mirror of
https://github.com/carbon-language/carbon-lang.git
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Jon Meow
2e9e4f4cb3
Adds FATAL for things that are most likely programming errors in executable_semantics.
87 lines
2.8 KiB
C++
87 lines
2.8 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_SYNTAX_PAREN_CONTENTS_H_
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#define EXECUTABLE_SEMANTICS_SYNTAX_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/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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struct Element {
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std::optional<std::string> name;
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const Term* term;
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};
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// If this object represents a single term, with no name and no trailing
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// comma, this method returns that term. This typically means the parentheses
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// can be interpreted as grouping.
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auto SingleTerm() const -> std::optional<const Term*>;
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// Converts `elements` to std::vector<TupleElement>. TupleElement must
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// have a constructor that takes a std::string and a const Term*.
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//
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// TODO: Find a way to deduce TupleElement from Term.
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template <typename TupleElement>
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auto TupleElements(int line_num) const -> std::vector<TupleElement>;
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std::vector<Element> 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<const Term*> {
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if (elements.size() == 1 && !elements.front().name.has_value() &&
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!has_trailing_comma) {
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return elements.front().term;
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} else {
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return std::nullopt;
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}
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}
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template <typename Term>
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template <typename TupleElement>
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auto ParenContents<Term>::TupleElements(int line_num) const
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-> std::vector<TupleElement> {
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std::vector<TupleElement> result;
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int i = 0;
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bool seen_named_member = false;
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for (auto element : elements) {
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if (element.name.has_value()) {
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seen_named_member = true;
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result.push_back(TupleElement(*element.name, element.term));
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} else {
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if (seen_named_member) {
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FATAL_PROGRAM_ERROR(line_num)
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<< "positional members must come before named members";
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}
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result.push_back(TupleElement(std::to_string(i), element.term));
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}
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++i;
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}
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return result;
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}
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} // namespace Carbon
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#endif // EXECUTABLE_SEMANTICS_SYNTAX_PAREN_CONTENTS_H_
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