Add/rename vm.obj_len, obj_len_opt

vm/src/builtins/iter.rs

@@ -70,9 +70,7 @@ impl PySequenceIterator {
         let hint = if self.reversed {
             pos + 1
         } else {
-            let len = vm._len(&self.obj).unwrap_or_else(|| {
-                Err(vm.new_type_error("sequence has no __len__ method".to_owned()))
-            })?;
+            let len = vm.obj_len(&self.obj)?;
             len as isize - pos
         };
         Ok(hint)

vm/src/builtins/make_module.rs

@@ -440,12 +440,7 @@ mod decl {
 
     #[pyfunction]
     fn len(obj: PyObjectRef, vm: &VirtualMachine) -> PyResult<usize> {
-        vm._len(&obj).unwrap_or_else(|| {
-            Err(vm.new_type_error(format!(
-                "object of type '{}' has no len()",
-                obj.class().name
-            )))
-        })
+        vm.obj_len(&obj)
     }
 
     #[pyfunction]

vm/src/iterator.rs

@@ -108,7 +108,7 @@ pub fn stop_iter_value(vm: &VirtualMachine, exc: &PyBaseExceptionRef) -> PyResul
 }
 
 pub fn length_hint(vm: &VirtualMachine, iter: PyObjectRef) -> PyResult<Option<usize>> {
-    if let Some(len) = vm._len(&iter) {
+    if let Some(len) = vm.obj_len_opt(&iter) {
         match len {
             Ok(len) => return Ok(Some(len)),
             Err(e) => {

vm/src/vm.rs

@@ -1525,7 +1525,7 @@ impl VirtualMachine {
         hash(&obj, self)
     }
 
-    pub fn _len(&self, obj: &PyObjectRef) -> Option<PyResult<usize>> {
+    pub fn obj_len_opt(&self, obj: &PyObjectRef) -> Option<PyResult<usize>> {
         self.get_method(obj.clone(), "__len__").map(|len| {
             let len = self.invoke(&len?, ())?;
             let len = len
@@ -1547,6 +1547,15 @@ impl VirtualMachine {
         })
     }
 
+    pub fn obj_len(&self, obj: &PyObjectRef) -> PyResult<usize> {
+        self.obj_len_opt(obj).unwrap_or_else(|| {
+            Err(self.new_type_error(format!(
+                "object of type '{}' has no len()",
+                obj.class().name
+            )))
+        })
+    }
+
     // https://docs.python.org/3/reference/expressions.html#membership-test-operations
     fn _membership_iter_search(&self, haystack: PyObjectRef, needle: PyObjectRef) -> PyResult {
         let iter = iterator::get_iter(self, &haystack)?;