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https://github.com/carbon-language/carbon-lang.git
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Jon Meow
49013ae1cc
This is based on discussion on #732: that we should probably parse the invalid whitespace, then reject it as part of string validation, rather than having different parses. I worry the question of "how is this parsed" may lead to subtly unexpected results if we aren't consistent, so I'm switching the logic from the lexer to the unescape library (and also adjusting the list of rejected whitespace).
99 lines
2.5 KiB
C++
99 lines
2.5 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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#include "common/string_helpers.h"
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#include "common/check.h"
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#include "llvm/ADT/StringExtras.h"
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namespace Carbon {
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// Carbon only takes uppercase hex input.
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static auto FromHex(char c) -> std::optional<char> {
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if (c >= '0' && c <= '9') {
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return c - '0';
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}
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if (c >= 'A' && c <= 'F') {
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return 10 + c - 'A';
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}
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return std::nullopt;
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}
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auto UnescapeStringLiteral(llvm::StringRef source)
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-> std::optional<std::string> {
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std::string ret;
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ret.reserve(source.size());
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size_t i = 0;
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while (i < source.size()) {
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char c = source[i];
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switch (c) {
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case '\\':
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++i;
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if (i == source.size()) {
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return std::nullopt;
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}
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switch (source[i]) {
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case 'n':
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ret.push_back('\n');
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break;
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case 'r':
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ret.push_back('\r');
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break;
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case 't':
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ret.push_back('\t');
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break;
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case '0':
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if (i + 1 < source.size() && llvm::isDigit(source[i + 1])) {
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// \0[0-9] is reserved.
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return std::nullopt;
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}
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ret.push_back('\0');
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break;
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case '"':
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ret.push_back('"');
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break;
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case '\'':
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ret.push_back('\'');
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break;
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case '\\':
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ret.push_back('\\');
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break;
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case 'x': {
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i += 2;
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if (i >= source.size()) {
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return std::nullopt;
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}
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std::optional<char> c1 = FromHex(source[i - 1]);
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std::optional<char> c2 = FromHex(source[i]);
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if (c1 == std::nullopt || c2 == std::nullopt) {
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return std::nullopt;
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}
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ret.push_back(16 * *c1 + *c2);
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break;
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}
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case 'u':
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FATAL() << "\\u is not yet supported in string literals";
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default:
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// Unsupported.
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return std::nullopt;
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}
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break;
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case '\t':
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// Disallow non-` ` horizontal whitespace:
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// https://github.com/carbon-language/carbon-lang/blob/trunk/docs/design/lexical_conventions/whitespace.md
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// TODO: This doesn't handle unicode whitespace.
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return std::nullopt;
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default:
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ret.push_back(c);
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break;
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}
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++i;
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}
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return ret;
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}
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} // namespace Carbon
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