Rollup merge of rust-lang#66737 - GuillaumeGomez:err-codes-cleanup, r=Dylan-DPC

Error codes cleanup

r? @Dylan-DPC

Author: tmandry

Diff for: src/librustc_error_codes/error_codes/E0062.md

@@ -1,6 +1,6 @@
-This error indicates that during an attempt to build a struct or struct-like
-enum variant, one of the fields was specified more than once. Erroneous code
-example:
+A struct's or struct-like enum variant's field was specified more than once.
+
+Erroneous code example:
 
 ```compile_fail,E0062
 struct Foo {
@@ -15,7 +15,9 @@ fn main() {
 }
 ```
 
-Each field should be specified exactly one time. Example:
+This error indicates that during an attempt to build a struct or struct-like
+enum variant, one of the fields was specified more than once. Each field should
+be specified exactly one time. Example:
 
 ```
 struct Foo {

Diff for: src/librustc_error_codes/error_codes/E0063.md

@@ -1,5 +1,6 @@
-This error indicates that during an attempt to build a struct or struct-like
-enum variant, one of the fields was not provided. Erroneous code example:
+A struct's or struct-like enum variant's field was not provided.
+
+Erroneous code example:
 
 ```compile_fail,E0063
 struct Foo {

Diff for: src/librustc_error_codes/error_codes/E0067.md

@@ -1,33 +1,15 @@
-The left-hand side of a compound assignment expression must be a place
-expression. A place expression represents a memory location and includes
-item paths (ie, namespaced variables), dereferences, indexing expressions,
-and field references.
+An invalid left-hand side expression was used on an assignment operation.
 
-Let's start with some erroneous code examples:
+Erroneous code example:
 
 ```compile_fail,E0067
-use std::collections::LinkedList;
-
-// Bad: assignment to non-place expression
-LinkedList::new() += 1;
-
-// ...
-
-fn some_func(i: &mut i32) {
-    i += 12; // Error : '+=' operation cannot be applied on a reference !
-}
+12 += 1; // error!
 ```
 
-And now some working examples:
+You need to have a place expression to be able to assign it something. For
+example:
 
 ```
-let mut i : i32 = 0;
-
-i += 12; // Good !
-
-// ...
-
-fn some_func(i: &mut i32) {
-    *i += 12; // Good !
-}
+let mut x: i8 = 12;
+x += 1; // ok!
 ```

Diff for: src/librustc_error_codes/error_codes/E0069.md

@@ -1,5 +1,7 @@
 The compiler found a function whose body contains a `return;` statement but
-whose return type is not `()`. An example of this is:
+whose return type is not `()`.
+
+Erroneous code example:
 
 ```compile_fail,E0069
 // error

Diff for: src/librustc_error_codes/error_codes/E0070.md

@@ -1,41 +1,43 @@
-The left-hand side of an assignment operator must be a place expression. A
-place expression represents a memory location and can be a variable (with
-optional namespacing), a dereference, an indexing expression or a field
-reference.
+An assignment operator was used on a non-place expression.
 
-More details can be found in the [Expressions] section of the Reference.
-
-[Expressions]: https://doc.rust-lang.org/reference/expressions.html#places-rvalues-and-temporaries
-
-Now, we can go further. Here are some erroneous code examples:
+Erroneous code examples:
 
 ```compile_fail,E0070
 struct SomeStruct {
     x: i32,
-    y: i32
+    y: i32,
 }
 
-const SOME_CONST : i32 = 12;
+const SOME_CONST: i32 = 12;
 
 fn some_other_func() {}
 
 fn some_function() {
-    SOME_CONST = 14; // error : a constant value cannot be changed!
-    1 = 3; // error : 1 isn't a valid place!
-    some_other_func() = 4; // error : we cannot assign value to a function!
-    SomeStruct.x = 12; // error : SomeStruct a structure name but it is used
-                       // like a variable!
+    SOME_CONST = 14; // error: a constant value cannot be changed!
+    1 = 3; // error: 1 isn't a valid place!
+    some_other_func() = 4; // error: we cannot assign value to a function!
+    SomeStruct::x = 12; // error: SomeStruct a structure name but it is used
+                        //        like a variable!
 }
 ```
 
+The left-hand side of an assignment operator must be a place expression. A
+place expression represents a memory location and can be a variable (with
+optional namespacing), a dereference, an indexing expression or a field
+reference.
+
+More details can be found in the [Expressions] section of the Reference.
+
+[Expressions]: https://doc.rust-lang.org/reference/expressions.html#places-rvalues-and-temporaries
+
 And now let's give working examples:
 
 ```
 struct SomeStruct {
     x: i32,
-    y: i32
+    y: i32,
 }
-let mut s = SomeStruct {x: 0, y: 0};
+let mut s = SomeStruct { x: 0, y: 0 };
 
 s.x = 3; // that's good !