Rollup merge of rust-lang#66443 - GuillaumeGomez:port-erased-cleanup, r=Mark-Simulacrum

Port erased cleanup

Just realised that the changes I made in rust-lang#65965 were removed after the move of all error codes so here it is. I made them into separate commits to make the history look better this time.

r? @Mark-Simulacrum

Author: tmandry

src/librustc_error_codes/error_codes.rs

@@ -1,6 +1,11 @@
 // Error messages for EXXXX errors.  Each message should start and end with a
 // new line, and be wrapped to 80 characters.  In vim you can `:set tw=80` and
 // use `gq` to wrap paragraphs. Use `:set tw=0` to disable.
+//
+// /!\ IMPORTANT /!\
+//
+// Error messages' format must follow the RFC 1567 available here:
+// https://github.com/rust-lang/rfcs/pull/1567
 
 crate::register_diagnostics! {
 

src/librustc_error_codes/error_codes/E0023.md

@@ -1,6 +1,6 @@
-A pattern used to match against an enum variant must provide a sub-pattern for
-each field of the enum variant. This error indicates that a pattern attempted to
-extract an incorrect number of fields from a variant.
+A pattern attempted to extract an incorrect number of fields from a variant.
+
+Erroneous code example:
 
 ```
 enum Fruit {
@@ -9,6 +9,9 @@ enum Fruit {
 }
 ```
 
+A pattern used to match against an enum variant must provide a sub-pattern for
+each field of the enum variant.
+
 Here the `Apple` variant has two fields, and should be matched against like so:
 
 ```

src/librustc_error_codes/error_codes/E0025.md

@@ -1,5 +1,6 @@
-Each field of a struct can only be bound once in a pattern. Erroneous code
-example:
+Each field of a struct can only be bound once in a pattern.
+
+Erroneous code example:
 
 ```compile_fail,E0025
 struct Foo {

src/librustc_error_codes/error_codes/E0026.md

@@ -1,51 +1,34 @@
-This error indicates that a struct pattern attempted to extract a non-existent
-field from a struct. Struct fields are identified by the name used before the
-colon `:` so struct patterns should resemble the declaration of the struct type
-being matched.
+A struct pattern attempted to extract a non-existent field from a struct.
 
-```
-// Correct matching.
-struct Thing {
-    x: u32,
-    y: u32
-}
-
-let thing = Thing { x: 1, y: 2 };
-
-match thing {
-    Thing { x: xfield, y: yfield } => {}
-}
-```
-
-If you are using shorthand field patterns but want to refer to the struct field
-by a different name, you should rename it explicitly.
-
-Change this:
+Erroneous code example:
 
 ```compile_fail,E0026
 struct Thing {
     x: u32,
-    y: u32
+    y: u32,
 }
 
 let thing = Thing { x: 0, y: 0 };
 
 match thing {
-    Thing { x, z } => {}
+    Thing { x, z } => {} // error: `Thing::z` field doesn't exist
 }
 ```
 
-To this:
+If you are using shorthand field patterns but want to refer to the struct field
+by a different name, you should rename it explicitly. Struct fields are
+identified by the name used before the colon `:` so struct patterns should
+resemble the declaration of the struct type being matched.
 
 ```
 struct Thing {
     x: u32,
-    y: u32
+    y: u32,
 }
 
 let thing = Thing { x: 0, y: 0 };
 
 match thing {
-    Thing { x, y: z } => {}
+    Thing { x, y: z } => {} // we renamed `y` to `z`
 }
 ```

src/librustc_error_codes/error_codes/E0027.md

@@ -1,8 +1,7 @@
-This error indicates that a pattern for a struct fails to specify a sub-pattern
-for every one of the struct's fields. Ensure that each field from the struct's
-definition is mentioned in the pattern, or use `..` to ignore unwanted fields.
+A pattern for a struct fails to specify a sub-pattern for every one of the
+struct's fields.
 
