Rollup merge of rust-lang#48143 - nikomatsakis:termination_trait_in_t…

…ests, r=eddyb

Termination trait in tests

Support the `Termination` trait in unit tests (cc rust-lang#43301)

Also, a drive-by fix for rust-lang#47075.

This is joint work with @bkchr.

src/librustc_driver/driver.rs

@@ -818,7 +818,8 @@ pub fn phase_2_configure_and_expand_inner<'a, F>(sess: &'a Session,
                                          &mut resolver,
                                          sess.opts.test,
                                          krate,
-                                         sess.diagnostic())
+                                         sess.diagnostic(),
+                                         &sess.features.borrow())
     });
 
     // If we're actually rustdoc then there's no need to actually compile

src/libstd/lib.rs

@@ -500,11 +500,6 @@ mod memchr;
 // The runtime entry point and a few unstable public functions used by the
 // compiler
 pub mod rt;
-// The trait to support returning arbitrary types in the main function
-mod termination;
-
-#[unstable(feature = "termination_trait", issue = "43301")]
-pub use self::termination::Termination;
 
 // Include a number of private modules that exist solely to provide
 // the rustdoc documentation for primitive types. Using `include!`

src/libstd/process.rs

@@ -1392,6 +1392,73 @@ pub fn id() -> u32 {
     ::sys::os::getpid()
 }
 
+#[cfg(target_arch = "wasm32")]
+mod exit {
+    pub const SUCCESS: i32 = 0;
+    pub const FAILURE: i32 = 1;
+}
+#[cfg(not(target_arch = "wasm32"))]
+mod exit {
+    use libc;
+    pub const SUCCESS: i32 = libc::EXIT_SUCCESS;
+    pub const FAILURE: i32 = libc::EXIT_FAILURE;
+}
+
+/// A trait for implementing arbitrary return types in the `main` function.
+///
+/// The c-main function only supports to return integers as return type.
+/// So, every type implementing the `Termination` trait has to be converted
+/// to an integer.
+///
+/// The default implementations are returning `libc::EXIT_SUCCESS` to indicate
+/// a successful execution. In case of a failure, `libc::EXIT_FAILURE` is returned.
+#[cfg_attr(not(test), lang = "termination")]
+#[unstable(feature = "termination_trait_lib", issue = "43301")]
+#[rustc_on_unimplemented =
+  "`main` can only return types that implement {Termination}, not `{Self}`"]
+pub trait Termination {
+    /// Is called to get the representation of the value as status code.
+    /// This status code is returned to the operating system.
+    fn report(self) -> i32;
+}
+
+#[unstable(feature = "termination_trait_lib", issue = "43301")]
+impl Termination for () {
+    fn report(self) -> i32 { exit::SUCCESS }
+}
+
+#[unstable(feature = "termination_trait_lib", issue = "43301")]
+impl<T: Termination, E: fmt::Debug> Termination for Result<T, E> {
+    fn report(self) -> i32 {
+        match self {
+            Ok(val) => val.report(),
+            Err(err) => {
+                eprintln!("Error: {:?}", err);
+                exit::FAILURE
+            }
+        }
+    }
+}
+
+#[unstable(feature = "termination_trait_lib", issue = "43301")]
+impl Termination for ! {
+    fn report(self) -> i32 { unreachable!(); }
+}
+
+#[unstable(feature = "termination_trait_lib", issue = "43301")]
+impl Termination for bool {
+    fn report(self) -> i32 {
+        if self { exit::SUCCESS } else { exit::FAILURE }
+    }
+}
+
+#[unstable(feature = "termination_trait_lib", issue = "43301")]
+impl Termination for i32 {
+    fn report(self) -> i32 {
+        self
+    }
+}
+
 #[cfg(all(test, not(any(target_os = "cloudabi", target_os = "emscripten"))))]
 mod tests {
     use io::prelude::*;

src/libstd/rt.rs

@@ -68,7 +68,7 @@ fn lang_start_internal(main: &(Fn() -> i32 + Sync + ::panic::RefUnwindSafe),
 
 #[cfg(not(test))]
 #[lang = "start"]
-fn lang_start<T: ::termination::Termination + 'static>
+fn lang_start<T: ::process::Termination + 'static>
     (main: fn() -> T, argc: isize, argv: *const *const u8) -> isize
 {
     lang_start_internal(&move || main().report(), argc, argv)

src/libsyntax/ext/build.rs

@@ -319,14 +319,8 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
                 types: Vec<P<ast::Ty>>,
                 bindings: Vec<ast::TypeBinding> )
                 -> ast::Path {
-        use syntax::parse::token;
-
         let last_identifier = idents.pop().unwrap();
         let mut segments: Vec<ast::PathSegment> = Vec::new();
-        if global &&
-           !idents.first().map_or(false, |&ident| token::Ident(ident).is_path_segment_keyword()) {
-            segments.push(ast::PathSegment::crate_root(span));
-        }
 
         segments.extend(idents.into_iter().map(|i| ast::PathSegment::from_ident(i, span)));
         let parameters = if !lifetimes.is_empty() || !types.is_empty() || !bindings.is_empty() {
@@ -335,7 +329,9 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
             None
         };
         segments.push(ast::PathSegment { identifier: last_identifier, span, parameters });
-        ast::Path { span, segments }
+        let path = ast::Path { span, segments };
+
+        if global { path.default_to_global() } else { path }
     }
 
     /// Constructs a qualified path.