Rollup merge of rust-lang#47298 - cramertj:path-as-modrs, r=nikomatsakis

Treat #[path] files as mod.rs files

Fixes rust-lang#46936, cc @briansmith, @SergioBenitez, @nikomatsakis.

This (insta-stable) change treats files included via `#[path = "bla.rs"] mod foo;` as though they were `mod.rs` files. Namely, it allows them to include `mod` statements and looks for the child modules in sibling directories, rather than in relative `modname/childmodule.rs` files as happens for non-`mod.rs` files.

This change makes the `non_modrs_mods` feature backwards compatible with the existing usage in https://github.com/briansmith/ring, several versions of which are currently broken in beta. If we decide to merge, this change should be backported to beta.

cc rust-lang#37872

r? @jseyfried

src/libsyntax/parse/parser.rs

@@ -5894,10 +5894,14 @@ impl<'a> Parser<'a> {
         if let Some(path) = Parser::submod_path_from_attr(outer_attrs, &self.directory.path) {
             return Ok(ModulePathSuccess {
                 directory_ownership: match path.file_name().and_then(|s| s.to_str()) {
-                    Some("mod.rs") => DirectoryOwnership::Owned { relative: None },
-                    Some(_) => {
-                        DirectoryOwnership::Owned { relative: Some(id) }
-                    }
+                    // All `#[path]` files are treated as though they are a `mod.rs` file.
+                    // This means that `mod foo;` declarations inside `#[path]`-included
+                    // files are siblings,
+                    //
+                    // Note that this will produce weirdness when a file named `foo.rs` is
+                    // `#[path]` included and contains a `mod foo;` declaration.
+                    // If you encounter this, it's your own darn fault :P
+                    Some(_) => DirectoryOwnership::Owned { relative: None },
                     _ => DirectoryOwnership::UnownedViaMod(true),
                 },
                 path,

src/test/ui/non_modrs_mods/non_modrs_mods.stderr

@@ -34,14 +34,5 @@ error: mod statements in non-mod.rs files are unstable (see issue #44660)
    = help: add #![feature(non_modrs_mods)] to the crate attributes to enable
    = help: on stable builds, rename this file to inner_foors_mod/mod.rs
 
-error: mod statements in non-mod.rs files are unstable (see issue #44660)
-  --> $DIR/some_crazy_attr_mod_dir/arbitrary_name.rs:11:9
-   |
-11 | pub mod inner_modrs_mod;
-   |         ^^^^^^^^^^^^^^^
-   |
-   = help: add #![feature(non_modrs_mods)] to the crate attributes to enable
-   = help: on stable builds, rename this file to attr_mod/mod.rs
-
-error: aborting due to 5 previous errors
+error: aborting due to 4 previous errors