[clang-tools-extra] [clang-tidy] Add readability-use-builtin-literals check (PR #76065)

[Piotr Zegar via cfe-commits]

================
@@ -0,0 +1,161 @@
+//===--- UseBuiltinLiteralsCheck.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 "UseBuiltinLiteralsCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/StringRef.h"
+#include <optional>
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::readability {
+
+namespace {
+
+using RuleOnStd = bool (*)(const LangStandard &LS);
+
+struct Replacement {
+  Replacement(StringRef Seq, const RuleOnStd Std = nullptr)
+      : Seq(Seq), Std(Std) {}
+  bool operator()(const LangOptions &LO) const {
+    return Std ? Std(LangStandard::getLangStandardForKind(LO.LangStd)) : true;
+  }
+  StringRef Seq;
+  RuleOnStd Std;
+};
+
+} // namespace
+
+static const llvm::Regex CharRegex("^(u8|u|U|L)?");
+static const llvm::StringMap<Replacement> CharPrefix({
+    {"char", {""}},
+    {"char8_t", {"u8"}},
+    {"char16_t", {"u"}},
+    {"char32_t", {"U"}},
+    {"wchar_t", {"L"}},
+});
+
+static const llvm::Regex
+    IntRegex("(([uU]?[lL]{0,2})|([lL]{0,2}[uU]?)|([uU]?[zZ]?)|([zZ]?[uU]?))?$");
+static const llvm::StringMap<Replacement> IntSuffix({
+    {"int", {""}},
+    {"unsigned int", {"u"}},
+    {"long", {"L"}},
+    {"unsigned long", {"uL"}},
+    {"long long", {"LL"}},
+    {"unsigned long long", {"uLL"}},
+    {"size_t", {"uz", [](const auto &LS) { return LS.isCPlusPlus23(); }}},
+    {"std::size_t", {"uz", [](const auto &LS) { return LS.isCPlusPlus23(); }}},
+});
+
+static const llvm::Regex FloatRegex(
+    "([fF]|[lL]|([fF]16)|([fF]32)|([fF]64)|([fF]128)|((bf|BF)16))?$");
+static const llvm::StringMap<Replacement> FloatSuffix({
+    {"double", {""}},
+    {"float", {"f"}},
+    {"long double", {"L"}},
+    {"std::float16_t", {"f16"}},
+    {"std::float32_t", {"f32"}},
+    {"std::float64_t", {"f64"}},
+    {"std::float128_t", {"f128"}},
+    {"std::bfloat16_t", {"bf16"}},
+    {"float16_t", {"f16"}},
+    {"float32_t", {"f32"}},
+    {"float64_t", {"f64"}},
+    {"float128_t", {"f128"}},
+    {"bfloat16_t", {"bf16"}},
+});
+
+void UseBuiltinLiteralsCheck::registerMatchers(MatchFinder *Finder) {
+  static const auto Literal = has(ignoringParenImpCasts(
+      expr(anyOf(characterLiteral().bind("char"), integerLiteral().bind("int"),
+                 floatLiteral().bind("float")))
+          .bind("lit")));
+  Finder->addMatcher(
+      traverse(TK_IgnoreUnlessSpelledInSource,
+               explicitCastExpr(anyOf(Literal, has(initListExpr(Literal))))
+                   .bind("expr")),
+      this);
+}
+
+static StringRef getRawStringRef(const SourceRange &Range,
+                                 const SourceManager &Sources,
+                                 const LangOptions &LangOpts) {
+  CharSourceRange TextRange = Lexer::getAsCharRange(Range, Sources, LangOpts);
+  return Lexer::getSourceText(TextRange, Sources, LangOpts);
+}
+
+void UseBuiltinLiteralsCheck::check(const MatchFinder::MatchResult &Result) {
+
+  const auto &SM = *Result.SourceManager;
+  const auto &Nodes = Result.Nodes;
+
+  const auto *MatchedCast = Nodes.getNodeAs<ExplicitCastExpr>("expr");
+  const auto *Lit = Nodes.getNodeAs<Expr>("lit");
+  assert(MatchedCast && Lit);
+
+  StringRef LitText = getRawStringRef(Lit->getExprLoc(), SM, getLangOpts());
+  std::string CastType = MatchedCast->getTypeAsWritten().getAsString();
+  std::string Fix; // Replacement string for the fix-it hint.
+  std::optional<StringRef> Seq; // Literal sequence, prefix or suffix.
+
+  if (const auto *CharLit = Nodes.getNodeAs<CharacterLiteral>("char");
+      CharLit && CharPrefix.contains(CastType)) {
+    if (const Replacement &Rep = CharPrefix.at(CastType); Rep(getLangOpts())) {
+
+      Seq = Rep.Seq;
+      if (!CharLit->getLocation().isMacroID()) {
+        Fix.append(Rep.Seq);
+        Fix.append(CharRegex.sub("", LitText.str()));
+      }
+    }
+  } else if (const auto *IntLit = Nodes.getNodeAs<IntegerLiteral>("int");
+             IntLit && IntSuffix.contains(CastType)) {
+    if (const Replacement &Rep = IntSuffix.at(CastType); Rep(getLangOpts())) {
+
+      Seq = Rep.Seq;
+      if (!IntLit->getLocation().isMacroID()) {
+        Fix.append(IntRegex.sub("", LitText.str()));
+        Fix.append(Rep.Seq);
+      }
+    }
+  } else if (const auto *FloatLit = Nodes.getNodeAs<FloatingLiteral>("float");
+             FloatLit && FloatSuffix.contains(CastType)) {
+    if (const Replacement &Rep = FloatSuffix.at(CastType); Rep(getLangOpts())) {
+
+      Seq = Rep.Seq;
+      if (!FloatLit->getLocation().isMacroID()) {
+        Fix.append(FloatRegex.sub("", LitText.str()));
+        Fix.append(Rep.Seq);
+      }
+    }
+  }
+
+  const TypeLoc CastTypeLoc = MatchedCast->getTypeInfoAsWritten()->getTypeLoc();
+
+  if (!Fix.empty() && !CastTypeLoc.getBeginLoc().isMacroID()) {
+
+    // Recommend fix-it when no part of the explicit cast comes from a macro.
+    diag(MatchedCast->getExprLoc(),
+         "use built-in literal instead of explicit cast")
+        << FixItHint::CreateReplacement(MatchedCast->getSourceRange(), Fix);
+  } else if (Seq && MatchedCast->getExprLoc().isMacroID()) {
----------------
PiotrZSL wrote:

use early exit in line 140, if we do not have Seq then we do not have Fix also. In such case no point to check this cast.

https://github.com/llvm/llvm-project/pull/76065