Revert "[clang-format] Link the braces of a block in UnwrappedLineParser"

[owenpan]

Summary

But keep the added test case and also add another test case.

Fixes https://github.com/llvm/llvm-project/issues/59417.

This reverts commit e33243c950ac.

clang/lib/Format/UnwrappedLineParser.cpp

FormatToken *UnwrappedLineParser::parseBlock(
 
   if (MacroBlock ? !FormatTok->is(TT_MacroBlockEnd)
                  : !FormatTok->is(tok::r_brace)) {
     Line->Level = InitialLevel;
     FormatTok->setBlockKind(BK_Block);
     return IfLBrace;
   }
 
-  Tok->MatchingParen = FormatTok;
-  FormatTok->MatchingParen = Tok;
-
   const bool IsFunctionRBrace =
       FormatTok->is(tok::r_brace) && Tok->is(TT_FunctionLBrace);
 
   auto RemoveBraces = [=]() mutable {
     if (!SimpleBlock)
       return false;
     assert(Tok->isOneOf(TT_ControlStatementLBrace, TT_ElseLBrace));
     assert(FormatTok->is(tok::r_brace));
if (Tok->is(TT_ElseLBrace))
       return true;
     if (WrappedOpeningBrace) {
       assert(Index > 0);
       --Index; // The line above the wrapped l_brace.
       Tok = nullptr;
     }
     return mightFitOnOneLine((*CurrentLines)[Index], Tok);
   };
-  Tok->Optional = RemoveBraces();
+  if (RemoveBraces()) {
+    Tok->MatchingParen = FormatTok;
+    FormatTok->MatchingParen = Tok;
+  }
 
   size_t PPEndHash = computePPHash();
 
   // Munch the closing brace.
   nextToken(/*LevelDifference=*/-AddLevels);
 
   // When this is a function block and there is an unnecessary semicolon
   // afterwards then mark it as optional (so the RemoveSemi pass can get rid of
static void markOptionalBraces(FormatToken *LeftBrace) {
   FormatToken *RightBrace = LeftBrace->MatchingParen;
   if (!RightBrace) {
     assert(!LeftBrace->Optional);
     return;
   }
 
   assert(RightBrace->is(tok::r_brace));
   assert(RightBrace->MatchingParen == LeftBrace);
+  assert(LeftBrace->Optional == RightBrace->Optional);
 
-  RightBrace->Optional = LeftBrace->Optional;
-}
-
-static void resetOptional(FormatToken *LeftBrace) {
-  if (!LeftBrace)
-    return;
-
-  const auto *RightBrace = LeftBrace->MatchingParen;
-  const bool IsOptionalRightBrace = RightBrace && RightBrace->Optional;
-  assert(LeftBrace->Optional || !IsOptionalRightBrace);
-
-  if (!IsOptionalRightBrace)
-    LeftBrace->Optional = false;
+  LeftBrace->Optional = true;
+  RightBrace->Optional = true;
 }
 
 void UnwrappedLineParser::handleAttributes() {
   // Handle AttributeMacro, e.g. `if (x) UNLIKELY`.
   if (FormatTok->is(TT_AttributeMacro))
     nextToken();
   handleCppAttributes();
 }
if (isBlockBegin(*FormatTok)) {
     else
       NeedsUnwrappedLine = true;
   } else {
     parseUnbracedBody();
   }
 
   if (Style.RemoveBracesLLVM) {
     assert(!NestedTooDeep.empty());
-    KeepIfBraces = KeepIfBraces || (IfLeftBrace && !IfLeftBrace->Optional) ||
+    KeepIfBraces = KeepIfBraces ||
+                   (IfLeftBrace && !IfLeftBrace->MatchingParen) ||
                    NestedTooDeep.back() || IfBlockKind == IfStmtKind::IfOnly ||
                    IfBlockKind == IfStmtKind::IfElseIf;
   }
 
   bool KeepElseBraces = KeepIfBraces;
   FormatToken *ElseLeftBrace = nullptr;
   IfStmtKind Kind = IfStmtKind::IfOnly;
 
