1 //===- RedundantStringInitCheck.cpp - clang-tidy ----------------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "RedundantStringInitCheck.h"
11 #include "../utils/Matchers.h"
12 #include "clang/ASTMatchers/ASTMatchers.h"
13 
14 using namespace clang::ast_matchers;
15 using namespace clang::tidy::matchers;
16 
17 namespace clang {
18 namespace tidy {
19 namespace readability {
20 
21 void RedundantStringInitCheck::registerMatchers(MatchFinder *Finder) {
22   if (!getLangOpts().CPlusPlus)
23     return;
24 
25   // Match string constructor.
26   const auto StringConstructorExpr = expr(anyOf(
27       cxxConstructExpr(argumentCountIs(1),
28                        hasDeclaration(cxxMethodDecl(hasName("basic_string")))),
29       // If present, the second argument is the alloc object which must not
30       // be present explicitly.
31       cxxConstructExpr(argumentCountIs(2),
32                        hasDeclaration(cxxMethodDecl(hasName("basic_string"))),
33                        hasArgument(1, cxxDefaultArgExpr()))));
34 
35   // Match a string constructor expression with an empty string literal.
36   const auto EmptyStringCtorExpr = cxxConstructExpr(
37       StringConstructorExpr,
38       hasArgument(0, ignoringParenImpCasts(stringLiteral(hasSize(0)))));
39 
40   const auto EmptyStringCtorExprWithTemporaries =
41       cxxConstructExpr(StringConstructorExpr,
42                        hasArgument(0, ignoringImplicit(EmptyStringCtorExpr)));
43 
44   // Match a variable declaration with an empty string literal as initializer.
45   // Examples:
46   //     string foo = "";
47   //     string bar("");
48   Finder->addMatcher(
49       namedDecl(
50           varDecl(hasType(cxxRecordDecl(hasName("basic_string"))),
51                   hasInitializer(expr(ignoringImplicit(anyOf(
52                                           EmptyStringCtorExpr,
53                                           EmptyStringCtorExprWithTemporaries)))
54                                      .bind("expr"))),
55           unless(parmVarDecl()))
56           .bind("decl"),
57       this);
58 }
59 
60 void RedundantStringInitCheck::check(const MatchFinder::MatchResult &Result) {
61   const auto *CtorExpr = Result.Nodes.getNodeAs<Expr>("expr");
62   const auto *Decl = Result.Nodes.getNodeAs<NamedDecl>("decl");
63   diag(CtorExpr->getExprLoc(), "redundant string initialization")
64       << FixItHint::CreateReplacement(CtorExpr->getSourceRange(),
65                                       Decl->getName());
66 }
67 
68 } // namespace readability
69 } // namespace tidy
70 } // namespace clang
71