librustc: Forbid inherent implementations that aren't adjacent to the

type they provide an implementation for.

This breaks code like:

    mod foo {
        struct Foo { ... }
    }

    impl foo::Foo {
        ...
    }

Change this code to:

    mod foo {
        struct Foo { ... }

        impl Foo {
            ...
        }
    }

Additionally, if you used the I/O path extension methods `stat`,
`lstat`, `exists`, `is_file`, or `is_dir`, note that these methods have
been moved to the the `std::io::fs::PathExtensions` trait. This breaks
code like:

    fn is_it_there() -> bool {
        Path::new("/foo/bar/baz").exists()
    }

Change this code to:

    use std::io::fs::PathExtensions;

    fn is_it_there() -> bool {
        Path::new("/foo/bar/baz").exists()
    }

Closes #17059.

RFC #155.

[breaking-change]

3 files changed, 28 insertions, 14 deletions

diff --git a/src/libstd/io/fs.rs b/src/libstd/io/fs.rs
index 3d6bb96063e..b7b7d1fb93d 100644
--- a/src/libstd/io/fs.rs
+++ b/src/libstd/io/fs.rs
@@ -31,6 +31,7 @@ particular bits of it, etc.
 
 ```rust
 # #![allow(unused_must_use)]
+use std::io::fs::PathExtensions;
 use std::io::{File, fs};
 
 let path = Path::new("foo.txt");
@@ -622,8 +623,9 @@ pub fn rmdir(path: &Path) -> IoResult<()> {
 /// # Example
 ///
 /// ```rust
-/// use std::io;
+/// use std::io::fs::PathExtensions;
 /// use std::io::fs;
+/// use std::io;
 ///
 /// // one possible implementation of fs::walk_dir only visiting files
 /// fn visit_dirs(dir: &Path, cb: |&Path|) -> io::IoResult<()> {
@@ -868,13 +870,14 @@ impl Seek for File {
     }
 }
 
-impl path::Path {
+/// Utility methods for paths.
+pub trait PathExtensions {
     /// Get information on the file, directory, etc at this path.
     ///
     /// Consult the `fs::stat` documentation for more info.
     ///
     /// This call preserves identical runtime/error semantics with `file::stat`.
-    pub fn stat(&self) -> IoResult<FileStat> { stat(self) }
+    fn stat(&self) -> IoResult<FileStat>;
 
     /// Get information on the file, directory, etc at this path, not following
     /// symlinks.
@@ -882,31 +885,39 @@ impl path::Path {
     /// Consult the `fs::lstat` documentation for more info.
     ///
     /// This call preserves identical runtime/error semantics with `file::lstat`.
-    pub fn lstat(&self) -> IoResult<FileStat> { lstat(self) }
+    fn lstat(&self) -> IoResult<FileStat>;
 
     /// Boolean value indicator whether the underlying file exists on the local
     /// filesystem. Returns false in exactly the cases where `fs::stat` fails.
-    pub fn exists(&self) -> bool {
-        self.stat().is_ok()
-    }
+    fn exists(&self) -> bool;
 
     /// Whether the underlying implementation (be it a file path, or something
     /// else) points at a "regular file" on the FS. Will return false for paths
     /// to non-existent locations or directories or other non-regular files
     /// (named pipes, etc). Follows links when making this determination.
-    pub fn is_file(&self) -> bool {
-        match self.stat() {
-            Ok(s) => s.kind == io::TypeFile,
-            Err(..) => false
-        }
-    }
+    fn is_file(&self) -> bool;
 
     /// Whether the underlying implementation (be it a file path, or something
     /// else) is pointing at a directory in the underlying FS. Will return
     /// false for paths to non-existent locations or if the item is not a
     /// directory (eg files, named pipes, etc). Follows links when making this
     /// determination.
-    pub fn is_dir(&self) -> bool {
+    fn is_dir(&self) -> bool;
+}
+
+impl PathExtensions for path::Path {
+    fn stat(&self) -> IoResult<FileStat> { stat(self) }
+    fn lstat(&self) -> IoResult<FileStat> { lstat(self) }
+    fn exists(&self) -> bool {
+        self.stat().is_ok()
+    }
+    fn is_file(&self) -> bool {
+        match self.stat() {
+            Ok(s) => s.kind == io::TypeFile,
+            Err(..) => false
+        }
+    }
+    fn is_dir(&self) -> bool {
         match self.stat() {
             Ok(s) => s.kind == io::TypeDirectory,
             Err(..) => false
diff --git a/src/libstd/io/mod.rs b/src/libstd/io/mod.rs
index 0d0c9e933b0..7a2bcab8706 100644
--- a/src/libstd/io/mod.rs
+++ b/src/libstd/io/mod.rs
@@ -1721,6 +1721,7 @@ pub enum FileType {
 /// # Example
 ///
 /// ```
+/// # use std::io::fs::PathExtensions;
 /// # fn main() {}
 /// # fn foo() {
 /// let info = match Path::new("foo.txt").stat() {
diff --git a/src/libstd/path/mod.rs b/src/libstd/path/mod.rs
index 5a5068f4d01..d84848545bd 100644
--- a/src/libstd/path/mod.rs
+++ b/src/libstd/path/mod.rs
@@ -53,6 +53,8 @@ actually operates on the path; it is only intended for display.
 ## Example
 
 ```rust
+use std::io::fs::PathExtensions;
+
 let mut path = Path::new("/tmp/path");
 println!("path: {}", path.display());
 path.set_filename("foo");