Index: clang/lib/Format/TokenAnnotator.cpp
===================================================================
--- clang/lib/Format/TokenAnnotator.cpp
+++ clang/lib/Format/TokenAnnotator.cpp
@@ -421,8 +421,8 @@
       if (CurrentToken->isOneOf(tok::r_square, tok::r_brace))
         return false;
 
-      if (CurrentToken->is(tok::l_brace))
-        OpeningParen.setType(TT_Unknown); // Not TT_ObjCBlockLParen
+      if (CurrentToken->is(tok::l_brace) && OpeningParen.is(TT_ObjCBlockLParen))
+        OpeningParen.setType(TT_Unknown);
       if (CurrentToken->is(tok::comma) && CurrentToken->Next &&
           !CurrentToken->Next->HasUnescapedNewline &&
           !CurrentToken->Next->isTrailingComment())
Index: clang/unittests/Format/FormatTest.cpp
===================================================================
--- clang/unittests/Format/FormatTest.cpp
+++ clang/unittests/Format/FormatTest.cpp
@@ -23891,9 +23891,9 @@
   verifyFormat(
       "template <typename T> concept C = decltype([]() -> std::true_type {\n"
       "                                    return {};\n"
-      "                                  }())::value\n"
-      "                                  && requires(T t) { t.bar(); } &&\n"
-      "                                  sizeof(T) <= 8;",
+      "                                  }())::value &&\n"
+      "                                  requires(T t) { t.bar(); } && "
+      "sizeof(T) <= 8;",
       Style);
 
   verifyFormat("template <typename T> concept Semiregular =\n"
Index: clang/unittests/Format/TokenAnnotatorTest.cpp
===================================================================
--- clang/unittests/Format/TokenAnnotatorTest.cpp
+++ clang/unittests/Format/TokenAnnotatorTest.cpp
@@ -331,6 +331,14 @@
   EXPECT_TOKEN(Tokens[13], tok::l_brace, TT_RequiresExpressionLBrace);
   EXPECT_TOKEN(Tokens[29], tok::kw_requires,
                TT_RequiresClauseInARequiresExpression);
+
+  // Invalid Code, but we don't want to crash. See http://llvm.org/PR54350.
+  Tokens = annotate("bool r10 = requires (struct new_struct { int x; } s) { "
+                    "requires true; };");
+  ASSERT_EQ(Tokens.size(), 21u) << Tokens;
+  EXPECT_TOKEN(Tokens[3], tok::kw_requires, TT_RequiresExpression);
+  EXPECT_TOKEN(Tokens[4], tok::l_paren, TT_RequiresExpressionLParen);
+  EXPECT_TOKEN(Tokens[14], tok::l_brace, TT_RequiresExpressionLBrace);
 }
 
 TEST_F(TokenAnnotatorTest, RequiresDoesNotChangeParsingOfTheRest) {