[clang-format] Fix SplitEmptyRecord affecting SplitEmptyFunction.

[curdeius]

Summary

Fixes https://github.com/llvm/llvm-project/issues/50051.

Given the style:

BraceWrapping
  AfterFunction: true
 SplitEmptyFunction: true
 SplitEmptyRecord: false
...

The code that should be like:

void f(int aaaaaaaaaaaaaaaaaaaaaaaaaaaa,
       int bbbbbbbbbbbbbbbbbbbbbbbb)
{
}

gets the braces merged together:

void f(int aaaaaaaaaaaaaaaaaaaaaaaaaaaa,
       int bbbbbbbbbbbbbbbbbbbbbbbb)
{}

[MyDeveloperDay]

LGTM, less the clang-format oddities

clang/lib/Format/UnwrappedLineFormatter.cpp

if (Style.BraceWrapping.SplitEmptyRecord &&
               return 0;
           }
         }
       }
     }
 
     // Try to merge a block with left brace wrapped that wasn't yet covered
     if (TheLine->Last->is(tok::l_brace)) {
-      return !Style.BraceWrapping.AfterFunction ||
+      bool ShouldMerge = false;
+      if (TheLine->First->isOneOf(tok::kw_class, tok::kw_struct)) {
+        ShouldMerge = !Style.BraceWrapping.AfterClass ||
                       (I[1]->First->is(tok::r_brace) &&
-                      !Style.BraceWrapping.SplitEmptyRecord)
-                 ? tryMergeSimpleBlock(I, E, Limit)
-                 : 0;
+                       !Style.BraceWrapping.SplitEmptyRecord);
+      } else {
+        ShouldMerge = !Style.BraceWrapping.AfterFunction ||
+                      (I[1]->First->is(tok::r_brace) &&
+                       !Style.BraceWrapping.SplitEmptyFunction);
+      }
+      return ShouldMerge ? tryMergeSimpleBlock(I, E, Limit) : 0;
     }
     // Try to merge a function block with left brace wrapped
     if (I[1]->First->is(TT_FunctionLBrace) &&
         Style.BraceWrapping.AfterFunction) {
       if (I[1]->Last->is(TT_LineComment))
         return 0;
 
       // Check for Limit <= 2 to account for the " {".

clang/unittests/Format/FormatTest.cpp

verifyFormat("int aaaaaaaaaaaaaa(int bbbbbbbbbbbbbb)\n"
                "{}",
                Style);
   verifyFormat("int aaaaaaaaaaaaaa(int bbbbbbbbbbbbbb)\n"
                "{\n"
                "  return 0;\n"
                "}",
                Style);
 }
+
+TEST_F(FormatTest, SplitEmptyFunctionButNotRecord) {
+  FormatStyle Style = getLLVMStyle();
+  Style.AllowShortFunctionsOnASingleLine = FormatStyle::SFS_None;
+  Style.BreakBeforeBraces = FormatStyle::BS_Custom;
+  Style.BraceWrapping.AfterFunction = true;
+  Style.BraceWrapping.SplitEmptyFunction = true;
+  Style.BraceWrapping.SplitEmptyRecord = false;
+  Style.ColumnLimit = 40;
+
+  verifyFormat("class C {};", Style);
+  verifyFormat("struct C {};", Style);
+  verifyFormat("void f(int aaaaaaaaaaaaaaaaaaaaaaaaaaaa,\n"
+               "       int bbbbbbbbbbbbbbbbbbbbbbbb)\n"
+               "{\n"
+               "}",
+               Style);
+  verifyFormat("class C {\n"
+               "  C()\n"
+               "      : aaaaaaaaaaaaaaaaaaaaaaaaaaaa(),\n"
+               "        bbbbbbbbbbbbbbbbbbb()\n"
+               "  {\n"
+               "  }\n"
+               "  void\n"
+               "  m(int aaaaaaaaaaaaaaaaaaaaaaaaaaaa,\n"
+               "    int bbbbbbbbbbbbbbbbbbbbbbbb)\n"
+               "  {\n"
+               "  }\n"
+               "};",
+               Style);
+}
+
 TEST_F(FormatTest, KeepShortFunctionAfterPPElse) {
   FormatStyle Style = getLLVMStyle();
   Style.AllowShortFunctionsOnASingleLine = FormatStyle::SFS_All;
   verifyFormat("#ifdef A\n"
                "int f() {}\n"
                "#else\n"
                "int g() {}\n"
                "#endif",