Revert "fn replace_string_in_place"

This reverts commit 234f9d2.

build.rs

@@ -10,7 +10,6 @@ use std::io;
 use std::io::BufRead;
 use std::io::BufReader;
 use std::iter::Iterator;
-use std::ops::Range;
 use std::path::{Path, PathBuf};
 use std::time::Instant;
 use unicode_segmentation::UnicodeSegmentation;
@@ -58,26 +57,8 @@ impl WordsData {
     fn read_lines(&self) -> impl Iterator<Item = String> {
         read_lines_of_file(Path::new(self.path.as_str()))
             .expect("Reading file should not fail.")
-            .filter_map(|mut word: String| {
-                if word.is_empty() {
-                    return None;
-                }
-                replace_string_in_place(
-                    &mut word,
-                    #[inline]
-                    |ch| {
-                        ch.is_uppercase().then(
-                            #[inline]
-                            || ch.to_lowercase(),
-                        )
-                    },
-                    #[inline]
-                    |string, range, repl| {
-                        string.replace_range(range, repl.to_string().as_str())
-                    },
-                );
-                Some(word)
-            })
+            .filter(|word| !word.is_empty())
+            .map(|word| word.to_lowercase())
             .map(self.conv)
     }
 
@@ -175,38 +156,22 @@ fn str_contains_umlaut(string: String) -> bool {
 #[allow(clippy::ptr_arg)]
 #[allow(clippy::needless_pass_by_value)]
 fn replace_umlauts(mut string: String) -> String {
-    replace_string_in_place(
-        &mut string,
-        #[inline]
-        |ch| {
+    while let Some((idx, ch, repl_index)) =
+        string.char_indices().find_map(|(idx, ch)| {
             UMLAUTS
                 .iter()
                 .position(|u| u == &ch)
-                .and_then(|repl_idx| ASCII_UMLAUT_REPLACEMENTS.get(repl_idx))
-                .copied()
-        },
-        #[inline]
-        |s, range, repl| s.replace_range(range, repl),
-    );
-    string
-}
-
-#[inline]
-fn replace_string_in_place<S, RR, RC>(
-    string: &mut String,
-    replace_char: RC,
-    replace_range: RR,
-) where
-    RC: Fn(char) -> Option<S>,
-    RR: Fn(&mut String, Range<usize>, S),
-{
-    while let Some((idx, ch, repl)) = string
-        .char_indices()
-        .rev()
-        .find_map(|(idx, ch)| replace_char(ch).map(|repl| (idx, ch, repl)))
+                .map(|repl_idx| (idx, ch, repl_idx))
+        })
     {
-        replace_range(string, idx..idx + ch.len_utf8(), repl);
+        string.replace_range(
+            idx..idx + ch.len_utf8(),
+            ASCII_UMLAUT_REPLACEMENTS
+                .get(repl_index)
+                .expect("Can find replacement"),
+        );
     }
+    string
 }
 
 const WORDS_DIR: &str = "./words/";