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carbon-lang/toolchain/parse/testdata/generics/interface/fail_associated_constants.carbon
T
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
//
// AUTOUPDATE
// TIP: To test this file alone, run:
// TIP: bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/parse/testdata/generics/interface/fail_associated_constants.carbon
// TIP: To dump output, run:
// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/parse/testdata/generics/interface/fail_associated_constants.carbon
// --- fail_tuple_pattern.carbon
library "[[@TEST_NAME]]";
interface I {
// CHECK:STDERR: fail_tuple_pattern.carbon:[[@LINE+4]]:7: error: expected identifier in associated constant declaration [ExpectedAssociatedConstantIdentifier]
// CHECK:STDERR: let (T: type, U: type);
// CHECK:STDERR: ^
// CHECK:STDERR:
let (T: type, U: type);
}
// --- fail_tuple_pattern_with_default.carbon
library "[[@TEST_NAME]]";
interface I {
// CHECK:STDERR: fail_tuple_pattern_with_default.carbon:[[@LINE+4]]:15: error: expected identifier in associated constant declaration [ExpectedAssociatedConstantIdentifier]
// CHECK:STDERR: default let (T: type, U: type) = ({}, {});
// CHECK:STDERR: ^
// CHECK:STDERR:
default let (T: type, U: type) = ({}, {});
}
// --- fail_var_pattern.carbon
library "[[@TEST_NAME]]";
interface I {
// CHECK:STDERR: fail_var_pattern.carbon:[[@LINE+4]]:7: error: expected identifier in associated constant declaration [ExpectedAssociatedConstantIdentifier]
// CHECK:STDERR: let var T: type;
// CHECK:STDERR: ^~~
// CHECK:STDERR:
let var T: type;
}
// --- fail_var_pattern_with_default.carbon
library "[[@TEST_NAME]]";
interface I {
// CHECK:STDERR: fail_var_pattern_with_default.carbon:[[@LINE+4]]:15: error: expected identifier in associated constant declaration [ExpectedAssociatedConstantIdentifier]
// CHECK:STDERR: default let var T: type = {};
// CHECK:STDERR: ^~~
// CHECK:STDERR:
default let var T: type = {};
}
// --- fail_not_constant.carbon
library "[[@TEST_NAME]]";
interface I {
// CHECK:STDERR: fail_not_constant.carbon:[[@LINE+4]]:7: error: phase keyword is not allowed on an associated constant [PhaseKeywordInAssociatedConstant]
// CHECK:STDERR: let runtime a: {.b: ()};
// CHECK:STDERR: ^~~~~~~
// CHECK:STDERR:
let runtime a: {.b: ()};
}
// --- fail_template.carbon
library "[[@TEST_NAME]]";
interface I {
// CHECK:STDERR: fail_template.carbon:[[@LINE+4]]:7: error: phase keyword is not allowed on an associated constant [PhaseKeywordInAssociatedConstant]
// CHECK:STDERR: let template T: type;
// CHECK:STDERR: ^~~~~~~~
// CHECK:STDERR:
let template T: type;
}
// --- fail_generic.carbon
library "[[@TEST_NAME]]";
interface I {
// CHECK:STDERR: fail_generic.carbon:[[@LINE+4]]:7: error: phase keyword is not allowed on an associated constant [PhaseKeywordInAssociatedConstant]
// CHECK:STDERR: let generic a: type;
// CHECK:STDERR: ^~~~~~~
// CHECK:STDERR:
let generic a: type;
}
// --- fail_underscore.carbon
library "[[@TEST_NAME]]";
interface I {
// CHECK:STDERR: fail_underscore.carbon:[[@LINE+4]]:7: error: expected identifier in associated constant declaration [ExpectedAssociatedConstantIdentifier]
// CHECK:STDERR: let _: {};
// CHECK:STDERR: ^
// CHECK:STDERR:
let _: {};
}
// --- fail_missing_colon.carbon
library "[[@TEST_NAME]]";
interface I {
// CHECK:STDERR: fail_missing_colon.carbon:[[@LINE+4]]:8: error: expected `:` in associated constant declaration [ExpectedAssociatedConstantColon]
// CHECK:STDERR: let a;
// CHECK:STDERR: ^
// CHECK:STDERR:
let a;
}
// CHECK:STDOUT: - filename: fail_tuple_pattern.carbon
// CHECK:STDOUT: parse_tree: [
// CHECK:STDOUT: {kind: 'FileStart', text: ''},
// CHECK:STDOUT: {kind: 'LibraryIntroducer', text: 'library'},
