[llvm-bugs] [Bug 29145] New: ParmVarDecl corresponding to unnamed parameter incorrectly has a name

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=29145

            Bug ID: 29145
           Summary: ParmVarDecl corresponding to unnamed parameter
                    incorrectly has a name
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: lukasza at chromium.org
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

clang version 4.0.0 (trunk 277962)

Expected behavior:

    1. The ParmVarDecl corresponding to
           void f(int);
       declaration on line 5 should have
       1) no identifier
       2) no name

    2. I can safely generate replacements of text inside parm.getLocation() 
       (e.g. rename "dataSize" to "data_size").

Actual behavior:

    1. There are 2 ParmVarDecls on line 5.
       One of these ParmVarDecls has a non-empty name and identifier.

    2. Generating replacements based on parm.getLocation() would
       butcher the source code.

    3. Output of the repro program below:

        Name = ''
        Identifier = '0x0'            <-- looking good so far...
        Line = 'input.cc:5:19'
        ---------------------------------
        Name = 'dataSize'             <-- THIS IS THE BUG
        Identifier = '0x3a05f98'
        Line = 'input.cc:5:19'
        ---------------------------------
        Name = ''
        Identifier = '0x0'
        Line = 'input.cc:3:13'        <- please ignore ParmVarDecls from other
lines
        ---------------------------------
        Name = 'dataSize'
        Identifier = '0x3a05f98'
        Line = 'input.cc:9:28'        <- please ignore ParmVarDecls from other
lines

Repro:

#include <memory>

#include "clang/AST/ASTContext.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/ASTMatchers/ASTMatchers.h"
#include "clang/ASTMatchers/ASTMatchersMacros.h"
#include "clang/Basic/CharInfo.h"
#include "clang/Frontend/FrontendActions.h"
#include "clang/Tooling/CommonOptionsParser.h"
#include "clang/Tooling/Refactoring.h"
#include "clang/Tooling/Tooling.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/TargetSelect.h"

using namespace clang::ast_matchers;

class ReproMatchCallback : public MatchFinder::MatchCallback {
 public:
  void run(const MatchFinder::MatchResult& result) override {
    const clang::ParmVarDecl* parm =
result.Nodes.getNodeAs<clang::ParmVarDecl>("decl");
    if (!parm)
      return;

    llvm::outs() << "---------------------------------\n";
    llvm::outs() << "Name = '" << parm->getName() << "'\n";
    llvm::outs() << "Identifier = '" << parm->getIdentifier() << "'\n";
    llvm::outs() << "Line = '" <<
parm->getLocation().printToString(result.Context->getSourceManager()) << "'\n";
  }
};

int main(int argc, const char* argv[]) {
  llvm::InitializeNativeTarget();
  llvm::InitializeNativeTargetAsmParser();
  llvm::cl::OptionCategory category("Repro.");
  clang::tooling::CommonOptionsParser options(argc, argv, category);
  clang::tooling::ClangTool tool(options.getCompilations(),
                                 options.getSourcePathList());

  const char* code = R"code(            // line 1
      template <typename T>             // line 2
      class Class {                     // line 3
       public:                          // line 4
        void f(int);  // <- NO NAME!    // line 5
      };                                // line 6
                                        // line 7
      template <typename T>             // line 8
      void Class<T>::f(int dataSize){}; // line 9
                                        // line 10
      void foo() {                      // line 11
        Class<char>().f(123);           // line 12
      };                                // line 13
  )code";

  auto matcher = id("decl", parmVarDecl());

  MatchFinder match_finder;
  ReproMatchCallback match_callback;
  match_finder.addMatcher(matcher, &match_callback);
  std::unique_ptr<clang::tooling::FrontendActionFactory> factory =
      clang::tooling::newFrontendActionFactory(&match_finder);
  clang::tooling::runToolOnCode(factory->create(), code);
  return 0;
}

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