perf(builtin): pattern-based fast paths for char predicates

builtin/char.mbt

@@ -136,7 +136,7 @@ pub fn Char::is_ascii_uppercase(self : Self) -> Bool {
 /// Checks if the value is an ASCII whitespace character:
 /// U+0020 SPACE, U+0009 HORIZONTAL TAB, U+000A LINE FEED, U+000B VERTICAL TAB, U+000C FORM FEED, or U+000D CARRIAGE RETURN.
 pub fn Char::is_ascii_whitespace(self : Self) -> Bool {
-  self is ('\u{20}' | '\u{09}' | '\u{0A}' | '\u{0B}' | '\u{0C}' | '\u{0D}')
+  self is ('\u{09}'..='\u{0D}' | ' ')
 }
 
 ///|
@@ -164,10 +164,11 @@ pub fn Char::is_digit(self : Self, radix : UInt) -> Bool {
 ///|
 /// Returns true if this char has the White_Space property.
 pub fn Char::is_whitespace(self : Self) -> Bool {
+  if self <= '\u{20}' {
+    return self is ('\u{09}'..='\u{0D}' | ' ')
+  }
   self
-  is ('\u0009'..='\u000D'
-  | '\u0020'
-  | '\u0085'
+  is ('\u0085'
   | '\u00A0'
   | '\u1680'
   | '\u2000'..='\u200A'
@@ -181,9 +182,14 @@ pub fn Char::is_whitespace(self : Self) -> Bool {
 ///|
 /// Returns true if this char has one of the general categories for numbers.
 pub fn Char::is_numeric(self : Self) -> Bool {
+  if self is ('0'..='9') {
+    return true
+  }
+  if self < '\u{B2}' {
+    return false
+  }
   self
-  is ('\u0030'..='\u0039'
-  | '\u00B2'
+  is ('\u00B2'
   | '\u00B3'
   | '\u00B9'
   | '\u00BC'

