Fix ICE when '__init__' returns any other type than '()'

analyzer/src/traversal/functions.rs

@@ -63,6 +63,11 @@ pub fn func_def(
             .transpose()?
             .unwrap_or_else(|| Tuple::empty().into());
 
+        // `__init__` must not return any type other than `()`.
+        if name == "__init__" && !return_type.is_empty_tuple() {
+            return Err(SemanticError::type_error());
+        }
+
         let attributes: FunctionAttributes = contract_scope
             .borrow_mut()
             .add_function(

compiler/tests/compile_errors.rs

@@ -71,6 +71,7 @@ use std::fs;
     case("return_addition_with_mixed_types.fe", "TypeError"),
     case("return_call_to_fn_with_param_type_mismatch.fe", "TypeError"),
     case("return_call_to_fn_without_return.fe", "TypeError"),
+    case("return_from_init.fe", "TypeError"),
     case("return_lt_mixed_types.fe", "TypeError"),
     case("strict_boolean_if_else.fe", "TypeError"),
     case("string_capacity_mismatch.fe", "StringCapacityMismatch"),

compiler/tests/fixtures/compile_errors/return_from_init.fe

@@ -0,0 +1,3 @@
+contract C:
+    pub def __init__() -> i32:
+        return 0

newsfragments/323.bugfix.md

@@ -0,0 +1,9 @@
+Ensure analyzer rejects code that uses return values for `__init__` functions.
+
+An example that now produces a compile time error:
+
+```
+contract C:
+    pub def __init__() -> i32:
+        return 0
+```