Fix error codes explanation' code examples
diff --git a/src/librustc_error_codes/error_codes/E0445.md b/src/librustc_error_codes/error_codes/E0445.md
index 9cc62b2..e6a28a9 100644
--- a/src/librustc_error_codes/error_codes/E0445.md
+++ b/src/librustc_error_codes/error_codes/E0445.md
@@ -12,6 +12,8 @@
pub trait Bar : Foo {} // error: private trait in public interface
pub struct Bar2<T: Foo>(pub T); // same error
pub fn foo<T: Foo> (t: T) {} // same error
+
+fn main() {}
```
To solve this error, please ensure that the trait is also public. The trait
@@ -26,4 +28,6 @@
pub trait Bar : Foo {} // ok!
pub struct Bar2<T: Foo>(pub T); // ok!
pub fn foo<T: Foo> (t: T) {} // ok!
+
+fn main() {}
```
diff --git a/src/librustc_error_codes/error_codes/E0446.md b/src/librustc_error_codes/error_codes/E0446.md
index d014447..77a1834 100644
--- a/src/librustc_error_codes/error_codes/E0446.md
+++ b/src/librustc_error_codes/error_codes/E0446.md
@@ -12,6 +12,8 @@
Bar(0)
}
}
+
+fn main() {}
```
To solve this error, please ensure that the type is also public. The type
@@ -27,4 +29,6 @@
Bar(0)
}
}
+
+fn main() {}
```
diff --git a/src/librustc_error_codes/error_codes/E0491.md b/src/librustc_error_codes/error_codes/E0491.md
index 1ccaf71..d45663f 100644
--- a/src/librustc_error_codes/error_codes/E0491.md
+++ b/src/librustc_error_codes/error_codes/E0491.md
@@ -3,30 +3,34 @@
Erroneous code example:
```compile_fail,E0491
-trait SomeTrait<'a> {
- type Output;
+struct Foo<'a> {
+ x: fn(&'a i32),
}
-impl<'a, T> SomeTrait<'a> for T {
- type Output = &'a T; // compile error E0491
+trait Trait<'a, 'b> {
+ type Out;
+}
+
+impl<'a, 'b> Trait<'a, 'b> for usize {
+ type Out = &'a Foo<'b>; // error!
}
```
-Here, the problem is that a reference type like `&'a T` is only valid
-if all the data in T outlives the lifetime `'a`. But this impl as written
-is applicable to any lifetime `'a` and any type `T` -- we have no guarantee
-that `T` outlives `'a`. To fix this, you can add a where clause like
-`where T: 'a`.
+Here, the problem is that the compiler cannot be sure that the `'b` lifetime
+will live longer than `'a`, which should be mandatory in order to be sure that
+`Trait::Out` will always have a reference pointing to an existing type. So in
+this case, we just need to tell the compiler than `'b` must outlive `'a`:
```
-trait SomeTrait<'a> {
- type Output;
+struct Foo<'a> {
+ x: fn(&'a i32),
}
-impl<'a, T> SomeTrait<'a> for T
-where
- T: 'a,
-{
- type Output = &'a T; // compile error E0491
+trait Trait<'a, 'b> {
+ type Out;
+}
+
+impl<'a, 'b: 'a> Trait<'a, 'b> for usize { // we added the lifetime enforcement
+ type Out = &'a Foo<'b>; // it now works!
}
```
