Improve error handling

src/cli/error.rs

@@ -1,19 +1,35 @@
 use std::result;
 
-use crate::{eval, files};
+use crate::eval;
+use crate::files::Files;
 
 #[derive(Debug, thiserror::Error)]
 pub enum Error {
-    #[error("{0}")]
-    Files(#[from] files::Error),
     #[error("{0}")]
     Eval(#[from] eval::Error),
-    #[error("No number specified")]
-    NoNumber,
     #[error("No entry with number {0}")]
     NoSuchEntry(usize),
     #[error("Not a task")]
     NotATask(Vec<usize>),
 }
 
+impl Error {
+    pub fn print(&self, files: &Files) {
+        match self {
+            Error::Eval(e) => e.print(files),
+            Error::NoSuchEntry(n) => eprintln!("No entry with number {}", n),
+            Error::NotATask(ns) => {
+                if ns.is_empty() {
+                    eprintln!("Not a task.");
+                } else if ns.len() == 1 {
+                    eprintln!("{} is not a task.", ns[0]);
+                } else {
+                    let ns = ns.iter().map(|n| n.to_string()).collect::<Vec<_>>();
+                    eprintln!("{} are not tasks.", ns.join(", "));
+                }
+            }
+        }
+    }
+}
+
 pub type Result<T> = result::Result<T, Error>;