llvm-project/clang-tools-extra/clangd/HeuristicResolver.cpp

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//===--- HeuristicResolver.cpp ---------------------------*- C++-*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "HeuristicResolver.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/ExprCXX.h"
namespace clang {
namespace clangd {
// Convenience lambdas for use as the 'Filter' parameter of
// HeuristicResolver::resolveDependentMember().
const auto NoFilter = [](const NamedDecl *D) { return true; };
const auto NonStaticFilter = [](const NamedDecl *D) {
return D->isCXXInstanceMember();
};
const auto StaticFilter = [](const NamedDecl *D) {
return !D->isCXXInstanceMember();
};
const auto ValueFilter = [](const NamedDecl *D) { return isa<ValueDecl>(D); };
const auto TypeFilter = [](const NamedDecl *D) { return isa<TypeDecl>(D); };
const auto TemplateFilter = [](const NamedDecl *D) {
return isa<TemplateDecl>(D);
};
// Helper function for HeuristicResolver::resolveDependentMember()
// which takes a possibly-dependent type `T` and heuristically
// resolves it to a CXXRecordDecl in which we can try name lookup.
CXXRecordDecl *resolveTypeToRecordDecl(const Type *T) {
assert(T);
if (const auto *RT = T->getAs<RecordType>())
return dyn_cast<CXXRecordDecl>(RT->getDecl());
if (const auto *ICNT = T->getAs<InjectedClassNameType>())
T = ICNT->getInjectedSpecializationType().getTypePtrOrNull();
if (!T)
return nullptr;
const auto *TST = T->getAs<TemplateSpecializationType>();
if (!TST)
return nullptr;
const ClassTemplateDecl *TD = dyn_cast_or_null<ClassTemplateDecl>(
TST->getTemplateName().getAsTemplateDecl());
if (!TD)
return nullptr;
return TD->getTemplatedDecl();
}
const Type *HeuristicResolver::getPointeeType(const Type *T) const {
if (!T)
return nullptr;
if (T->isPointerType()) {
return T->getAs<PointerType>()->getPointeeType().getTypePtrOrNull();
}
// Try to handle smart pointer types.
// Look up operator-> in the primary template. If we find one, it's probably a
// smart pointer type.
auto ArrowOps = resolveDependentMember(
T, Ctx.DeclarationNames.getCXXOperatorName(OO_Arrow), NonStaticFilter);
if (ArrowOps.empty())
return nullptr;
// Getting the return type of the found operator-> method decl isn't useful,
// because we discarded template arguments to perform lookup in the primary
// template scope, so the return type would just have the form U* where U is a
// template parameter type.
// Instead, just handle the common case where the smart pointer type has the
// form of SmartPtr<X, ...>, and assume X is the pointee type.
auto *TST = T->getAs<TemplateSpecializationType>();
if (!TST)
return nullptr;
if (TST->getNumArgs() == 0)
return nullptr;
const TemplateArgument &FirstArg = TST->getArg(0);
if (FirstArg.getKind() != TemplateArgument::Type)
return nullptr;
return FirstArg.getAsType().getTypePtrOrNull();
}
std::vector<const NamedDecl *> HeuristicResolver::resolveMemberExpr(
const CXXDependentScopeMemberExpr *ME) const {
// If the expression has a qualifier, first try resolving the member
// inside the qualifier's type.
// Note that we cannot use a NonStaticFilter in either case, for a couple
// of reasons:
// 1. It's valid to access a static member using instance member syntax,
// e.g. `instance.static_member`.
// 2. We can sometimes get a CXXDependentScopeMemberExpr for static
// member syntax too, e.g. if `X::static_member` occurs inside
// an instance method, it's represented as a CXXDependentScopeMemberExpr
// with `this` as the base expression as `X` as the qualifier
// (which could be valid if `X` names a base class after instantiation).
if (NestedNameSpecifier *NNS = ME->getQualifier()) {
if (const Type *QualifierType = resolveNestedNameSpecifierToType(NNS)) {
auto Decls =
resolveDependentMember(QualifierType, ME->getMember(), NoFilter);
if (!Decls.empty())
return Decls;
}
}
// If that didn't yield any results, try resolving the member inside
// the expression's base type.
const Type *BaseType = ME->getBaseType().getTypePtrOrNull();
if (ME->isArrow()) {
BaseType = getPointeeType(BaseType);
}
if (!BaseType)
return {};
if (const auto *BT = BaseType->getAs<BuiltinType>()) {
// If BaseType is the type of a dependent expression, it's just
// represented as BultinType::Dependent which gives us no information. We
// can get further by analyzing the depedent expression.