if (isBlockBegin(*FormatTok)) {
           parseBlock(/*MustBeDeclaration=*/false, /*AddLevels=*/1u,
                      /*MunchSemi=*/true, KeepElseBraces, &ElseBlockKind);
       if (FormatTok->is(tok::kw_else)) {
         KeepElseBraces = KeepElseBraces ||
                          ElseBlockKind == IfStmtKind::IfOnly ||
                          ElseBlockKind == IfStmtKind::IfElseIf;
       } else if (FollowedByIf && IfLBrace && !IfLBrace->Optional) {
         KeepElseBraces = true;
-        assert(ElseLeftBrace->Optional);
         assert(ElseLeftBrace->MatchingParen);
-        ElseLeftBrace->MatchingParen->Optional = true;
+        markOptionalBraces(ElseLeftBrace);
       }
       addUnwrappedLine();
     } else if (FormatTok->is(tok::kw_if)) {
       const FormatToken *Previous = Tokens->getPreviousToken();
       assert(Previous);
       const bool IsPrecededByComment = Previous->is(tok::comment);
       if (IsPrecededByComment) {
         addUnwrappedLine();
if (NeedsUnwrappedLine)
       addUnwrappedLine();
   }
 
   if (!Style.RemoveBracesLLVM)
     return nullptr;
 
   assert(!NestedTooDeep.empty());
   KeepElseBraces = KeepElseBraces ||
-                   (ElseLeftBrace && !ElseLeftBrace->Optional) ||
+                   (ElseLeftBrace && !ElseLeftBrace->MatchingParen) ||
                    NestedTooDeep.back();
 
   NestedTooDeep.pop_back();
 
   if (!KeepIfBraces && !KeepElseBraces) {
     markOptionalBraces(IfLeftBrace);
     markOptionalBraces(ElseLeftBrace);
+  } else if (IfLeftBrace) {
+    FormatToken *IfRightBrace = IfLeftBrace->MatchingParen;
+    if (IfRightBrace) {
+      assert(IfRightBrace->MatchingParen == IfLeftBrace);
+      assert(!IfLeftBrace->Optional);
+      assert(!IfRightBrace->Optional);
+      IfLeftBrace->MatchingParen = nullptr;
+      IfRightBrace->MatchingParen = nullptr;
+    }
   }
-
-  resetOptional(IfLeftBrace);
-  resetOptional(ElseLeftBrace);
 
   if (IfKind)
     *IfKind = Kind;
 
   return IfLeftBrace;
 }
 
 void UnwrappedLineParser::parseTryCatch() {
if (isBlockBegin(*FormatTok)) {
     CompoundStatementIndenter Indenter(this, Style, Line->Level);
     parseBlock(/*MustBeDeclaration=*/false, /*AddLevels=*/1u,
                /*MunchSemi=*/true, KeepBraces);
     if (!KeepBraces) {
       assert(!NestedTooDeep.empty());
       if (!NestedTooDeep.back())
         markOptionalBraces(LeftBrace);
     }
-    resetOptional(LeftBrace);
     if (WrapRightBrace)
       addUnwrappedLine();
   } else {
     parseUnbracedBody();
   }
 
   if (!KeepBraces)
     NestedTooDeep.pop_back();

clang/unittests/Format/BracesRemoverTest.cpp

verifyFormat("while (0)\n"
                "return a;",
                "while (0) {\n"
                "  if (a) {\n"
                "    return b;\n"
                "}}\n"
                "return a;",
                Style);
 
+  verifyFormat("if (a)\n"
+               "#ifdef FOO\n"
+               "  if (b)\n"
+               "    bar = c;\n"
+               "  else\n"
+               "#endif\n"
+               "  {\n"
+               "    foo = d;\n"
+               "#ifdef FOO\n"
+               "    bar = e;\n"
+               "#else\n"
+               "  bar = f;\n" // FIXME: should be indented 1 more level.
+               "#endif\n"
+               "  }\n"
+               "else\n"
+               "  bar = g;",
+               "if (a)\n"
+               "#ifdef FOO\n"
+               "  if (b)\n"
+               "    bar = c;\n"
+               "  else\n"
+               "#endif\n"
+               "  {\n"
+               "    foo = d;\n"
+               "#ifdef FOO\n"
+               "    bar = e;\n"
+               "#else\n"
+               "    bar = f;\n"
+               "#endif\n"
+               "  }\n"
+               "else {\n"
+               "  bar = g;\n"
+               "}",
+               Style);
+
   Style.ColumnLimit = 65;
   verifyFormat("if (condition) {\n"
                "  ff(Indices,\n"
                "     [&](unsigned LHSI, unsigned RHSI) { return true; });\n"
                "} else {\n"
                "  ff(Indices,\n"
                "     [&](unsigned LHSI, unsigned RHSI) { return true; });\n"
                "}",