mirror of
https://github.com/carbon-language/carbon-lang.git
synced 2026-09-24 20:30:14 +01:00
Jon Ross-Perkins
35d15a390c
Per [#toolchain discussion](https://discord.com/channels/655572317891461132/655578254970716160/1176632520834560211) We'd at one point been trying to put `[[nodiscard]]` everywhere, but then we stopped because it had felt verbose without finding many issues (plus, people plain forgot to add it). Some history in #888. Since newer code gets added without it, we now have code like: ``` auto GetLineInfo(Line line) -> LineInfo&; [[nodiscard]] auto GetLineInfo(Line line) const -> const LineInfo&; auto AddLine(LineInfo info) -> Line; auto GetTokenInfo(Token token) -> TokenInfo&; [[nodiscard]] auto GetTokenInfo(Token token) const -> const TokenInfo&; auto AddToken(TokenInfo info) -> Token; [[nodiscard]] auto GetTokenPrintWidths(Token token) const -> PrintWidths; ``` Here, the lack of `[[nodiscard]]` doesn't mean anything: for example, `GetLineInfo` should not have its result discarded if it's called. But the mix could be confusing for readers. As a resolution, remove the attribute. `[[nodiscard]]` should be treated like other attributes going forward, which essentially means "avoid in general, add a comment to explain why the attribute is needed" rather than use-as-default.
86 lines
3.2 KiB
C++
86 lines
3.2 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 CARBON_TOOLCHAIN_SOURCE_SOURCE_BUFFER_H_
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#define CARBON_TOOLCHAIN_SOURCE_SOURCE_BUFFER_H_
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#include <memory>
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#include <string>
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#include "llvm/ADT/StringRef.h"
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#include "llvm/Support/MemoryBuffer.h"
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#include "llvm/Support/VirtualFileSystem.h"
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#include "toolchain/diagnostics/diagnostic_emitter.h"
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namespace Carbon {
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// A buffer of Carbon source code.
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//
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// This class holds a buffer of Carbon source code as text and makes it
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// available for use in the rest of the Carbon compiler. It owns the memory for
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// the underlying source code text and ensures it lives as long as the buffer
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// objects.
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//
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// Every buffer of source code text is notionally loaded from a Carbon source
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// file, even if provided directly when constructing the buffer. The name that
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// should be used for that Carbon source file is also retained and made
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// available.
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//
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// Because the underlying memory for the source code text may have been read
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// from a file, and we may want to use facilities like `mmap` to simply map that
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// file into memory, the buffer itself is not copyable to avoid needing to
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// define copy semantics for a mapped file. We can relax this restriction with
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// some implementation complexity in the future if needed.
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class SourceBuffer {
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public:
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// Opens and reads the contents of stdin. Returns a SourceBuffer on success.
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// Prints an error and returns nullopt on failure.
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static auto CreateFromStdin(DiagnosticConsumer& consumer)
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-> std::optional<SourceBuffer>;
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// Opens the requested file. Returns a SourceBuffer on success. Prints an
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// error and returns nullopt on failure.
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static auto CreateFromFile(llvm::vfs::FileSystem& fs,
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llvm::StringRef filename,
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DiagnosticConsumer& consumer)
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-> std::optional<SourceBuffer>;
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// Use one of the factory functions above to create a source buffer.
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SourceBuffer() = delete;
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auto filename() const -> llvm::StringRef { return filename_; }
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auto text() const -> llvm::StringRef { return text_->getBuffer(); }
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[[nodiscard]] auto is_regular_file() const -> bool {
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return is_regular_file_;
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}
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private:
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// Creates a `SourceBuffer` from the given `llvm::MemoryBuffer`. Prints an
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// error and returns nullopt on failure.
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static auto CreateFromMemoryBuffer(
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llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> buffer,
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llvm::StringRef filename, bool is_regular_file,
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DiagnosticConsumer& consumer) -> std::optional<SourceBuffer>;
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explicit SourceBuffer(std::string filename,
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std::unique_ptr<llvm::MemoryBuffer> text,
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bool is_regular_file)
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: filename_(std::move(filename)),
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text_(std::move(text)),
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is_regular_file_(is_regular_file) {}
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std::string filename_;
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std::unique_ptr<llvm::MemoryBuffer> text_;
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// Whether this buffer is a regular file, rather than stdin or a named pipe or
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// similar.
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bool is_regular_file_;
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};
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} // namespace Carbon
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#endif // CARBON_TOOLCHAIN_SOURCE_SOURCE_BUFFER_H_
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