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//===--- ExpectedTypes.h - Simplified C++ types -----------------*- C++-*--===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// A simplified model of C++ types that can be used to check whether they are
// convertible between each other for the purposes of code completion ranking
// without looking at the ASTs. Note that we don't aim to fully mimic the C++
// conversion rules, merely try to have a model that gives useful improvements
// to the code completion ranking.
// We define an encoding of AST types as opaque strings, which can be stored in
// the index. Similar types (such as `int` and `long`) are folded together,
// forming equivalence classes with the same encoding.
#include "clang/AST/Type.h"
#include "llvm/ADT/StringRef.h"
namespace clang {
class CodeCompletionResult;
namespace clangd {
/// A representation of a type that can be computed based on clang AST and
/// compared for equality. The encoding is stable between different ASTs, this
/// allows the representation to be stored in the index and compared with types
/// coming from a different AST later.
/// OpaqueType is a strongly-typedefed std::string, you can get the underlying
/// string with raw().
class OpaqueType {
/// Create a type from a code completion result.
static llvm::Optional<OpaqueType>
fromCompletionResult(ASTContext &Ctx, const CodeCompletionResult &R);
/// Construct an instance from a clang::QualType. This is usually a
/// PreferredType from a clang's completion context.
static llvm::Optional<OpaqueType> fromType(ASTContext &Ctx, QualType Type);
/// Get the raw byte representation of the type. You can only rely on the
/// types being equal iff their raw representation is the same. The particular
/// details of the used encoding might change over time and one should not
/// rely on it.
llvm::StringRef raw() const { return Data; }
friend bool operator==(const OpaqueType &L, const OpaqueType &R) {
return L.Data == R.Data;
friend bool operator!=(const OpaqueType &L, const OpaqueType &R) {
return !(L == R);
static llvm::Optional<OpaqueType> encode(ASTContext &Ctx, QualType Type);
explicit OpaqueType(std::string Data);
std::string Data;
} // namespace clangd
} // namespace clang