[clang-tools-extra] [clang-tidy] Add new check: `readability-redundant-typename` (PR #161574)

[Baranov Victor via cfe-commits]

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@@ -0,0 +1,71 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "RedundantTypenameCheck.h"
+#include "clang/AST/TypeLoc.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/Basic/Diagnostic.h"
+#include "clang/Sema/DeclSpec.h"
+
+using namespace clang::ast_matchers;
+using namespace clang::ast_matchers::internal;
+
+namespace clang::tidy::readability {
+
+void RedundantTypenameCheck::registerMatchers(MatchFinder *Finder) {
+  // NOLINTNEXTLINE(readability-identifier-naming)
+  const VariadicDynCastAllOfMatcher<TypeLoc, TypedefTypeLoc> typedefTypeLoc;
+  Finder->addMatcher(typedefTypeLoc().bind("typeloc"), this);
+
+  if (!getLangOpts().CPlusPlus20)
+    return;
+
+  // NOLINTBEGIN(readability-identifier-naming)
+  const VariadicDynCastAllOfMatcher<Stmt, CXXNamedCastExpr> cxxNamedCastExpr;
+  const auto inImplicitTypenameContext = [&] {
+    return anyOf(hasParent(typedefNameDecl()),
+                 hasParent(templateTypeParmDecl()),
+                 hasParent(nonTypeTemplateParmDecl()),
+                 hasParent(cxxNamedCastExpr()), hasParent(cxxNewExpr()),
+                 hasParent(friendDecl()), hasParent(fieldDecl()),
+                 hasParent(parmVarDecl(hasParent(expr(requiresExpr())))),
+                 hasParent(parmVarDecl(hasParent(typeLoc(hasParent(namedDecl(
+                     anyOf(cxxMethodDecl(), hasParent(friendDecl()),
+                           functionDecl(has(nestedNameSpecifier()))))))))),
+                 // Match return types.
+                 hasParent(functionDecl(unless(cxxConversionDecl()))));
+  };
+  // NOLINTEND(readability-identifier-naming)
+  Finder->addMatcher(typeLoc(inImplicitTypenameContext()).bind("typeloc"),
+                     this);
+}
+
+void RedundantTypenameCheck::check(const MatchFinder::MatchResult &Result) {
+  const SourceLocation TypenameKeywordLoc = [&] {
+    if (const auto *TTL = Result.Nodes.getNodeAs<TypedefTypeLoc>("typeloc"))
+      return TTL->getElaboratedKeywordLoc();
+
+    TypeLoc InnermostTypeLoc = *Result.Nodes.getNodeAs<TypeLoc>("typeloc");
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vbvictor wrote:

Could we make different matched node names, e.g. "typedefTypeloc" and "typeloc". Same names for different matchers confused me a little.

https://github.com/llvm/llvm-project/pull/161574