1 files changed, 109 insertions, 0 deletions
diff --git a/clang-tools-extra/clang-tidy/readability/ShrinkToFitCheck.cpp b/clang-tools-extra/clang-tidy/readability/ShrinkToFitCheck.cpp
new file mode 100644
index 00000000000..1c9e0a8117a
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+++ b/clang-tools-extra/clang-tidy/readability/ShrinkToFitCheck.cpp
@@ -0,0 +1,109 @@
+//===--- ShrinkToFitCheck.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 "ShrinkToFitCheck.h"
+
+#include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/StringSet.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+
+namespace {
+bool isShrinkableContainer(llvm::StringRef ClassName) {
+  static const llvm::StringSet<> Shrinkables = [] {
+    llvm::StringSet<> RetVal;
+    RetVal.insert("std::deque");
+    RetVal.insert("std::basic_string");
+    RetVal.insert("std::vector");
+    return RetVal;
+  }();
+  return Shrinkables.find(ClassName) != Shrinkables.end();
+}
+}
+
+namespace clang {
+namespace ast_matchers {
+AST_MATCHER(NamedDecl, stlShrinkableContainer) {
+  return isShrinkableContainer(Node.getQualifiedNameAsString());
+}
+} // namespace ast_matchesr
+} // namespace clang
+
+namespace clang {
+namespace tidy {
+
+void ShrinkToFitCheck::registerMatchers(MatchFinder *Finder) {
+  // Swap as a function need not to be considered, because rvalue can not
+  // be bound to a non-const reference.
+  const auto ShrinkableAsMember =
+      memberExpr(member(valueDecl().bind("ContainerDecl")));
+  const auto ShrinkableAsDecl =
+      declRefExpr(hasDeclaration(valueDecl().bind("ContainerDecl")));
+  const auto CopyCtorCall = constructExpr(
+      hasArgument(0, anyOf(ShrinkableAsMember, ShrinkableAsDecl,
+                           unaryOperator(has(ShrinkableAsMember)),
+                           unaryOperator(has(ShrinkableAsDecl)))));
+  const auto SwapParam = expr(anyOf(
+      memberExpr(member(equalsBoundNode("ContainerDecl"))),
+      declRefExpr(hasDeclaration(equalsBoundNode("ContainerDecl"))),
+      unaryOperator(has(memberExpr(member(equalsBoundNode("ContainerDecl"))))),
+      unaryOperator(
+          has(declRefExpr(hasDeclaration(equalsBoundNode("ContainerDecl")))))));
+
+  Finder->addMatcher(
+      memberCallExpr(on(hasType(namedDecl(stlShrinkableContainer()))),
+                     callee(methodDecl(hasName("swap"))),
+                     has(memberExpr(hasDescendant(CopyCtorCall))),
+                     hasArgument(0, SwapParam.bind("ContainerToShrink")),
+                     unless(isInTemplateInstantiation()))
+          .bind("CopyAndSwapTrick"),
+      this);
+}
+
+void ShrinkToFitCheck::check(const MatchFinder::MatchResult &Result) {
+  const LangOptions &Opts = Result.Context->getLangOpts();
+
+  if (!Opts.CPlusPlus11)
+    return;
+
+  const auto *MemberCall =
+      Result.Nodes.getNodeAs<CXXMemberCallExpr>("CopyAndSwapTrick");
+  const auto *Container = Result.Nodes.getNodeAs<Expr>("ContainerToShrink");
+  FixItHint Hint;
+
+  if (!MemberCall->getLocStart().isMacroID()) {
+    std::string ReplacementText;
+    if (const auto *UnaryOp = llvm::dyn_cast<UnaryOperator>(Container)) {
+      ReplacementText =
+          Lexer::getSourceText(CharSourceRange::getTokenRange(
+                                   UnaryOp->getSubExpr()->getSourceRange()),
+                               *Result.SourceManager, Opts);
+      ReplacementText += "->shrink_to_fit()";
+    } else {
+      ReplacementText = Lexer::getSourceText(
+          CharSourceRange::getTokenRange(Container->getSourceRange()),
+          *Result.SourceManager, Opts);
+      ReplacementText += ".shrink_to_fit()";
+    }
+
+    Hint = FixItHint::CreateReplacement(MemberCall->getSourceRange(),
+                                        ReplacementText);
+  }
+
+  diag(MemberCall->getLocStart(), "the shrink_to_fit method should be used "
+                                  "to reduce the capacity of a shrinkable "
+                                  "container")
+      << Hint;
+}
+
+} // namespace tidy
+} // namespace clang