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carbon-lang/toolchain/check/testdata/facet/combine.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/convert.carbon
//
// AUTOUPDATE
// TIP: To test this file alone, run:
// TIP: bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/check/testdata/facet/combine.carbon
// TIP: To dump output, run:
// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/check/testdata/facet/combine.carbon
// --- fail_name_collision.carbon
library "[[@TEST_NAME]]";
interface A {
fn G();
}
interface B {
fn G();
}
class C {}
impl C as A {
fn G();
}
impl C as B {
fn G() {}
}
fn F() {
// TODO: This error message is wrong here, we are not using `extend`.
// CHECK:STDERR: fail_name_collision.carbon:[[@LINE+4]]:14: error: ambiguous use of name `G` found in multiple extended scopes [NameAmbiguousDueToExtend]
// CHECK:STDERR: ({} as C).((A & B).G)();
// CHECK:STDERR: ^~~~~~~~~
// CHECK:STDERR:
({} as C).((A & B).G)();
}
// --- combine.carbon
library "[[@TEST_NAME]]";
interface A {}
interface B {
fn BB(self);
}
class C {}
impl C as A {}
impl C as B {
fn BB(unused self) {}
}
fn G[T: A & B](unused t: T) {}
fn F() {
({} as C).((A & B).BB)();
(({} as C) as (C as (A & B))).((A & B).BB)();
(({} as C) as (C as (A & B))).(B.BB)();
G({} as C);
}
// --- generic_interface.carbon
library "[[@TEST_NAME]]";
interface A(T: type) {}
interface B {}
class P1 {}
class P2 {}
class C {}
impl C as A(P1) {}
impl C as B {}
fn G[T: A(P1) & B](unused t: T) {}
fn F() {
G({} as C);
}
// --- fail_wrong_generic_interface.carbon
library "[[@TEST_NAME]]";
interface A(T: type) {}
interface B {}
class P1 {}
class P2 {}
class C {}
impl C as A(P1) {}
impl C as B {}
fn G[T: A(P2) & B](unused t: T) {}
fn F() {
// CHECK:STDERR: fail_wrong_generic_interface.carbon:[[@LINE+7]]:3: error: cannot convert type `C` into type implementing `A(P2) & B` [ConversionFailureTypeToFacet]
// CHECK:STDERR: G({} as C);
// CHECK:STDERR: ^~~~~~~~~~
// CHECK:STDERR: fail_wrong_generic_interface.carbon:[[@LINE-6]]:1: note: while deducing parameters of generic declared here [DeductionGenericHere]
// CHECK:STDERR: fn G[T: A(P2) & B](unused t: T) {}
// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// CHECK:STDERR:
G({} as C);
}
// --- generic_forall_impl.carbon
library "[[@TEST_NAME]]";
interface Iface {}
interface GenericIface(T: type) {}
class GenericClass(T: type) {}
class ImplIface {}
impl ImplIface as Iface {}
class C {}
impl C as Iface {}
impl forall [IfaceType: Iface] C as GenericIface(GenericClass(IfaceType)) {}
fn G[T: Iface & GenericIface(GenericClass(ImplIface))](unused t: T) {}
fn F() {
G({} as C);
}
// --- compare_equal.carbon
library "[[@TEST_NAME]]";
class WrapType(T: type) {}
fn AssertSame[T: type](unused a: WrapType(T), unused b: WrapType(T)) {}
fn Type(generic T: type) -> WrapType(T) { return {}; }
interface I;
interface J;
interface K(T: type);
fn TestIncomplete() {
AssertSame(Type(I), Type(I & I));
AssertSame(Type(I), Type(I & I & I));
AssertSame(Type(I & J), Type(J & I));
AssertSame(Type(I & J), Type(I & I & J));
AssertSame(Type(I & J), Type(I & J & I));
AssertSame(Type(I & J), Type(J & I & I));
AssertSame(Type(I & K({})), Type(K({}) & I));
AssertSame(Type(I & K({}) & K(())), Type(K(()) & K({}) & I));
}
interface I {}
interface J {}
interface K(T: type) {}
fn TestComplete() {
AssertSame(Type(I), Type(I & I));
AssertSame(Type(I), Type(I & I & I));
AssertSame(Type(I & J), Type(J & I));
AssertSame(Type(I & J), Type(I & I & J));
AssertSame(Type(I & J), Type(I & J & I));
AssertSame(Type(I & J), Type(J & I & I));
AssertSame(Type(I & K({})), Type(K({}) & I));
AssertSame(Type(I & K({}) & K(())), Type(K(()) & K({}) & I));
}
// --- fail_compare_not_equal.carbon
library "[[@TEST_NAME]]";
class WrapType(T: type) {}
fn Same[T: type](unused a: WrapType(T), unused b: WrapType(T)) {}
fn Type(generic T: type) -> WrapType(T) { return {}; }
interface I {}
interface J {}
interface K {}
fn Test() {
// CHECK:STDERR: fail_compare_not_equal.carbon:[[@LINE+7]]:3: error: inconsistent deductions for value of generic parameter `T` [DeductionInconsistent]
// CHECK:STDERR: Same(Type(I & J), Type(K & I & J));
// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// CHECK:STDERR: fail_compare_not_equal.carbon:[[@LINE-11]]:1: note: while deducing parameters of generic declared here [DeductionGenericHere]
// CHECK:STDERR: fn Same[T: type](unused a: WrapType(T), unused b: WrapType(T)) {}
// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// CHECK:STDERR:
Same(Type(I & J), Type(K & I & J));
}
// --- fail_compare_not_equal_parameterized.carbon
library "[[@TEST_NAME]]";
class WrapType(T: type) {}
fn Same[T: type](unused a: WrapType(T), unused b: WrapType(T)) {}
fn Type(generic T: type) -> WrapType(T) { return {}; }
interface I {}
interface J(T: type) {}
fn Test() {
// CHECK:STDERR: fail_compare_not_equal_parameterized.carbon:[[@LINE+7]]:3: error: inconsistent deductions for value of generic parameter `T` [DeductionInconsistent]
// CHECK:STDERR: Same(Type(I & J(())), Type(J({}) & I));
// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// CHECK:STDERR: fail_compare_not_equal_parameterized.carbon:[[@LINE-10]]:1: note: while deducing parameters of generic declared here [DeductionGenericHere]
// CHECK:STDERR: fn Same[T: type](unused a: WrapType(T), unused b: WrapType(T)) {}
// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// CHECK:STDERR:
Same(Type(I & J(())), Type(J({}) & I));
}
// --- fail_compare_not_equal_parameterized_extra.carbon
library "[[@TEST_NAME]]";
class WrapType(T: type) {}
fn Same[T: type](unused a: WrapType(T), unused b: WrapType(T)) {}
fn Type(generic T: type) -> WrapType(T) { return {}; }
interface I {}
interface J(T: type) {}
fn Test() {
// CHECK:STDERR: fail_compare_not_equal_parameterized_extra.carbon:[[@LINE+7]]:3: error: inconsistent deductions for value of generic parameter `T` [DeductionInconsistent]
// CHECK:STDERR: Same(Type(I & J(())), Type(J(()) & J({}) & I));
// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// CHECK:STDERR: fail_compare_not_equal_parameterized_extra.carbon:[[@LINE-10]]:1: note: while deducing parameters of generic declared here [DeductionGenericHere]
// CHECK:STDERR: fn Same[T: type](unused a: WrapType(T), unused b: WrapType(T)) {}
// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// CHECK:STDERR:
Same(Type(I & J(())), Type(J(()) & J({}) & I));
}
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