锈迹斑斑_端_匹配类型不匹配

我有下面的代码来计算忽略标点符号的单词数。

use std::collections::HashMap;

fn word_count(words: &str) -> HashMap<String, u32> {
    let mut hm: HashMap<String, u32> = HashMap::new();
    words
        .split_whitespace()
        .map(|word| word.trim_end_matches(char::is_ascii_punctuation))
        .map(|word| {
            hm.entry(word.to_string())
                .and_modify(|val| *val += 1)
                .or_insert(0)
        });
    hm
}

但编译器抱怨

error[E0631]: type mismatch in function arguments
 --> src/lib.rs:7:26
  |
7 |         .map(|word| word.trim_end_matches(char::is_ascii_punctuation))
  |                          ^^^^^^^^^^^^^^^^
  |                          |
  |                          expected signature of `fn(char) -> _`
  |                          found signature of `for<'r> fn(&'r char) -> _`
  |
  = note: required because of the requirements on the impl of `std::str::pattern::Pattern<'_>` for `for<'r> fn(&'r char) -> bool {std::char::methods::<impl char>::is_ascii_punctuation}`

我搞不清这个错误的真正含义,也弄不清我的用法与文档中的用法有何不同 trim_end_matches : assert_eq!("123foo1bar123".trim_end_matches(char::is_numeric), "123foo1bar");