#[feature(type_alias_impl_trait)] 이거 안 쓰면 나오는 에러

rust1_74/b01_opaque_types01/README.md

@@ -2,6 +2,44 @@
 
 https://github.com/rust-lang/rust/issues/63063
 
+```
+$ cargo r
+   Compiling b01_opaque_types01 v0.1.0 (/Users/globalyoung/Documents/test/test/rust/rust_release/rust1_74/b01_opaque_types01)
+warning: type alias `Foo` is never used
+ --> src/main.rs:4:6
+  |
+4 | type Foo<T> = impl MyTrait;
+  |      ^^^
+  |
+  = note: `#[warn(dead_code)]` on by default
+
+warning: fields `a`, `b`, and `c` are never read
+ --> src/main.rs:7:5
+  |
+6 | struct MyStruct<A, B, C> {
+  |        -------- fields in this struct
+7 |     a: A,
+  |     ^
+8 |     b: B,
+  |     ^
+9 |     c: C,
+  |     ^
+
+warning: function `foo` is never used
+  --> src/main.rs:13:4
+   |
+13 | fn foo<T>(t: T) -> Foo<T> {
+   |    ^^^
+
+warning: `b01_opaque_types01` (bin "b01_opaque_types01") generated 3 warnings
+    Finished dev [unoptimized + debuginfo] target(s) in 0.19s
+     Running `target/debug/b01_opaque_types01`
+Hello, world!
+```
+
+
+- ```#![feature(type_alias_impl_trait)]``` 이거 안 쓰면 나오는 에러 
+
 ```
 `impl Trait` in type aliases is unstable
  --> src/main.rs:2:15

rust1_74/b01_opaque_types01/src/main.rs

@@ -1,4 +1,6 @@
+#![feature(type_alias_impl_trait)]
 trait MyTrait {}
+
 type Foo<T> = impl MyTrait;
 
 struct MyStruct<A, B, C> {