Extend ASCII fast paths of char methods beyond ASCII

Author: Jules-Bertholet

library/core/src/char/methods.rs

@@ -777,8 +777,9 @@ impl char {
     #[inline]
     pub fn is_alphabetic(self) -> bool {
         match self {
-            'a'..='z' | 'A'..='Z' => true,
-            c => c > '\x7f' && unicode::Alphabetic(c),
+            'A'..='Z' | 'a'..='z' => true,
+            '\0'..='\u{A9}' => false,
+            _ => unicode::Alphabetic(self),
         }
     }
 
@@ -819,7 +820,8 @@ impl char {
     pub const fn is_lowercase(self) -> bool {
         match self {
             'a'..='z' => true,
-            c => c > '\x7f' && unicode::Lowercase(c),
+            '\0'..='\u{A9}' => false,
+            _ => unicode::Lowercase(self),
         }
     }
 
@@ -860,7 +862,8 @@ impl char {
     pub const fn is_uppercase(self) -> bool {
         match self {
             'A'..='Z' => true,
-            c => c > '\x7f' && unicode::Uppercase(c),
+            '\0'..='\u{BF}' => false,
+            _ => unicode::Uppercase(self),
         }
     }
 
@@ -893,7 +896,8 @@ impl char {
     pub const fn is_whitespace(self) -> bool {
         match self {
             ' ' | '\x09'..='\x0d' => true,
-            c => c > '\x7f' && unicode::White_Space(c),
+            '\0'..='\u{84}' => false,
+            _ => unicode::White_Space(self),
         }
     }
 
@@ -920,10 +924,10 @@ impl char {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn is_alphanumeric(self) -> bool {
-        if self.is_ascii() {
-            self.is_ascii_alphanumeric()
-        } else {
-            unicode::Alphabetic(self) || unicode::N(self)
+        match self {
+            '0'..='9' | 'A'..='Z' | 'a'..='z' => true,
+            '\0'..='\u{A9}' => false,
+            _ => unicode::Alphabetic(self) || unicode::N(self),
         }
     }
 
@@ -969,7 +973,7 @@ impl char {
     #[must_use]
     #[inline]
     pub(crate) fn is_grapheme_extended(self) -> bool {
-        !self.is_ascii() && unicode::Grapheme_Extend(self)
+        self > '\u{02FF}' && unicode::Grapheme_Extend(self)
     }
 
     /// Returns `true` if this `char` has the `Cased` property.
@@ -985,7 +989,11 @@ impl char {
     #[doc(hidden)]
     #[unstable(feature = "char_internals", reason = "exposed only for libstd", issue = "none")]
     pub fn is_cased(self) -> bool {
-        if self.is_ascii() { self.is_ascii_alphabetic() } else { unicode::Cased(self) }
+        match self {
+            'A'..='Z' | 'a'..='z' => true,
+            '\0'..='\u{A9}' => false,
+            _ => unicode::Cased(self),
+        }
     }
 
     /// Returns `true` if this `char` has the `Case_Ignorable` property.
@@ -1047,7 +1055,8 @@ impl char {
     pub fn is_numeric(self) -> bool {
         match self {
             '0'..='9' => true,
-            c => c > '\x7f' && unicode::N(c),
+            '\0'..='\u{B1}' => false,
+            _ => unicode::N(self),
         }
     }