Function generated_expr_cases 

pub fn generated_expr_cases(
    cx: &mut Cx,
    language: &Symbol,
    codec: &Symbol,
    space: &ExprSpace,
    budget: usize,
) -> Vec<ExprRoundTripCase>

Projects generated expressions into matrix expression round-trip cases.

Each case stores codec-rendered source text when the codec can encode the expression. Expressions outside that codec surface remain explicit generated cases with fallback source text, so later runners observe a diagnostic or gap instead of a silent pass. Generated cases never affect curated badges.