Use todo!() instead of unimplemented!()

The difference is one of intent, and the actual panic message.
See the docs why todo is more appropriate:
https://doc.rust-lang.org/stable/std/macro.todo.html

[no important files changed]

closes #1598

Author: senekor

concepts/structs/about.md

@@ -32,7 +32,7 @@ Lastly, methods can be defined on structs inside of an `impl` block:
 impl Item {
     // initializes and returns a new instance of our Item struct
     fn new() -> Self {
-        unimplemented!()
+        todo!()
     }
 }
 ```

exercises/concept/assembly-line/src/lib.rs

@@ -1,7 +1,7 @@
 pub fn production_rate_per_hour(speed: u8) -> f64 {
-    unimplemented!("calculate hourly production rate at speed: {speed}")
+    todo!("calculate hourly production rate at speed: {speed}")
 }
 
 pub fn working_items_per_minute(speed: u8) -> u32 {
-    unimplemented!("calculate the amount of working items at speed: {speed}")
+    todo!("calculate the amount of working items at speed: {speed}")
 }

exercises/concept/csv-builder/src/lib.rs

@@ -9,16 +9,16 @@ pub struct CsvRecordBuilder {
 impl CsvRecordBuilder {
     // Create a new builder
     pub fn new() -> Self {
-        unimplemented!("implement the `CsvRecordBuilder::new` method")
+        todo!("implement the `CsvRecordBuilder::new` method")
     }
 
     /// Adds an item to the list separated by a space and a comma.
     pub fn add(&mut self, val: &str) {
-        unimplemented!("implement the `CsvRecordBuilder::add` method, adding {val}")
+        todo!("implement the `CsvRecordBuilder::add` method, adding {val}")
     }
 
     /// Consumes the builder and returns the comma separated list
     pub fn build(self) -> String {
-        unimplemented!("implement the `CsvRecordBuilder::build` method")
+        todo!("implement the `CsvRecordBuilder::build` method")
     }
 }

exercises/concept/health-statistics/.docs/introduction.md

@@ -32,7 +32,7 @@ Lastly, methods can be defined on structs inside of an `impl` block:
 impl Item {
     // initializes and returns a new instance of our Item struct
     fn new() -> Self {
-        unimplemented!()
+        todo!()
     }
 }
 ```

exercises/concept/health-statistics/src/lib.rs

@@ -10,26 +10,26 @@ pub struct User {
 
 impl User {
     pub fn new(name: String, age: u32, weight: f32) -> Self {
-        unimplemented!()
+        todo!()
     }
 
     pub fn name(&self) -> &str {
-        unimplemented!()
+        todo!()
     }
 
     pub fn age(&self) -> u32 {
-        unimplemented!()
+        todo!()
     }
 
     pub fn weight(&self) -> f32 {
-        unimplemented!()
+        todo!()
     }
 
     pub fn set_age(&mut self, new_age: u32) {
-        unimplemented!()
+        todo!()
     }
 
     pub fn set_weight(&mut self, new_weight: f32) {
-        unimplemented!()
+        todo!()
     }
 }

exercises/concept/low-power-embedded-game/.docs/hints.md

@@ -18,6 +18,6 @@
 
 ## 3. Implement a `manhattan` method on a `Position` tuple struct
 
-- Don't worry about method syntax; just replacing the `unimplemented` portion within the `impl Position` block will do the right thing.
+- Don't worry about method syntax; just replacing the `todo` portion within the `impl Position` block will do the right thing.
 - Consider that some values within a `Position` may be negative, but a distance is never negative.
 - Calculating the absolute value is [built-in](https://doc.rust-lang.org/std/primitive.i16.html#method.abs)

exercises/concept/low-power-embedded-game/src/lib.rs

@@ -3,11 +3,11 @@
 #![allow(unused)]
 
 pub fn divmod(dividend: i16, divisor: i16) -> (i16, i16) {
-    unimplemented!("implement `fn divmod`");
+    todo!("implement `fn divmod`");
 }
 
 pub fn evens<T>(iter: impl Iterator<Item = T>) -> impl Iterator<Item = T> {
-    unimplemented!("implement `fn evens`");
+    todo!("implement `fn evens`");
     // TODO: remove this; it's only necessary to allow this function to compile
     // before the student has done any work.
     std::iter::empty()
@@ -16,6 +16,6 @@ pub fn evens<T>(iter: impl Iterator<Item = T>) -> impl Iterator<Item = T> {
 pub struct Position(pub i16, pub i16);
 impl Position {
     pub fn manhattan(&self) -> i16 {
-        unimplemented!("implement `fn manhattan`")
+        todo!("implement `fn manhattan`")
     }
 }

exercises/concept/lucians-luscious-lasagna/src/lib.rs

@@ -1,19 +1,19 @@
 pub fn expected_minutes_in_oven() -> i32 {
-    unimplemented!("return expected minutes in the oven")
+    todo!("return expected minutes in the oven")
 }
 
 pub fn remaining_minutes_in_oven(actual_minutes_in_oven: i32) -> i32 {
-    unimplemented!(
+    todo!(
         "calculate remaining minutes in oven given actual minutes in oven: {actual_minutes_in_oven}"
     )
 }
 
 pub fn preparation_time_in_minutes(number_of_layers: i32) -> i32 {
-    unimplemented!("calculate preparation time in minutes for number of layers: {number_of_layers}")
+    todo!("calculate preparation time in minutes for number of layers: {number_of_layers}")
 }
 
 pub fn elapsed_time_in_minutes(number_of_layers: i32, actual_minutes_in_oven: i32) -> i32 {
-    unimplemented!(
+    todo!(
         "calculate elapsed time in minutes for number of layers {number_of_layers} and actual minutes in oven {actual_minutes_in_oven}"
     )
 }

exercises/concept/magazine-cutout/.docs/instructions.md

@@ -13,7 +13,7 @@ You'll start with the following stubbed function signature:
 
 ```rust
 pub fn can_construct_note(magazine: &[&str], note: &[&str]) -> bool {
-    unimplemented!()
+    todo!()
 }
 ```
 

exercises/concept/magazine-cutout/src/lib.rs

@@ -5,5 +5,5 @@
 use std::collections::HashMap;
 
 pub fn can_construct_note(magazine: &[&str], note: &[&str]) -> bool {
-    unimplemented!()
+    todo!()
 }