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llvm-project/clang/test/SemaCXX/conversion-function.cpp
Matheus Izvekov 15f3cd6bfc
[clang] Implement ElaboratedType sugaring for types written bare 
Without this patch, clang will not wrap in an ElaboratedType node types written
without a keyword and nested name qualifier, which goes against the intent that
we should produce an AST which retains enough details to recover how things are
written.

The lack of this sugar is incompatible with the intent of the type printer
default policy, which is to print types as written, but to fall back and print
them fully qualified when they are desugared.

An ElaboratedTypeLoc without keyword / NNS uses no storage by itself, but still
requires pointer alignment due to pre-existing bug in the TypeLoc buffer
handling.

---

Troubleshooting list to deal with any breakage seen with this patch:

1) The most likely effect one would see by this patch is a change in how
   a type is printed. The type printer will, by design and default,
   print types as written. There are customization options there, but
   not that many, and they mainly apply to how to print a type that we
   somehow failed to track how it was written. This patch fixes a
   problem where we failed to distinguish between a type
   that was written without any elaborated-type qualifiers,
   such as a 'struct'/'class' tags and name spacifiers such as 'std::',
   and one that has been stripped of any 'metadata' that identifies such,
   the so called canonical types.
   Example:
   ```
   namespace foo {
     struct A {};
     A a;
   };
   ```
   If one were to print the type of `foo::a`, prior to this patch, this
   would result in `foo::A`. This is how the type printer would have,
   by default, printed the canonical type of A as well.
   As soon as you add any name qualifiers to A, the type printer would
   suddenly start accurately printing the type as written. This patch
   will make it print it accurately even when written without
   qualifiers, so we will just print `A` for the initial example, as
   the user did not really write that `foo::` namespace qualifier.

2) This patch could expose a bug in some AST matcher. Matching types
   is harder to get right when there is sugar involved. For example,
   if you want to match a type against being a pointer to some type A,
   then you have to account for getting a type that is sugar for a
   pointer to A, or being a pointer to sugar to A, or both! Usually
   you would get the second part wrong, and this would work for a
   very simple test where you don't use any name qualifiers, but
   you would discover is broken when you do. The usual fix is to
   either use the matcher which strips sugar, which is annoying
   to use as for example if you match an N level pointer, you have
   to put N+1 such matchers in there, beginning to end and between
   all those levels. But in a lot of cases, if the property you want
   to match is present in the canonical type, it's easier and faster
   to just match on that... This goes with what is said in 1), if
   you want to match against the name of a type, and you want
   the name string to be something stable, perhaps matching on
   the name of the canonical type is the better choice.

3) This patch could expose a bug in how you get the source range of some
   TypeLoc. For some reason, a lot of code is using getLocalSourceRange(),
   which only looks at the given TypeLoc node. This patch introduces a new,
   and more common TypeLoc node which contains no source locations on itself.
   This is not an inovation here, and some other, more rare TypeLoc nodes could
   also have this property, but if you use getLocalSourceRange on them, it's not
   going to return any valid locations, because it doesn't have any. The right fix
   here is to always use getSourceRange() or getBeginLoc/getEndLoc which will dive
   into the inner TypeLoc to get the source range if it doesn't find it on the
   top level one. You can use getLocalSourceRange if you are really into
   micro-optimizations and you have some outside knowledge that the TypeLocs you are
   dealing with will always include some source location.

4) Exposed a bug somewhere in the use of the normal clang type class API, where you
   have some type, you want to see if that type is some particular kind, you try a
   `dyn_cast` such as `dyn_cast<TypedefType>` and that fails because now you have an
   ElaboratedType which has a TypeDefType inside of it, which is what you wanted to match.
   Again, like 2), this would usually have been tested poorly with some simple tests with
   no qualifications, and would have been broken had there been any other kind of type sugar,
   be it an ElaboratedType or a TemplateSpecializationType or a SubstTemplateParmType.
   The usual fix here is to use `getAs` instead of `dyn_cast`, which will look deeper
   into the type. Or use `getAsAdjusted` when dealing with TypeLocs.
   For some reason the API is inconsistent there and on TypeLocs getAs behaves like a dyn_cast.