Expr *Base = ME->isImplicitAccess() ? nullptr : ME->getBase();
if (Base && BT->getKind() == BuiltinType::Dependent) {
BaseType = resolveExprToType(Base);
}
}
return resolveDependentMember(BaseType, ME->getMember(), NoFilter);
}
std::vector<const NamedDecl *> HeuristicResolver::resolveDeclRefExpr(
const DependentScopeDeclRefExpr *RE) const {
return resolveDependentMember(RE->getQualifier()->getAsType(),
RE->getDeclName(), StaticFilter);
}
std::vector<const NamedDecl *>
HeuristicResolver::resolveTypeOfCallExpr(const CallExpr *CE) const {
const auto *CalleeType = resolveExprToType(CE->getCallee());
if (!CalleeType)
return {};
if (const auto *FnTypePtr = CalleeType->getAs<PointerType>())
CalleeType = FnTypePtr->getPointeeType().getTypePtr();
if (const FunctionType *FnType = CalleeType->getAs<FunctionType>()) {
if (const auto *D =
resolveTypeToRecordDecl(FnType->getReturnType().getTypePtr())) {
return {D};
}
}
return {};
}
std::vector<const NamedDecl *>
HeuristicResolver::resolveCalleeOfCallExpr(const CallExpr *CE) const {
if (const auto *ND = dyn_cast_or_null<NamedDecl>(CE->getCalleeDecl())) {
return {ND};
}
return resolveExprToDecls(CE->getCallee());
}
std::vector<const NamedDecl *> HeuristicResolver::resolveUsingValueDecl(
const UnresolvedUsingValueDecl *UUVD) const {
return resolveDependentMember(UUVD->getQualifier()->getAsType(),
UUVD->getNameInfo().getName(), ValueFilter);
}
std::vector<const NamedDecl *> HeuristicResolver::resolveDependentNameType(
const DependentNameType *DNT) const {
return resolveDependentMember(
resolveNestedNameSpecifierToType(DNT->getQualifier()),
DNT->getIdentifier(), TypeFilter);
}
std::vector<const NamedDecl *>
HeuristicResolver::resolveTemplateSpecializationType(
const DependentTemplateSpecializationType *DTST) const {
return resolveDependentMember(
resolveNestedNameSpecifierToType(DTST->getQualifier()),
DTST->getIdentifier(), TemplateFilter);
}
const Type *resolveDeclsToType(const std::vector<const NamedDecl *> &Decls) {
if (Decls.size() != 1) // Names an overload set -- just bail.
return nullptr;
if (const auto *TD = dyn_cast<TypeDecl>(Decls[0])) {
return TD->getTypeForDecl();
}
if (const auto *VD = dyn_cast<ValueDecl>(Decls[0])) {
return VD->getType().getTypePtrOrNull();
}
return nullptr;
}
std::vector<const NamedDecl *>
HeuristicResolver::resolveExprToDecls(const Expr *E) const {
if (const auto *ME = dyn_cast<CXXDependentScopeMemberExpr>(E)) {
return resolveMemberExpr(ME);
}
if (const auto *RE = dyn_cast<DependentScopeDeclRefExpr>(E)) {
return resolveDeclRefExpr(RE);
}
if (const auto *OE = dyn_cast<OverloadExpr>(E)) {
return {OE->decls_begin(), OE->decls_end()};
}
if (const auto *CE = dyn_cast<CallExpr>(E)) {
return resolveTypeOfCallExpr(CE);
}
if (const auto *ME = dyn_cast<MemberExpr>(E))
return {ME->getMemberDecl()};
return {};
}
const Type *HeuristicResolver::resolveExprToType(const Expr *E) const {
std::vector<const NamedDecl *> Decls = resolveExprToDecls(E);
if (!Decls.empty())
return resolveDeclsToType(Decls);
return E->getType().getTypePtr();
}
const Type *HeuristicResolver::resolveNestedNameSpecifierToType(
const NestedNameSpecifier *NNS) const {
if (!NNS)
return nullptr;
// The purpose of this function is to handle the dependent (Kind ==
// Identifier) case, but we need to recurse on the prefix because
// that may be dependent as well, so for convenience handle
// the TypeSpec cases too.
switch (NNS->getKind()) {
case NestedNameSpecifier::TypeSpec:
case NestedNameSpecifier::TypeSpecWithTemplate:
return NNS->getAsType();
case NestedNameSpecifier::Identifier: {
return resolveDeclsToType(resolveDependentMember(
resolveNestedNameSpecifierToType(NNS->getPrefix()),
NNS->getAsIdentifier(), TypeFilter));
}
default:
break;
}
return nullptr;
}
std::vector<const NamedDecl *> HeuristicResolver::resolveDependentMember(
const Type *T, DeclarationName Name,
llvm::function_ref<bool(const NamedDecl *ND)> Filter) const {
if (!T)
return {};
if (auto *ET = T->getAs<EnumType>()) {
auto Result = ET->getDecl()->lookup(Name);
return {Result.begin(), Result.end()};
}
if (auto *RD = resolveTypeToRecordDecl(T)) {
if (!RD->hasDefinition())
return {};
RD = RD->getDefinition();
return RD->lookupDependentName(Name, Filter);
}
return {};
}
} // namespace clangd
} // namespace clang