[clang-format] Fix a bug in formatting goto labels in macros (#92494)

Fixes #92300.

Author: owenca

clang/lib/Format/UnwrappedLineParser.cpp

@@ -1189,12 +1189,6 @@ void UnwrappedLineParser::parsePPDefine() {
     return;
   }
 
-  if (FormatTok->is(tok::identifier) &&
-      Tokens->peekNextToken()->is(tok::colon)) {
-    nextToken();
-    nextToken();
-  }
-
   // Errors during a preprocessor directive can only affect the layout of the
   // preprocessor directive, and thus we ignore them. An alternative approach
   // would be to use the same approach we use on the file level (no
@@ -1681,7 +1675,8 @@ void UnwrappedLineParser::parseStructuralElement(
     if (!Style.isJavaScript() && !Style.isVerilog() && !Style.isTableGen() &&
         Tokens->peekNextToken()->is(tok::colon) && !Line->MustBeDeclaration) {
       nextToken();
-      Line->Tokens.begin()->Tok->MustBreakBefore = true;
+      if (!Line->InMacroBody || CurrentLines->size() > 1)
+        Line->Tokens.begin()->Tok->MustBreakBefore = true;
       FormatTok->setFinalizedType(TT_GotoLabelColon);
       parseLabel(!Style.IndentGotoLabels);
       if (HasLabel)

clang/unittests/Format/FormatTest.cpp

@@ -3124,6 +3124,7 @@ TEST_F(FormatTest, FormatsLabels) {
                "    g();\n"
                "  }\n"
                "}");
+
   FormatStyle Style = getLLVMStyle();
   Style.IndentGotoLabels = false;
   verifyFormat("void f() {\n"
@@ -3163,6 +3164,13 @@ TEST_F(FormatTest, FormatsLabels) {
                "  }\n"
                "}",
                Style);
+
+  Style.ColumnLimit = 15;
+  verifyFormat("#define FOO   \\\n"
+               "label:        \\\n"
+               "  break;",
+               Style);
+
   // The opening brace may either be on the same unwrapped line as the colon or
   // on a separate one. The formatter should recognize both.
   Style = getLLVMStyle();

clang/unittests/Format/TokenAnnotatorTest.cpp

@@ -2579,15 +2579,28 @@ TEST_F(TokenAnnotatorTest, UnderstandsLabels) {
   auto Tokens = annotate("{ x: break; }");
   ASSERT_EQ(Tokens.size(), 7u) << Tokens;
   EXPECT_TOKEN(Tokens[2], tok::colon, TT_GotoLabelColon);
+
   Tokens = annotate("{ case x: break; }");
   ASSERT_EQ(Tokens.size(), 8u) << Tokens;
   EXPECT_TOKEN(Tokens[3], tok::colon, TT_CaseLabelColon);
+
   Tokens = annotate("{ x: { break; } }");
   ASSERT_EQ(Tokens.size(), 9u) << Tokens;
   EXPECT_TOKEN(Tokens[2], tok::colon, TT_GotoLabelColon);
+
   Tokens = annotate("{ case x: { break; } }");
   ASSERT_EQ(Tokens.size(), 10u) << Tokens;
   EXPECT_TOKEN(Tokens[3], tok::colon, TT_CaseLabelColon);
+
+  Tokens = annotate("#define FOO label:");
+  ASSERT_EQ(Tokens.size(), 6u) << Tokens;
+  EXPECT_TOKEN(Tokens[4], tok::colon, TT_GotoLabelColon);
+
+  Tokens = annotate("#define FOO \\\n"
+                    "label: \\\n"
+                    "  break;");
+  ASSERT_EQ(Tokens.size(), 8u) << Tokens;
+  EXPECT_TOKEN(Tokens[4], tok::colon, TT_GotoLabelColon);
 }
 
 TEST_F(TokenAnnotatorTest, UnderstandsNestedBlocks) {