clang-tools-extra/clang-tidy/readability/AvoidConstParamsInDecls.cpp

   1 //===--- AvoidConstParamsInDecls.cpp - clang-tidy--------------------------===//
   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 #include "AvoidConstParamsInDecls.h"
  10 #include "../utils/LexerUtils.h"
  11 #include "clang/ASTMatchers/ASTMatchFinder.h"
  12 #include "clang/ASTMatchers/ASTMatchers.h"
  13 #include "clang/Lex/Lexer.h"
  14
  15 using namespace clang::ast_matchers;
  16
  17 namespace clang::tidy::readability {
  18 namespace {
  19
  20 SourceRange getTypeRange(const ParmVarDecl &Param) {
  21   return {Param.getBeginLoc(), Param.getLocation().getLocWithOffset(-1)};
  22 }
  23
  24 // Finds the location of the qualifying `const` token in the `ParmValDecl`'s
  25 // return type. Returns `std::nullopt` when the parm type is not
  26 // `const`-qualified like when the type is an alias or a macro.
  27 static std::optional<Token>
  28 findConstToRemove(const ParmVarDecl &Param,
  29                   const MatchFinder::MatchResult &Result) {
  30
  31   CharSourceRange FileRange = Lexer::makeFileCharRange(
  32       CharSourceRange::getTokenRange(getTypeRange(Param)),
  33       *Result.SourceManager, Result.Context->getLangOpts());
  34
  35   if (FileRange.isInvalid())
  36     return std::nullopt;
  37
  38   return tidy::utils::lexer::getQualifyingToken(
  39       tok::kw_const, FileRange, *Result.Context, *Result.SourceManager);
  40 }
  41
  42 } // namespace
  43
  44 void AvoidConstParamsInDecls::storeOptions(ClangTidyOptions::OptionMap &Opts) {
  45   Options.store(Opts, "IgnoreMacros", IgnoreMacros);
  46 }
  47
  48 void AvoidConstParamsInDecls::registerMatchers(MatchFinder *Finder) {
  49   const auto ConstParamDecl =
  50       parmVarDecl(hasType(qualType(isConstQualified()))).bind("param");
  51   Finder->addMatcher(functionDecl(unless(isDefinition()),
  52                                   has(typeLoc(forEach(ConstParamDecl))))
  53                          .bind("func"),
  54                      this);
  55 }
  56
  57 void AvoidConstParamsInDecls::check(const MatchFinder::MatchResult &Result) {
  58   const auto *Func = Result.Nodes.getNodeAs<FunctionDecl>("func");
  59   const auto *Param = Result.Nodes.getNodeAs<ParmVarDecl>("param");
  60
  61   if (!Param->getType().isLocalConstQualified())
  62     return;
  63
  64   if (IgnoreMacros &&
  65       (Param->getBeginLoc().isMacroID() || Param->getEndLoc().isMacroID())) {
  66     // Suppress the check if macros are involved.
  67     return;
  68   }
  69
  70   const auto Tok = findConstToRemove(*Param, Result);
  71   const auto ConstLocation = Tok ? Tok->getLocation() : Param->getBeginLoc();
  72
  73   auto Diag = diag(ConstLocation,
  74                    "parameter %0 is const-qualified in the function "
  75                    "declaration; const-qualification of parameters only has an "
  76                    "effect in function definitions");
  77   if (Param->getName().empty()) {
  78     for (unsigned int I = 0; I < Func->getNumParams(); ++I) {
  79       if (Param == Func->getParamDecl(I)) {
  80         Diag << (I + 1);
  81         break;
  82       }
  83     }
  84   } else {
  85     Diag << Param;
  86   }
  87
  88   if (Param->getBeginLoc().isMacroID() != Param->getEndLoc().isMacroID()) {
  89     // Do not offer a suggestion if the part of the variable declaration comes
  90     // from a macro.
  91     return;
  92   }
  93   if (!Tok)
  94     return;
  95
  96   Diag << FixItHint::CreateRemoval(
  97       CharSourceRange::getTokenRange(Tok->getLocation(), Tok->getLocation()));
  98 }
  99
 100 } // namespace clang::tidy::readability