test: cover compatibility method addition diagnostics

docs/ADVANCED_STATIC_TYPING.md

@@ -159,6 +159,26 @@ ENDCLASS
 
 This matching `CALL player.score WITH 4` path is included in focused validation.
 
+The same compatibility method return check explains an addition mistake instead of
+falling back to a generic return error:
+
+```claro
+CLASS Player
+    TEACH total TAKES amount RETURNS NUMBER
+        CHECK TYPE amount IS NUMBER
+        RETURN amount + "oops"
+    LEARNED
+ENDCLASS
+```
+
+`claro typecheck` reports:
+
+```text
+Type mismatch for return from Player.total: addition needs NUMBER values, but "oops" looks like TEXT.
+```
+
+This negative compatibility fixture is part of focused release validation.
+
 Compatibility methods support numeric subtraction in the same focused way:
 
 ```claro

docs/CURRENT_STATUS.md

@@ -53,7 +53,7 @@ Ready now:
 - `TYPE OF` and `CHECK TYPE`
 - `CHECK TYPE` rejects unknown expected type names with a beginner-facing list of supported types
 - typed list/map checks through `claro typecheck`, including a nested `LIST OF MAP` insertion example
-- simple function and object-method return checks with `TEACH name ... RETURNS TYPE`, including learner-facing diagnostics for unknown declared return types, mismatched or not-yet-inferable `RETURN` expressions (including method-specific diagnostics naming the class and method, with modern and compatibility method coverage), empty `RETURN` statements, declarations that contain no `RETURN`, and declarations whose only return is inside an incomplete conditional; `RETURNS` is case-insensitive like other Claro keywords and has positive coverage in both modern and compatibility function forms, including lowercase compatibility declarations and lowercase compatibility method declarations, plus a lowercase compatibility-method mismatch diagnostic; `CHECK TYPE` parameter metadata also informs arithmetic return-expression checking, including method return expressions; positive function-return coverage includes numeric multiplication; compatibility methods now have dedicated positive numeric addition, subtraction, division, and multiplication return fixtures; NUMBER return diagnostics name a known TEXT operand and arithmetic operation instead of hiding the cause behind a generic mismatch, with focused addition, subtraction, multiplication, and division coverage for functions and methods; typed methods can also return class-declared fields by simple name, with positive and mismatch coverage
+- simple function and object-method return checks with `TEACH name ... RETURNS TYPE`, including learner-facing diagnostics for unknown declared return types, mismatched or not-yet-inferable `RETURN` expressions (including method-specific diagnostics naming the class and method, with modern and compatibility method coverage), empty `RETURN` statements, declarations that contain no `RETURN`, and declarations whose only return is inside an incomplete conditional; `RETURNS` is case-insensitive like other Claro keywords and has positive coverage in both modern and compatibility function forms, including lowercase compatibility declarations and lowercase compatibility method declarations, plus a lowercase compatibility-method mismatch diagnostic; `CHECK TYPE` parameter metadata also informs arithmetic return-expression checking, including method return expressions; positive function-return coverage includes numeric multiplication; compatibility methods now have dedicated positive numeric addition, subtraction, division, and multiplication return fixtures plus a compatibility addition diagnostic fixture; NUMBER return diagnostics name a known TEXT operand and arithmetic operation instead of hiding the cause behind a generic mismatch, with focused addition, subtraction, multiplication, and division coverage for functions and methods; typed methods can also return class-declared fields by simple name, with positive and mismatch coverage
 - a narrow function/method argument check: `CHECK TYPE parameter IS TYPE` inside a function or simple object method lets `claro typecheck` accept correct checked calls, catch mismatched `DO`, `CALL ... WITH`, `DO object.method ...`, and compatibility `CALL object.method WITH ...` arguments, including checked methods that appear after another method in the same class, report missing checked function and method arguments, report missing unchecked arguments for simple functions and simple object methods in both modern `DO` and compatibility `CALL ... WITH` forms, treat empty compatibility calls such as `CALL greet WITH` and `CALL player.rename WITH` as missing-argument mistakes, catch extra arguments to simple functions and checked methods even when the checked method appears after another method in the same class, catch modern `DO` and compatibility `CALL ... WITH` calls to undeclared simple functions, explain when `DO object.method ...` or compatibility `CALL object.method WITH ...` happens before the object is created with `NEW` even if the method name is also wrong, and catch modern plus compatibility calls to undeclared object methods with a class-specific `TEACH` hint
