(Field)) &&
+          Field->getAccess() != AS_private) {
+        assert(Field->getAccess() != AS_none);
+        assert(Bases.find(Base) == Bases.end());
+        Bases[Base] = Field;
+        return true;
+      }
+    }
+    return false;
+  };
+
+  CXXBasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/true,
+                     /*DetectVirtual=*/true);
+  if (!RD->lookupInBases(FieldShadowed, Paths))
+    return;
+
+  for (const auto &P : Paths) {
+    auto Base = P.back().Base->getType()->getAsCXXRecordDecl();
+    auto It = Bases.find(Base);
+    // Skip duplicated bases
+    if (It == Bases.end())
+      continue;
+    auto BaseField = It->second;
+    assert(BaseField->getAccess() != AS_private);
+    if (AS_none !=
+        CXXRecordDecl::MergeAccess(P.Access, BaseField->getAccess())) {
+      Diag(Loc, diag::warn_shadow_field)
+        << FieldName.getAsString() << RD->getName() << Base->getName();
+      Diag(BaseField->getLocation(), diag::note_shadow_field);
+      Bases.erase(It);
+    }
+  }
+}
+
 /// ActOnCXXMemberDeclarator - This is invoked when a C++ class member
 /// declarator is parsed. 'AS' is the access specifier, 'BW' specifies the
 /// bitfield width if there is one, 'InitExpr' specifies the initializer if
@@ -2957,6 +3007,11 @@ Sema::ActOnCXXMemberDeclarator(Scope *S, AccessSpecifier AS, Declarator &D,
       if (!Member)
         return nullptr;
     }
+
+    // Check for any possible shadowed member variables
+    if (const auto *RD = cast<CXXRecordDecl>(CurContext))
+      CheckShadowInheritedFields(Loc, Name, RD);
+
   } else {
     Member = HandleDeclarator(S, D, TemplateParameterLists);
     if (!Member)