finish generics

exercises/generics/generics1.rs

@@ -3,9 +3,7 @@
 
 // Execute `rustlings hint generics1` for hints!
 
-// I AM NOT DONE
-
 fn main() {
-    let mut shopping_list: Vec<?> = Vec::new();
+    let mut shopping_list: Vec<_> = Vec::new();
     shopping_list.push("milk");
 }

exercises/generics/generics2.rs

@@ -3,14 +3,12 @@
 
 // Execute `rustlings hint generics2` for hints!
 
-// I AM NOT DONE
-
-struct Wrapper {
-    value: u32,
+struct Wrapper<T> {
+    value: T,
 }
 
-impl Wrapper {
-    pub fn new(value: u32) -> Self {
+impl<T> Wrapper<T> {
+    pub fn new(value: T) -> Self {
         Wrapper { value }
     }
 }

exercises/generics/generics3.rs

@@ -10,15 +10,18 @@
 
 // Execute 'rustlings hint generics3' for hints!
 
-// I AM NOT DONE
+pub trait ReportCardGrade: std::fmt::Display {}
 
-pub struct ReportCard {
-    pub grade: f32,
+impl ReportCardGrade for f32 {}
+impl ReportCardGrade for &str {}
+
+pub struct ReportCard<T: ReportCardGrade> {
+    pub grade: T,
     pub student_name: String,
     pub student_age: u8,
 }
 
-impl ReportCard {
+impl<T: ReportCardGrade> ReportCard<T> {
     pub fn print(&self) -> String {
         format!("{} ({}) - achieved a grade of {}",
             &self.student_name, &self.student_age, &self.grade)
@@ -46,7 +49,7 @@ mod tests {
     fn generate_alphabetic_report_card() {
         // TODO: Make sure to change the grade here after you finish the exercise.
         let report_card = ReportCard {
-            grade: 2.1,
+            grade: "A+",
             student_name: "Gary Plotter".to_string(),
             student_age: 11,
         };