Add complex (but unconditional) Unicode case mapping. Fix #25800

As a result, the iterator returned by `char::to_uppercase` sometimes
yields two or three `char`s instead of just one.

Author: SimonSapin

src/etc/unicode.py

@@ -104,11 +104,11 @@ def load_unicode_data(f):
         # generate char to char direct common and simple conversions
         # uppercase to lowercase
         if lowcase != "" and code_org != lowcase:
-            to_lower[code] = int(lowcase, 16)
+            to_lower[code] = (int(lowcase, 16), 0, 0)
 
         # lowercase to uppercase
         if upcase != "" and code_org != upcase:
-            to_upper[code] = int(upcase, 16)
+            to_upper[code] = (int(upcase, 16), 0, 0)
 
         # store decomposition, if given
         if decomp != "":
@@ -146,6 +146,31 @@ def load_unicode_data(f):
 
     return (canon_decomp, compat_decomp, gencats, combines, to_upper, to_lower)
 
+def load_special_casing(f, to_upper, to_lower):
+    fetch(f)
+    for line in fileinput.input(f):
+        data = line.split('#')[0].split(';')
+        if len(data) == 5:
+            code, lower, title, upper, _comment = data
+        elif len(data) == 6:
+            code, lower, title, upper, condition, _comment = data
+            if condition.strip():  # Only keep unconditional mappins
+                continue
+        else:
+            continue
+        code = code.strip()
+        lower = lower.strip()
+        title = title.strip()
+        upper = upper.strip()
+        key = int(code, 16)
+        for (map_, values) in [(to_lower, lower), (to_upper, upper)]:
+            if values != code:
+                values = [int(i, 16) for i in values.split()]
+                for _ in range(len(values), 3):
+                    values.append(0)
+                assert len(values) == 3
+                map_[key] = values
+
 def group_cats(cats):
     cats_out = {}
     for cat in cats:
@@ -279,7 +304,7 @@ def load_east_asian_width(want_widths, except_cats):
     return widths
 
 def escape_char(c):
-    return "'\\u{%x}'" % c
+    return "'\\u{%x}'" % c if c != 0 else "'\\0'"
 
 def emit_bsearch_range_table(f):
     f.write("""
@@ -328,21 +353,21 @@ def emit_conversions_module(f, to_upper, to_lower):
     use core::option::Option::{Some, None};
     use core::result::Result::{Ok, Err};
 
-    pub fn to_lower(c: char) -> char {
+    pub fn to_lower(c: char) -> [char; 3] {
         match bsearch_case_table(c, to_lowercase_table) {
-          None        => c,
+          None        => [c, '\\0', '\\0'],
           Some(index) => to_lowercase_table[index].1
         }
     }
 
-    pub fn to_upper(c: char) -> char {
+    pub fn to_upper(c: char) -> [char; 3] {
         match bsearch_case_table(c, to_uppercase_table) {
-            None        => c,
+            None        => [c, '\\0', '\\0'],
             Some(index) => to_uppercase_table[index].1
         }
     }
 
-    fn bsearch_case_table(c: char, table: &'static [(char, char)]) -> Option<usize> {
+    fn bsearch_case_table(c: char, table: &'static [(char, [char; 3])]) -> Option<usize> {
         match table.binary_search_by(|&(key, _)| {
             if c == key { Equal }
             else if key < c { Less }
@@ -355,9 +380,17 @@ def emit_conversions_module(f, to_upper, to_lower):
 
