[llvm] [clang] [clang-tools-extra] [clang-tidy] modernize-use-digit-separator issue #35414 (PR #76153)

[Piotr Zegar via llvm-commits]

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@@ -0,0 +1,39 @@
+//===--- UseDigitSeparatorCheck.h - clang-tidy ------------------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USEDIGITSEPARATORCHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USEDIGITSEPARATORCHECK_H
+
+#include "../ClangTidyCheck.h"
+
+namespace clang::tidy::modernize {
+
+/// The check that looks for long integral constants and inserts the digits
+/// separator (') appropriately. Groupings:
+///     - decimal integral constants, groups of 3 digits, e.g. int x = 1'000;
+///     - binary integral constants, groups of 4 digits, e.g. int x =
+///     0b0010'0011;
+///     - octal integral constants, groups of 3 digits, e.g. int x = 0377'777;
+///     - hexadecimal integral constants, groups of 4 digits, e.g. unsigned long
+///     x = 0xffff'0000;
+///     - floating-point constants, group into 3 digits on either side of the
+///     decimal point, e.g. float x = 3'456.001'25f;
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/modernize/use-digit-separator.html
+class UseDigitSeparatorCheck : public ClangTidyCheck {
+public:
+  UseDigitSeparatorCheck(StringRef Name, ClangTidyContext *Context)
+      : ClangTidyCheck(Name, Context) {}
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
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PiotrZSL wrote:

use TK_IgnoreUnlessSpelledInSource here to exclude implicit code, look into other checks to see how it's done.
also verify 

https://github.com/llvm/llvm-project/pull/76153