1//===--- HeuristicResolver.h - Resolution of dependent names -----*- C++-*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#ifndef LLVM_CLANG_SEMA_HEURISTICRESOLVER_H
10#define LLVM_CLANG_SEMA_HEURISTICRESOLVER_H
11
12#include "clang/AST/Decl.h"
13#include <vector>
14
15namespace clang {
16
17class ASTContext;
18class CallExpr;
19class CXXBasePath;
20class CXXDependentScopeMemberExpr;
21class DeclarationName;
22class DependentScopeDeclRefExpr;
23class FunctionProtoTypeLoc;
24class NamedDecl;
25class Type;
26class UnresolvedUsingValueDecl;
27
28// This class handles heuristic resolution of declarations and types in template
29// code.
30//
31// As a compiler, clang only needs to perform certain types of processing on
32// template code (such as resolving dependent names to declarations, or
33// resolving the type of a dependent expression) after instantiation. Indeed,
34// C++ language features such as template specialization mean such resolution
35// cannot be done accurately before instantiation.
36//
37// However, template code is written and read in uninstantiated form, and clangd
38// would like to provide editor features like go-to-definition in template code
39// where possible. To this end, clangd attempts to resolve declarations and
40// types in uninstantiated code by using heuristics, understanding that the
41// results may not be fully accurate but that this is better than nothing.
42//
43// At this time, the heuristic used is a simple but effective one: assume that
44// template instantiations are based on the primary template definition and not
45// not a specialization. More advanced heuristics may be added in the future.
46class HeuristicResolver {
47public:
48 HeuristicResolver(ASTContext &Ctx) : Ctx(Ctx) {}
49
50 // Try to heuristically resolve certain types of expressions, declarations, or
51 // types to one or more likely-referenced declarations.
52 std::vector<const NamedDecl *>
53 resolveMemberExpr(const CXXDependentScopeMemberExpr *ME) const;
54 std::vector<const NamedDecl *>
55 resolveDeclRefExpr(const DependentScopeDeclRefExpr *RE) const;
56 std::vector<const NamedDecl *>
57 resolveCalleeOfCallExpr(const CallExpr *CE) const;
58 std::vector<const NamedDecl *>
59 resolveUsingValueDecl(const UnresolvedUsingValueDecl *UUVD) const;
60 std::vector<const NamedDecl *>
61 resolveDependentNameType(const DependentNameType *DNT) const;
62 std::vector<const NamedDecl *> resolveTemplateSpecializationType(
63 const TemplateSpecializationType *TST) const;
64
65 // Try to heuristically resolve a dependent nested name specifier
66 // to the type it likely denotes. Note that *dependent* name specifiers always
67 // denote types, not namespaces.
68 QualType resolveNestedNameSpecifierToType(NestedNameSpecifier NNS) const;
69
70 // Perform an imprecise lookup of a dependent name in `RD`.
71 // This function does not follow strict semantic rules and should be used
72 // only when lookup rules can be relaxed, e.g. indexing.
73 std::vector<const NamedDecl *>
74 lookupDependentName(CXXRecordDecl *RD, DeclarationName Name,
75 llvm::function_ref<bool(const NamedDecl *ND)> Filter);
76
77 // Given the type T of a dependent expression that appears of the LHS of a
78 // "->", heuristically find a corresponding pointee type in whose scope we
79 // could look up the name appearing on the RHS.
80 const QualType getPointeeType(QualType T) const;
81
82 // Heuristically resolve a possibly-dependent type `T` to a TagDecl
83 // in which a member's name can be looked up.
84 TagDecl *resolveTypeToTagDecl(QualType T) const;
85
86 // Simplify the type `Type`.
87 // `E` is the expression whose type `Type` is, if known. This sometimes
88 // contains information relevant to the type that's not stored in `Type`
89 // itself.
90 // If `UnwrapPointer` is true, exactly only pointer type will be unwrapped
91 // during simplification, and the operation fails if no pointer type is found.
92 QualType simplifyType(QualType Type, const Expr *E, bool UnwrapPointer);
93
94 // Try to heuristically resolve the type of a possibly-dependent expression
95 // `E`.
96 QualType resolveExprToType(const Expr *E) const;
97
98 // Given an expression `Fn` representing the callee in a function call,
99 // if the call is through a function pointer, try to find the declaration of
100 // the corresponding function pointer type, so that we can recover argument
101 // names from it.
102 FunctionProtoTypeLoc getFunctionProtoTypeLoc(const Expr *Fn) const;
103
104private:
105 ASTContext &Ctx;
106};
107
108} // namespace clang
109
110#endif
111