================
@@ -0,0 +1,94 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "RedundantConstCheck.h"
+#include "../utils/LexerUtils.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include <optional>
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::readability {
+
+static std::optional<Token>
+findConstToRemove(const VarDecl *VD, const MatchFinder::MatchResult &Result) {
+ const SourceManager &SM = *Result.SourceManager;
+
+ const SourceLocation NameBeginLoc = VD->getQualifier()
+ ? VD->getQualifierLoc().getBeginLoc()
+ : VD->getLocation();
+
+ const bool IsPointer = VD->getType()->isPointerType() ||
+ VD->getType()->isNullPtrType() ||
+ VD->getType()->isMemberPointerType();
+
+ // If the 'findPreviousTokenKind' below fails,
+ // we know it is a pointer but cannot find the start token.
+ // This can happen when either type is aliased or `auto` was used.
+ // e.g: constexpr const auto const str = "hello";
+ // In cases like this, Clang already warns about the use of const
+ // as duplicate, so we can safely ignore these cases.
+ const SourceLocation ConstSearchStartLoc =
+ !IsPointer
+ ? VD->getBeginLoc()
+ : utils::lexer::findPreviousTokenKind(
+ NameBeginLoc, SM, Result.Context->getLangOpts(), tok::star);
+
+ if (ConstSearchStartLoc.isInvalid())
+ return std::nullopt;
+
+ const CharSourceRange FileRange = Lexer::makeFileCharRange(
+ CharSourceRange::getCharRange(ConstSearchStartLoc, NameBeginLoc), SM,
+ Result.Context->getLangOpts());
+
+ if (!FileRange.isValid())
+ return std::nullopt;
+
+ return utils::lexer::getQualifyingToken(tok::kw_const, FileRange,
+ *Result.Context, SM);
+}
+
+RedundantConstCheck::RedundantConstCheck(StringRef Name,
+ ClangTidyContext *Context)
+ : ClangTidyCheck(Name, Context) {}
+
+void RedundantConstCheck::registerMatchers(MatchFinder *Finder) {
+ Finder->addMatcher(
+ varDecl(isConstexpr(),
unless(hasType(referenceType()))).bind("var_decl"),
+ this);
+}
+
+void RedundantConstCheck::check(const MatchFinder::MatchResult &Result) {
+ const auto *VD = Result.Nodes.getNodeAs<VarDecl>("var_decl");
+
+ // Since we cannot tell the difference between `constexpr const` and
+ // `constexpr` from the AST only, if we cannot find the actual `const` token,
+ // we cannot do anything
+ const std::optional<Token> Tok = findConstToRemove(VD, Result);
+ if (!Tok)
+ return;
+
+ const auto ConstRange =
+ CharSourceRange::getCharRange(Tok->getLocation(), Tok->getEndLoc());
+ diag(Tok->getLocation(),
+ "redundant use of `const`; `constexpr` already implies `const`.")
+ << ConstRange << FixItHint::CreateRemoval(ConstRange);
----------------
localspook wrote:
Since you're removing a single token, you shouldn't need to construct the
removal range manually, you can just remove the `SourceLoc`. Also, is `<<
ConstRange` necessary? I would imagine the `const` token will already be
underlined, because it's being removed.
```suggestion
diag(Tok->getLocation(),
"redundant use of `const`; `constexpr` already implies `const`.")
<< FixItHint::CreateRemoval(Tok->getLocation());
```
https://github.com/llvm/llvm-project/pull/189733
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