5) It could be a bug in this patch perhaps.

Let me know if you need any help!

Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>

Differential Revision: https://reviews.llvm.org/D112374
2022-07-27 11:10:54 +02:00

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// RUN: %clang_cc1 -std=c++2b -fsyntax-only -verify=expected -triple %itanium_abi_triple -Wbind-to-temporary-copy %s
// RUN: %clang_cc1 -std=c++20 -fsyntax-only -verify=expected -triple %itanium_abi_triple -Wbind-to-temporary-copy %s
// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify=expected,cxx98_11,cxx11 -triple %itanium_abi_triple -Wbind-to-temporary-copy %s
// RUN: %clang_cc1 -std=c++98 -fsyntax-only -verify=expected,cxx98_11,cxx98 -triple %itanium_abi_triple -Wbind-to-temporary-copy %s
class X {
public:
operator bool();
operator int() const;
bool f() {
return operator bool();
}
float g() {
return operator float(); // expected-error{{use of undeclared 'operator float'}}
}
static operator short(); // expected-error{{conversion function must be a non-static member function}}
};
operator int(); // expected-error{{conversion function must be a non-static member function}}
operator int; // expected-error{{'operator int' cannot be the name of a variable or data member}}
typedef int func_type(int);
typedef int array_type[10];
class Y {
public:
void operator bool(int, ...) const; // expected-error{{conversion function cannot have a return type}} \
// expected-error{{conversion function cannot have any parameters}}
operator bool(int a = 4, int b = 6) const; // expected-error{{conversion function cannot have any parameters}}
operator float(...) const; // expected-error{{conversion function cannot be variadic}}
operator func_type(); // expected-error{{conversion function cannot convert to a function type}}
operator array_type(); // expected-error{{conversion function cannot convert to an array type}}
};
typedef int INT;
typedef INT* INT_PTR;
class Z {
operator int(); // expected-note {{previous declaration is here}}
operator int**(); // expected-note {{previous declaration is here}}
operator INT(); // expected-error{{conversion function cannot be redeclared}}
operator INT_PTR*(); // expected-error{{conversion function cannot be redeclared}}
};
class A { };
class B : public A {
public:
operator A&() const; // expected-warning{{conversion function converting 'B' to its base class 'A' will never be used}}
operator const void() const; // expected-warning{{conversion function converting 'B' to 'const void' will never be used}}
operator const B(); // expected-warning{{conversion function converting 'B' to itself will never be used}}
};
class BaseA {};
class DerivedA;
class BaseB {
virtual operator BaseA &() = 0;
virtual operator DerivedA &() = 0;
};
class DerivedA : public BaseA, BaseB {
virtual operator BaseA &(); // OK. Overrides BaseB::operatorBaseA&()
virtual operator DerivedA &(); // OK. Overrides BaseB::operatorDerivedA&()
};
class DerivedB : public BaseA {
virtual operator DerivedB &(); // expected-warning{{conversion function converting 'DerivedB' to itself will never be used}}
virtual operator BaseA &(); // expected-warning{{conversion function converting 'DerivedB' to its base class 'BaseA' will never be used}}
};
// This used to crash Clang.
struct Flip;
struct Flop {
Flop();
Flop(const Flip&); // expected-note{{candidate constructor}}
};
struct Flip {
operator Flop() const; // expected-note{{candidate function}}
};
Flop flop = Flip(); // expected-error {{conversion from 'Flip' to 'Flop' is ambiguous}}
// This tests that we don't add the second conversion declaration to the list of user conversions
struct C {
operator const char *() const;
};
C::operator const char*() const { return 0; }
void f(const C& c) {
const char* v = c;
}
