Files
carbon-lang/explorer/testdata/class/fail_direct_base_class_init.carbon
T
Adrien LeravatandRichard Smith 46f4887cf7 Explorer: support .base to initialize parent class from struct (#2361)
Relates to https://github.com/carbon-language/carbon-lang/issues/1881

- Add support for `.base` field in structs for [parent class initialization](https://github.com/carbon-language/carbon-lang/blob/trunk/docs/design/classes.md#constructors)
    - Disabling base class initialization without `.base`
- Support class constructors (`Create() -> Self`) for base classes
- Direct access to base class(es) attributes with `object.var` remains unaffected

Changes:
- Add `TypeChecker::FieldTypesWithBase` to help assessing if a struct with `base` fields can be converted to a class
- Add a new `base_type()` attribute+getter to `NominalClassDeclaration` to as a first step to allow resolving parametrized classes
- Add a new `base` attribute+getter to `NominalClassValue` that contains the base class `NominalClassValue`. It is currently used mainly to get and set members of a class object.
- Add `Interpreter::ConvertClassWithBase` to build `NominalClassValue` from a init struct, that contains `.base` fields with either `NominalClassValue` or `StructValue`
- Add `FindClassField` to find a field in a class or its base classes
- Remove superfluous `ClassDeclaration::base()` in favor of `ClassDeclaration::base_type()`

Limitations;
- Though some work is done in that direction, parametrized base class where time is not know at the declaration site are not supported. Namely the example below does not compile
```
base class A(T:! Type) {}
class B(T:! Type) extends A(T) {}
```
But this one is functional already
```
base class A(T:! Type) {}
class B extends A(i32) {}
```

Co-authored-by: Richard Smith <richard@metafoo.co.uk>
2022-11-29 13:14:30 -08:00

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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
//
// AUTOUPDATE
// RUN: %{not} %{explorer-run}
// RUN: %{not} %{explorer-run-trace}
package ExplorerTest api;
base class A {
var a: i32;
}
class B extends A {
var b: i32;
}
fn Main() -> i32 {
// CHECK:STDERR: COMPILATION ERROR: {{.*}}/explorer/testdata/class/fail_direct_base_class_init.carbon:[[@LINE+1]]: type error in name binding: '{.a: i32, .b: i32}' is not implicitly convertible to 'class B'
var b: B = {.a=0, .b=1};
return 0;
}