mirror of
https://github.com/carbon-language/carbon-lang.git
synced 2026-09-25 21:30:11 +01:00
Geoff Romer
bb28d37eed
Rationale: Based on the status of #478 and #505, Carbon won't have this feature for a while, and it will be simpler not to support it on spec in the meantime.
52 lines
1.7 KiB
C++
52 lines
1.7 KiB
C++
// 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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#ifndef EXECUTABLE_SEMANTICS_AST_PAREN_CONTENTS_H_
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#define EXECUTABLE_SEMANTICS_AST_PAREN_CONTENTS_H_
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#include <optional>
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#include <string>
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#include <vector>
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#include "executable_semantics/ast/source_location.h"
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#include "executable_semantics/common/error.h"
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namespace Carbon {
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// Represents the syntactic contents of an expression or pattern delimited by
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// parentheses. In those syntaxes, parentheses can be used either for grouping
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// or for forming a tuple, depending on their context and the syntax of their
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// contents; this class helps calling code resolve that ambiguity. Since that
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// ambiguity is purely syntactic, this class should only be needed during
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// parsing.
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//
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// `Term` is the type of the syntactic grouping being built, and the type of
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// the individual syntactic units it's built from; typically it should be
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// either `Expression` or `Pattern`.
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template <typename Term>
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struct ParenContents {
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// If this object represents a single term with no trailing comma, this
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// method returns that term. This typically means the parentheses can be
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// interpreted as grouping.
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auto SingleTerm() const -> std::optional<Nonnull<Term*>>;
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std::vector<Nonnull<Term*>> elements;
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bool has_trailing_comma;
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};
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// Implementation details only below here.
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template <typename Term>
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auto ParenContents<Term>::SingleTerm() const -> std::optional<Nonnull<Term*>> {
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if (elements.size() == 1 && !has_trailing_comma) {
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return elements.front();
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} else {
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return std::nullopt;
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}
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}
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} // namespace Carbon
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#endif // EXECUTABLE_SEMANTICS_AST_PAREN_CONTENTS_H_
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