test: cover compatibility method unknown returns

docs/ROADMAP.md

@@ -39,7 +39,7 @@ See `CURRENT_STATUS.md` for the detailed feature matrix.
 6. Continue narrowing expression diagnostics: known TEXT operands now remain visible through arithmetic, with focused numeric-subtraction, numeric-division, and numeric-multiplication positives plus text-operand addition, subtraction, multiplication, and division coverage. Text concatenation into TEXT fields is covered in both operand orders, including field-to-field concatenation. Each numeric operator gives specific guidance naming the text operand. `CHECK TYPE` also rejects misspelled expected type names before comparing values.
 - Keep IDE metadata aligned with the current beginner syntax: typed-language keywords such as `RETURNS`, `CHECK`, and `TYPE` are now included in the metadata used by editor helpers.
 - Keep compatibility-call coverage aligned with modern calls: empty `CALL object.method WITH` forms now have a focused missing-argument diagnostic fixture alongside the modern `DO object.method` case.
-Keep declared return types honest: `claro typecheck` now reports friendly diagnostics for unknown declared return types, mismatched, not-yet-inferable, and empty return expressions, declarations with no `RETURN`, and incomplete conditional branches, when a simple function or object method declares `RETURNS TYPE`; the declaration keyword is case-insensitive like other Claro keywords, with positive coverage in modern and compatibility function forms, including lowercase compatibility declarations and lowercase compatibility method declarations, plus a lowercase compatibility-method mismatch fixture. Complete `IF`/`ELSE` return branches, including nested complete conditionals in functions and methods, are accepted, and modern and compatibility function syntax plus compatibility method syntax are covered by focused fixtures. `CHECK TYPE` parameter metadata also informs arithmetic return-expression checking, including object methods; typed methods can also return class-declared fields by simple name, with positive and mismatch fixtures, and unknown method return expressions now have a dedicated diagnostic fixture. Full path-sensitive analysis across nested conditionals and loops remains planned.
+Keep declared return types honest: `claro typecheck` now reports friendly diagnostics for unknown declared return types, mismatched, not-yet-inferable, and empty return expressions, declarations with no `RETURN`, and incomplete conditional branches, when a simple function or object method declares `RETURNS TYPE`; the declaration keyword is case-insensitive like other Claro keywords, with positive coverage in modern and compatibility function forms, including lowercase compatibility declarations and lowercase compatibility method declarations, plus a lowercase compatibility-method mismatch fixture. Complete `IF`/`ELSE` return branches, including nested complete conditionals in functions and methods, are accepted, and modern and compatibility function syntax plus compatibility method syntax are covered by focused fixtures. `CHECK TYPE` parameter metadata also informs arithmetic return-expression checking, including object methods; typed methods can also return class-declared fields by simple name, with positive and mismatch fixtures, and unknown method return expressions now have dedicated modern and compatibility diagnostic fixtures. Full path-sensitive analysis across nested conditionals and loops remains planned.
 
 ## Complete-platform milestones