-For example:
+Erroneous code example:
 
 ```compile_fail,E0027
 struct Dog {
@@ -18,7 +17,8 @@ match d {
 }
 ```
 
-This is correct (explicit):
+To fix this error, ensure that each field from the struct's definition is
+mentioned in the pattern, or use `..` to ignore unwanted fields. Example:
 
 ```
 struct Dog {

src/librustc_error_codes/error_codes/E0029.md

@@ -1,8 +1,6 @@
-In a match expression, only numbers and characters can be matched against a
-range. This is because the compiler checks that the range is non-empty at
-compile-time, and is unable to evaluate arbitrary comparison functions. If you
-want to capture values of an orderable type between two end-points, you can use
-a guard.
+Something other than numbers and characters has been used for a range.
+
+Erroneous code example:
 
 ```compile_fail,E0029
 let string = "salutations !";
@@ -20,3 +18,9 @@ match string {
     _ => {}
 }
 ```
+
+In a match expression, only numbers and characters can be matched against a
+range. This is because the compiler checks that the range is non-empty at
+compile-time, and is unable to evaluate arbitrary comparison functions. If you
+want to capture values of an orderable type between two end-points, you can use
+a guard.

src/librustc_error_codes/error_codes/E0033.md

@@ -1,8 +1,6 @@
-This error indicates that a pointer to a trait type cannot be implicitly
-dereferenced by a pattern. Every trait defines a type, but because the
-size of trait implementers isn't fixed, this type has no compile-time size.
-Therefore, all accesses to trait types must be through pointers. If you
-encounter this error you should try to avoid dereferencing the pointer.
+A trait type has been dereferenced.
+
+Erroneous code example:
 
 ```compile_fail,E0033
 # trait SomeTrait { fn method_one(&self){} fn method_two(&self){} }
@@ -17,7 +15,13 @@ trait_obj.method_one();
 trait_obj.method_two();
 ```
 
+A pointer to a trait type cannot be implicitly dereferenced by a pattern. Every
+trait defines a type, but because the size of trait implementers isn't fixed,
+this type has no compile-time size. Therefore, all accesses to trait types must
+be through pointers. If you encounter this error you should try to avoid
+dereferencing the pointer.
+
 You can read more about trait objects in the [Trait Objects] section of the
 Reference.
 
-[Trait Objects]: https://doc.rust-lang.org/reference/types.html#trait-objects
+[Trait Objects]: https://doc.rust-lang.org/reference/types.html#trait-objects

src/librustc_error_codes/error_codes/E0034.md

@@ -1,5 +1,7 @@
 The compiler doesn't know what method to call because more than one method
-has the same prototype. Erroneous code example:
+has the same prototype.
+
+Erroneous code example:
 
 ```compile_fail,E0034
 struct Test;

src/librustc_error_codes/error_codes/E0040.md

@@ -1,8 +1,6 @@
-It is not allowed to manually call destructors in Rust. It is also not
-necessary to do this since `drop` is called automatically whenever a value goes
-out of scope.
+It is not allowed to manually call destructors in Rust.
 
-Here's an example of this error:
+Erroneous code example:
 
 ```compile_fail,E0040
 struct Foo {
@@ -20,3 +18,22 @@ fn main() {
     x.drop(); // error: explicit use of destructor method
 }
 ```
+
+It is unnecessary to do this since `drop` is called automatically whenever a
+value goes out of scope. However, if you really need to drop a value by hand,
+you can use the `std::mem::drop` function:
+
+```
+struct Foo {
+    x: i32,
+}
+impl Drop for Foo {
+    fn drop(&mut self) {
+        println!("kaboom");
+    }
+}
+fn main() {
+    let mut x = Foo { x: -7 };
+    drop(x); // ok!
+}
+```

src/librustc_error_codes/error_codes/E0044.md

@@ -1,4 +1,5 @@
 You cannot use type or const parameters on foreign items.
+
 Example of erroneous code:
 
 ```compile_fail,E0044