Fix treatment of types defined in function prototype

[sepavloff]

Summary

Types defined in function prototype are diagnosed earlier in C++ compilation.
They are put into declaration context where the prototype is introduced. Later on,
when FunctionDecl object is created, these types are moved into the function context.

This patch fixes PR19018 and PR18963.

[rsmith]

LGTM

test/SemaCXX/type-definition-in-specifier.cpp

44

Does this still work if you put something more complex into the struct definition? (For instance, if it tries to reference a member of the surrounding struct, or if it has member functions, or similar.)

[sepavloff]

Closed by commit rL211718 (authored by @sepavloff).

[sepavloff]

Thank you for review.

2014-06-24 23:24 GMT+07:00 Richard Smith <[e-mail]>:

LGTM

Comment at: test/SemaCXX/type-definition-in-specifier.cpp:44
@@ +43,3 @@
+ void func4(struct t19018 {int qq;} x); expected-error{{cannot be
defined in a parameter type}}
+ void func5(struct {int qq;} x); expected-error{{cannot be defined in
a parameter type}}

+};

Does this still work if you put something more complex into the struct
definition? (For instance, if it tries to reference a member of the
surrounding struct, or if it has member functions, or similar.)

It still works, corresponding testcases are added. However, access to a
member of the surrounding struct is resolved as for nested types, the code:

struct aaa {

int xx;
void func5(struct { int qq() { return xx; }; } x);

};

produces also a message:

error: use of non-static data member 'xx' of 'aaa' from nested type ''

I don't know if this behavior need to be fixed, as type defined in
prototype itself is erroneous.

Thanks,
--Serge

lib/AST/Decl.cpp

 
 void FunctionDecl::setDeclsInPrototypeScope(ArrayRef<NamedDecl *> NewDecls) {
   assert(DeclsInPrototypeScope.empty() && "Already has prototype decls!");
 
   if (!NewDecls.empty()) {
     NamedDecl **A = new (getASTContext()) NamedDecl*[NewDecls.size()];
     std::copy(NewDecls.begin(), NewDecls.end(), A);
     DeclsInPrototypeScope = ArrayRef<NamedDecl *>(A, NewDecls.size());
+    // Move declarations introduced in prototype to the function context.
+    for (auto I : NewDecls) {
+      DeclContext *DC = I->getDeclContext();
+      // Forward-declared reference to an enumeration is not added to
+      // declaration scope, so skip declaration that is absent from its
+      // declaration contexts.
+      if (DC->containsDecl(I)) {
+          DC->removeDecl(I);
+          I->setDeclContext(this);
+          addDecl(I);
+      }
+    }
   }
 }
 
 /// getMinRequiredArguments - Returns the minimum number of arguments
 /// needed to call this function. This may be fewer than the number of
 /// function parameters, if some of the parameters have default
 /// arguments (in C++) or are parameter packs (C++11).
 unsigned FunctionDecl::getMinRequiredArguments() const {

lib/Sema/SemaDecl.cpp

if (Name && SS.isNotEmpty()) {
     if (!getLangOpts().CPlusPlus && TUK != TUK_Reference) {
       // FIXME: This makes sure that we ignore the contexts associated
       // with C structs, unions, and enums when looking for a matching
       // tag declaration or definition. See the similar lookup tweak
       // in Sema::LookupName; is there a better way to deal with this?
       while (isa<RecordDecl>(SearchDC) || isa<EnumDecl>(SearchDC))
         SearchDC = SearchDC->getParent();
     }
-  } else if (S->isFunctionPrototypeScope()) {
-    // If this is an enum declaration in function prototype scope, set its
-    // initial context to the translation unit.
-    // FIXME: [citation needed]
-    SearchDC = Context.getTranslationUnitDecl();
   }
 
   if (Previous.isSingleResult() &&
       Previous.getFoundDecl()->isTemplateParameter()) {
     // Maybe we will complain about the shadowed template parameter.
     DiagnoseTemplateParameterShadow(NameLoc, Previous.getFoundDecl());
     // Just pretend that we didn't see the previous declaration.
     Previous.clear();
if (isExplicitSpecialization)
         << 2
         << FixItHint::CreateRemoval(ModulePrivateLoc);
     // __module_private__ does not apply to local classes. However, we only
     // diagnose this as an error when the declaration specifiers are
     // freestanding. Here, we just ignore the __module_private__.
     else if (!SearchDC->isFunctionOrMethod())
       New->setModulePrivate();
   }
-  
   // If this is a specialization of a member class (of a class template),
   // check the specialization.
   if (isExplicitSpecialization && CheckMemberSpecialization(New, Previous))
     Invalid = true;
-           
-  if (Invalid)
-    New->setInvalidDecl();
-
-  if (Attr)
-    ProcessDeclAttributeList(S, New, Attr);
-
   // If we're declaring or defining a tag in function prototype scope in C,
   // note that this type can only be used within the function and add it to
   // the list of decls to inject into the function definition scope.
-  if (!getLangOpts().CPlusPlus && (Name || Kind == TTK_Enum) &&
+  if ((Name || Kind == TTK_Enum) &&
       getNonFieldDeclScope(S)->isFunctionPrototypeScope()) {
+    if (getLangOpts().CPlusPlus) {
+      // C++ [dcl.fct]p6:
+      //   Types shall not be defined in return or parameter types.
+      if (TUK == TUK_Definition && !IsTypeSpecifier) {
+        Diag(Loc, diag::err_type_defined_in_param_type)
+            << Name;
+        Invalid = true;
+      }
+    } else {
       Diag(Loc, diag::warn_decl_in_param_list) << Context.getTagDeclType(New);
+    }
     DeclsInPrototypeScope.push_back(New);
   }
 
