C#: Add precedence-aware parenthesization utility#7068
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knutwannheden merged 12 commits intomainfrom Mar 20, 2026
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Precedence-aware parenthesization/unwrapping utility for the C# SDK, modeled after Java's ParenthesizeVisitor and UnwrapParentheses.
- Add IsPattern, RangeExpression, SwitchExpression, WithExpression, Lambda to GetPrecedence dispatch and visitor methods - Handle pattern combinator (and/or/not) precedence as separate sub-domain - Add right-associativity handling for ?? in NeedsParentheses - Expand IsUnwrappable structural parent list (ForLoop, FixedStatement, etc.) - Include C#-specific types in MaybeParenthesize fast-exit check - Document IsAssociative return values - Fix Parenthesize helper to use expr.WithPrefix() not J.SetPrefix()
Five tasks: CSharpPrecedences, CSharpParenthesizeVisitor, CSharpUnwrapParentheses, template integration, final verification.
The C# parser models ?? as Ternary with a NullCoalescing marker, not as CsBinary.NullCoalescing. Update GetPrecedence, IsAssociative, IsRightAssociative, and tests to handle both representations.
…Apply Auto-parenthesizes expression substitutions after template application, matching Java's JavaTemplate integration pattern.
- Unary inside different unary no longer gets unnecessary parens: all prefix unary operators are at the same precedence level (13), so -(~x), ~(!x), etc. are always unambiguous - Ternary inside ternary now gets parens: C# parses a ? b : c ? d : e right-to-left, so the left ternary as a condition needs wrapping
- TypeCast no longer over-parenthesized: uses precedence-based logic instead of unconditional wrapping (prec 13 binds tighter than binary) - Add VisitLambda override for recursive visitor (prec -2 like assignment) - Add Lambda to IsPattern parent check in NeedsParenthesesInContext - IsRightAssociative check now verifies both child and parent - MaybeWrapAssignment now checks IsPattern parent - NeedsParentheses parent parameter typed as Expression (was object)
Demonstrates that CSharpTemplate.Apply auto-parenthesizes when a substitution produces a lower-precedence expression in a higher-precedence context: replacing + with - inside a * context preserves the parens.
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Summary
CSharpPrecedences(internal): C# operator precedence table derived from the language spec, withGetPrecedence,NeedsParentheses,Parenthesize, andIsAssociativemethodsCSharpParenthesizeVisitor: visitor that adds parentheses where needed based on operator precedence and context, with staticMaybeParenthesizeentry point for template integrationCSharpUnwrapParentheses: visitor that safely removes parentheses from a specific node when semantics are preservedMaybeParenthesizeintoCSharpTemplate.Applyso template substitutions auto-parenthesizeThis eliminates the need for recipe authors to manually decide when parentheses are needed. Currently 8+ recipes in recipes-csharp re-implement their own
NeedsParentheseschecks with inconsistent logic.Test plan
CSharpPrecedencesTests)CSharpParenthesizeVisitorTests)CSharpUnwrapParenthesesTests):rewrite-csharp:csharpBuildsucceedsInvertIf,SimplifyBooleanComparison) to use the new utility