[clang] [clang-format] Add an option to format integer and float literal case (PR #151590)

[via cfe-commits]

================
@@ -0,0 +1,347 @@
+//===--- NumericLiteralCaseFixer.cpp -----------------------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file implements NumericLiteralCaseFixer that standardizes character
+/// case within numeric literal constants.
+///
+//===----------------------------------------------------------------------===//
+
+#include "NumericLiteralCaseFixer.h"
+
+#include "llvm/ADT/StringExtras.h"
+
+#include <algorithm>
+
+namespace clang {
+namespace format {
+
+using CharTransformFn = char (*)(char C);
+namespace {
+
+/// @brief Collection of std::transform predicates for each part of a numeric
+/// literal
+struct FormatParameters {
+  FormatParameters(FormatStyle::LanguageKind Language,
+                   const FormatStyle::NumericLiteralCaseStyle &CaseStyle);
+
+  CharTransformFn Prefix;
+  CharTransformFn HexDigit;
+  CharTransformFn FloatExponentSeparator;
+  CharTransformFn Suffix;
+
+  char Separator;
+};
+
+/// @brief Parse a single numeric constant from text into ranges that are
+/// appropriate for applying NumericLiteralCaseStyle rules.
+class QuickNumericalConstantParser {
+public:
+  QuickNumericalConstantParser(const StringRef &IntegerLiteral,
+                               const FormatParameters &Transforms);
+
+  /// @brief Reformats the numeric constant if needed.
+  /// Calling this method invalidates the object's state.
+  /// @return std::nullopt if no reformatting is required. std::optional<>
+  /// containing the reformatted string otherwise.
+  std::optional<std::string> formatIfNeeded() &&;
+
+private:
+  const StringRef &IntegerLiteral;
+  const FormatParameters &Transforms;
+
+  std::string Formatted;
+
+  std::string::iterator PrefixBegin;
+  std::string::iterator PrefixEnd;
+  std::string::iterator HexDigitBegin;
+  std::string::iterator HexDigitEnd;
+  std::string::iterator FloatExponentSeparatorBegin;
+  std::string::iterator FloatExponentSeparatorEnd;
+  std::string::iterator SuffixBegin;
+  std::string::iterator SuffixEnd;
+
+  void parse();
+  void applyFormatting();
+};
+
+} // namespace
+
+static char noOpTransform(char C) { return C; }
+
+static CharTransformFn getTransform(int8_t config_value) {
+  switch (config_value) {
+  case FormatStyle::NLCS_Always:
+    return llvm::toUpper;
+  case FormatStyle::NLCS_Never:
+    return llvm::toLower;
+  case FormatStyle::NLCS_Leave:
+  default:
+    return noOpTransform;
+  }
+}
+
+/// @brief Test if Suffix matches a C++ literal reserved by the library.
+/// Matches against all suffixes reserved in the C++23 standard
+static bool matchesReservedSuffix(StringRef Suffix) {
+  static const std::array<StringRef, 11> SortedReservedSuffixes = {
+      "d", "h", "i", "if", "il", "min", "ms", "ns", "s", "us", "y"};
+
----------------
owenca wrote:

I'd stick with `assert`, which is turned off in Release build. Also, LLVM codebase is still at C++17.

https://github.com/llvm/llvm-project/pull/151590