release/21.x: [clang-format] Fix a crash on BAS_BlockIndent (#164047)

clang/lib/Format/ContinuationIndenter.cpp

@@ -411,7 +411,7 @@ bool ContinuationIndenter::mustBreak(const LineState &State) {
   }
   if (CurrentState.BreakBeforeClosingBrace &&
       (Current.closesBlockOrBlockTypeList(Style) ||
-       (Current.is(tok::r_brace) &&
+       (Current.is(tok::r_brace) && Current.MatchingParen &&
         Current.isBlockIndentedInitRBrace(Style)))) {
     return true;
   }

clang/lib/Format/FormatToken.cpp

@@ -53,12 +53,13 @@ bool FormatToken::isTypeOrIdentifier(const LangOptions &LangOpts) const {
 
 bool FormatToken::isBlockIndentedInitRBrace(const FormatStyle &Style) const {
   assert(is(tok::r_brace));
+  assert(MatchingParen);
+  assert(MatchingParen->is(tok::l_brace));
   if (!Style.Cpp11BracedListStyle ||
       Style.AlignAfterOpenBracket != FormatStyle::BAS_BlockIndent) {
     return false;
   }
   const auto *LBrace = MatchingParen;
-  assert(LBrace && LBrace->is(tok::l_brace));
   if (LBrace->is(BK_BracedInit))
     return true;
   if (LBrace->Previous && LBrace->Previous->is(tok::equal))

clang/unittests/Format/FormatTest.cpp

@@ -9727,6 +9727,19 @@ TEST_F(FormatTest, ParenthesesAndOperandAlignment) {
                Style);
 }
 
+TEST_F(FormatTest, BlockIndentAndNamespace) {
+  auto Style = getLLVMStyleWithColumns(120);
+  Style.AllowShortNamespacesOnASingleLine = true;
+  Style.AlignAfterOpenBracket = FormatStyle::BAS_BlockIndent;
+
+  verifyNoCrash(
+      "namespace {\n"
+      "void xxxxxxxxxxxxxxxxxxxxx(nnnnn::TTTTTTTTTTTTT const *mmmm,\n"
+      "                           YYYYYYYYYYYYYYYYY &yyyyyyyyyyyyyy);\n"
+      "} //",
+      Style);
+}
+
 TEST_F(FormatTest, BreaksConditionalExpressions) {
   verifyFormat(
       "aaaa(aaaaaaaaaaaaaaaaaaaa, aaaaaaaaaaaaaaaaaaaaaaaaaa\n"