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1 //===- RedundantStringInitCheck.cpp - clang-tidy ----------------*- C++ -*-===//
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2 //
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3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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4 // See https://llvm.org/LICENSE.txt for license information.
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5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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6 //
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7 //===----------------------------------------------------------------------===//
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8
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9 #include "RedundantStringInitCheck.h"
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10 #include "../utils/Matchers.h"
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11 #include "../utils/OptionsUtils.h"
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12 #include "clang/ASTMatchers/ASTMatchers.h"
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252
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13 #include <optional>
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150
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14
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15 using namespace clang::ast_matchers;
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16 using namespace clang::tidy::matchers;
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17
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252
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18 namespace clang::tidy::readability {
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150
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19
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221
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20 const char DefaultStringNames[] =
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21 "::std::basic_string_view;::std::basic_string";
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150
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22
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236
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23 static std::vector<StringRef> removeNamespaces(ArrayRef<StringRef> Names) {
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24 std::vector<StringRef> Result;
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150
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25 Result.reserve(Names.size());
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236
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26 for (StringRef Name : Names) {
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27 StringRef::size_type ColonPos = Name.rfind(':');
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150
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28 Result.push_back(
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236
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29 Name.drop_front(ColonPos == StringRef::npos ? 0 : ColonPos + 1));
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150
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30 }
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31 return Result;
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32 }
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33
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34 static const CXXConstructExpr *
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35 getConstructExpr(const CXXCtorInitializer &CtorInit) {
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36 const Expr *InitExpr = CtorInit.getInit();
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37 if (const auto *CleanUpExpr = dyn_cast<ExprWithCleanups>(InitExpr))
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38 InitExpr = CleanUpExpr->getSubExpr();
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39 return dyn_cast<CXXConstructExpr>(InitExpr);
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40 }
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41
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252
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42 static std::optional<SourceRange>
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43 getConstructExprArgRange(const CXXConstructExpr &Construct) {
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44 SourceLocation B, E;
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45 for (const Expr *Arg : Construct.arguments()) {
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46 if (B.isInvalid())
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47 B = Arg->getBeginLoc();
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48 if (Arg->getEndLoc().isValid())
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49 E = Arg->getEndLoc();
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50 }
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51 if (B.isInvalid() || E.isInvalid())
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252
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52 return std::nullopt;
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150
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53 return SourceRange(B, E);
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54 }
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55
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56 RedundantStringInitCheck::RedundantStringInitCheck(StringRef Name,
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57 ClangTidyContext *Context)
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58 : ClangTidyCheck(Name, Context),
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59 StringNames(utils::options::parseStringList(
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60 Options.get("StringNames", DefaultStringNames))) {}
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61
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62 void RedundantStringInitCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
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63 Options.store(Opts, "StringNames", DefaultStringNames);
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64 }
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65
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66 void RedundantStringInitCheck::registerMatchers(MatchFinder *Finder) {
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236
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67 const auto HasStringTypeName = hasAnyName(StringNames);
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68 const auto HasStringCtorName = hasAnyName(removeNamespaces(StringNames));
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150
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69
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70 // Match string constructor.
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71 const auto StringConstructorExpr = expr(
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72 anyOf(cxxConstructExpr(argumentCountIs(1),
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221
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73 hasDeclaration(cxxMethodDecl(HasStringCtorName))),
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150
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74 // If present, the second argument is the alloc object which must
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75 // not be present explicitly.
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76 cxxConstructExpr(argumentCountIs(2),
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221
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77 hasDeclaration(cxxMethodDecl(HasStringCtorName)),
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78 hasArgument(1, cxxDefaultArgExpr()))));
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79
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80 // Match a string constructor expression with an empty string literal.