// Test. Conversion in base class is visible in derived class.
class XB {
public:
operator int(); // expected-note {{candidate function}}
};
class Yb : public XB {
public:
operator char(); // expected-note {{candidate function}}
};
void f(Yb& a) {
if (a) { } // expected-error {{conversion from 'Yb' to 'bool' is ambiguous}}
int i = a; // OK. calls XB::operator int();
char ch = a; // OK. calls Yb::operator char();
}
// Test conversion + copy construction. This is a pure C++98 test.
// However we may extend implicit moves into C++98, we must make sure the
// result here is not changed.
class AutoPtrRef { };
class AutoPtr {
AutoPtr(AutoPtr &); // cxx98-note {{declared private here}}
public:
AutoPtr();
AutoPtr(AutoPtrRef);
operator AutoPtrRef();
};
AutoPtr make_auto_ptr();
AutoPtr test_auto_ptr(bool Cond) {
AutoPtr p1( make_auto_ptr() );
AutoPtr p;
if (Cond)
return p; // cxx98-error {{calling a private constructor}}
return AutoPtr();
}
struct A1 {
A1(const char *);
~A1();
private:
A1(const A1 &); // cxx98_11-note 2 {{declared private here}}
};
A1 f() {
// FIXME: redundant diagnostics!
return "Hello"; // cxx98_11-error {{calling a private constructor}}
// cxx98-warning@-1 {{an accessible copy constructor}}
// cxx11-warning@-2 {{copying parameter of type 'A1' when binding a reference to a temporary would invoke an inaccessible constructor in C++98}}
}
namespace source_locations {
template<typename T>
struct sneaky_int {
typedef int type;
};
template<typename T, typename U>
struct A { };
template<typename T>
struct A<T, T> : A<T, int> { };
struct E {
template<typename T>
operator A<T, typename sneaky_int<T>::type>&() const; // expected-note{{candidate function}}
};
void f() {
A<float, float> &af = E(); // expected-error{{no viable conversion}}
A<float, int> &af2 = E();
const A<float, int> &caf2 = E();
}
// Check
template<typename T>
struct E2 {
operator T
* // expected-error{{'operator type-parameter-0-0 *' declared as a pointer to a reference of type 'int &'}}
() const;
};
E2<int&> e2i; // expected-note{{in instantiation}}
}
namespace crazy_declarators {
struct A {
(&operator bool())(); // expected-error {{use a typedef to declare a conversion to 'bool (&)()'}}
*operator int(); // expected-error {{put the complete type after 'operator'}}
// No suggestion of using a typedef here; that's not possible.
template<typename T> (&operator T())();
#if __cplusplus <= 199711L
// expected-error-re@-2 {{cannot specify any part of a return type in the declaration of a conversion function{{$}}}}
#else
// expected-error-re@-4 {{cannot specify any part of a return type in the declaration of a conversion function; use an alias template to declare a conversion to 'T (&)()'{{$}}}}
#endif
};
}
namespace smart_ptr {
class Y {
class YRef { };
Y(Y&);
public:
Y();
Y(YRef);
operator YRef(); // expected-note{{candidate function}}
};
struct X { // expected-note{{candidate constructor (the implicit copy constructor) not}}
#if __cplusplus >= 201103L
// expected-note@-2 {{candidate constructor (the implicit move constructor) not}}
#endif
explicit X(Y); // expected-note {{not a candidate}}
};
Y make_Y();
X f() {
X x = make_Y(); // expected-error{{no viable conversion from 'Y' to 'X'}}
X x2(make_Y());
return X(Y());
}
}
struct Any {
Any(...);
};
struct Other {
Other(const Other &);
Other();
};
void test_any() {
Any any = Other();
#if __cplusplus <= 199711L
// expected-error@-2 {{cannot pass object of non-POD type 'Other' through variadic constructor; call will abort at runtime}}
#else
// expected-error@-4 {{cannot pass object of non-trivial type 'Other' through variadic constructor; call will abort at runtime}}
#endif
}
namespace PR7055 {
// Make sure that we don't allow too many conversions in an
// auto_ptr-like template. In particular, we can't create multiple