+  if (Invalid)
+    New->setInvalidDecl();
+
+  if (Attr)
+    ProcessDeclAttributeList(S, New, Attr);
+
   // Set the lexical context. If the tag has a C++ scope specifier, the
   // lexical context will be different from the semantic context.
   New->setLexicalDeclContext(CurContext);
 
   // Mark this as a friend decl if applicable.
   // In Microsoft mode, a friend declaration also acts as a forward
   // declaration so we always pass true to setObjectOfFriendDecl to make
   // the tag name visible.

test/Sema/decl-in-prototype.c

 };
 
 int f5(struct aA { struct ab { int j; } b; struct ab { char glorx; } glorx; } *); // expected-warning {{declaration of 'struct aA' will not be visible}} expected-warning {{redefinition of 'ab' will not be visible}} expected-warning {{redefinition of 'ab' will not be visible}}
 
 void f6(struct z {int b;} c) { // expected-warning {{declaration of 'struct z' will not be visible outside of this function}}
     struct z d;
     d.b = 4;
 }
+
+void pr19018_1 (enum e19018 { qq } x); // expected-warning{{declaration of 'enum e19018' will not be visible outside of this function}}
+enum e19018 qq; //expected-error{{tentative definition has type 'enum e19018' that is never completed}} \
+                //expected-note{{forward declaration of 'enum e19018'}}

test/SemaCXX/type-definition-in-specifier.cpp

void f0() {
   struct S3 { int x; } s3;
 
   (void)static_cast<struct S4 { int x; } *>(0); // expected-error{{cannot be defined}}
 }
 
 struct S5 { int x; } f1() { return S5(); } // expected-error{{result type}}
 
 void f2(struct S6 { int x; } p); // expected-error{{parameter type}}
+
+struct pr19018 {
+  short foo6 (enum bar0 {qq} bar3); // expected-error{{cannot be defined in a parameter type}}
+};
+
+void pr19018_1 (enum e19018_1 {qq} x); // expected-error{{cannot be defined in a parameter type}}
+void pr19018_1a (enum e19018_1 {qq} x); // expected-error{{cannot be defined in a parameter type}}
+e19018_1 x2;  // expected-error{{unknown type name 'e19018_1'}}
+
+void pr19018_2 (enum {qq} x); // expected-error{{cannot be defined in a parameter type}}
+void pr19018_3 (struct s19018_2 {int qq;} x); // expected-error{{cannot be defined in a parameter type}}
+void pr19018_4 (struct {int qq;} x); // expected-error{{cannot be defined in a parameter type}}
+
+struct pr19018a {
+  void func1(enum t19018 {qq} x); // expected-error{{cannot be defined in a parameter type}}
+  void func2(enum t19018 {qq} x); // expected-error{{cannot be defined in a parameter type}}
+  void func3(enum {qq} x);        // expected-error{{cannot be defined in a parameter type}}
+  void func4(struct t19018 {int qq;} x);  // expected-error{{cannot be defined in a parameter type}}
+  void func5(struct {int qq;} x); // expected-error{{cannot be defined in a parameter type}}
+};
+
+struct s19018b {
+  void func1 (enum en_2 {qq} x); // expected-error{{cannot be defined in a parameter type}}
+  en_2 x1;  // expected-error{{unknown type name 'en_2'}}
+  void func2 (enum en_3 {qq} x); // expected-error{{cannot be defined in a parameter type}}
+  enum en_3 x2; // expected-error{{ISO C++ forbids forward references to 'enum' types}} \
+                // expected-error{{field has incomplete type 'enum en_3'}} \
+                // expected-note{{forward declaration of 'en_3'}}
+};
+
+struct pr18963 {
+  short bar5 (struct foo4 {} bar2); // expected-error{{'foo4' cannot be defined in a parameter type}}
+  long foo5 (float foo6 = foo4);  // expected-error{{use of undeclared identifier 'foo4'}}
+};