Enhance -Wshadow to warn when shadowing typedefs or type aliases

hyp · hyp · commit 348c144d50fb · 2017-04-03T16:43:21.000Z
Enhance -Wshadow to emit a warning when typedefs or type aliases are shadowed. Fixes bug https://bugs.llvm.org//show_bug.cgi?id=28676. Patch by Ahmed Asadi. Differential Revision: https://reviews.llvm.org/D31235 llvm-svn: 299363
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -369,7 +369,9 @@ def warn_decl_shadow :
           "local variable|"
           "variable in %2|"
           "static data member of %2|"
-          "field of %2}1">,
+          "field of %2|"
+          "typedef in %2|"
+          "type alias in %2}1">,
   InGroup<Shadow>, DefaultIgnore;
 def warn_decl_shadow_uncaptured_local :
   Warning<warn_decl_shadow.Text>,
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
@@ -1738,8 +1738,11 @@ class Sema {
 
   static bool adjustContextForLocalExternDecl(DeclContext *&DC);
   void DiagnoseFunctionSpecifiers(const DeclSpec &DS);
+  NamedDecl *getShadowedDeclaration(const TypedefNameDecl *D,
+                                    const LookupResult &R);
   NamedDecl *getShadowedDeclaration(const VarDecl *D, const LookupResult &R);
-  void CheckShadow(VarDecl *D, NamedDecl *ShadowedDecl, const LookupResult &R);
+  void CheckShadow(NamedDecl *D, NamedDecl *ShadowedDecl,
+                   const LookupResult &R);
   void CheckShadow(Scope *S, VarDecl *D);
 
   /// Warn if 'E', which is an expression that is about to be modified, refers
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
@@ -5530,6 +5530,10 @@ Sema::CheckTypedefForVariablyModifiedType(Scope *S, TypedefNameDecl *NewTD) {
 NamedDecl*
 Sema::ActOnTypedefNameDecl(Scope *S, DeclContext *DC, TypedefNameDecl *NewTD,
                            LookupResult &Previous, bool &Redeclaration) {
+
+  // Find the shadowed declaration before filtering for scope.
+  NamedDecl *ShadowedDecl = getShadowedDeclaration(NewTD, Previous);
+
   // Merge the decl with the existing one if appropriate. If the decl is
   // in an outer scope, it isn't the same thing.
   FilterLookupForScope(Previous, DC, S, /*ConsiderLinkage*/false,
@@ -5540,6 +5544,9 @@ Sema::ActOnTypedefNameDecl(Scope *S, DeclContext *DC, TypedefNameDecl *NewTD,
     MergeTypedefNameDecl(S, NewTD, Previous);
   }
 
+  if (ShadowedDecl && !Redeclaration)
+    CheckShadow(NewTD, ShadowedDecl, Previous);
+
   // If this is the C FILE type, notify the AST context.
   if (IdentifierInfo *II = NewTD->getIdentifier())
     if (!NewTD->isInvalidDecl() &&
@@ -6671,13 +6678,25 @@ NamedDecl *Sema::ActOnVariableDeclarator(
 }
 
 /// Enum describing the %select options in diag::warn_decl_shadow.
-enum ShadowedDeclKind { SDK_Local, SDK_Global, SDK_StaticMember, SDK_Field };
+enum ShadowedDeclKind {
+  SDK_Local,
+  SDK_Global,
+  SDK_StaticMember,
+  SDK_Field,
+  SDK_Typedef,
+  SDK_Using
+};
 
 /// Determine what kind of declaration we're shadowing.
 static ShadowedDeclKind computeShadowedDeclKind(const NamedDecl *ShadowedDecl,
                                                 const DeclContext *OldDC) {
-  if (isa<RecordDecl>(OldDC))
+  if (isa<TypeAliasDecl>(ShadowedDecl))
+    return SDK_Using;
+  else if (isa<TypedefDecl>(ShadowedDecl))
+    return SDK_Typedef;
+  else if (isa<RecordDecl>(OldDC))
     return isa<FieldDecl>(ShadowedDecl) ? SDK_Field : SDK_StaticMember;
+
   return OldDC->isFileContext() ? SDK_Global : SDK_Local;
 }
 
