Don't complain if non-callable __bool__ is the last entry in a boolop

Summary:
This matches the runtime: Python won't evaluate `_.__bool__()` unless it
actually needs truthiness information; it's actually legal to use a
non-boolable as the last value.

Reviewed By: yangdanny97

Differential Revision: D85481912

fbshipit-source-id: 71b03b47c14035098e6f3f36cbfb3f6c998e157e

Author: stroxler

pyrefly/lib/alt/expr.rs

@@ -1014,7 +1014,7 @@ impl<'a, Ans: LookupAnswer> AnswersSolver<'a, Ans> {
             let hint = hint.or_else(|| Some(HintRef::new(&t_acc, None)));
             let mut t = self.expr_infer_with_hint(value, hint, errors);
             self.expand_vars_mut(&mut t);
-            if should_shortcircuit(&t, value.range()) {
+            if i < last_index && should_shortcircuit(&t, value.range()) {
                 t_acc = self.union(t_acc, t);
                 break;
             }

pyrefly/lib/test/operators.rs

@@ -483,12 +483,10 @@ assert_type(int() if Falsey() else str(), str)
 
 # Test the use of a non-boolean-convertable type in boolean operators.
 #
-# TODO(stroxler): This behavior is conservative: the rightmost entry of a
-# boolean expression is actually not evaluated as a bool by the runtime (unless
-# the entire value is used as a boolean inside some other AST element), so the
-# type error on the second line is arguably a false-positive.
+# The runtime only uses truthiness in short-circuiting here, so it is actually
+# legal to use a non-boolable value as the rightmost entry of a bool op.
 assert_type(NotBoolable() or int(), int | NotBoolable)  # E: Expected `__bool__` to be a callable, got `int`
-assert_type(int() or NotBoolable(), int | NotBoolable)  # E: Expected `__bool__` to be a callable, got `int`
+assert_type(int() or NotBoolable(), int | NotBoolable)
 "#,
 );