// CHECK:STDOUT: {kind: 'LibraryName', text: '"tuple_pattern"'},
// CHECK:STDOUT: {kind: 'LibraryDecl', text: ';', subtree_size: 3},
// CHECK:STDOUT: {kind: 'InterfaceIntroducer', text: 'interface'},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'I'},
// CHECK:STDOUT: {kind: 'InterfaceDefinitionStart', text: '{', subtree_size: 3},
// CHECK:STDOUT: {kind: 'AssociatedConstantIntroducer', text: 'let'},
// CHECK:STDOUT: {kind: 'AssociatedConstantDecl', text: ';', has_error: yes, subtree_size: 2},
// CHECK:STDOUT: {kind: 'InterfaceDefinition', text: '}', subtree_size: 6},
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]
// CHECK:STDOUT: - filename: fail_tuple_pattern_with_default.carbon
// CHECK:STDOUT: parse_tree: [
// CHECK:STDOUT: {kind: 'FileStart', text: ''},
// CHECK:STDOUT: {kind: 'LibraryIntroducer', text: 'library'},
// CHECK:STDOUT: {kind: 'LibraryName', text: '"tuple_pattern_with_default"'},
// CHECK:STDOUT: {kind: 'LibraryDecl', text: ';', subtree_size: 3},
// CHECK:STDOUT: {kind: 'InterfaceIntroducer', text: 'interface'},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'I'},
// CHECK:STDOUT: {kind: 'InterfaceDefinitionStart', text: '{', subtree_size: 3},
// CHECK:STDOUT: {kind: 'AssociatedConstantIntroducer', text: 'let'},
// CHECK:STDOUT: {kind: 'DefaultModifier', text: 'default'},
// CHECK:STDOUT: {kind: 'AssociatedConstantDecl', text: ';', has_error: yes, subtree_size: 3},
// CHECK:STDOUT: {kind: 'InterfaceDefinition', text: '}', subtree_size: 7},
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]
// CHECK:STDOUT: - filename: fail_var_pattern.carbon
// CHECK:STDOUT: parse_tree: [
// CHECK:STDOUT: {kind: 'FileStart', text: ''},
// CHECK:STDOUT: {kind: 'LibraryIntroducer', text: 'library'},
// CHECK:STDOUT: {kind: 'LibraryName', text: '"var_pattern"'},
// CHECK:STDOUT: {kind: 'LibraryDecl', text: ';', subtree_size: 3},
// CHECK:STDOUT: {kind: 'InterfaceIntroducer', text: 'interface'},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'I'},
// CHECK:STDOUT: {kind: 'InterfaceDefinitionStart', text: '{', subtree_size: 3},
// CHECK:STDOUT: {kind: 'AssociatedConstantIntroducer', text: 'let'},
// CHECK:STDOUT: {kind: 'AssociatedConstantDecl', text: ';', has_error: yes, subtree_size: 2},
// CHECK:STDOUT: {kind: 'InterfaceDefinition', text: '}', subtree_size: 6},
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]
// CHECK:STDOUT: - filename: fail_var_pattern_with_default.carbon
// CHECK:STDOUT: parse_tree: [
// CHECK:STDOUT: {kind: 'FileStart', text: ''},
// CHECK:STDOUT: {kind: 'LibraryIntroducer', text: 'library'},
// CHECK:STDOUT: {kind: 'LibraryName', text: '"var_pattern_with_default"'},
// CHECK:STDOUT: {kind: 'LibraryDecl', text: ';', subtree_size: 3},
// CHECK:STDOUT: {kind: 'InterfaceIntroducer', text: 'interface'},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'I'},
// CHECK:STDOUT: {kind: 'InterfaceDefinitionStart', text: '{', subtree_size: 3},
// CHECK:STDOUT: {kind: 'AssociatedConstantIntroducer', text: 'let'},
// CHECK:STDOUT: {kind: 'DefaultModifier', text: 'default'},
// CHECK:STDOUT: {kind: 'AssociatedConstantDecl', text: ';', has_error: yes, subtree_size: 3},
// CHECK:STDOUT: {kind: 'InterfaceDefinition', text: '}', subtree_size: 7},
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]
// CHECK:STDOUT: - filename: fail_not_constant.carbon
// CHECK:STDOUT: parse_tree: [
// CHECK:STDOUT: {kind: 'FileStart', text: ''},
// CHECK:STDOUT: {kind: 'LibraryIntroducer', text: 'library'},
// CHECK:STDOUT: {kind: 'LibraryName', text: '"not_constant"'},
// CHECK:STDOUT: {kind: 'LibraryDecl', text: ';', subtree_size: 3},
// CHECK:STDOUT: {kind: 'InterfaceIntroducer', text: 'interface'},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'I'},