 """)
     emit_table(f, "to_lowercase_table",
-        sorted(to_lower.iteritems(), key=operator.itemgetter(0)), is_pub=False)
+        sorted(to_lower.iteritems(), key=operator.itemgetter(0)),
+        is_pub=False,
+        t_type = "&'static [(char, [char; 3])]",
+        pfun=lambda x: "(%s,[%s,%s,%s])" % (
+            escape_char(x[0]), escape_char(x[1][0]), escape_char(x[1][1]), escape_char(x[1][2])))
     emit_table(f, "to_uppercase_table",
-        sorted(to_upper.iteritems(), key=operator.itemgetter(0)), is_pub=False)
+        sorted(to_upper.iteritems(), key=operator.itemgetter(0)),
+        is_pub=False,
+        t_type = "&'static [(char, [char; 3])]",
+        pfun=lambda x: "(%s,[%s,%s,%s])" % (
+            escape_char(x[0]), escape_char(x[1][0]), escape_char(x[1][1]), escape_char(x[1][2])))
     f.write("}\n\n")
 
 def emit_grapheme_module(f, grapheme_table, grapheme_cats):
@@ -592,6 +625,7 @@ def optimize_width_table(wtable):
 """ % unicode_version)
         (canon_decomp, compat_decomp, gencats, combines,
                 to_upper, to_lower) = load_unicode_data("UnicodeData.txt")
+        load_special_casing("SpecialCasing.txt", to_upper, to_lower)
         want_derived = ["XID_Start", "XID_Continue", "Alphabetic", "Lowercase", "Uppercase"]
         derived = load_properties("DerivedCoreProperties.txt", want_derived)
         scripts = load_properties("Scripts.txt", [])

src/libcollectionstest/char.rs

@@ -0,0 +1,32 @@
+// Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use collections::vec::Vec;
+
+#[test]
+fn char_to_lowercase() {
+    assert_iter_eq('A'.to_lowercase(), &['a']);
+    assert_iter_eq('É'.to_lowercase(), &['é']);
+    assert_iter_eq('Dž'.to_lowercase(), &['dž']);
+}
+
+#[test]
+fn char_to_uppercase() {
+    assert_iter_eq('a'.to_uppercase(), &['A']);
+    assert_iter_eq('é'.to_uppercase(), &['É']);
+    assert_iter_eq('Dž'.to_uppercase(), &['DŽ']);
+    assert_iter_eq('ß'.to_uppercase(), &['S', 'S']);
+    assert_iter_eq('fi'.to_uppercase(), &['F', 'I']);
+    assert_iter_eq('ᾀ'.to_uppercase(), &['Ἀ', 'Ι']);
+}
+
+fn assert_iter_eq<I: Iterator<Item=char>>(iter: I, expected: &[char]) {
+    assert_eq!(iter.collect::<Vec<_>>(), expected);
+}

src/libcollectionstest/lib.rs

@@ -37,6 +37,7 @@ extern crate rustc_unicode;
 mod binary_heap;
 mod bit;
 mod btree;
+mod char;  // char isn't really a collection, but didn't find a better place for this.
 mod enum_set;
 mod fmt;
 mod linked_list;

src/librustc_unicode/char.rs

@@ -29,7 +29,7 @@
 #![doc(primitive = "char")]
 
 use core::char::CharExt as C;
-use core::option::Option::{self, Some};
+use core::option::Option::{self, Some, None};
 use core::iter::Iterator;
 use tables::{derived_property, property, general_category, conversions, charwidth};
 
@@ -47,24 +47,67 @@ pub use tables::UNICODE_VERSION;
 /// the [`to_lowercase` method](../primitive.char.html#method.to_lowercase) on
 /// characters.
 #[stable(feature = "rust1", since = "1.0.0")]
-pub struct ToLowercase(Option<char>);
+pub struct ToLowercase(CaseMappingIter);
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl Iterator for ToLowercase {
     type Item = char;
-    fn next(&mut self) -> Option<char> { self.0.take() }
+    fn next(&mut self) -> Option<char> { self.0.next() }
 }
 
 /// An iterator over the uppercase mapping of a given character, returned from
 /// the [`to_uppercase` method](../primitive.char.html#method.to_uppercase) on
 /// characters.
 #[stable(feature = "rust1", since = "1.0.0")]
-pub struct ToUppercase(Option<char>);
+pub struct ToUppercase(CaseMappingIter);
 
