A record that declares operator == doesn't compile in C# (CS0111) or Rust (E0119) because the record already supplies equality #301

What's wrong

A ClassDeclaration { IsRecord = true } with a member FunctionDeclaration("==") { Kind = FunctionKind.Operator } generates output that doesn't compile in two targets.

• C#: the generator writes public record class Point with the user's operator ==, and the comparison-pair logic from C#: declaring only one of a comparison operator pair (==/!=, </>, <=/>=) generates code that fails with CS0216 #236 (MissingComparisonPartners, Coder/Languages/CSharpGenerator.cs around L321) adds operator !=. A C# record already synthesises both operators, so the compiler rejects both:

  • error CS0111: Type 'Point' already defines a member called 'op_Equality' with the same parameter types
  • the same error for op_Inequality

  Declaring only != fails the same way, because the partner logic then adds ==.

• Rust: the record gets #[derive(Clone, Debug, PartialEq)] (Coder/Languages/RustGenerator.cs around L591-595), and the declared == becomes impl PartialEq for Point { fn eq ... } (the operator-trait mapping around L229 and L813). The result is error[E0119]: conflicting implementations of trait 'PartialEq' for type 'Point'.

Reproduction

Build this AST: a record Point with an int x field and bool operator ==(Point rhs) returning true. Generate C# and Rust, then compile the output with dotnet build and rustc. You get the errors above. The same AST without IsRecord compiles in both targets.

Suggested fix

• C#: when a record declares == or !=, don't emit the operator itself and don't run MissingComparisonPartners for ==/!=. Either write the user's equality as public virtual bool Equals(Point? other) (records let you override that), or write the inexpressible note.
• Rust: leave PartialEq out of the record's derive list when the type declares == (or !=), so the user's impl PartialEq is the only one.

Acceptance criteria

• C# and Rust compile tests (*GeneratedSourceCompilesTests) cover:
  • a record that declares ==
  • a record that declares only !=
• Records that don't declare equality operators keep their current output.