[clang-tidy] Add check readability-redundant-declaration

Finds redundant variable and function declarations.

  extern int X;
  extern int X;  // <- redundant

Differential Revision: https://reviews.llvm.org/D24656

llvm-svn: 285689

1 files changed, 71 insertions, 0 deletions

diff --git a/clang-tools-extra/clang-tidy/readability/RedundantDeclarationCheck.cpp b/clang-tools-extra/clang-tidy/readability/RedundantDeclarationCheck.cpp
new file mode 100644
index 00000000000..44aa7a5a18e
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/readability/RedundantDeclarationCheck.cpp
@@ -0,0 +1,71 @@
+//===--- RedundantDeclarationCheck.cpp - clang-tidy------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "RedundantDeclarationCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace readability {
+
+void RedundantDeclarationCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(namedDecl(anyOf(varDecl(), functionDecl())).bind("Decl"), this);
+}
+
+void RedundantDeclarationCheck::check(const MatchFinder::MatchResult &Result) {
+  const NamedDecl *D = Result.Nodes.getNodeAs<NamedDecl>("Decl");
+  const auto *Prev = D->getPreviousDecl();
+  if (!Prev)
+    return;
+  if (Prev->getLocation() == D->getLocation())
+    return;
+
+  const SourceManager &SM = *Result.SourceManager;
+
+  const bool DifferentHeaders =
+       !SM.isInMainFile(D->getLocation()) &&
+       !SM.isWrittenInSameFile(Prev->getLocation(), D->getLocation());
+
+  bool MultiVar = false;
+  if (const auto *VD = dyn_cast<VarDecl>(D)) {
+    if (VD->getPreviousDecl()->getStorageClass() == SC_Extern &&
+        VD->getStorageClass() != SC_Extern)
+      return;
+    // Is this a multivariable declaration?
+    for (const auto Other : VD->getDeclContext()->decls()) {
+      if (Other != D && Other->getLocStart() == VD->getLocStart()) {
+        MultiVar = true;
+        break;
+      }
+    }
+  } else {
+    const auto *FD = cast<FunctionDecl>(D);
+    if (FD->isThisDeclarationADefinition())
+      return;
+  }
+
+  SourceLocation EndLoc = Lexer::getLocForEndOfToken(
+      D->getSourceRange().getEnd(), 0, SM, Result.Context->getLangOpts());
+  {
+    auto Diag = diag(D->getLocation(), "redundant %0 declaration")
+                << D;
+    if (!MultiVar && !DifferentHeaders)
+      Diag << FixItHint::CreateRemoval(
+          SourceRange(D->getSourceRange().getBegin(), EndLoc));
+  }
+  diag(Prev->getLocation(), "previously declared here", DiagnosticIDs::Note);
+}
+
+} // namespace readability
+} // namespace tidy
+} // namespace clang