From 747f777a2441f3b5192eb5d7b84d5b5f14186c78 Mon Sep 17 00:00:00 2001
From: ChJR <chjr8815@gmail.com>
Date: Fri, 16 Aug 2019 18:01:39 +0900
Subject: [PATCH 1/4] Add test code from the CPython
 repository(Lib/test/test_bool.py).

---
 tests/snippets/bools.py | 37 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 36 insertions(+), 1 deletion(-)

diff --git a/tests/snippets/bools.py b/tests/snippets/bools.py
index c33fcff0fc..5becc16455 100644
--- a/tests/snippets/bools.py
+++ b/tests/snippets/bools.py
@@ -137,4 +137,39 @@ def __len__(self):
 
 
 with assertRaises(TypeError):
-    bool(TestLenThrowError())
\ No newline at end of file
+    bool(TestLenThrowError())
+
+# Verify that TypeError occurs when bad things are returned
+# from __bool__().  This isn't really a bool test, but
+# it's related.
+def check(o):
+    with assertRaises(TypeError):
+        bool(o)
+
+class Foo(object):
+    def __bool__(self):
+        return self
+check(Foo())
+
+class Bar(object):
+    def __bool__(self):
+        return "Yes"
+check(Bar())
+
+class Baz(int):
+    def __bool__(self):
+        return self
+check(Baz())
+
+# __bool__() must return a bool not an int
+class Spam(int):
+    def __bool__(self):
+        return 1
+check(Spam())
+
+class Eggs:
+    def __len__(self):
+        return -1
+
+with assertRaises(ValueError):
+    bool(Eggs())
\ No newline at end of file

From 7b980920b9c92e57a47a81815d2e58c2741b023e Mon Sep 17 00:00:00 2001
From: ChJR <chjr8815@gmail.com>
Date: Sun, 8 Sep 2019 17:09:47 +0900
Subject: [PATCH 2/4] Check __bool__() returns only bool value

---
 vm/src/obj/objbool.rs | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/vm/src/obj/objbool.rs b/vm/src/obj/objbool.rs
index 91d47c6266..c68df24b5f 100644
--- a/vm/src/obj/objbool.rs
+++ b/vm/src/obj/objbool.rs
@@ -29,6 +29,13 @@ pub fn boolval(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<bool> {
             // If descriptor returns Error, propagate it further
             let method = method_or_err?;
             let bool_obj = vm.invoke(&method, PyFuncArgs::default())?;
+            if !objtype::isinstance(&bool_obj, &vm.ctx.bool_type()) {
+                return Err(vm.new_type_error(format!(
+                    "__bool__ should return bool, returned type {}",
+                    bool_obj.class().name
+                )));
+            }
+
             match bool_obj.payload::<PyInt>() {
                 Some(int_obj) => !int_obj.as_bigint().is_zero(),
                 None => {

From 21821b7a726bf9fc6340d7c555de66038a1b4f26 Mon Sep 17 00:00:00 2001
From: ChJR <chjr8815@gmail.com>
Date: Sun, 8 Sep 2019 17:42:02 +0900
Subject: [PATCH 3/4] Throw ValueError when __len__() is a negative value

---
 vm/src/obj/objbool.rs | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/vm/src/obj/objbool.rs b/vm/src/obj/objbool.rs
index c68df24b5f..aa4a777ffc 100644
--- a/vm/src/obj/objbool.rs
+++ b/vm/src/obj/objbool.rs
@@ -1,3 +1,4 @@
+use num_bigint::Sign;
 use num_traits::Zero;
 
 use crate::function::PyFuncArgs;
@@ -51,7 +52,16 @@ pub fn boolval(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<bool> {
                 let method = method_or_err?;
                 let bool_obj = vm.invoke(&method, PyFuncArgs::default())?;
                 match bool_obj.payload::<PyInt>() {
-                    Some(int_obj) => !int_obj.as_bigint().is_zero(),
+                    Some(int_obj) => {
+                        let len_val = int_obj.as_bigint();
+                        if len_val.sign() == Sign::Minus {
+                            return Err(
+                                vm.new_value_error("__len__() should return >= 0".to_string())
+                            );
+                        }
+
+                        !len_val.is_zero()
+                    }
                     None => {
                         return Err(vm.new_type_error(format!(
                             "{} object cannot be interpreted as integer",

From da020293d23bc1281513e48972c776b93b4bca9e Mon Sep 17 00:00:00 2001
From: ChJR <chjr8815@gmail.com>
Date: Sun, 8 Sep 2019 18:19:52 +0900
Subject: [PATCH 4/4] Refactor boolval()

---
 vm/src/obj/objbool.rs | 10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/vm/src/obj/objbool.rs b/vm/src/obj/objbool.rs
index aa4a777ffc..eef179353d 100644
--- a/vm/src/obj/objbool.rs
+++ b/vm/src/obj/objbool.rs
@@ -37,15 +37,7 @@ pub fn boolval(vm: &VirtualMachine, obj: PyObjectRef) -> PyResult<bool> {
                 )));
             }
 
-            match bool_obj.payload::<PyInt>() {
-                Some(int_obj) => !int_obj.as_bigint().is_zero(),
-                None => {
-                    return Err(vm.new_type_error(format!(
-                        "__bool__ should return bool, returned type {}",
-                        bool_obj.class().name
-                    )))
-                }
-            }
+            get_value(&bool_obj)
         }
         None => match vm.get_method(obj.clone(), "__len__") {
             Some(method_or_err) => {