[clang-format] Handle C++ Core Guidelines suppression tags (#86458)

Fixes #86451.

Author: owenca

clang/lib/Format/TokenAnnotator.cpp

@@ -4827,6 +4827,10 @@ bool TokenAnnotator::spaceRequiredBefore(const AnnotatedLine &Line,
         Right.is(TT_TemplateOpener)) {
       return true;
     }
+    if (Left.is(tok::identifier) && Right.is(tok::numeric_constant) &&
+        Right.TokenText[0] == '.') {
+      return false;
+    }
   } else if (Style.isProto()) {
     if (Right.is(tok::period) &&
         Left.isOneOf(Keywords.kw_optional, Keywords.kw_required,

clang/unittests/Format/FormatTest.cpp

@@ -12075,6 +12075,7 @@ TEST_F(FormatTest, UnderstandsSquareAttributes) {
   verifyFormat("SomeType s [[gnu::unused]] (InitValue);");
   verifyFormat("SomeType s [[using gnu: unused]] (InitValue);");
   verifyFormat("[[gsl::suppress(\"clang-tidy-check-name\")]] void f() {}");
+  verifyFormat("[[suppress(type.5)]] int uninitialized_on_purpose;");
   verifyFormat("void f() [[deprecated(\"so sorry\")]];");
   verifyFormat("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\n"
                "    [[unused]] aaaaaaaaaaaaaaaaaaaaaaa(int i);");