test: cover compatibility method return types

CHANGELOG.md

@@ -2,6 +2,11 @@
 
 ## Unreleased
 
+### Validate compatibility method return types
+
+- Added focused coverage proving that the older `TEACH ... TAKES ... RETURNS TYPE` / `LEARNED` method syntax receives the same learner-facing return-type diagnostic as modern methods.
+- Added the compatibility method fixture to the complete typecheck diagnostics validator.
+
 ### Validate compatibility function return types
 
 - Added focused coverage proving that the older `TEACH ... TAKES ... RETURNS TYPE` / `LEARNED` syntax receives the same learner-facing return-type diagnostic as modern functions.

README.md

@@ -173,7 +173,7 @@ END
 
 The same focused check applies to methods such as `Player.score RETURNS NUMBER`; a wrong return reports the full method name, for example: `Type mismatch for return from Player.score: expected NUMBER, but this value looks like TEXT.`
 
-The older compatibility spelling keeps the same return check. For example, `TEACH square TAKES amount RETURNS NUMBER` with `LEARNED` and `CALL square WITH 4` is checked before it runs, so older lessons get the same type-safety feedback.
+The older compatibility spelling keeps the same return check for functions and methods. For example, `TEACH square TAKES amount RETURNS NUMBER` with `LEARNED` and `CALL square WITH 4` is checked before it runs, so older lessons get the same type-safety feedback. A compatibility method such as `TEACH score TAKES amount RETURNS NUMBER` inside a class is checked the same way.
 
 If a function or method declares `RETURNS TYPE` but uses `RETURN` without a value, the checker points out the missing expression:
 

tests/typecheck_method_compat_return_bad.claro

@@ -0,0 +1,9 @@
+CLASS Player
+    TEACH score TAKES amount RETURNS NUMBER
+        CHECK TYPE amount IS NUMBER
+        RETURN "oops"
+    LEARNED
+ENDCLASS
+
+NEW Player player
+CALL player.score WITH 4

tools/validate_typecheck_diagnostics.py

@@ -37,6 +37,9 @@ EXPECTED = {
     "tests/typecheck_method_return_bad.claro": [
         "tests/typecheck_method_return_bad.claro:3: Type mismatch for return from Player.score: expected NUMBER, but this value looks like TEXT.",
     ],
+    "tests/typecheck_method_compat_return_bad.claro": [
+        "tests/typecheck_method_compat_return_bad.claro:4: Type mismatch for return from Player.score: expected NUMBER, but this value looks like TEXT.",
+    ],
     "tests/typecheck_method_return_expression_bad.claro": [
         "tests/typecheck_method_return_expression_bad.claro:4: Type mismatch for return from Player.label: expected TEXT, but this value looks like NUMBER.",
     ],