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diff --git a/clang-tidy/abseil/DurationUnnecessaryConversionCheck.cpp b/clang-tidy/abseil/DurationUnnecessaryConversionCheck.cpp
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+++ b/clang-tidy/abseil/DurationUnnecessaryConversionCheck.cpp
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+//===--- DurationUnnecessaryConversionCheck.cpp - clang-tidy
+//-----------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "DurationUnnecessaryConversionCheck.h"
+#include "DurationRewriter.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Tooling/FixIt.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace abseil {
+
+void DurationUnnecessaryConversionCheck::registerMatchers(MatchFinder *Finder) {
+  for (const auto &Scale : {"Hours", "Minutes", "Seconds", "Milliseconds",
+                            "Microseconds", "Nanoseconds"}) {
+    std::string DurationFactory = (llvm::Twine("::absl::") + Scale).str();
+    std::string FloatConversion =
+        (llvm::Twine("::absl::ToDouble") + Scale).str();
+    std::string IntegerConversion =
+        (llvm::Twine("::absl::ToInt64") + Scale).str();
+
+    // Matcher which matches the current scale's factory with a `1` argument,
+    // e.g. `absl::Seconds(1)`.
+    auto factory_matcher = cxxConstructExpr(hasArgument(
+        0,
+        callExpr(callee(functionDecl(hasName(DurationFactory))),
+                 hasArgument(0, ignoringImpCasts(integerLiteral(equals(1)))))));
+
+    // Matcher which matches either inverse function and binds its argument,
+    // e.g. `absl::ToDoubleSeconds(dur)`.
+    auto inverse_function_matcher = callExpr(
+        callee(functionDecl(hasAnyName(FloatConversion, IntegerConversion))),
+        hasArgument(0, expr().bind("arg")));
+
+    // Matcher which matches a duration divided by the factory_matcher above,
+    // e.g. `dur / absl::Seconds(1)`.
+    auto division_operator_matcher = cxxOperatorCallExpr(
+        hasOverloadedOperatorName("/"), hasArgument(0, expr().bind("arg")),
+        hasArgument(1, factory_matcher));
+
+    // Matcher which matches a duration argument to `FDivDuration`,
+    // e.g. `absl::FDivDuration(dur, absl::Seconds(1))`
+    auto fdiv_matcher = callExpr(
+        callee(functionDecl(hasName("::absl::FDivDuration"))),
+        hasArgument(0, expr().bind("arg")), hasArgument(1, factory_matcher));
+
+    Finder->addMatcher(
+        callExpr(callee(functionDecl(hasName(DurationFactory))),
+                 hasArgument(0, anyOf(inverse_function_matcher,
+                                      division_operator_matcher, fdiv_matcher)))
+            .bind("call"),
+        this);
+  }
+}
+
+void DurationUnnecessaryConversionCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto *OuterCall = Result.Nodes.getNodeAs<Expr>("call");
+  const auto *Arg = Result.Nodes.getNodeAs<Expr>("arg");
+
+  if (isInMacro(Result, OuterCall))
+    return;
+
+  diag(OuterCall->getBeginLoc(),
+       "remove unnecessary absl::Duration conversions")
+      << FixItHint::CreateReplacement(
+             OuterCall->getSourceRange(),
+             tooling::fixit::getText(*Arg, *Result.Context));
+}
+
+} // namespace abseil
+} // namespace tidy
+} // namespace clang