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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
40 lines
2.3 KiB
Plaintext
40 lines
2.3 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/choice/parameterized.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/choice/parameterized.carbon
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choice OptionalElement(T: type) {
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Element(value: T),
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None,
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}
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// CHECK:STDOUT: - filename: parameterized.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: 'ChoiceIntroducer', text: 'choice'},
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// CHECK:STDOUT: {kind: 'IdentifierNameMaybeBeforeSignature', text: 'OptionalElement'},
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// CHECK:STDOUT: {kind: 'ExplicitParamListStart', text: '('},
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// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'T'},
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// CHECK:STDOUT: {kind: 'CompileTimeBindingPatternStart', text: ':', subtree_size: 2},
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// CHECK:STDOUT: {kind: 'TypeTypeLiteral', text: 'type'},
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// CHECK:STDOUT: {kind: 'CompileTimeBindingPattern', text: ':', subtree_size: 4},
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// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', subtree_size: 6},
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// CHECK:STDOUT: {kind: 'ChoiceDefinitionStart', text: '{', subtree_size: 9},
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// CHECK:STDOUT: {kind: 'IdentifierNameMaybeBeforeSignature', text: 'Element'},
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// CHECK:STDOUT: {kind: 'ExplicitParamListStart', text: '('},
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// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'value'},
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// CHECK:STDOUT: {kind: 'IdentifierNameExpr', text: 'T'},
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// CHECK:STDOUT: {kind: 'LetBindingPattern', text: ':', subtree_size: 3},
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// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', subtree_size: 5},
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// CHECK:STDOUT: {kind: 'ChoiceAlternativeListComma', text: ','},
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// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'None'},
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// CHECK:STDOUT: {kind: 'ChoiceAlternativeListComma', text: ','},
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// CHECK:STDOUT: {kind: 'ChoiceDefinition', text: '}', subtree_size: 19},
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// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
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// CHECK:STDOUT: ]
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