// temporary objects when binding to a reference.
struct auto_ptr {
struct auto_ptr_ref { };
auto_ptr(auto_ptr&);
auto_ptr(auto_ptr_ref);
explicit auto_ptr(int *);
operator auto_ptr_ref();
};
struct X {
X(auto_ptr);
};
X f() {
X x(auto_ptr(new int));
return X(auto_ptr(new int));
}
auto_ptr foo();
X e(foo());
struct Y {
Y(X);
};
Y f2(foo());
}
namespace PR7934 {
typedef unsigned char uint8;
struct MutablePtr {
MutablePtr() : ptr(0) {}
void *ptr;
operator void*() { return ptr; }
private:
operator uint8*() { return reinterpret_cast<uint8*>(ptr); }
operator const char*() const { return reinterpret_cast<const char*>(ptr); }
};
void fake_memcpy(const void *);
void use() {
MutablePtr ptr;
fake_memcpy(ptr);
}
}
namespace rdar8018274 {
struct X { };
struct Y {
operator const struct X *() const;
};
struct Z : Y {
operator struct X * ();
};
void test() {
Z x;
(void) (x != __null);
}
struct Base {
operator int();
};
struct Derived1 : Base { };
struct Derived2 : Base { };
struct SuperDerived : Derived1, Derived2 {
using Derived1::operator int;
};
struct UeberDerived : SuperDerived {
operator long();
};
void test2(UeberDerived ud) {
int i = ud; // expected-error{{ambiguous conversion from derived class 'UeberDerived' to base class 'rdar8018274::Base'}}
}
struct Base2 {
operator int();
};
struct Base3 {
operator int();
};
struct Derived23 : Base2, Base3 {
using Base2::operator int;
};
struct ExtraDerived23 : Derived23 { };
void test3(ExtraDerived23 ed) {
int i = ed;
}
}
namespace PR8065 {
template <typename T> struct Iterator;
template <typename T> struct Container;
template<>
struct Iterator<int> {
typedef Container<int> container_type;
};
template <typename T>
struct Container {
typedef typename Iterator<T>::container_type X;
operator X(void) { return X(); }
};
Container<int> test;
}
namespace PR8034 {
struct C {
operator int();
private:
template <typename T> operator T();
};
int x = C().operator int();
}
namespace PR9336 {
template<class T>
struct generic_list
{
template<class Container>
operator Container()
{
Container ar;
T* i;
ar[0]=*i;
return ar;
}
};
template<class T>
struct array
{
T& operator[](int);
const T& operator[](int)const;
};
generic_list<generic_list<int> > l;
array<array<int> > a = l;
}
namespace PR8800 {
struct A;
struct C {
operator A&();
};
void f() {
C c;
A& a1(c);
A& a2 = c;
A& a3 = static_cast<A&>(c);
A& a4 = (A&)c;
}
}
namespace PR12712 {
struct A {};
struct B {
operator A();
operator A() const;
};
struct C : B {};
A f(const C c) { return c; }
}
namespace PR18234 {
struct A {
operator enum E { e } (); // expected-error {{'PR18234::A::E' cannot be defined in a type specifier}}
operator struct S { int n; } (); // expected-error {{'PR18234::A::S' cannot be defined in a type specifier}}
// expected-note@-1 {{candidate constructor (the implicit copy constructor) not viable: no known conversion from 'struct A' to 'const PR18234::A::S &' for 1st argument}}
#if __cplusplus >= 201103L
// expected-note@-3 {{candidate constructor (the implicit move constructor) not viable: no known conversion from 'struct A' to 'PR18234::A::S &&' for 1st argument}}
#endif
} a;
A::S s = a; // expected-error {{no viable conversion from 'struct A' to 'A::S'}}
A::E e = a;
bool k1 = e == A::e; // expected-error {{no member named 'e'}}
bool k2 = e.n == 0;
}
namespace PR30595 {
struct S {
const operator int(); // expected-error {{cannot specify any part of a return type in the declaration of a conversion function; put the complete type after 'operator'}}
const operator int() const; // expected-error {{cannot specify any part of a return type}}
volatile const operator int(); // expected-error {{cannot specify any part of a return type}}
operator const int() const;
};
}
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