Files
carbon-lang/toolchain/check/testdata/class/fail_modifiers.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/convert.carbon
//
// AUTOUPDATE
// TIP: To test this file alone, run:
// TIP: bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/check/testdata/class/fail_modifiers.carbon
// TIP: To dump output, run:
// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/check/testdata/class/fail_modifiers.carbon
// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+7]]:9: error: `private` repeated on declaration [ModifierRepeated]
// CHECK:STDERR: private private class DuplicatePrivate;
// CHECK:STDERR: ^~~~~~~
// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: note: `private` previously appeared here [ModifierPrevious]
// CHECK:STDERR: private private class DuplicatePrivate;
// CHECK:STDERR: ^~~~~~~
// CHECK:STDERR:
private private class DuplicatePrivate;
// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: error: `abstract` not allowed on `class` forward declaration, only definition [ModifierOnlyAllowedOnDefinition]
// CHECK:STDERR: abstract class AbstractDecl;
// CHECK:STDERR: ^~~~~~~~
// CHECK:STDERR:
abstract class AbstractDecl;
// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+7]]:9: error: `protected` not allowed on declaration with `private` [ModifierNotAllowedWith]
// CHECK:STDERR: private protected class TwoAccess;
// CHECK:STDERR: ^~~~~~~~~
// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: note: `private` previously appeared here [ModifierPrevious]
// CHECK:STDERR: private protected class TwoAccess;
// CHECK:STDERR: ^~~~~~~
// CHECK:STDERR:
private protected class TwoAccess;
// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: error: `base` not allowed on `class` forward declaration, only definition [ModifierOnlyAllowedOnDefinition]
// CHECK:STDERR: base class BaseDecl;
// CHECK:STDERR: ^~~~
// CHECK:STDERR:
base class BaseDecl;
// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+7]]:10: error: `abstract` repeated on declaration [ModifierRepeated]
// CHECK:STDERR: abstract abstract class TwoAbstract { }
// CHECK:STDERR: ^~~~~~~~
// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: note: `abstract` previously appeared here [ModifierPrevious]
// CHECK:STDERR: abstract abstract class TwoAbstract { }
// CHECK:STDERR: ^~~~~~~~
// CHECK:STDERR:
abstract abstract class TwoAbstract { }
// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+15]]:19: error: `base` not allowed on declaration with `virtual` [ModifierNotAllowedWith]
// CHECK:STDERR: protected virtual base class Virtual {}
// CHECK:STDERR: ^~~~
// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+12]]:11: note: `virtual` previously appeared here [ModifierPrevious]
// CHECK:STDERR: protected virtual base class Virtual {}
// CHECK:STDERR: ^~~~~~~
// CHECK:STDERR:
// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+8]]:1: error: `protected` not allowed; requires class scope [ModifierProtectedNotAllowed]
// CHECK:STDERR: protected virtual base class Virtual {}
// CHECK:STDERR: ^~~~~~~~~
// CHECK:STDERR:
// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:11: error: `virtual` not allowed on `class` declaration [ModifierNotAllowedOnDeclaration]
// CHECK:STDERR: protected virtual base class Virtual {}
// CHECK:STDERR: ^~~~~~~
// CHECK:STDERR:
protected virtual base class Virtual {}
// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+7]]:10: error: `protected` must appear before `abstract` [ModifierMustAppearBefore]
// CHECK:STDERR: abstract protected class WrongOrder { }
// CHECK:STDERR: ^~~~~~~~~
// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: note: `abstract` previously appeared here [ModifierPrevious]
// CHECK:STDERR: abstract protected class WrongOrder { }
// CHECK:STDERR: ^~~~~~~~
// CHECK:STDERR:
abstract protected class WrongOrder { }
// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+7]]:10: error: `base` not allowed on declaration with `abstract` [ModifierNotAllowedWith]
// CHECK:STDERR: abstract base class AbstractAndBase {}
// CHECK:STDERR: ^~~~
// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:1: note: `abstract` previously appeared here [ModifierPrevious]
// CHECK:STDERR: abstract base class AbstractAndBase {}
// CHECK:STDERR: ^~~~~~~~
// CHECK:STDERR:
abstract base class AbstractAndBase {}
abstract class AbstractWithDefinition {
// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:30: error: definition of `abstract` function [DefinedAbstractFunction]
// CHECK:STDERR: abstract fn F(unused self) {}
// CHECK:STDERR: ^
// CHECK:STDERR:
abstract fn F(unused self) {}
abstract fn G(self);
}
// CHECK:STDERR: fail_modifiers.carbon:[[@LINE+4]]:42: error: definition of `abstract` function [DefinedAbstractFunction]
// CHECK:STDERR: fn AbstractWithDefinition.G(unused self) {
// CHECK:STDERR: ^
// CHECK:STDERR:
fn AbstractWithDefinition.G(unused self) {
}