@@ -6692,28 +6711,44 @@ static SourceLocation getCaptureLocation(const LambdaScopeInfo *LSI,
   return SourceLocation();
 }
 
+static bool shouldWarnIfShadowedDecl(const DiagnosticsEngine &Diags,
+                                     const LookupResult &R) {
+  // Only diagnose if we're shadowing an unambiguous field or variable.
+  if (R.getResultKind() != LookupResult::Found)
+    return false;
+
+  // Return false if warning is ignored.
+  return !Diags.isIgnored(diag::warn_decl_shadow, R.getNameLoc());
+}
+
 /// \brief Return the declaration shadowed by the given variable \p D, or null
 /// if it doesn't shadow any declaration or shadowing warnings are disabled.
 NamedDecl *Sema::getShadowedDeclaration(const VarDecl *D,
                                         const LookupResult &R) {
-  // Return if warning is ignored.
-  if (Diags.isIgnored(diag::warn_decl_shadow, R.getNameLoc()))
+  if (!shouldWarnIfShadowedDecl(Diags, R))
     return nullptr;
 
   // Don't diagnose declarations at file scope.
   if (D->hasGlobalStorage())
     return nullptr;
 
-  // Only diagnose if we're shadowing an unambiguous field or variable.
-  if (R.getResultKind() != LookupResult::Found)
-    return nullptr;
-
   NamedDecl *ShadowedDecl = R.getFoundDecl();
   return isa<VarDecl>(ShadowedDecl) || isa<FieldDecl>(ShadowedDecl)
              ? ShadowedDecl
              : nullptr;
 }
 
+/// \brief Return the declaration shadowed by the given typedef \p D, or null
+/// if it doesn't shadow any declaration or shadowing warnings are disabled.
+NamedDecl *Sema::getShadowedDeclaration(const TypedefNameDecl *D,
+                                        const LookupResult &R) {
+  if (!shouldWarnIfShadowedDecl(Diags, R))
+    return nullptr;
+
+  NamedDecl *ShadowedDecl = R.getFoundDecl();
+  return isa<TypedefNameDecl>(ShadowedDecl) ? ShadowedDecl : nullptr;
+}
+
 /// \brief Diagnose variable or built-in function shadowing.  Implements
 /// -Wshadow.
 ///
@@ -6723,7 +6758,7 @@ NamedDecl *Sema::getShadowedDeclaration(const VarDecl *D,
 /// \param ShadowedDecl the declaration that is shadowed by the given variable
 /// \param R the lookup of the name
 ///
-void Sema::CheckShadow(VarDecl *D, NamedDecl *ShadowedDecl,
+void Sema::CheckShadow(NamedDecl *D, NamedDecl *ShadowedDecl,
                        const LookupResult &R) {
   DeclContext *NewDC = D->getDeclContext();
 
@@ -6735,13 +6770,13 @@ void Sema::CheckShadow(VarDecl *D, NamedDecl *ShadowedDecl,
 
     // Fields shadowed by constructor parameters are a special case. Usually
     // the constructor initializes the field with the parameter.
-    if (isa<CXXConstructorDecl>(NewDC) && isa<ParmVarDecl>(D)) {
-      // Remember that this was shadowed so we can either warn about its
-      // modification or its existence depending on warning settings.
-      D = D->getCanonicalDecl();
-      ShadowingDecls.insert({D, FD});
-      return;
-    }
+    if (isa<CXXConstructorDecl>(NewDC))
+      if (const auto PVD = dyn_cast<ParmVarDecl>(D)) {
+        // Remember that this was shadowed so we can either warn about its
+        // modification or its existence depending on warning settings.
+        ShadowingDecls.insert({PVD->getCanonicalDecl(), FD});
+        return;
+      }
   }
 
