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diff --git a/build/clang-plugin/mozsearch-plugin/from-clangd/HeuristicResolver.cpp b/build/clang-plugin/mozsearch-plugin/from-clangd/HeuristicResolver.cpp new file mode 100644 index 0000000000..460b9be592 --- /dev/null +++ b/build/clang-plugin/mozsearch-plugin/from-clangd/HeuristicResolver.cpp @@ -0,0 +1,268 @@ +//===--- 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->castAs<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->template_arguments().size() == 0) + return nullptr; + const TemplateArgument &FirstArg = TST->template_arguments()[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 BuiltinType::Dependent which gives us no information. We + // can get further by analyzing the dependent 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 diff --git a/build/clang-plugin/mozsearch-plugin/from-clangd/HeuristicResolver.h b/build/clang-plugin/mozsearch-plugin/from-clangd/HeuristicResolver.h new file mode 100644 index 0000000000..2b66e4bd9b --- /dev/null +++ b/build/clang-plugin/mozsearch-plugin/from-clangd/HeuristicResolver.h @@ -0,0 +1,102 @@ +//===--- HeuristicResolver.h - Resolution of dependent names -----*- 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 +// +//===----------------------------------------------------------------------===// + +#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_HEURISTICRESOLVER_H +#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_HEURISTICRESOLVER_H + +#include "clang/AST/Decl.h" +#include <vector> + +namespace clang { + +class ASTContext; +class CallExpr; +class CXXDependentScopeMemberExpr; +class DeclarationName; +class DependentScopeDeclRefExpr; +class NamedDecl; +class Type; +class UnresolvedUsingValueDecl; + +namespace clangd { + +// This class heuristic resolution of declarations and types in template code. +// +// As a compiler, clang only needs to perform certain types of processing on +// template code (such as resolving dependent names to declarations, or +// resolving the type of a dependent expression) after instantiation. Indeed, +// C++ language features such as template specialization mean such resolution +// cannot be done accurately before instantiation +// +// However, template code is written and read in uninstantiated form, and clangd +// would like to provide editor features like go-to-definition in template code +// where possible. To this end, clangd attempts to resolve declarations and +// types in uninstantiated code by using heuristics, understanding that the +// results may not be fully accurate but that this is better than nothing. +// +// At this time, the heuristic used is a simple but effective one: assume that +// template instantiations are based on the primary template definition and not +// not a specialization. More advanced heuristics may be added in the future. +class HeuristicResolver { +public: + HeuristicResolver(ASTContext &Ctx) : Ctx(Ctx) {} + + // Try to heuristically resolve certain types of expressions, declarations, or + // types to one or more likely-referenced declarations. + std::vector<const NamedDecl *> + resolveMemberExpr(const CXXDependentScopeMemberExpr *ME) const; + std::vector<const NamedDecl *> + resolveDeclRefExpr(const DependentScopeDeclRefExpr *RE) const; + std::vector<const NamedDecl *> + resolveTypeOfCallExpr(const CallExpr *CE) const; + std::vector<const NamedDecl *> + resolveCalleeOfCallExpr(const CallExpr *CE) const; + std::vector<const NamedDecl *> + resolveUsingValueDecl(const UnresolvedUsingValueDecl *UUVD) const; + std::vector<const NamedDecl *> + resolveDependentNameType(const DependentNameType *DNT) const; + std::vector<const NamedDecl *> resolveTemplateSpecializationType( + const DependentTemplateSpecializationType *DTST) const; + + // Try to heuristically resolve a dependent nested name specifier + // to the type it likely denotes. Note that *dependent* name specifiers always + // denote types, not namespaces. + const Type * + resolveNestedNameSpecifierToType(const NestedNameSpecifier *NNS) const; + + // Given the type T of a dependent expression that appears of the LHS of a + // "->", heuristically find a corresponding pointee type in whose scope we + // could look up the name appearing on the RHS. + const Type *getPointeeType(const Type *T) const; + +private: + ASTContext &Ctx; + + // Given a tag-decl type and a member name, heuristically resolve the + // name to one or more declarations. + // The current heuristic is simply to look up the name in the primary + // template. This is a heuristic because the template could potentially + // have specializations that declare different members. + // Multiple declarations could be returned if the name is overloaded + // (e.g. an overloaded method in the primary template). + // This heuristic will give the desired answer in many cases, e.g. + // for a call to vector<T>::size(). + std::vector<const NamedDecl *> resolveDependentMember( + const Type *T, DeclarationName Name, + llvm::function_ref<bool(const NamedDecl *ND)> Filter) const; + + // Try to heuristically resolve the type of a possibly-dependent expression + // `E`. + const Type *resolveExprToType(const Expr *E) const; + std::vector<const NamedDecl *> resolveExprToDecls(const Expr *E) const; +}; + +} // namespace clangd +} // namespace clang + +#endif diff --git a/build/clang-plugin/mozsearch-plugin/from-clangd/README.md b/build/clang-plugin/mozsearch-plugin/from-clangd/README.md new file mode 100644 index 0000000000..334cf4913a --- /dev/null +++ b/build/clang-plugin/mozsearch-plugin/from-clangd/README.md @@ -0,0 +1,10 @@ +The facilities in this subdirectory are copied over from clangd +(https://clangd.llvm.org/). + +The files here are currently copies of the following upstream files: +https://github.com/llvm/llvm-project/blob/48bc71505e03694caac6afb2431ff1157a2382a8/clang-tools-extra/clangd/HeuristicResolver.h +https://github.com/llvm/llvm-project/blob/48bc71505e03694caac6afb2431ff1157a2382a8/clang-tools-extra/clangd/HeuristicResolver.cpp + +If, in the future, these facilities are moved from clangd to +to libclangTooling and exposed in the clang API headers, we can +switch to consuming them from there directly. |