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aa8a5f174d
* Replaced std::exit() with return llvm::Expected/llvm::Error<T> for expected errors like invalid syntax. * Use llvm::formatv() for formatting lexer error messages. x * Addresed merge errors. * Fixed impl scope. * Made ErrorBuilder::operator<< nodiscard, to catch code forgetting 'return' in 'return FATAL_COMPILATION_ERROR()'. * FatalComplationError() -> ParseAndLexContext::RecordLexerError(). Other usages of ERROR_TOKEN in lexer.lpp were actually supposed to be END_OF_FILE. * Update executable_semantics/syntax/parse_and_lex_context.h Co-authored-by: Jon Meow <jperkins@google.com> * Code review fixes. * Update executable_semantics/syntax/parser.ypp Co-authored-by: Jon Meow <jperkins@google.com> * More code review fixes. * Update executable_semantics/interpreter/type_checker.h Co-authored-by: Jon Meow <jperkins@google.com> * Yet more code review fixes... * Update executable_semantics/syntax/lexer.lpp Co-authored-by: Jon Meow <jperkins@google.com> * code review comments * Update executable_semantics/interpreter/interpreter.cpp Co-authored-by: Geoff Romer <gromer@google.com> * Apply suggestions from code review Co-authored-by: Jon Meow <jperkins@google.com> * Update executable_semantics/syntax/lexer.lpp Co-authored-by: Jon Meow <jperkins@google.com> * code review * code review * Apply suggestions from code review Co-authored-by: Jon Meow <jperkins@google.com> * formatted code * review comments * Switched to the new ErrorOr<V> error implementation * code review comments * fixed comment * restored ostream.h as #976 makes the change unnecesary * review comments Co-authored-by: Jon Meow <jperkins@google.com> Co-authored-by: Geoff Romer <gromer@google.com>
110 lines
2.8 KiB
C++
110 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 COMMON_ERROR_H_
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#define COMMON_ERROR_H_
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#include <string>
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#include "common/check.h"
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#include "common/ostream.h"
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#include "llvm/ADT/Twine.h"
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namespace Carbon {
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// Success values should be represented as the presence of a value in ErrorOr,
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// using `ErrorOr<Success>` and `return Success();` if no value needs to be
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// returned.
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struct Success {};
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// Tracks an error message.
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class [[nodiscard]] Error {
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public:
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// Represents an error state.
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explicit Error(llvm::Twine message) : message_(message.str()) {
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CHECK(!message_.empty()) << "Errors must have a message.";
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}
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Error(Error&& other) noexcept : message_(std::move(other.message_)) {}
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// Prints the error string. Note this marks as used.
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void Print(llvm::raw_ostream& out) const { out << message(); }
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// Returns the error message.
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auto message() const -> const std::string& { return message_; }
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private:
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// The error message.
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std::string message_;
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};
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// Holds a value of type `T`, or an Error explaining why the value is
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// unavailable.
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template <typename T>
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class [[nodiscard]] ErrorOr {
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public:
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// Constructs with an error; the error must not be Error::Success().
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// Implicit for easy construction on returns.
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// NOLINTNEXTLINE(google-explicit-constructor)
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ErrorOr(Error err) : val_(std::move(err)) {}
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// Constructs with a value.
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// Implicit for easy construction on returns.
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// NOLINTNEXTLINE(google-explicit-constructor)
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ErrorOr(T val) : val_(std::move(val)) {}
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// Moves held state.
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ErrorOr(ErrorOr&& other) noexcept : val_(std::move(other.val_)) {}
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// Returns true for success.
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auto ok() const -> bool { return std::holds_alternative<T>(val_); }
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// Returns the contained error.
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// REQUIRES: `ok()` is false.
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auto error() const& -> const Error& {
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CHECK(!ok());
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return std::get<Error>(val_);
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}
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auto error() && -> Error {
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CHECK(!ok());
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return std::get<Error>(std::move(val_));
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}
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// Returns the contained value.
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// REQUIRES: `ok()` is true.
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auto operator*() -> T& {
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CHECK(ok());
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return std::get<T>(val_);
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}
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// Returns the contained value.
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// REQUIRES: `ok()` is true.
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auto operator*() const -> const T& {
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CHECK(ok());
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return std::get<T>(val_);
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}
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// Returns the contained value.
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// REQUIRES: `ok()` is true.
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auto operator->() -> T* {
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CHECK(ok());
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return &std::get<T>(val_);
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}
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// Returns the contained value.
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// REQUIRES: `ok()` is true.
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auto operator->() const -> const T* {
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CHECK(ok());
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return &std::get<T>(val_);
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}
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private:
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// Either an error message or
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std::variant<Error, T> val_;
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};
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} // namespace Carbon
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#endif // COMMON_ERROR_H_
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