   if (VarDecl *shadowedVar = dyn_cast<VarDecl>(ShadowedDecl))
@@ -6759,7 +6794,8 @@ void Sema::CheckShadow(VarDecl *D, NamedDecl *ShadowedDecl,
 
   unsigned WarningDiag = diag::warn_decl_shadow;
   SourceLocation CaptureLoc;
-  if (isa<VarDecl>(ShadowedDecl) && NewDC && isa<CXXMethodDecl>(NewDC)) {
+  if (isa<VarDecl>(D) && isa<VarDecl>(ShadowedDecl) && NewDC &&
+      isa<CXXMethodDecl>(NewDC)) {
     if (const auto *RD = dyn_cast<CXXRecordDecl>(NewDC->getParent())) {
       if (RD->isLambda() && OldDC->Encloses(NewDC->getLexicalParent())) {
         if (RD->getLambdaCaptureDefault() == LCD_None) {
@@ -6773,7 +6809,8 @@ void Sema::CheckShadow(VarDecl *D, NamedDecl *ShadowedDecl,
           // Remember that this was shadowed so we can avoid the warning if the
           // shadowed decl isn't captured and the warning settings allow it.
           cast<LambdaScopeInfo>(getCurFunction())
-              ->ShadowingDecls.push_back({D, cast<VarDecl>(ShadowedDecl)});
+              ->ShadowingDecls.push_back(
+                  {cast<VarDecl>(D), cast<VarDecl>(ShadowedDecl)});
           return;
         }
       }
diff --git a/clang/test/SemaCXX/warn-shadow.cpp b/clang/test/SemaCXX/warn-shadow.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -verify -fsyntax-only -Wshadow-all %s
+// RUN: %clang_cc1 -verify -fsyntax-only -std=c++11 -Wshadow-all %s
 
 namespace {
   int i; // expected-note {{previous declaration is here}}
@@ -7,14 +7,21 @@ namespace {
 namespace one {
 namespace two {
   int j; // expected-note {{previous declaration is here}}
+  typedef int jj; // expected-note 2 {{previous declaration is here}}
+  using jjj=int; // expected-note 2 {{previous declaration is here}}
 }
 }
 
 namespace xx {
   int m;
+  typedef int mm;
+  using mmm=int;
+
 }
 namespace yy {
   int m;
+  typedef char mm;
+  using mmm=char;
 }
 
 using namespace one::two;
@@ -25,14 +32,19 @@ void foo() {
   int i; // expected-warning {{declaration shadows a variable in namespace '(anonymous)'}}
   int j; // expected-warning {{declaration shadows a variable in namespace 'one::two'}}
   int m;
+  int mm;
+  int mmm;
 }
 
 class A {
-  static int data; // expected-note {{previous declaration}}
-  // expected-note@+1 {{previous declaration}}
+  static int data; // expected-note 1 {{previous declaration}}
+  // expected-note@+1 1 {{previous declaration}}
   int field;
   int f1, f2, f3, f4; // expected-note 8 {{previous declaration is here}}
 
+  typedef int a1; // expected-note 2 {{previous declaration}}
+  using a2=int; // expected-note 2 {{previous declaration}}
+
   // The initialization is safe, but the modifications are not.
   A(int f1, int f2, int f3, int f4) // expected-note-re 4 {{variable 'f{{[0-4]}}' is declared here}}
 	  : f1(f1) {
@@ -50,6 +62,28 @@ class A {
   void test() {
     char *field; // expected-warning {{declaration shadows a field of 'A'}}
     char *data; // expected-warning {{declaration shadows a static data member of 'A'}}
+    char *a1; // no warning 
+    char *a2; // no warning
+    char *jj; // no warning
+    char *jjj; // no warning
+  }
+
+  void test2() {
+    typedef char field; // no warning
+    typedef char data; // no warning
+    typedef char a1; // expected-warning {{declaration shadows a typedef in 'A'}}
+    typedef char a2; // expected-warning {{declaration shadows a type alias in 'A'}}
+    typedef char jj; // expected-warning {{declaration shadows a typedef in namespace 'one::two'}}
+    typedef char jjj; // expected-warning {{declaration shadows a type alias in namespace 'one::two'}}
+  }
+
+  void test3() {
+    using field=char; // no warning
+    using data=char; // no warning
+    using a1=char; // expected-warning {{declaration shadows a typedef in 'A'}}
+    using a2=char; // expected-warning {{declaration shadows a type alias in 'A'}}
+    using jj=char; // expected-warning {{declaration shadows a typedef in namespace 'one::two'}}
+    using jjj=char; // expected-warning {{declaration shadows a type alias in namespace 'one::two'}}
   }
 };
 