 - a narrow object-field assignment/check-type check for simple `NEW Class object` plus direct `SET object.field value` and `CHECK TYPE object.field IS TYPE` cases when the class declares `HAS field TYPE`; validation now covers correct NUMBER, TEXT, and YESNO direct assignments, explicitly typed field assignments, dedicated positive NUMBER/TEXT/YESNO `CHECK TYPE` metadata fixtures, simple and chained object aliases for both field assignments and `CHECK TYPE` metadata (including a chained TEXT-field check), aliased object-method calls including chained aliases in modern `DO` and compatibility `CALL ... WITH` forms (with a dedicated positive modern `DO` chained-alias fixture), field-to-field, compound arithmetic field expressions, and arithmetic/text expression result types, negative NUMBER/TEXT/YESNO field `CHECK TYPE` metadata mismatches, NUMBER/TEXT/YESNO-expectation unknown-field `CHECK TYPE` diagnostics, missing-object field assignment and `CHECK TYPE` diagnostics, NUMBER/TEXT/YESNO wrong-type diagnostics, field collection when a `HAS` field appears after a simple method, NUMBER/TEXT/YESNO-valued unknown-field diagnostics for direct assignments to undeclared fields including explicitly typed assignments, numeric and text results from simple arithmetic/text expressions in object-field assignments, plus a plain beginner-facing unknown-field diagnostic when the assigned expression type is not inferable yet
 

docs/ROADMAP.md

@@ -37,7 +37,7 @@ See `CURRENT_STATUS.md` for the detailed feature matrix.
 4. Add small examples for each foundation feature before adding bigger syntax. The object-field foundation now includes positive and negative validation for field expressions such as `SET player.score player.name`, `SET player.score player.score + 1`, `SET player.name player.score + 1`, explicitly typed field assignments, explicit typed assignments to undeclared fields, simple and chained aliases such as `SET alias player`, `SET backup alias`, followed by `SET backup.score ...` or `CHECK TYPE backup.score IS ...`, chained aliases in object-method calls through both modern `DO` and compatibility `CALL ... WITH` forms (including a dedicated positive modern `DO` fixture), and arithmetic/text expression mismatches; typed containers also accept a map with nested type metadata when it is added to a `LIST OF MAP`; broader alias/control-flow checking remains planned.
 5. Keep the focused typecheck validator complete: every `typecheck_*.claro` fixture, including positive fixtures, is now exercised by both the standalone diagnostic validator and `claro validate`.
 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. Typed function returns now include positive subtraction and division examples alongside multiplication. Text concatenation into TEXT fields is covered in both operand orders, including field-to-field concatenation. Each numeric operator names the text operand and explains that it needs NUMBER values. `CHECK TYPE` also rejects misspelled expected type names.
-- Keep typed method return examples balanced: numeric addition, subtraction, division, and multiplication now have dedicated positive compatibility `TAKES` / `LEARNED` method fixtures in the focused validator, alongside the existing method return mismatch diagnostics.
+- Keep typed method return examples balanced: numeric addition, subtraction, division, and multiplication now have dedicated positive compatibility `TAKES` / `LEARNED` method fixtures in the focused validator, alongside compatibility addition mismatch coverage and the existing method return mismatch diagnostics.
 - 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; positive numeric multiplication return coverage now sits beside the mismatch fixtures, including a dedicated compatibility-method multiplication success fixture; 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, and NUMBER return expressions with known TEXT arithmetic operands identify the operation and offending operand, including focused addition, subtraction, multiplication, and division coverage for functions and methods. Full path-sensitive analysis across nested conditionals and loops remains planned.