Add tests for module suggestions

Author: GuillaumeGomez

src/libsyntax/parse/parser.rs

@@ -57,6 +57,7 @@ use symbol::{Symbol, keywords};
 use util::ThinVec;
 
 use std::collections::HashSet;
+use std::env;
 use std::mem;
 use std::path::{Path, PathBuf};
 use std::rc::Rc;
@@ -5132,17 +5133,29 @@ impl<'a> Parser<'a> {
             let mut err = self.diagnostic().struct_span_err(id_sp,
                 "cannot declare a new module at this location");
             if id_sp != syntax_pos::DUMMY_SP {
-                let full_path = self.sess.codemap().span_to_filename(id_sp);
-                let path = Path::new(&full_path);
-                let filename = path.file_stem().unwrap();
-                let parent = path.parent().unwrap_or(Path::new(""))
-                                          .to_str().unwrap_or("").to_owned();
-                let path = format!("{}/{}",
-                                   if parent.len() == 0 { "." } else { &parent },
-                                   filename.to_str().unwrap_or(""));
-                err.span_note(id_sp,
-                              &format!("maybe move this module `{0}` to its own directory \
-                                        via `{0}/mod.rs`", path));
+                let mut src_path = PathBuf::from(self.sess.codemap().span_to_filename(id_sp));
+                if let Some(stem) = src_path.clone().file_stem() {
+                    let mut dest_path = src_path.clone();
+                    dest_path.set_file_name(stem);
+                    dest_path.push("mod.rs");
+                    if let Ok(cur_dir) = env::current_dir() {
+                        let tmp = if let (Ok(src_path), Ok(dest_path)) =
+                            (Path::new(&src_path).strip_prefix(&cur_dir),
+                             Path::new(&dest_path).strip_prefix(&cur_dir)) {
+                            Some((src_path.to_path_buf(), dest_path.to_path_buf()))
+                        } else {
+                            None
+                        };
+                        if let Some(tmp) = tmp {
+                            src_path = tmp.0;
+                            dest_path = tmp.1;
+                        }
+                    }
+                    err.span_note(id_sp,
+                                  &format!("maybe move this module `{}` to its own \
+                                            directory via `{}`", src_path.to_string_lossy(),
+                                           dest_path.to_string_lossy()));
+                }
             }
             if paths.path_exists {
                 err.span_note(id_sp,

src/test/compile-fail/auxiliary/foo/bar.rs

@@ -0,0 +1,11 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub mod baz;

src/test/compile-fail/auxiliary/foo/mod.rs

@@ -0,0 +1,11 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+pub mod bar;

src/test/compile-fail/invalid-module-declaration.rs

@@ -0,0 +1,20 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// ignore-tidy-linelength
+
+// error-pattern: cannot declare a new module at this location
+// error-pattern: maybe move this module `src/test/compile-fail/auxiliary/foo/bar.rs` to its own directory via `src/test/compile-fail/auxiliary/foo/bar/mod.rs`
+
+mod auxiliary {
+    mod foo;
+}
+
+fn main() {}