1 //===--- IgnoreExpr.h - Ignore intermediate Expressions -----------------===//
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 // This file defines common functions to ignore intermediate expression nodes
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #ifndef LLVM_CLANG_AST_IGNOREEXPR_H
14 #define LLVM_CLANG_AST_IGNOREEXPR_H
15 
16 #include "clang/AST/Expr.h"
17 #include "clang/AST/ExprCXX.h"
18 
19 namespace clang {
20 namespace detail {
21 /// Given an expression E and functions Fn_1,...,Fn_n : Expr * -> Expr *,
22 /// Return Fn_n(...(Fn_1(E)))
23 inline Expr *IgnoreExprNodesImpl(Expr *E) { return E; }
24 template <typename FnTy, typename... FnTys>
25 Expr *IgnoreExprNodesImpl(Expr *E, FnTy &&Fn, FnTys &&... Fns) {
26   return IgnoreExprNodesImpl(Fn(E), std::forward<FnTys>(Fns)...);
27 }
28 } // namespace detail
29 
30 /// Given an expression E and functions Fn_1,...,Fn_n : Expr * -> Expr *,
31 /// Recursively apply each of the functions to E until reaching a fixed point.
32 /// Note that a null E is valid; in this case nothing is done.
33 template <typename... FnTys> Expr *IgnoreExprNodes(Expr *E, FnTys &&... Fns) {
34   Expr *LastE = nullptr;
35   while (E != LastE) {
36     LastE = E;
37     E = detail::IgnoreExprNodesImpl(E, std::forward<FnTys>(Fns)...);
38   }
39   return E;
40 }
41 
42 template <typename... FnTys>
43 const Expr *IgnoreExprNodes(const Expr *E, FnTys &&...Fns) {
44   return IgnoreExprNodes(const_cast<Expr *>(E), std::forward<FnTys>(Fns)...);
45 }
46 
47 inline Expr *IgnoreImplicitCastsSingleStep(Expr *E) {
48   if (auto *ICE = dyn_cast<ImplicitCastExpr>(E))
49     return ICE->getSubExpr();
50 
51   if (auto *FE = dyn_cast<FullExpr>(E))
52     return FE->getSubExpr();
53 
54   return E;
55 }
56 
57 inline Expr *IgnoreImplicitCastsExtraSingleStep(Expr *E) {
58   // FIXME: Skip MaterializeTemporaryExpr and SubstNonTypeTemplateParmExpr in
59   // addition to what IgnoreImpCasts() skips to account for the current
60   // behaviour of IgnoreParenImpCasts().
61   Expr *SubE = IgnoreImplicitCastsSingleStep(E);
62   if (SubE != E)
63     return SubE;
64 
65   if (auto *MTE = dyn_cast<MaterializeTemporaryExpr>(E))
66     return MTE->getSubExpr();
67 
68   if (auto *NTTP = dyn_cast<SubstNonTypeTemplateParmExpr>(E))
69     return NTTP->getReplacement();
70 
71   return E;
72 }
73 
74 inline Expr *IgnoreCastsSingleStep(Expr *E) {
75   if (auto *CE = dyn_cast<CastExpr>(E))
76     return CE->getSubExpr();
77 
78   if (auto *FE = dyn_cast<FullExpr>(E))
79     return FE->getSubExpr();
80 
81   if (auto *MTE = dyn_cast<MaterializeTemporaryExpr>(E))
82     return MTE->getSubExpr();
83 
84   if (auto *NTTP = dyn_cast<SubstNonTypeTemplateParmExpr>(E))
85     return NTTP->getReplacement();
86 
87   return E;
88 }
89 
90 inline Expr *IgnoreLValueCastsSingleStep(Expr *E) {
91   // Skip what IgnoreCastsSingleStep skips, except that only
92   // lvalue-to-rvalue casts are skipped.
93   if (auto *CE = dyn_cast<CastExpr>(E))
94     if (CE->getCastKind() != CK_LValueToRValue)
95       return E;
96 
97   return IgnoreCastsSingleStep(E);
98 }
99 
100 inline Expr *IgnoreBaseCastsSingleStep(Expr *E) {
101   if (auto *CE = dyn_cast<CastExpr>(E))
102     if (CE->getCastKind() == CK_DerivedToBase ||
103         CE->getCastKind() == CK_UncheckedDerivedToBase ||
104         CE->getCastKind() == CK_NoOp)
105       return CE->getSubExpr();
106 
107   return E;
108 }
109 
110 inline Expr *IgnoreImplicitSingleStep(Expr *E) {
111   Expr *SubE = IgnoreImplicitCastsSingleStep(E);
112   if (SubE != E)
113     return SubE;
114 
115   if (auto *MTE = dyn_cast<MaterializeTemporaryExpr>(E))
116     return MTE->getSubExpr();
117 
118   if (auto *BTE = dyn_cast<CXXBindTemporaryExpr>(E))
119     return BTE->getSubExpr();
120 
121   return E;
122 }
123 
124 inline Expr *IgnoreElidableImplicitConstructorSingleStep(Expr *E) {
125   auto *CCE = dyn_cast<CXXConstructExpr>(E);
126   if (CCE && CCE->isElidable() && !isa<CXXTemporaryObjectExpr>(CCE)) {
127     unsigned NumArgs = CCE->getNumArgs();
128     if ((NumArgs == 1 ||
129          (NumArgs > 1 && CCE->getArg(1)->isDefaultArgument())) &&
130         !CCE->getArg(0)->isDefaultArgument() && !CCE->isListInitialization())
131       return CCE->getArg(0);
132   }
133   return E;
134 }
135 
136 inline Expr *IgnoreImplicitAsWrittenSingleStep(Expr *E) {
137   if (auto *ICE = dyn_cast<ImplicitCastExpr>(E))
138     return ICE->getSubExprAsWritten();
139 
140   return IgnoreImplicitSingleStep(E);
141 }
142 
143 inline Expr *IgnoreParensOnlySingleStep(Expr *E) {
144   if (auto *PE = dyn_cast<ParenExpr>(E))
145     return PE->getSubExpr();
146   return E;
147 }
148 
149 inline Expr *IgnoreParensSingleStep(Expr *E) {
150   if (auto *PE = dyn_cast<ParenExpr>(E))
151     return PE->getSubExpr();
152 
153   if (auto *UO = dyn_cast<UnaryOperator>(E)) {
154     if (UO->getOpcode() == UO_Extension)
155       return UO->getSubExpr();
156   }
157 
158   else if (auto *GSE = dyn_cast<GenericSelectionExpr>(E)) {
159     if (!GSE->isResultDependent())
160       return GSE->getResultExpr();
161   }
162 
163   else if (auto *CE = dyn_cast<ChooseExpr>(E)) {
164     if (!CE->isConditionDependent())
165       return CE->getChosenSubExpr();
166   }
167 
168   return E;
169 }
170 
171 } // namespace clang
172 
173 #endif // LLVM_CLANG_AST_IGNOREEXPR_H
174