@@ -63,13 +97,23 @@ class B : A {
 namespace rdar8900456 {
 struct Foo {
   static void Baz();
+  static void Baz1();
+  static void Baz2();
 private:
   int Bar;
 };
 
 void Foo::Baz() {
   double Bar = 12; // Don't warn.
 }
+
+void Foo::Baz1() {
+  typedef int Bar; // Don't warn.
+}
+
+void Foo::Baz2() {
+  using Bar=int; // Don't warn.
+}
 }
 
 // http://llvm.org/PR9160
@@ -87,7 +131,9 @@ struct S {
 };
 }
 
-extern int bob; // expected-note {{previous declaration is here}}
+extern int bob; // expected-note 1 {{previous declaration is here}}
+typedef int bob1; // expected-note 2 {{previous declaration is here}}
+using bob2=int; // expected-note 2 {{previous declaration is here}}
 
 // rdar://8883302
 void rdar8883302() {
@@ -96,6 +142,20 @@ void rdar8883302() {
 
 void test8() {
   int bob; // expected-warning {{declaration shadows a variable in the global namespace}}
+  int bob1; //no warning
+  int bob2; // no warning
+}
+
+void test9() {
+  typedef int bob; // no warning
+  typedef int bob1; // expected-warning {{declaration shadows a typedef in the global namespace}}
+  typedef int bob2; // expected-warning {{declaration shadows a type alias in the global namespace}}
+}
+
+void test10() {
+  using bob=int; // no warning
+  using bob1=int; // expected-warning {{declaration shadows a typedef in the global namespace}}
+  using bob2=int; // expected-warning {{declaration shadows a type alias in the global namespace}}
 }
 
 namespace rdar29067894 {
@@ -104,6 +164,35 @@ void avoidWarningWhenRedefining(int b) { // expected-note {{previous definition
   int a = 0; // expected-note {{previous definition is here}}
   int a = 1; // expected-error {{redefinition of 'a'}}
   int b = 2; // expected-error {{redefinition of 'b'}}
+
+  using c=char; // expected-note {{previous definition is here}}
+  using c=int; // expected-error {{type alias redefinition with different types ('int' vs 'char')}}
+
+  typedef char d; // expected-note {{previous definition is here}}
+  typedef int d; // expected-error {{typedef redefinition with different types ('int' vs 'char')}}
+
+  using e=char; // expected-note {{previous definition is here}}
+  typedef int e; // expected-error {{type alias redefinition with different types ('int' vs 'char')}}
+
+  int f; // expected-note {{previous definition is here}}
+  using f=int; // expected-error {{redefinition of 'f'}}
+
+  using g=int; // expected-note {{previous definition is here}}
+  int g; // expected-error {{redefinition of 'g'}}
+
+  typedef int h; // expected-note {{previous definition is here}}
+  int h; // expected-error {{redefinition of 'h'}}
+
+  int k; // expected-note {{previous definition is here}}
+  typedef int k; // expected-error {{redefinition of 'k'}}
+
+  using l=char; // no warning or error.
+  using l=char; // no warning or error.
+  typedef char l; // no warning or error.
+ 
+  typedef char n; // no warning or error. 
+  typedef char n; // no warning or error.
+  using n=char; // no warning or error.
 }
 
 }
