C# 14 lets a type declare "void operator +=(T)" and friends: void-returning
instance methods under the op_*Assignment metadata names. Only that exact shape
becomes SymbolKind.Operator, and only while the new setting is on, because other
languages use the same names for unrelated methods: F# mangles
"static member (+=)" to a static, value-returning op_AdditionAssignment, and
C++/CLI emits value-returning instance operators. Those, and every method when
the setting is off, stay plain methods with a surfaced [SpecialName].
Assisted-by: Claude:claude-opus-5:Claude Code
Siegfried Pammer