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81 const auto EmptyStringCtorExpr = cxxConstructExpr(
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82 StringConstructorExpr,
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83 hasArgument(0, ignoringParenImpCasts(stringLiteral(hasSize(0)))));
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84
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85 const auto EmptyStringCtorExprWithTemporaries =
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86 cxxConstructExpr(StringConstructorExpr,
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87 hasArgument(0, ignoringImplicit(EmptyStringCtorExpr)));
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88
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89 const auto StringType = hasType(hasUnqualifiedDesugaredType(
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221
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90 recordType(hasDeclaration(cxxRecordDecl(HasStringTypeName)))));
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91 const auto EmptyStringInit = traverse(
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92 TK_AsIs, expr(ignoringImplicit(anyOf(
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93 EmptyStringCtorExpr, EmptyStringCtorExprWithTemporaries))));
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150
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94
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95 // Match a variable declaration with an empty string literal as initializer.
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96 // Examples:
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97 // string foo = "";
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98 // string bar("");
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99 Finder->addMatcher(
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100 traverse(TK_AsIs,
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101 namedDecl(varDecl(StringType, hasInitializer(EmptyStringInit))
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102 .bind("vardecl"),
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103 unless(parmVarDecl()))),
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150
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104 this);
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105 // Match a field declaration with an empty string literal as initializer.
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106 Finder->addMatcher(
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107 namedDecl(fieldDecl(StringType, hasInClassInitializer(EmptyStringInit))
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108 .bind("fieldDecl")),
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109 this);
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110 // Matches Constructor Initializers with an empty string literal as
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111 // initializer.
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112 // Examples:
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113 // Foo() : SomeString("") {}
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114 Finder->addMatcher(
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115 cxxCtorInitializer(
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116 isWritten(),
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117 forField(allOf(StringType, optionally(hasInClassInitializer(
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118 EmptyStringInit.bind("empty_init"))))),
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119 withInitializer(EmptyStringInit))
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120 .bind("ctorInit"),
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121 this);
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122 }
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123
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124 void RedundantStringInitCheck::check(const MatchFinder::MatchResult &Result) {
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125 if (const auto *VDecl = Result.Nodes.getNodeAs<VarDecl>("vardecl")) {
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126 // VarDecl's getSourceRange() spans 'string foo = ""' or 'string bar("")'.
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127 // So start at getLocation() to span just 'foo = ""' or 'bar("")'.
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128 SourceRange ReplaceRange(VDecl->getLocation(), VDecl->getEndLoc());
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129 diag(VDecl->getLocation(), "redundant string initialization")
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130 << FixItHint::CreateReplacement(ReplaceRange, VDecl->getName());
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131 }
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132 if (const auto *FDecl = Result.Nodes.getNodeAs<FieldDecl>("fieldDecl")) {
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133 // FieldDecl's getSourceRange() spans 'string foo = ""'.
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134 // So start at getLocation() to span just 'foo = ""'.
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135 SourceRange ReplaceRange(FDecl->getLocation(), FDecl->getEndLoc());
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136 diag(FDecl->getLocation(), "redundant string initialization")
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137 << FixItHint::CreateReplacement(ReplaceRange, FDecl->getName());
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138 }
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139 if (const auto *CtorInit =
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140 Result.Nodes.getNodeAs<CXXCtorInitializer>("ctorInit")) {
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141 if (const FieldDecl *Member = CtorInit->getMember()) {
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142 if (!Member->hasInClassInitializer() ||
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143 Result.Nodes.getNodeAs<Expr>("empty_init")) {
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144 // The String isn't declared in the class with an initializer or its
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145 // declared with a redundant initializer, which will be removed. Either
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146 // way the string will be default initialized, therefore we can remove
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147 // the constructor initializer entirely.
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148 diag(CtorInit->getMemberLocation(), "redundant string initialization")
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149 << FixItHint::CreateRemoval(CtorInit->getSourceRange());
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150 return;
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151 }
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152 }
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153 const CXXConstructExpr *Construct = getConstructExpr(*CtorInit);
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154 if (!Construct)
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155 return;
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252
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156 if (std::optional<SourceRange> RemovalRange =
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157 getConstructExprArgRange(*Construct))
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158 diag(CtorInit->getMemberLocation(), "redundant string initialization")
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159 << FixItHint::CreateRemoval(*RemovalRange);
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160 }
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161 }
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162
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252
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163 } // namespace clang::tidy::readability
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