Fix {str|bytes|bytearray}.{isascii,islower,isupper}

vm/src/obj/objbyteinner.rs

@@ -611,7 +611,7 @@ impl PyByteInner {
     }
 
     pub fn isascii(&self) -> bool {
-        !self.elements.is_empty() && self.elements.iter().all(|x| char::from(*x).is_ascii())
+        self.elements.iter().all(|x| char::from(*x).is_ascii())
     }
 
     pub fn isdigit(&self) -> bool {
@@ -619,25 +619,39 @@ impl PyByteInner {
     }
 
     pub fn islower(&self) -> bool {
-        !self.elements.is_empty()
-            && self
-                .elements
-                .iter()
-                .filter(|x| !char::from(**x).is_whitespace())
-                .all(|x| char::from(*x).is_lowercase())
-    }
-
-    pub fn isspace(&self) -> bool {
-        !self.elements.is_empty() && self.elements.iter().all(|x| char::from(*x).is_whitespace())
+        // CPython _Py_bytes_islower
+        let mut cased = false;
+        for b in self.elements.iter() {
+            let c = *b as char;
+            if c.is_uppercase() {
+                return false;
+            } else if !cased && c.is_lowercase() {
+                cased = true
+            }
+        }
+        cased
     }
 
     pub fn isupper(&self) -> bool {
+        // CPython _Py_bytes_isupper
+        let mut cased = false;
+        for b in self.elements.iter() {
+            let c = *b as char;
+            if c.is_lowercase() {
+                return false;
+            } else if !cased && c.is_uppercase() {
+                cased = true
+            }
+        }
+        cased
+    }
+
+    pub fn isspace(&self) -> bool {
         !self.elements.is_empty()
             && self
                 .elements
                 .iter()
-                .filter(|x| !char::from(**x).is_whitespace())
-                .all(|x| char::from(*x).is_uppercase())
+                .all(|x| char::from(*x).is_ascii_whitespace())
     }
 
     pub fn istitle(&self) -> bool {

vm/src/obj/objstr.rs

@@ -9,7 +9,6 @@ use std::string::ToString;
 use num_traits::ToPrimitive;
 use unic::ucd::category::GeneralCategory;
 use unic::ucd::ident::{is_xid_continue, is_xid_start};
-use unic::ucd::is_cased;
 use unicode_casing::CharExt;
 
 use super::objbytes::{PyBytes, PyBytesRef};
@@ -826,29 +825,31 @@ impl PyString {
         !self.value.is_empty() && self.value.chars().all(|c| c.is_ascii_whitespace())
     }
 
-    // Return true if all cased characters in the string are uppercase and there is at least one cased character, false otherwise.
+    // Return true if all cased characters in the string are lowercase and there is at least one cased character, false otherwise.
     #[pymethod]
-    fn isupper(&self) -> bool {
+    fn islower(&self) -> bool {
+        // CPython unicode_islower_impl
         let mut cased = false;
         for c in self.value.chars() {
-            if is_cased(c) && c.is_uppercase() {
-                cased = true
-            } else if is_cased(c) && c.is_lowercase() {
+            if c.is_uppercase() {
                 return false;
+            } else if !cased && c.is_lowercase() {
+                cased = true
             }
         }
         cased
     }
 
-    // Return true if all cased characters in the string are lowercase and there is at least one cased character, false otherwise.
+    // Return true if all cased characters in the string are uppercase and there is at least one cased character, false otherwise.
     #[pymethod]
-    fn islower(&self) -> bool {
+    fn isupper(&self) -> bool {
+        // CPython unicode_isupper_impl
         let mut cased = false;
         for c in self.value.chars() {
-            if is_cased(c) && c.is_lowercase() {
-                cased = true
-            } else if is_cased(c) && c.is_uppercase() {
+            if c.is_lowercase() {
                 return false;
+            } else if !cased && c.is_uppercase() {
+                cased = true
             }
         }
         cased