 #[stable(feature = "rust1", since = "1.0.0")]
 impl Iterator for ToUppercase {
     type Item = char;
-    fn next(&mut self) -> Option<char> { self.0.take() }
+    fn next(&mut self) -> Option<char> { self.0.next() }
+}
+
+
+enum CaseMappingIter {
+    Three(char, char, char),
+    Two(char, char),
+    One(char),
+    Zero
+}
+
+impl CaseMappingIter {
+    fn new(chars: [char; 3]) -> CaseMappingIter {
+        if chars[2] == '\0' {
+            if chars[1] == '\0' {
+                CaseMappingIter::One(chars[0])  // Including if chars[0] == '\0'
+            } else {
+                CaseMappingIter::Two(chars[0], chars[1])
+            }
+        } else {
+            CaseMappingIter::Three(chars[0], chars[1], chars[2])
+        }
+    }
+}
+
+impl Iterator for CaseMappingIter {
+    type Item = char;
+    fn next(&mut self) -> Option<char> {
+        match *self {
+            CaseMappingIter::Three(a, b, c) => {
+                *self = CaseMappingIter::Two(b, c);
+                Some(a)
+            }
+            CaseMappingIter::Two(b, c) => {
+                *self = CaseMappingIter::One(c);
+                Some(b)
+            }
+            CaseMappingIter::One(c) => {
+                *self = CaseMappingIter::Zero;
+                Some(c)
+            }
+            CaseMappingIter::Zero => None,
+        }
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -397,45 +440,45 @@ impl char {
 
     /// Converts a character to its lowercase equivalent.
     ///
-    /// The case-folding performed is the common or simple mapping. See
-    /// `to_uppercase()` for references and more information.
+    /// This performs complex unconditional mappings with no tailoring.
+    /// See `to_uppercase()` for references and more information.
     ///
     /// # Return value
     ///
     /// Returns an iterator which yields the characters corresponding to the
     /// lowercase equivalent of the character. If no conversion is possible then
-    /// the input character is returned.
+    /// an iterator with just the input character is returned.
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn to_lowercase(self) -> ToLowercase {
-        ToLowercase(Some(conversions::to_lower(self)))
+        ToLowercase(CaseMappingIter::new(conversions::to_lower(self)))
     }
 
     /// Converts a character to its uppercase equivalent.
     ///
-    /// The case-folding performed is the common or simple mapping: it maps
-    /// one Unicode codepoint to its uppercase equivalent according to the
-    /// Unicode database [1]. The additional [`SpecialCasing.txt`] is not yet
-    /// considered here, but the iterator returned will soon support this form
-    /// of case folding.
+    /// This performs complex unconditional mappings with no tailoring:
+    /// it maps one Unicode character to its uppercase equivalent
+    /// according to the Unicode database [1]
+    /// and the additional complex mappings [`SpecialCasing.txt`].
+    /// Conditional mappings (based on context or language) are not considerd here.
     ///
     /// A full reference can be found here [2].
     ///
     /// # Return value
     ///
     /// Returns an iterator which yields the characters corresponding to the
     /// uppercase equivalent of the character. If no conversion is possible then
-    /// the input character is returned.
+    /// an iterator with just the input character is returned.
     ///
     /// [1]: ftp://ftp.unicode.org/Public/UNIDATA/UnicodeData.txt
     ///
     /// [`SpecialCasing.txt`]: ftp://ftp.unicode.org/Public/UNIDATA/SpecialCasing.txt
     ///
-    /// [2]: http://www.unicode.org/versions/Unicode4.0.0/ch03.pdf#G33992
+    /// [2]: http://www.unicode.org/versions/Unicode7.0.0/ch03.pdf#G33992
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn to_uppercase(self) -> ToUppercase {
-        ToUppercase(Some(conversions::to_upper(self)))
+        ToUppercase(CaseMappingIter::new(conversions::to_upper(self)))
     }
 
     /// Returns this character's displayed width in columns, or `None` if it is a