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Export abstract methods as pure virtual (#7578)

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`abstract fn` was exported to C++ as a plain virtual function rather
than a pure virtual one, so the class wasn't abstract and could be
instantiated from C++.

Abstract functions no longer get a thunk since there is no definition to
call. The tests are prefixed with `fail_` since an abstract class still
errors on `Core.Destroy` regardless.
This commit is contained in:
arhwx
2026-07-30 00:29:53 +00:00
committed by GitHub
parent 198e447e4a
commit 8f224222a1
3 changed files with 60 additions and 1 deletions
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toolchain/check/testdata/interop/cpp/class/export/base.carbon
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@@ -145,6 +145,57 @@ class Derived : public Carbon::Abstract {
};
''';
// --- fail_variable_with_abstract_method.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_variable_with_abstract_method.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 {
abstract fn F(self);
}
inline Cpp '''
// CHECK:STDERR: fail_variable_with_abstract_method.carbon:[[@LINE+7]]:18: error: variable type 'Carbon::Abstract' is an abstract class [CppInteropParseError]
// CHECK:STDERR: 24 | Carbon::Abstract x;
// CHECK:STDERR: | ^
// CHECK:STDERR: fail_variable_with_abstract_method.carbon:[[@LINE-7]]:22: note: unimplemented pure virtual method 'F' in 'Abstract' [CppInteropParseNote]
// CHECK:STDERR: 13 | abstract fn F(self);
// CHECK:STDERR: | ^
// CHECK:STDERR:
Carbon::Abstract x;
''';
// --- fail_todo_abstract_method_overridden_in_cpp.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_method_overridden_in_cpp.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 {
abstract fn F(ref self);
}
// A C++ class that overrides the abstract method can be instantiated.
inline Cpp '''
struct Derived : Carbon::Abstract {
void F() & override {}
};
Derived d;
''';
// --- override_virtual_dtor.carbon
library "[[@TEST_NAME]]";