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Allow interop with classes with virtual base classes. (#6413)

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For now, treat such classes as being final, since we can't correctly
derive from them.

This removes the last category of C++ class that we are entirely unable
to interop with, and is a prerequisite for interop with C++ iostreams
(which have a virtual base class).
This commit is contained in:
Richard Smith
2025-11-21 16:45:38 +00:00
committed by GitHub
parent 8866e39085
commit 13fbe3c1f3
4 changed files with 329 additions and 75 deletions
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toolchain/check/testdata/interop/cpp/class/base.carbon
Vendored
+112 -14
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@@ -298,20 +298,6 @@ library "[[@TEST_NAME]]";
import Cpp library "virtual_inheritance.h";
fn Convert(p: Cpp.B*) -> Cpp.A* {
// CHECK:STDERR: fail_todo_use_virtual_inheritance.carbon:[[@LINE+21]]:3: error: semantics TODO: `class with virtual bases` [SemanticsTodo]
// CHECK:STDERR: return p;
// CHECK:STDERR: ^~~~~~~~~
// CHECK:STDERR: fail_todo_use_virtual_inheritance.carbon:[[@LINE+18]]:3: note: while completing C++ type `Cpp.B` [InCppTypeCompletion]
// CHECK:STDERR: return p;
// CHECK:STDERR: ^~~~~~~~~
// CHECK:STDERR:
// CHECK:STDERR: fail_todo_use_virtual_inheritance.carbon:[[@LINE+14]]:3: error: semantics TODO: `class with virtual bases` [SemanticsTodo]
// CHECK:STDERR: return p;
// CHECK:STDERR: ^~~~~~~~~
// CHECK:STDERR: fail_todo_use_virtual_inheritance.carbon:[[@LINE+11]]:3: note: while completing C++ type `Cpp.B` [InCppTypeCompletion]
// CHECK:STDERR: return p;
// CHECK:STDERR: ^~~~~~~~~
// CHECK:STDERR:
// CHECK:STDERR: fail_todo_use_virtual_inheritance.carbon:[[@LINE+7]]:3: error: cannot implicitly convert expression of type `Cpp.B*` to `Cpp.A*` [ConversionFailure]
// CHECK:STDERR: return p;
// CHECK:STDERR: ^~~~~~~~~
@@ -322,6 +308,118 @@ fn Convert(p: Cpp.B*) -> Cpp.A* {
return p;
}
// --- diamond.h
struct A {
int a;
};
struct B : virtual A {
int b;
};
struct C : virtual A {
int c;
};
struct D : B, C {
int d;
};
// --- fail_todo_use_diamond.carbon
library "[[@TEST_NAME]]";
import Cpp library "diamond.h";
fn ConvertBA(p: Cpp.B*) -> Cpp.A* {
// CHECK:STDERR: fail_todo_use_diamond.carbon:[[@LINE+7]]:3: error: cannot implicitly convert expression of type `Cpp.B*` to `Cpp.A*` [ConversionFailure]
// CHECK:STDERR: return p;
// CHECK:STDERR: ^~~~~~~~~
// CHECK:STDERR: fail_todo_use_diamond.carbon:[[@LINE+4]]:3: note: type `Cpp.B*` does not implement interface `Core.ImplicitAs(Cpp.A*)` [MissingImplInMemberAccessNote]
// CHECK:STDERR: return p;
// CHECK:STDERR: ^~~~~~~~~
// CHECK:STDERR:
return p;
}
fn ConvertCA(p: Cpp.C*) -> Cpp.A* {
// CHECK:STDERR: fail_todo_use_diamond.carbon:[[@LINE+7]]:3: error: cannot implicitly convert expression of type `Cpp.C*` to `Cpp.A*` [ConversionFailure]
// CHECK:STDERR: return p;
// CHECK:STDERR: ^~~~~~~~~
// CHECK:STDERR: fail_todo_use_diamond.carbon:[[@LINE+4]]:3: note: type `Cpp.C*` does not implement interface `Core.ImplicitAs(Cpp.A*)` [MissingImplInMemberAccessNote]
