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little KitchenandRichard Smith
8edd5eb9a1
## Summary
Fixes the toolchain incorrectly allowing `{}` initialization for
non-aggregate C++ classes.
## Problem
When importing an empty C++ class, the toolchain was treating it as a
Carbon empty struct, which allowed initialization from `{}`. This is
incorrect for non-aggregate classes (e.g., those with user-declared
constructors).
```carbon
import Cpp inline '''
struct X { X(); }; // non-aggregate (has user-declared constructor)
''';
fn Make() {
var x: Cpp.X = {}; // incorrectly accepted, should be rejected
}
```
## Solution
Added a check for `clang_def->isAggregate()` in `ImportClassObjectRepr`
so that only aggregate classes get the empty struct representation.
**Before:**
```cpp
if (clang_def->isEmpty() && !clang_def->getNumBases()) {
```
**After:**
```cpp
if (clang_def->isEmpty() && !clang_def->getNumBases() &&
clang_def->isAggregate()) {
```
## Testing
Added test file
`toolchain/check/testdata/interop/cpp/class/non_aggregate_init.carbon`
with:
- Non-aggregate class (`struct X { X(); }`) - should reject `{}`
initialization
- Aggregate class (`struct Y {}`) - should accept `{}` initialization
Note: I couldn't run tests locally due to clang version requirements
(needs >= 19, have 17). The CI should validate the changes.
Closes #6669
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
61 lines
2.1 KiB
Plaintext
61 lines
2.1 KiB
Plaintext
// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
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// Exceptions. See /LICENSE for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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// INCLUDE-FILE: toolchain/testing/testdata/min_prelude/primitives.carbon
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// EXTRA-ARGS: --target=x86_64-linux-gnu --clang-arg=-std=c++20
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//
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// AUTOUPDATE
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// TIP: To test this file alone, run:
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// TIP: bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/check/testdata/interop/cpp/class/non_aggregate_init.carbon
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// TIP: To dump output, run:
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// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/check/testdata/interop/cpp/class/non_aggregate_init.carbon
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// ============================================================================
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// Non-aggregate class should not be initializable from {}
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// ============================================================================
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// --- non_aggregate.h
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// A class with a user-declared constructor is not an aggregate.
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struct X {
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X();
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};
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// --- fail_non_aggregate_init.carbon
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library "[[@TEST_NAME]]";
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import Cpp library "non_aggregate.h";
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fn Make() {
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// CHECK:STDERR: fail_non_aggregate_init.carbon:[[@LINE+7]]:3: error: cannot implicitly convert expression of type `{}` to `Cpp.X` [ConversionFailure]
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// CHECK:STDERR: var _: Cpp.X = {};
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// CHECK:STDERR: ^~~~~~~~~~~~
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// CHECK:STDERR: fail_non_aggregate_init.carbon:[[@LINE+4]]:3: note: type `{}` does not implement interface `Core.ImplicitAs(Cpp.X)` [MissingImplInMemberAccessNote]
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// CHECK:STDERR: var _: Cpp.X = {};
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// CHECK:STDERR: ^~~~~~~~~~~~
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// CHECK:STDERR:
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var _: Cpp.X = {};
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}
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// ============================================================================
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// Aggregate class should be initializable from {}
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// ============================================================================
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// --- aggregate.h
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// A class with no user-declared constructors is an aggregate.
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struct Y {};
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// --- aggregate_init.carbon
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library "[[@TEST_NAME]]";
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import Cpp library "aggregate.h";
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fn Make() {
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// This should succeed because Y is an aggregate.
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var _: Cpp.Y = {};
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}
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