Files
carbon-lang/toolchain/check/testdata/interop/cpp/class/export/base.carbon
T
Chandler Carruthandjosh11b 7871237c15 Move self to the explicit () parameter list (proposal #7016) (#7272)
Implements proposal #7016: `self` moves from the deduced implicit list
(`fn F[self: Self]()`) to the front of the explicit list. Its type may
be written explicitly (`fn F(self: Self)`) or omitted, in which case it
defaults to `Self` (`fn F(self)`, `fn F(ref self)`); `self` in the
implicit list is rejected.

Throughout checking, `self` is modeled as the first explicit parameter.
Because a method is just a function whose first parameter is `self`, it
can also be called as an ordinary function with the receiver passed
explicitly (`Type.M(obj, ...)`), not only as `obj.M(...)`. A new
`SemIR::CallArgParamPatterns` helper chooses the parameters matched
against the explicit arguments, excluding a leading `self` only when it
is supplied as a method-call receiver; arity checking, conversion, and
generic deduction use it. The resulting SemIR and lowering are
unchanged: `self` is still `call_param0`, and witnesses, thunks, and
vtables are unaffected.

An omitted `self` type is parsed as a `SelfBindingPattern` node with no
type expression; checking synthesizes the `Self` type so it behaves
exactly like `self: Self`. However, the exact spelling used must match
between a forward declaration and a definition, following #3763's rules
around declaration matching.

Generated functions, thunks, and C++ interop import/export build `self`
as the first explicit parameter, and the `self`-type override (e.g.
Derived->Base for a virtual override) applies to the explicit `self`.
Placement is validated by new diagnostics: `SelfInImplicitParamList`,
`SelfNotFirstParam`, and `SelfOutsideParamList`. The benchmark source
generator and the documentation adopt the `(self)` shorthand; the
prelude, the examples, and the test data are migrated in the following
commits.

Assisted-by: Claude Code with Claude Opus 4.7

---------

Co-authored-by: josh11b <15258583+josh11b@users.noreply.github.com>
2026-06-10 15:30:43 +00:00

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// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
// INCLUDE-FILE: toolchain/testing/testdata/min_prelude/int.carbon
//
// AUTOUPDATE
// TIP: To test this file alone, run:
// TIP: bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/check/testdata/interop/cpp/class/export/base.carbon
// TIP: To dump output, run:
// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/check/testdata/interop/cpp/class/export/base.carbon
// --- derived_to_base.carbon
library "[[@TEST_NAME]]";
import Cpp;
base class A {}
class B {
extend base: A;
}
inline Cpp '''
Carbon::A* Convert(Carbon::B* p) {
return p;
}
''';
// --- name_lookup.carbon
library "[[@TEST_NAME]]";
import Cpp;
base class A {
fn F();
fn G(n: i32);
}
class B {
extend base: A;
fn G();
}
inline Cpp '''
void Qualified() {
Carbon::B::F();
Carbon::B::G();
}
void MemberAccess(Carbon::A *a, Carbon::B *b) {
b->F();
b->G();
}
''';
// --- fail_derive_from_final.carbon
library "[[@TEST_NAME]]";
import Cpp;
class Final {}
inline Cpp '''
// CHECK:STDERR: fail_derive_from_final.carbon:[[@LINE+5]]:12: error: base 'Final' is marked 'final' [CppInteropParseError]
// CHECK:STDERR: 13 | struct A : Carbon::Final {};
// CHECK:STDERR: | ^
// CHECK:STDERR: note: 'Final' declared here [CppInteropParseNote]
// CHECK:STDERR:
struct A : Carbon::Final {};
''';
// --- fail_abstract.carbon
library "[[@TEST_NAME]]";
import Cpp;
// TODO: Add a way to give a class a virtual destructor without C++ interop.
inline Cpp '''
struct VirtualDestructor {
virtual ~VirtualDestructor() {}
};
''';
// CHECK:STDERR: fail_abstract.carbon:[[@LINE+4]]:1: error: cannot access member of interface `Core.Destroy` in type `Abstract` that does not implement that interface [MissingImplInMemberAccess]
// CHECK:STDERR: abstract class Abstract {
// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~
// CHECK:STDERR:
abstract class Abstract {
extend base: Cpp.VirtualDestructor;
}
inline Cpp '''
// CHECK:STDERR: fail_abstract.carbon:[[@LINE+5]]:18: error: variable type 'Carbon::Abstract' is an abstract class [CppInteropParseError]
// CHECK:STDERR: 26 | Carbon::Abstract x;
// CHECK:STDERR: | ^
// CHECK:STDERR: note: unimplemented pure virtual method '~Abstract' in 'Abstract' [CppInteropParseNote]
// CHECK:STDERR:
Carbon::Abstract x;
''';
// --- fail_todo_abstract_nonvirtual_dtor.carbon
library "[[@TEST_NAME]]";
import Cpp;
// TODO: Find a way to export this to C++ as an abstract class, despite not
// having a vptr.
// CHECK:STDERR: fail_todo_abstract_nonvirtual_dtor.carbon:[[@LINE+8]]:1: error: semantics TODO: `exporting abstract class with no abstract methods and non-virtual destructor to C++` [SemanticsTodo]
// CHECK:STDERR: abstract class Abstract {}
// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~
// CHECK:STDERR:
// CHECK:STDERR: fail_todo_abstract_nonvirtual_dtor.carbon:[[@LINE+4]]:1: error: cannot access member of interface `Core.Destroy` in type `Abstract` that does not implement that interface [MissingImplInMemberAccess]
// CHECK:STDERR: abstract class Abstract {}
// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~
// CHECK:STDERR:
abstract class Abstract {}
inline Cpp '''
class Derived : public Carbon::Abstract {};
''';
// --- fail_todo_abstract_nonvirtual_dtor_but_virtual_fns.carbon
library "[[@TEST_NAME]]";
import Cpp;
// TODO: We should support generating a base subobject destructor for an
// abstract class, even though we refuse to generate a complete object
// destructor.
// CHECK:STDERR: fail_todo_abstract_nonvirtual_dtor_but_virtual_fns.carbon:[[@LINE+4]]:1: error: cannot access member of interface `Core.Destroy` in type `Abstract` that does not implement that interface [MissingImplInMemberAccess]
// CHECK:STDERR: abstract class Abstract {
// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~
// CHECK:STDERR:
abstract class Abstract {
// CHECK:STDERR: fail_todo_abstract_nonvirtual_dtor_but_virtual_fns.carbon:[[@LINE+10]]:3: error: initialization of abstract type `Abstract` [AbstractTypeInInit]
// CHECK:STDERR: abstract fn F(self);
// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~
// CHECK:STDERR: fail_todo_abstract_nonvirtual_dtor_but_virtual_fns.carbon:[[@LINE-4]]:1: note: class was declared abstract here [ClassAbstractHere]
// CHECK:STDERR: abstract class Abstract {
// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~
// CHECK:STDERR: fail_todo_abstract_nonvirtual_dtor_but_virtual_fns.carbon:[[@LINE+4]]:17: note: initializing function parameter [InCallToFunctionParam]
// CHECK:STDERR: abstract fn F(self);
// CHECK:STDERR: ^~~~
// CHECK:STDERR:
abstract fn F(self);
}
inline Cpp '''
class Derived : public Carbon::Abstract {
};
''';
// --- override_virtual_dtor.carbon
library "[[@TEST_NAME]]";
import Cpp;
inline Cpp '''
struct A {
virtual ~A() = 0;
};
''';
class B {
extend base: Cpp.A;
}
inline Cpp '''
Carbon::B b;
''';