fix: improve error messages when typing.Any type is encountered

src/puya/awst_build/context.py

@@ -186,9 +186,9 @@ def type_to_pytype(
                 return pytypes.NoneType
             case mypy.types.UninhabitedType():
                 raise CodeError("Cannot resolve empty type", loc)
-            case mypy.types.AnyType():
-                # TODO: look at type_of_any to improve error message
-                raise CodeError("Any type is not supported", loc)
+            case mypy.types.AnyType(type_of_any=type_of_any):
+                msg = _type_of_any_to_error_message(type_of_any, loc)
+                raise CodeError(msg, loc)
             case mypy.types.FunctionLike() as func_like:
                 if func_like.is_type_obj():
                     msg = "References to type objects are not supported"
@@ -219,3 +219,27 @@ def _parameterise_pytype(
                 type_args_resolved.append(self.type_to_pytype(ta, source_location=loc))
         result = generic.parameterise(type_args_resolved, loc)
         return result
+
+
+def _type_of_any_to_error_message(type_of_any: int, source_location: SourceLocation) -> str:
+    from mypy.types import TypeOfAny
+
+    match type_of_any:
+        case TypeOfAny.unannotated:
+            msg = "type annotation is required at this location"
+        case TypeOfAny.explicit | TypeOfAny.from_another_any:
+            msg = "Any type is not supported"
+        case TypeOfAny.from_unimported_type:
+            msg = "unknown type from import"
+        case TypeOfAny.from_omitted_generics:
+            msg = "type parameters are required at this location"
+        case TypeOfAny.from_error:
+            msg = "typing error prevents type resolution"
+        case TypeOfAny.special_form:
+            msg = "unsupported type form"
+        case TypeOfAny.implementation_artifact | TypeOfAny.suggestion_engine:
+            msg = "mypy cannot handle this type form, try providing an explicit annotation"
+        case _:
+            logger.debug(f"Unknown TypeOfAny value: {type_of_any}", location=source_location)
+            msg = "Any type is not supported"
+    return msg

src/puya/awst_build/subroutine.py

@@ -368,8 +368,8 @@ def _handle_proxy_assignment(
             raise InternalError("Assignment to self outside of a contract class", stmt_loc)
         if self.func_def.name != "__init__":
             raise CodeError(
-                f"{rvalue_pytyp} can only be assigned to a member variable"
-                " in the __init__ method",
+                f"{rvalue_pytyp.generic or rvalue_pytyp}"
+                " can only be assigned to a member variable in the __init__ method",
                 stmt_loc,
             )
         cref = self.contract_method_info.cref

tests/test_expected_output/expected_errors.test

@@ -299,7 +299,7 @@ class Derived3(Base):
 class Derived4(Base):
     def __init__(self) -> None:
         super().__init__()
-        self.bar_p = GlobalState(Bytes(b"bbb")) # type: ignore[arg-type] ## E: some error message here about redefining proxies
+        self.bar_p = GlobalState(Bytes(b"bbb")) # type: ignore[arg-type] ## E: Assignment target type algopy.UInt64 differs from expression value type algopy.Bytes
 
 
 ## case: void_state
@@ -309,7 +309,7 @@ class Con(Contract):
     x: None ## E: None is not supported as a value, only a return type
 
     def approval_program(self) -> bool:
-        self.x = log(b"")  # type: ignore[func-returns-value] ## E: None indicates an empty return and cannot be assigned
+        self.x = log(b"")  # type: ignore[func-returns-value] ## E: typing error prevents type resolution
         return True
 
     def clear_state_program(self) -> bool: