[clang-tools-extra] [Clang-Tidy] Add google-runtime-float Clang-Tidy check (PR #156763)

[Baranov Victor via cfe-commits]

================
@@ -0,0 +1,78 @@
+//===----------------------------------------------------------------------===//
+//
+// 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 "FloatTypesCheck.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+
+namespace clang {
+
+using namespace ast_matchers;
+
+namespace {
+
+AST_MATCHER(TypeLoc, isTypeLocValidAndNotInMacro) {
+  const SourceLocation Loc = Node.getBeginLoc();
+  return Loc.isValid() && !Loc.isMacroID();
+}
+
+AST_MATCHER(FloatingLiteral, isFLValidAndNotInMacro) {
+  const SourceLocation Loc = Node.getBeginLoc();
+  return Loc.isValid() && !Loc.isMacroID();
+}
+
+AST_MATCHER(TypeLoc, isLongDoubleType) {
+  TypeLoc TL = Node;
+  if (const auto QualLoc = Node.getAs<QualifiedTypeLoc>())
+    TL = QualLoc.getUnqualifiedLoc();
+
+  const auto BuiltinLoc = TL.getAs<BuiltinTypeLoc>();
+  if (!BuiltinLoc)
+    return false;
+
+  return BuiltinLoc.getTypePtr()->getKind() == BuiltinType::LongDouble;
+}
+
+AST_MATCHER(FloatingLiteral, isLongDoubleLiteral) {
+  if (const auto *BT = dyn_cast<BuiltinType>(Node.getType().getTypePtr()))
----------------
vbvictor wrote:

```suggestion
  if (const auto *BT = dyn_cast_if_present<BuiltinType>(Node.getType().getTypePtr()))
```
To propagate `null`, see https://llvm.org/docs/ProgrammersManual.html#the-isa-cast-and-dyn-cast-templates.

https://github.com/llvm/llvm-project/pull/156763