Clang-format (20): Incorrect behavior with BreakBinaryOperations

[kihot122]

I believe clang-format is incorrectly formatting dereference operator with BreakBinaryOperations: OnePerLine

In example code:
return segment < *this or *this < segment;

Clang-format should correctly infer '*' operator in this context is not a multiplication but rather a dereference of this pointer. Instead I get the following formatting:
return segment < *this or * this < segment;

Full config:
# clang-format >= 20 AccessModifierOffset: -4 AlignAfterOpenBracket: BlockIndent AllowAllArgumentsOnNextLine: false AllowShortBlocksOnASingleLine: Always AllowShortCaseExpressionOnASingleLine: true AllowShortCaseLabelsOnASingleLine: false AllowShortCompoundRequirementOnASingleLine: true AllowShortEnumsOnASingleLine: false AllowShortFunctionsOnASingleLine: Empty AllowShortLambdasOnASingleLine: All AlwaysBreakTemplateDeclarations: true BinPackArguments: false BinPackParameters: false BraceWrapping: AfterCaseLabel: true AfterClass: true AfterControlStatement: Always AfterEnum: true AfterFunction: true AfterNamespace: true AfterObjCDeclaration: true AfterStruct: true AfterUnion: true AfterExternBlock: true BeforeCatch: true BeforeElse: true BeforeLambdaBody: true BeforeWhile: true SplitEmptyFunction: false SplitEmptyNamespace: false SplitEmptyRecord: false BreakBeforeBraces: Custom BreakBinaryOperations: OnePerLine ColumnLimit: 250 IndentRequiresClause: false IndentWidth: 4 KeepEmptyLines: AtEndOfFile: false AtStartOfBlock: false AtStartOfFile: false TabWidth: 4 Standard: Latest PenaltyExcessCharacter: 100 PenaltyIndentedWhitespace: 10 PenaltyReturnTypeOnItsOwnLine: 1000 RequiresExpressionIndentation: OuterScope RequiresClausePosition: OwnLine SeparateDefinitionBlocks: Always

[kihot122]

I believe this feature was added in the following PR: #58014

[rymiel]

Bisected to a6d97de

llvm-project/clang/lib/Format/UnwrappedLineParser.cpp

Lines 1700 to 1705 in ddb5480

	if (IsCpp && FormatTok->isCppAlternativeOperatorKeyword()) {
	if (auto *Next = Tokens->peekNextToken(/*SkipComment=*/true);
	Next && Next->isBinaryOperator()) {
	FormatTok->Tok.setKind(tok::identifier);
	}
	}

Maybe this is the culprit? * can be a binary operator, but it shouldn't be in this situation.

[kihot122]

Hello, as the 20 release is closing in, is there an update on this regression?

[owenca]

@kihot122 this can be easily fixed after #128287 is merged.

[owenca]

Full config: # clang-format >= 20 AccessModifierOffset: -4 AlignAfterOpenBracket: BlockIndent AllowAllArgumentsOnNextLine: false AllowShortBlocksOnASingleLine: Always AllowShortCaseExpressionOnASingleLine: true AllowShortCaseLabelsOnASingleLine: false AllowShortCompoundRequirementOnASingleLine: true AllowShortEnumsOnASingleLine: false AllowShortFunctionsOnASingleLine: Empty AllowShortLambdasOnASingleLine: All AlwaysBreakTemplateDeclarations: true BinPackArguments: false BinPackParameters: false BraceWrapping: AfterCaseLabel: true AfterClass: true AfterControlStatement: Always AfterEnum: true AfterFunction: true AfterNamespace: true AfterObjCDeclaration: true AfterStruct: true AfterUnion: true AfterExternBlock: true BeforeCatch: true BeforeElse: true BeforeLambdaBody: true BeforeWhile: true SplitEmptyFunction: false SplitEmptyNamespace: false SplitEmptyRecord: false BreakBeforeBraces: Custom BreakBinaryOperations: OnePerLine ColumnLimit: 250 IndentRequiresClause: false IndentWidth: 4 KeepEmptyLines: AtEndOfFile: false AtStartOfBlock: false AtStartOfFile: false TabWidth: 4 Standard: Latest PenaltyExcessCharacter: 100 PenaltyIndentedWhitespace: 10 PenaltyReturnTypeOnItsOwnLine: 1000 RequiresExpressionIndentation: OuterScope RequiresClausePosition: OwnLine SeparateDefinitionBlocks: Always

Please repost the config in a code block.