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Chandler Carruth
8be274cf60
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
31 lines
1.7 KiB
Plaintext
31 lines
1.7 KiB
Plaintext
// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
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// Exceptions. See /LICENSE for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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// AUTOUPDATE
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// TIP: To test this file alone, run:
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// TIP: bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/parse/testdata/function/fail_template_form_param.carbon
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// TIP: To dump output, run:
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// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/parse/testdata/function/fail_template_form_param.carbon
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// `template` cannot be combined with a `:?` form binding.
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// CHECK:STDERR: fail_template_form_param.carbon:[[@LINE+4]]:6: error: `template` is only allowed on a generic binding [ExpectedGenericBindingPatternAfterTemplate]
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// CHECK:STDERR: fn F(template x:? Form);
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// CHECK:STDERR: ^~~~~~~~
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// CHECK:STDERR:
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fn F(template x:? Form);
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// CHECK:STDOUT: - filename: fail_template_form_param.carbon
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// CHECK:STDOUT: parse_tree: [
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// CHECK:STDOUT: {kind: 'FileStart', text: ''},
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// CHECK:STDOUT: {kind: 'FunctionIntroducer', text: 'fn'},
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// CHECK:STDOUT: {kind: 'IdentifierNameMaybeBeforeSignature', text: 'F'},
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// CHECK:STDOUT: {kind: 'ExplicitParamListStart', text: '('},
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// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'x'},
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// CHECK:STDOUT: {kind: 'IdentifierNameExpr', text: 'Form'},
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// CHECK:STDOUT: {kind: 'FormBindingPattern', text: ':?', has_error: yes, subtree_size: 3},
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// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', has_error: yes, subtree_size: 5},
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// CHECK:STDOUT: {kind: 'FunctionDecl', text: ';', subtree_size: 8},
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// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
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// CHECK:STDOUT: ]
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