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carbon-lang/toolchain/check/testdata/interop/cpp/class/export/class.carbon
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Chandler Carruth 8be274cf60 Replace :! binding syntax with phase keywords and contextual defaults (#7479)
Implement the toolchain side of proposal #7254, removing the `:!`
binding
syntax for generic and template parameters in favor of the keywords
`generic`,
`template`, and `runtime` plus contextual defaults for phase.

For valid programs this is semantics-preserving: each binding resolves
to the
same phase, and produces the same SemIR, as it did under `:!`/`:`. The
parser
derives a binding's phase from its syntactic context plus any explicit
phase
keyword; new diagnostics and error recovery for misused keywords are
described
below.

Implementation details for each component:

- Lexer: remove the `:!` (`ColonExclaim`) token, move its virtual
parse-node
  budget onto `:`, and add the `generic` and `runtime` keywords.
- Parser: thread a `BindingContext` (`ExplicitParam`, `DeducedParam`, or
`CompileTimeEntityParam`) from declaration introducers down through
parameter
lists to each binding pattern, using a one-token lookahead to
distinguish a
name-qualifier parameter list from a declaration's own final list.
Parameters
of a compile-time entity (`class`, `interface`, `constraint`, `choice`,
`alias`, `export`, `namespace`) and deduced `[]` parameters default to
checked
generic; explicit function parameters and local bindings default to
runtime.
`HandleBindingPattern` resolves the phase from that context plus the
keyword: a
`generic` keyword needs no node of its own (the phase is carried by the
  binding's node kind), while a `runtime` keyword is preserved as a
`RuntimeBindingName` node so `check` can name it in a diagnostic. A
phase
keyword that is merely redundant with the contextual default is
diagnosed
  here, without invalidating the parse tree.
- Check: a phase keyword that is invalid for its context (for example
`runtime`
on a checked-generic parameter) is diagnosed here, and recovers by
building an
error binding that still introduces the name so that later uses of it do
not
  produce cascading errors.

The removed `:!` syntax is now rejected as an ordinary parse error.

The `form`/`:?`/`->?` ("extended types") portion of proposal #7254 is
left for a
separate change.

Assisted-by: Claude Code
2026-07-11 01:22:44 +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/int.carbon
//
// AUTOUPDATE
// TIP: To test this file alone, run:
// TIP: bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/check/testdata/interop/cpp/class/export/class.carbon
// TIP: To dump output, run:
// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/check/testdata/interop/cpp/class/export/class.carbon
// --- static_members.carbon
library "[[@TEST_NAME]]";
import Cpp;
class A {
fn F() {}
}
inline Cpp '''
void G() {
Carbon::A::F();
}
''';
// --- nested.carbon
library "[[@TEST_NAME]]";
import Cpp;
class A {
class B {
class C {
}
}
}
inline Cpp '''
void G() {
Carbon::A::B::C *p = nullptr;
}
''';
// --- incomplete.carbon
library "[[@TEST_NAME]]";
import Cpp;
class A;
inline Cpp '''
Carbon::A *p = nullptr;
''';
// --- fail_incomplete_concrete.carbon
library "[[@TEST_NAME]]";
import Cpp;
// CHECK:STDERR: fail_incomplete_concrete.carbon:[[@LINE+4]]:1: error: class was forward declared here [ClassForwardDeclaredHere]
// CHECK:STDERR: class A;
// CHECK:STDERR: ^~~~~~~~
// CHECK:STDERR:
class A;
inline Cpp '''
// CHECK:STDERR: fail_incomplete_concrete.carbon:[[@LINE+4]]:11: error: variable has incomplete type 'Carbon::A' [CppInteropParseError]
// CHECK:STDERR: 16 | Carbon::A a;
// CHECK:STDERR: | ^
// CHECK:STDERR:
Carbon::A a;
''';
// --- fail_todo_monomorphization_failure.carbon
library "[[@TEST_NAME]]";
import Cpp;
class B(N: i32) {
var a: array(i8, N);
}
// TODO: Once we allow this, we should produce an "invalid array bound" error
// during monomorphization triggered by the C++ code.
alias T = B(-1);
inline Cpp '''
// CHECK:STDERR: fail_todo_monomorphization_failure.carbon:[[@LINE+8]]:1: error: semantics TODO: `interop with unsupported type` [SemanticsTodo]
// CHECK:STDERR: Carbon::T t;
// CHECK:STDERR: ^
// CHECK:STDERR:
// CHECK:STDERR: fail_todo_monomorphization_failure.carbon:[[@LINE+4]]:9: error: no type named 'T' in namespace 'Carbon' [CppInteropParseError]
// CHECK:STDERR: 22 | Carbon::T t;
// CHECK:STDERR: | ~~~~~~~~^
// CHECK:STDERR:
Carbon::T t;
''';