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carbon-lang/toolchain/check/testdata/let/fail_generic_import.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
// TODO: Add ranges and switch to "--dump-sem-ir-ranges=only".
// EXTRA-ARGS: --dump-sem-ir-ranges=if-present
//
// AUTOUPDATE
// TIP: To test this file alone, run:
// TIP: bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/check/testdata/let/fail_generic_import.carbon
// TIP: To dump output, run:
// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/check/testdata/let/fail_generic_import.carbon
// --- fail_implicit.carbon
package Implicit;
// CHECK:STDERR: fail_implicit.carbon:[[@LINE+4]]:13: error: semantics TODO: ``let` compile time binding outside function or interface` [SemanticsTodo]
// CHECK:STDERR: let generic T: type = i32;
// CHECK:STDERR: ^~~~~~~
// CHECK:STDERR:
let generic T: type = i32;
// --- fail_implicit.impl.carbon
impl package Implicit;
// TODO: Should this be valid?
// CHECK:STDERR: fail_implicit.impl.carbon:[[@LINE+4]]:8: error: cannot evaluate type expression [TypeExprEvaluationFailure]
// CHECK:STDERR: let a: T = 0;
// CHECK:STDERR: ^
// CHECK:STDERR:
let a: T = 0;
// CHECK:STDOUT: --- fail_implicit.carbon
// CHECK:STDOUT:
// CHECK:STDOUT: constants {
// CHECK:STDOUT: %type: type = facet_type <type> [concrete]
// CHECK:STDOUT: %.Self.frozen: %type = symbolic_binding .Self [symbolic_self]
// CHECK:STDOUT: %pattern_type.98f: type = pattern_type type [concrete]
// CHECK:STDOUT: %T.patt: %pattern_type.98f = value_binding_pattern T [concrete]
// CHECK:STDOUT: %int_32: Core.IntLiteral = int_value 32 [concrete]
// CHECK:STDOUT: %Int.type: type = generic_class_type @Int [concrete]
// CHECK:STDOUT: %Int.generic: %Int.type = struct_value () [concrete]
// CHECK:STDOUT: %i32: type = class_type @Int, @Int(%int_32) [concrete]
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: imports {
// CHECK:STDOUT: %Core: <namespace> = namespace file.%Core.import, [concrete] {
// CHECK:STDOUT: .Int = %Core.Int
// CHECK:STDOUT: import Core//prelude
// CHECK:STDOUT: import Core//prelude/...
// CHECK:STDOUT: }
// CHECK:STDOUT: %Core.Int: %Int.type = import_ref Core//prelude/parts/int, Int, loaded [concrete = constants.%Int.generic]
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: file {
// CHECK:STDOUT: package: <namespace> = namespace [concrete] {
// CHECK:STDOUT: .Core = imports.%Core
// CHECK:STDOUT: .T = %T
// CHECK:STDOUT: }
// CHECK:STDOUT: %Core.import = import Core
// CHECK:STDOUT: %.loc8_16.1: type = splice_block %.loc8_16.2 [concrete = type] {
// CHECK:STDOUT: %.Self.frozen: %type = symbolic_binding .Self [symbolic_self = constants.%.Self.frozen]
// CHECK:STDOUT: %.loc8_16.2: type = type_literal type [concrete = type]
// CHECK:STDOUT: }
// CHECK:STDOUT: %T: type = wrapper_binding T, @__global_init.%i32
// CHECK:STDOUT: name_binding_decl {
// CHECK:STDOUT: %T.patt: %pattern_type.98f = value_binding_pattern T [concrete = constants.%T.patt]
// CHECK:STDOUT: }
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: fn @__global_init() {
// CHECK:STDOUT: !entry:
// CHECK:STDOUT: %i32: type = type_literal constants.%i32 [concrete = constants.%i32]
// CHECK:STDOUT: return
// CHECK:STDOUT:
// CHECK:STDOUT: !observes:
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: --- fail_implicit.impl.carbon
// CHECK:STDOUT:
// CHECK:STDOUT: constants {
// CHECK:STDOUT: %int_0: Core.IntLiteral = int_value 0 [concrete]
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: imports {
// CHECK:STDOUT: %Implicit.T: type = import_ref Implicit//default, T, loaded
// CHECK:STDOUT: %Core: <namespace> = namespace file.%Core.import, [concrete] {
// CHECK:STDOUT: import Core//prelude
// CHECK:STDOUT: import Core//prelude/...
// CHECK:STDOUT: }
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: file {
// CHECK:STDOUT: package: <namespace> = namespace [concrete] {
// CHECK:STDOUT: .T = imports.%Implicit.T
// CHECK:STDOUT: .Core = imports.%Core
// CHECK:STDOUT: .a = %a
// CHECK:STDOUT: }
// CHECK:STDOUT: %Implicit.import = import Implicit
// CHECK:STDOUT: %default.import = import <none>
// CHECK:STDOUT: %Core.import = import Core
// CHECK:STDOUT: %T.ref: type = name_ref T, imports.%Implicit.T
// CHECK:STDOUT: %a: <error> = wrapper_binding a, <error> [concrete = <error>]
// CHECK:STDOUT: name_binding_decl {
// CHECK:STDOUT: %a.patt: <error> = value_binding_pattern a [concrete = <error>]
// CHECK:STDOUT: }
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: fn @__global_init() {
// CHECK:STDOUT: !entry:
// CHECK:STDOUT: %int_0: Core.IntLiteral = int_value 0 [concrete = constants.%int_0]
// CHECK:STDOUT: return
// CHECK:STDOUT:
// CHECK:STDOUT: !observes:
// CHECK:STDOUT: }
// CHECK:STDOUT:
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