// CHECK:STDERR: return p;
// CHECK:STDERR: ^~~~~~~~~
// CHECK:STDERR:
return p;
}
fn ConvertDB(p: Cpp.D*) -> Cpp.B* {
// CHECK:STDERR: fail_todo_use_diamond.carbon:[[@LINE+7]]:3: error: cannot implicitly convert expression of type `Cpp.D*` to `Cpp.B*` [ConversionFailure]
// CHECK:STDERR: return p;
// CHECK:STDERR: ^~~~~~~~~
// CHECK:STDERR: fail_todo_use_diamond.carbon:[[@LINE+4]]:3: note: type `Cpp.D*` does not implement interface `Core.ImplicitAs(Cpp.B*)` [MissingImplInMemberAccessNote]
// CHECK:STDERR: return p;
// CHECK:STDERR: ^~~~~~~~~
// CHECK:STDERR:
return p;
}
fn ConvertDC(p: Cpp.D*) -> Cpp.C* {
// CHECK:STDERR: fail_todo_use_diamond.carbon:[[@LINE+7]]:3: error: cannot implicitly convert expression of type `Cpp.D*` to `Cpp.C*` [ConversionFailure]
// CHECK:STDERR: return p;
// CHECK:STDERR: ^~~~~~~~~
// CHECK:STDERR: fail_todo_use_diamond.carbon:[[@LINE+4]]:3: note: type `Cpp.D*` does not implement interface `Core.ImplicitAs(Cpp.C*)` [MissingImplInMemberAccessNote]
// CHECK:STDERR: return p;
// CHECK:STDERR: ^~~~~~~~~
// CHECK:STDERR:
return p;
}
fn AccessBA(d: Cpp.D) -> i32 {
// CHECK:STDERR: fail_todo_use_diamond.carbon:[[@LINE+7]]:11: error: cannot convert expression of type `Cpp.D` to `Cpp.B` with `as` [ConversionFailure]
// CHECK:STDERR: return (d as Cpp.B).b;
// CHECK:STDERR: ^~~~~~~~~~
// CHECK:STDERR: fail_todo_use_diamond.carbon:[[@LINE+4]]:11: note: type `Cpp.D` does not implement interface `Core.As(Cpp.B)` [MissingImplInMemberAccessNote]
// CHECK:STDERR: return (d as Cpp.B).b;
// CHECK:STDERR: ^~~~~~~~~~
// CHECK:STDERR:
return (d as Cpp.B).b;
}
fn AccessCA(d: Cpp.D) -> i32 {
// CHECK:STDERR: fail_todo_use_diamond.carbon:[[@LINE+7]]:11: error: cannot convert expression of type `Cpp.D` to `Cpp.C` with `as` [ConversionFailure]
// CHECK:STDERR: return (d as Cpp.C).b;
// CHECK:STDERR: ^~~~~~~~~~
// CHECK:STDERR: fail_todo_use_diamond.carbon:[[@LINE+4]]:11: note: type `Cpp.D` does not implement interface `Core.As(Cpp.C)` [MissingImplInMemberAccessNote]
// CHECK:STDERR: return (d as Cpp.C).b;
// CHECK:STDERR: ^~~~~~~~~~
// CHECK:STDERR:
return (d as Cpp.C).b;
}
fn AccessDB(d: Cpp.D) -> i32 {
// CHECK:STDERR: fail_todo_use_diamond.carbon:[[@LINE+7]]:10: error: cannot implicitly convert expression of type `Cpp.D` to `Cpp.B` [ConversionFailure]
// CHECK:STDERR: return d.b;
// CHECK:STDERR: ^~~
// CHECK:STDERR: fail_todo_use_diamond.carbon:[[@LINE+4]]:10: note: type `Cpp.D` does not implement interface `Core.ImplicitAs(Cpp.B)` [MissingImplInMemberAccessNote]
// CHECK:STDERR: return d.b;
// CHECK:STDERR: ^~~
// CHECK:STDERR:
return d.b;
}
fn AccessDC(d: Cpp.D) -> i32 {
// CHECK:STDERR: fail_todo_use_diamond.carbon:[[@LINE+7]]:10: error: cannot implicitly convert expression of type `Cpp.D` to `Cpp.C` [ConversionFailure]
// CHECK:STDERR: return d.c;
// CHECK:STDERR: ^~~
// CHECK:STDERR: fail_todo_use_diamond.carbon:[[@LINE+4]]:10: note: type `Cpp.D` does not implement interface `Core.ImplicitAs(Cpp.C)` [MissingImplInMemberAccessNote]
// CHECK:STDERR: return d.c;
// CHECK:STDERR: ^~~
// CHECK:STDERR:
return d.c;
}
// --- final.h
struct A final {};