Rollup merge of #66774 - GuillaumeGomez:cleanup-err-codes-2, r=Dylan-DPC

Clean up error codes

r? @Dylan-DPC

src/librustc_error_codes/error_codes/E0071.md

@@ -1,5 +1,5 @@
-You tried to use structure-literal syntax to create an item that is
-not a structure or enum variant.
+A structure-literal syntax was used to create an item that is not a structure
+or enum variant.
 
 Example of erroneous code:
 
@@ -9,8 +9,8 @@ let t = U32 { value: 4 }; // error: expected struct, variant or union type,
                           // found builtin type `u32`
 ```
 
-To fix this, ensure that the name was correctly spelled, and that
-the correct form of initializer was used.
+To fix this, ensure that the name was correctly spelled, and that the correct
+form of initializer was used.
 
 For example, the code above can be fixed to:
 

src/librustc_error_codes/error_codes/E0072.md

@@ -1,20 +1,23 @@
-When defining a recursive struct or enum, any use of the type being defined
-from inside the definition must occur behind a pointer (like `Box` or `&`).
-This is because structs and enums must have a well-defined size, and without
-the pointer, the size of the type would need to be unbounded.
+A recursive type has infinite size because it doesn't have an indirection.
 
-Consider the following erroneous definition of a type for a list of bytes:
+Erroneous code example:
 
 ```compile_fail,E0072
-// error, invalid recursive struct type
 struct ListNode {
     head: u8,
-    tail: Option<ListNode>,
+    tail: Option<ListNode>, // error: no indirection here so impossible to
+                            //        compute the type's size
 }
 ```
 
-This type cannot have a well-defined size, because it needs to be arbitrarily
-large (since we would be able to nest `ListNode`s to any depth). Specifically,
+When defining a recursive struct or enum, any use of the type being defined
+from inside the definition must occur behind a pointer (like `Box`, `&` or
+`Rc`). This is because structs and enums must have a well-defined size, and
+without the pointer, the size of the type would need to be unbounded.
+
+In the example, the type cannot have a well-defined size, because it needs to be
+arbitrarily large (since we would be able to nest `ListNode`s to any depth).
+Specifically,
 
 ```plain
 size of `ListNode` = 1 byte for `head`

src/librustc_error_codes/error_codes/E0075.md

@@ -1,21 +1,23 @@
-The `#[simd]` attribute can only be applied to non empty tuple structs, because
-it doesn't make sense to try to use SIMD operations when there are no values to
-operate on.
+A `#[simd]` attribute was applied to an empty tuple struct.
 
-This will cause an error:
+Erroneous code example:
 
 ```compile_fail,E0075
 #![feature(repr_simd)]
 
 #[repr(simd)]
-struct Bad;
+struct Bad; // error!
 ```
 
-This will not:
+The `#[simd]` attribute can only be applied to non empty tuple structs, because
+it doesn't make sense to try to use SIMD operations when there are no values to
+operate on.
+
+Fixed example:
 
 ```
 #![feature(repr_simd)]
 
 #[repr(simd)]
-struct Good(u32);
+struct Good(u32); // ok!
 ```

src/librustc_error_codes/error_codes/E0076.md

@@ -1,21 +1,24 @@
-When using the `#[simd]` attribute to automatically use SIMD operations in tuple
-struct, the types in the struct must all be of the same type, or the compiler
-will trigger this error.
+All types in a tuple struct aren't the same when using the `#[simd]`
+attribute.
 
-This will cause an error:
+Erroneous code example:
 
 ```compile_fail,E0076
 #![feature(repr_simd)]
 
 #[repr(simd)]
-struct Bad(u16, u32, u32);
+struct Bad(u16, u32, u32); // error!
 ```
 
-This will not:
+When using the `#[simd]` attribute to automatically use SIMD operations in tuple
+struct, the types in the struct must all be of the same type, or the compiler
+will trigger this error.
+
+Fixed example:
 
 ```
 #![feature(repr_simd)]
 
 #[repr(simd)]
-struct Good(u32, u32, u32);
+struct Good(u32, u32, u32); // ok!
 ```

src/librustc_error_codes/error_codes/E0077.md

@@ -1,20 +1,23 @@
-When using the `#[simd]` attribute on a tuple struct, the elements in the tuple
-must be machine types so SIMD operations can be applied to them.
+A tuple struct's element isn't a machine type when using the `#[simd]`
+attribute.
 
-This will cause an error:
+Erroneous code example:
 
 ```compile_fail,E0077
 #![feature(repr_simd)]
 
 #[repr(simd)]
-struct Bad(String);
+struct Bad(String); // error!
 ```
 
-This will not:
+When using the `#[simd]` attribute on a tuple struct, the elements in the tuple
+must be machine types so SIMD operations can be applied to them.
+
+Fixed example:
 
 ```
 #![feature(repr_simd)]
 
 #[repr(simd)]
-struct Good(u32, u32, u32);
+struct Good(u32, u32, u32); // ok!
 ```