// CHECK:STDOUT: {kind: 'InterfaceDefinitionStart', text: '{', subtree_size: 3},
// CHECK:STDOUT: {kind: 'AssociatedConstantIntroducer', text: 'let'},
// CHECK:STDOUT: {kind: 'AssociatedConstantDecl', text: ';', has_error: yes, subtree_size: 2},
// CHECK:STDOUT: {kind: 'InterfaceDefinition', text: '}', subtree_size: 6},
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]
// CHECK:STDOUT: - filename: fail_template.carbon
// CHECK:STDOUT: parse_tree: [
// CHECK:STDOUT: {kind: 'FileStart', text: ''},
// CHECK:STDOUT: {kind: 'LibraryIntroducer', text: 'library'},
// CHECK:STDOUT: {kind: 'LibraryName', text: '"template"'},
// CHECK:STDOUT: {kind: 'LibraryDecl', text: ';', subtree_size: 3},
// CHECK:STDOUT: {kind: 'InterfaceIntroducer', text: 'interface'},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'I'},
// CHECK:STDOUT: {kind: 'InterfaceDefinitionStart', text: '{', subtree_size: 3},
// CHECK:STDOUT: {kind: 'AssociatedConstantIntroducer', text: 'let'},
// CHECK:STDOUT: {kind: 'AssociatedConstantDecl', text: ';', has_error: yes, subtree_size: 2},
// CHECK:STDOUT: {kind: 'InterfaceDefinition', text: '}', subtree_size: 6},
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]
// CHECK:STDOUT: - filename: fail_generic.carbon
// CHECK:STDOUT: parse_tree: [
// CHECK:STDOUT: {kind: 'FileStart', text: ''},
// CHECK:STDOUT: {kind: 'LibraryIntroducer', text: 'library'},
// CHECK:STDOUT: {kind: 'LibraryName', text: '"generic"'},
// CHECK:STDOUT: {kind: 'LibraryDecl', text: ';', subtree_size: 3},
// CHECK:STDOUT: {kind: 'InterfaceIntroducer', text: 'interface'},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'I'},
// CHECK:STDOUT: {kind: 'InterfaceDefinitionStart', text: '{', subtree_size: 3},
// CHECK:STDOUT: {kind: 'AssociatedConstantIntroducer', text: 'let'},
// CHECK:STDOUT: {kind: 'AssociatedConstantDecl', text: ';', has_error: yes, subtree_size: 2},
// CHECK:STDOUT: {kind: 'InterfaceDefinition', text: '}', subtree_size: 6},
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]
// CHECK:STDOUT: - filename: fail_underscore.carbon
// CHECK:STDOUT: parse_tree: [
// CHECK:STDOUT: {kind: 'FileStart', text: ''},
// CHECK:STDOUT: {kind: 'LibraryIntroducer', text: 'library'},
// CHECK:STDOUT: {kind: 'LibraryName', text: '"underscore"'},
// CHECK:STDOUT: {kind: 'LibraryDecl', text: ';', subtree_size: 3},
// CHECK:STDOUT: {kind: 'InterfaceIntroducer', text: 'interface'},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'I'},
// CHECK:STDOUT: {kind: 'InterfaceDefinitionStart', text: '{', subtree_size: 3},
// CHECK:STDOUT: {kind: 'AssociatedConstantIntroducer', text: 'let'},
// CHECK:STDOUT: {kind: 'AssociatedConstantDecl', text: ';', has_error: yes, subtree_size: 2},
// CHECK:STDOUT: {kind: 'InterfaceDefinition', text: '}', subtree_size: 6},
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]
// CHECK:STDOUT: - filename: fail_missing_colon.carbon
// CHECK:STDOUT: parse_tree: [
// CHECK:STDOUT: {kind: 'FileStart', text: ''},
// CHECK:STDOUT: {kind: 'LibraryIntroducer', text: 'library'},
// CHECK:STDOUT: {kind: 'LibraryName', text: '"missing_colon"'},
// CHECK:STDOUT: {kind: 'LibraryDecl', text: ';', subtree_size: 3},
// CHECK:STDOUT: {kind: 'InterfaceIntroducer', text: 'interface'},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'I'},
// CHECK:STDOUT: {kind: 'InterfaceDefinitionStart', text: '{', subtree_size: 3},
// CHECK:STDOUT: {kind: 'AssociatedConstantIntroducer', text: 'let'},
// CHECK:STDOUT: {kind: 'AssociatedConstantDecl', text: ';', has_error: yes, subtree_size: 2},
// CHECK:STDOUT: {kind: 'InterfaceDefinition', text: '}', subtree_size: 6},
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]
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