Rollup merge of #66777 - GuillaumeGomez:tidy-err-codes, r=Mark-Simulacrum

Put back tidy check on error codes

I just realized that the tidy checks were not run anymore on the error code long explanations. This add it back.

cc @Dylan-DPC
r? @Mark-Simulacrum

src/librustc_error_codes/error_codes/E0015.md

@@ -1,4 +1,5 @@
-A constant item was initialized with something that is not a constant expression.
+A constant item was initialized with something that is not a constant
+expression.
 
 Erroneous code example:
 

src/librustc_error_codes/error_codes/E0107.md

@@ -25,4 +25,3 @@ fn main() {
                     //        expected 0, found 1
 }
 ```
-

src/librustc_error_codes/error_codes/E0369.md

@@ -26,4 +26,3 @@ left and may require reallocation. This requires ownership of the string
 on the left. If something should be added to a string literal, move the
 literal to the heap by allocating it with `to_owned()` like in
 `"Your text".to_owned()`.
-

src/librustc_error_codes/error_codes/E0404.md

@@ -41,4 +41,3 @@ trait Foo {
 
 fn bar<T: Foo>(t: T) {} // ok!
 ```
-

src/librustc_error_codes/error_codes/E0458.md

@@ -10,4 +10,3 @@ Please specify a valid "kind" value, from one of the following:
 * static
 * dylib
 * framework
-

src/librustc_error_codes/error_codes/E0633.md

@@ -21,4 +21,3 @@ The `#[unwind]` attribute should be used as follows:
 
 NB. The default behavior here is "allowed", but this is unspecified
 and likely to change in the future.
-

src/librustc_error_codes/error_codes/E0635.md

@@ -5,4 +5,3 @@ Erroneous code example:
 ```compile_fail,E0635
 #![feature(nonexistent_rust_feature)] // error: unknown feature
 ```
-

src/librustc_error_codes/error_codes/E0636.md

@@ -7,4 +7,3 @@ Erroneous code example:
 #![feature(rust1)]
 #![feature(rust1)] // error: the feature `rust1` has already been declared
 ```
-

src/librustc_error_codes/error_codes/E0644.md

@@ -27,4 +27,3 @@ closure call itself by capturing a `&Fn()` object or `fn()` pointer
 that refers to itself. That is permitting, since the closure would be
 invoking itself via a virtual call, and hence does not directly
 reference its own *type*.
-

src/librustc_error_codes/error_codes/E0706.md

@@ -10,7 +10,8 @@ trait T {
 }
 ```
 
-`async fn`s return an `impl Future`, making the following two examples equivalent:
+`async fn`s return an `impl Future`, making the following two examples
+equivalent:
 
 ```edition2018,ignore (example-of-desugaring-equivalence)
 async fn foo() -> User {
@@ -23,8 +24,8 @@ fn foo(&self) -> impl Future<Output = User> + '_ {
 ```
 
 But when it comes to supporting this in traits, there are [a few implementation
-issues][async-is-hard]. One of them is returning `impl Trait` in traits is not supported,
-as it would require [Generic Associated Types] to be supported:
+issues][async-is-hard]. One of them is returning `impl Trait` in traits is not
+supported, as it would require [Generic Associated Types] to be supported:
 
 ```edition2018,ignore (example-of-desugaring-equivalence)
 impl MyDatabase {
@@ -40,13 +41,14 @@ impl MyDatabase {
 }
 ```
 
-Until these issues are resolved, you can use the [`async-trait` crate], allowing you to use
-`async fn` in traits by desugaring to "boxed futures"
+Until these issues are resolved, you can use the [`async-trait` crate], allowing
+you to use `async fn` in traits by desugaring to "boxed futures"
 (`Pin<Box<dyn Future + Send + 'async>>`).
 
-Note that using these trait methods will result in a heap allocation per-function-call. This is not
-a significant cost for the vast majority of applications, but should be considered when deciding
-whether to use this functionality in the public API of a low-level function that is expected to be
+Note that using these trait methods will result in a heap allocation
+per-function-call. This is not a significant cost for the vast majority of
+applications, but should be considered when deciding whether to use this
+functionality in the public API of a low-level function that is expected to be
 called millions of times a second.
 
 You might be interested in visiting the [async book] for further information.

src/librustc_error_codes/error_codes/E0745.md

@@ -11,7 +11,7 @@ fn temp_address() {
 
 To avoid the error, first bind the temporary to a named local variable.
 
-```ignore
+```ignore (not yet implemented)
 # #![feature(raw_ref_op)]
 fn temp_address() {
     let val = 2;

src/tools/tidy/src/style.rs

@@ -141,17 +141,28 @@ pub fn check(path: &Path, bad: &mut bool) {
     super::walk(path, &mut super::filter_dirs, &mut |entry, contents| {
         let file = entry.path();
         let filename = file.file_name().unwrap().to_string_lossy();
-        let extensions = [".rs", ".py", ".js", ".sh", ".c", ".cpp", ".h"];
+        let extensions = [".rs", ".py", ".js", ".sh", ".c", ".cpp", ".h", ".md"];
         if extensions.iter().all(|e| !filename.ends_with(e)) ||
            filename.starts_with(".#") {
             return
         }
 
+        if filename.ends_with(".md") &&
+           file.parent()
+               .unwrap()
+               .file_name()
+               .unwrap()
+               .to_string_lossy() != "error_codes" {
+            // We don't want to check all ".md" files (almost of of them aren't compliant
+            // currently), just the long error code explanation ones.
+            return;
+        }
+
         if contents.is_empty() {
             tidy_error!(bad, "{}: empty file", file.display());
         }
 
-        let max_columns = if filename == "error_codes.rs" {
+        let max_columns = if filename == "error_codes.rs" || filename.ends_with(".md") {
             ERROR_CODE_COLS
         } else {
             COLS