Wrap lines using the character width not count

Instead of counting the number of grapheme clusters per line, we now
count the character _widths_. This ensures that lines containing double
width characters are wrapped correctly.

Changelog: fixed

compiler/Cargo.toml

@@ -14,7 +14,7 @@ doctest = false
 ast = { path = "../ast" }
 types = { path = "../types" }
 location = { path = "../location" }
-unicode-segmentation = "^1.10"
+unicode-width = "^0.2"
 getopts = "^0.2"
 fnv = "^1.0"
 blake3 = "^1.5"

compiler/src/format.rs

@@ -12,7 +12,7 @@ use std::collections::HashSet;
 use std::fs::{read, write};
 use std::io::{stdin, stdout, Error as IoError, Read as _, Write as _};
 use std::path::PathBuf;
-use unicode_segmentation::UnicodeSegmentation as _;
+use unicode_width::UnicodeWidthStr;
 
 /// The characters to use for indentation.
 const INDENT: char = ' ';
@@ -79,7 +79,7 @@ enum Node {
     /// The arguments are:
     ///
     /// 1. The text that may include Unicode characters
-    /// 2. The number of grapheme clusters in the string
+    /// 2. The width (in cells) of the string.
     Unicode(String, usize),
 
     /// A node to include if the code is to be wrapped across lines.
@@ -149,7 +149,7 @@ impl Node {
     }
 
     fn unicode(text: String) -> Node {
-        let width = text.graphemes(true).count();
+        let width = text.width();
 
         Node::Unicode(text, width)
     }

std/fixtures/fmt/double_width_characters/input.inko

@@ -0,0 +1 @@
+let FULL_WEEKDAYS = ['日曜日', '月曜日', '火曜日', '水曜日', '木曜日', '金曜日', '土曜日']

std/fixtures/fmt/double_width_characters/output.inko

@@ -0,0 +1,9 @@
+let FULL_WEEKDAYS = [
+  '日曜日',
+  '月曜日',
+  '火曜日',
+  '水曜日',
+  '木曜日',
+  '金曜日',
+  '土曜日',
+]