char/predicate_reference_test.mbt

@@ -0,0 +1,204 @@
+// Copyright 2026 International Digital Economy Academy
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Exhaustive equivalence check for the restructured char predicates: the
+// reference functions below are the previous single flat patterns, kept
+// verbatim, and every Unicode scalar value is compared against them. Any
+// off-by-one in the restructured fast paths (a shifted range bound, a
+// dropped table entry) fails here with the exact code point.
+
+///|
+fn reference_is_ascii_whitespace(c : Char) -> Bool {
+  c is ('\u{20}' | '\u{09}' | '\u{0A}' | '\u{0B}' | '\u{0C}' | '\u{0D}')
+}
+
+///|
+fn reference_is_whitespace(c : Char) -> Bool {
+  c
+  is ('\u0009'..='\u000D'
+  | '\u0020'
+  | '\u0085'
+  | '\u00A0'
+  | '\u1680'
+  | '\u2000'..='\u200A'
+  | '\u2028'
+  | '\u2029'
+  | '\u202F'
+  | '\u205F'
+  | '\u3000')
+}
+
+///|
+fn reference_is_numeric(c : Char) -> Bool {
+  c
+  is ('\u0030'..='\u0039'
+  | '\u00B2'
+  | '\u00B3'
+  | '\u00B9'
+  | '\u00BC'
+  | '\u00BD'
+  | '\u00BE'
+  | '\u0660'..='\u0669'
+  | '\u06F0'..='\u06F9'
+  | '\u07C0'..='\u07F9'
+  | '\u0966'..='\u096F'
+  | '\u09E6'..='\u09EF'
+  | '\u09F4'..='\u09F9'
+  | '\u0A66'..='\u0A6F'
+  | '\u0AE6'..='\u0AEF'
+  | '\u0B66'..='\u0B6F'
+  | '\u0B72'..='\u0B77'
+  | '\u0BE6'..='\u0BEF'
+  | '\u0BF0'..='\u0BF2'
+  | '\u0C66'..='\u0C6F'
+  | '\u0C78'..='\u0C7E'
+  | '\u0CE6'..='\u0CEF'
+  | '\u0D58'..='\u0D5E'
+  | '\u0D66'..='\u0D6F'
+  | '\u0D70'..='\u0D78'
+  | '\u0DE6'..='\u0DEF'
+  | '\u0E50'..='\u0E59'
+  | '\u0ED0'..='\u0ED9'
+  | '\u0F20'..='\u0F33'
+  | '\u1040'..='\u1049'
+  | '\u1090'..='\u1099'
+  | '\u1369'..='\u137C'
+  | '\u16EE'..='\u16F0'
+  | '\u17E0'..='\u17E9'
+  | '\u17F0'..='\u17F9'
+  | '\u1810'..='\u1819'
+  | '\u1946'..='\u194F'
+  | '\u19D0'..='\u19DA'
+  | '\u1A80'..='\u1A89'
+  | '\u1A90'..='\u1A99'
+  | '\u1B50'..='\u1B59'
+  | '\u1BB0'..='\u1BB9'
+  | '\u1C40'..='\u1C49'
+  | '\u1C50'..='\u1C59'
+  | '\u2070'
+  | '\u2074'..='\u2079'
+  | '\u2080'..='\u2089'
+  | '\u2150'..='\u2189'
+  | '\u2460'..='\u249B'
+  | '\u24EA'..='\u24FF'
+  | '\u2776'..='\u2793'
+  | '\u2CFD'
+  | '\u3007'
+  | '\u3021'..='\u3029'
+  | '\u3038'..='\u303A'
+  | '\u3192'..='\u3195'
+  | '\u3220'..='\u3229'
+  | '\u3248'..='\u324F'
+  | '\u3251'..='\u325F'
+  | '\u3280'..='\u3289'
+  | '\u32B1'..='\u32BF'
+  | '\uA620'..='\uA629'
+  | '\uA6E6'..='\uA6EF'
+  | '\uA830'..='\uA835'
+  | '\uA8D0'..='\uA8D9'
+  | '\uA900'..='\uA909'
+  | '\uA9D0'..='\uA9D9'
+  | '\uA9F0'..='\uA9F9'
+  | '\uAA50'..='\uAA59'
+  | '\uABF0'..='\uABF9'
+  | '\uFF10'..='\uFF19'
+  | '\u{10107}'..='\u{10133}'
+  | '\u{10140}'..='\u{10178}'
+  | '\u{1018A}'..='\u{1018B}'
+  | '\u{102E1}'..='\u{102FB}'
+  | '\u{10320}'..='\u{10323}'
+  | '\u{10341}'
+  | '\u{1034A}'
+  | '\u{103D1}'..='\u{103D5}'
+  | '\u{104A0}'..='\u{104A9}'
+  | '\u{10858}'..='\u{1085F}'
+  | '\u{10879}'..='\u{1087F}'
+  | '\u{108A7}'..='\u{108AF}'
+  | '\u{108FB}'..='\u{108FF}'
+  | '\u{10916}'..='\u{1091B}'
+  | '\u{109BC}'..='\u{109BD}'
+  | '\u{109C0}'..='\u{109CF}'
+  | '\u{10A40}'..='\u{10A48}'
+  | '\u{10A7D}'..='\u{10A7E}'
+  | '\u{10A9D}'..='\u{10A9F}'
+  | '\u{10AEB}'..='\u{10AEF}'
+  | '\u{10B58}'..='\u{10B5F}'
+  | '\u{10B78}'..='\u{10B7F}'
+  | '\u{10BA9}'..='\u{10BAF}'
+  | '\u{10CFA}'..='\u{10CFF}'
+  | '\u{10D30}'..='\u{10D39}'
+  | '\u{10D40}'..='\u{10D49}'
+  | '\u{10E60}'..='\u{10E7E}'
+  | '\u{10F1D}'..='\u{10F26}'
+  | '\u{10F51}'..='\u{10F54}'
+  | '\u{10FC5}'..='\u{10FCB}'
+  | '\u{11052}'..='\u{1106F}'
+  | '\u{110F0}'..='\u{110F9}'
+  | '\u{11136}'..='\u{1113F}'
+  | '\u{111D0}'..='\u{111D9}'
+  | '\u{111E1}'..='\u{111F4}'
+  | '\u{112F0}'..='\u{112F9}'
+  | '\u{11450}'..='\u{11459}'
+  | '\u{114D0}'..='\u{114D9}'
+  | '\u{11650}'..='\u{11659}'
+  | '\u{116C0}'..='\u{116C9}'
+  | '\u{116D0}'..='\u{116E3}'
+  | '\u{11730}'..='\u{1173B}'
+  | '\u{118E0}'..='\u{118F2}'
+  | '\u{11950}'..='\u{11959}'
+  | '\u{11BF0}'..='\u{11BF9}'
+  | '\u{11C50}'..='\u{11C6C}'
+  | '\u{11D50}'..='\u{11D59}'
+  | '\u{11DA0}'..='\u{11DA9}'
+  | '\u{11F50}'..='\u{11F59}'
+  | '\u{11FC0}'..='\u{11FD4}'
+  | '\u{12400}'..='\u{1246E}'
+  | '\u{16130}'..='\u{16139}'
+  | '\u{16A60}'..='\u{16A69}'
+  | '\u{16AC0}'..='\u{16AC9}'
+  | '\u{16B50}'..='\u{16B59}'
+  | '\u{16B5B}'..='\u{16B61}'
+  | '\u{16D70}'..='\u{16D79}'
+  | '\u{16D80}'..='\u{16E96}'
+  | '\u{1CCF0}'..='\u{1CCF9}'
+  | '\u{1D2C0}'..='\u{1D2F3}'
+  | '\u{1D360}'..='\u{1D378}'
+  | '\u{1D7CE}'..='\u{1D7FF}'
+  | '\u{1E140}'..='\u{1E149}'
+  | '\u{1E2F0}'..='\u{1E2F9}'
+  | '\u{1E4F0}'..='\u{1E4F9}'
+  | '\u{1E5F1}'..='\u{1E5FA}'
+  | '\u{1E8C7}'..='\u{1E8CF}'
+  | '\u{1E950}'..='\u{1E959}'
+  | '\u{1EC71}'..='\u{1ECB4}'
+  | '\u{1ED01}'..='\u{1ED3D}'
+  | '\u{1F100}'..='\u{1F10C}'
+  | '\u{1FBF0}'..='\u{1FBF9}')
+}
+
+///|
+test "restructured char predicates agree with the flat reference patterns for every scalar" {
+  for code in 0..<=0x10FFFF {
+    guard code.to_char() is Some(c) else { continue }
+    if c.is_ascii_whitespace() != reference_is_ascii_whitespace(c) {
+      fail("is_ascii_whitespace mismatch at code point \{code}")
+    }
+    if c.is_whitespace() != reference_is_whitespace(c) {
+      fail("is_whitespace mismatch at code point \{code}")
+    }
+    if c.is_numeric() != reference_is_numeric(c) {
+      fail("is_numeric mismatch at code point \{code}")
+    }
+  }
+}