Rollup of 8 pull requests

Cargo.lock

@@ -3541,7 +3541,6 @@ dependencies = [
  "rustc_metadata",
  "rustc_mir",
  "rustc_parse",
- "rustc_plugin",
  "rustc_plugin_impl",
  "rustc_resolve",
  "rustc_save_analysis",
@@ -3770,13 +3769,6 @@ dependencies = [
  "syntax_pos",
 ]
 
-[[package]]
-name = "rustc_plugin"
-version = "0.0.0"
-dependencies = [
- "rustc_plugin_impl",
-]
-
 [[package]]
 name = "rustc_plugin_impl"
 version = "0.0.0"

src/librustc/session/config.rs

@@ -1331,6 +1331,8 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "for every macro invocation, print its name and arguments"),
     debug_macros: bool = (false, parse_bool, [TRACKED],
         "emit line numbers debug info inside macros"),
+    generate_arange_section: bool = (true, parse_bool, [TRACKED],
+        "generate DWARF address ranges for faster lookups"),
     keep_hygiene_data: bool = (false, parse_bool, [UNTRACKED],
         "don't clear the hygiene data after analysis"),
     keep_ast: bool = (false, parse_bool, [UNTRACKED],

src/librustc_codegen_llvm/llvm_util.rs

@@ -62,6 +62,9 @@ unsafe fn configure_llvm(sess: &Session) {
         if sess.opts.debugging_opts.disable_instrumentation_preinliner {
             add("-disable-preinline");
         }
+        if sess.opts.debugging_opts.generate_arange_section {
+            add("-generate-arange-section");
+        }
         if get_major_version() >= 8 {
             match sess.opts.debugging_opts.merge_functions
                   .unwrap_or(sess.target.target.options.merge_functions) {

src/librustc_driver/Cargo.toml

@@ -22,8 +22,7 @@ errors = { path = "../librustc_errors", package = "rustc_errors" }
 rustc_metadata = { path = "../librustc_metadata" }
 rustc_mir = { path = "../librustc_mir" }
 rustc_parse = { path = "../librustc_parse" }
-rustc_plugin = { path = "../librustc_plugin/deprecated" } # To get this in the sysroot
-rustc_plugin_impl = { path = "../librustc_plugin" }
+rustc_plugin_impl = { path = "../librustc_plugin_impl" }
 rustc_save_analysis = { path = "../librustc_save_analysis" }
 rustc_codegen_utils = { path = "../librustc_codegen_utils" }
 rustc_error_codes = { path = "../librustc_error_codes" }

src/librustc_driver/lib.rs

@@ -84,13 +84,6 @@ const ICE_REPORT_COMPILER_FLAGS_EXCLUDE: &[&str] = &["metadata", "extra-filename
 
 const ICE_REPORT_COMPILER_FLAGS_STRIP_VALUE: &[&str] = &["incremental"];
 
-pub fn source_name(input: &Input) -> FileName {
-    match *input {
-        Input::File(ref ifile) => ifile.clone().into(),
-        Input::Str { ref name, .. } => name.clone(),
-    }
-}
-
 pub fn abort_on_err<T>(result: Result<T, ErrorReported>, sess: &Session) -> T {
     match result {
         Err(..) => {

src/librustc_driver/pretty.rs

@@ -24,10 +24,6 @@ pub use self::PpSourceMode::*;
 pub use self::PpMode::*;
 use crate::abort_on_err;
 
-use crate::source_name;
-
-
-
 // This slightly awkward construction is to allow for each PpMode to
 // choose whether it needs to do analyses (which can consume the
 // Session) and then pass through the session (now attached to the
@@ -391,7 +387,7 @@ impl<'a, 'tcx> pprust_hir::PpAnn for TypedAnnotation<'a, 'tcx> {
 }
 
 fn get_source(input: &Input, sess: &Session) -> (String, FileName) {
-    let src_name = source_name(input);
+    let src_name = input.source_name();
     let src = String::clone(&sess.source_map()
         .get_source_file(&src_name)
         .unwrap()

src/librustc_error_codes/error_codes.rs

@@ -383,6 +383,7 @@ E0700: include_str!("./error_codes/E0700.md"),
 E0701: include_str!("./error_codes/E0701.md"),
 E0704: include_str!("./error_codes/E0704.md"),
 E0705: include_str!("./error_codes/E0705.md"),
+E0706: include_str!("./error_codes/E0706.md"),
 E0712: include_str!("./error_codes/E0712.md"),
 E0713: include_str!("./error_codes/E0713.md"),
 E0714: include_str!("./error_codes/E0714.md"),
@@ -595,7 +596,6 @@ E0744: include_str!("./error_codes/E0744.md"),
     E0696, // `continue` pointing to a labeled block
 //  E0702, // replaced with a generic attribute input check
     E0703, // invalid ABI
-    E0706, // `async fn` in trait
 //  E0707, // multiple elided lifetimes used in arguments of `async fn`
     E0708, // `async` non-`move` closures with parameters are not currently
            // supported

src/librustc_error_codes/error_codes/E0706.md

@@ -0,0 +1,57 @@
+ `async fn`s are not yet supported in traits in Rust.
+
+Erroneous code example:
+
+```compile_fail,edition2018
+trait T {
+    // Neither case is currently supported.
+    async fn foo() {}
+    async fn bar(&self) {}
+}
+```
+
+`async fn`s return an `impl Future`, making the following two examples equivalent:
+
+```edition2018,ignore (example-of-desugaring-equivalence)
+async fn foo() -> User {
+    unimplemented!()
+}
+// The async fn above gets desugared as follows:
+fn foo(&self) -> impl Future<Output = User> + '_ {
+    unimplemented!()
+}
+```
+
+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:
+
+```edition2018,ignore (example-of-desugaring-equivalence)
+impl MyDatabase {
+    async fn get_user(&self) -> User {
+        unimplemented!()
+    }
+}
+
+impl MyDatabase {
+    fn get_user(&self) -> impl Future<Output = User> + '_ {
+        unimplemented!()
+    }
+}
+```
+
+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
+called millions of times a second.
+
+You might be interested in visiting the [async book] for further information.
+
+[`async-trait` crate]: https://crates.io/crates/async-trait
+[async-is-hard]: https://smallcultfollowing.com/babysteps/blog/2019/10/26/async-fn-in-traits-are-hard/
+[Generic Associated Types]: https://github.com/rust-lang/rust/issues/44265
+[async book]: https://rust-lang.github.io/async-book/07_workarounds/06_async_in_traits.html

src/librustc_interface/Cargo.toml

@@ -31,7 +31,7 @@ rustc_passes = { path = "../librustc_passes" }
 rustc_typeck = { path = "../librustc_typeck" }
 rustc_lint = { path = "../librustc_lint" }
 rustc_errors = { path = "../librustc_errors" }
-rustc_plugin = { path = "../librustc_plugin", package = "rustc_plugin_impl" }
+rustc_plugin_impl = { path = "../librustc_plugin_impl" }
 rustc_privacy = { path = "../librustc_privacy" }
 rustc_resolve = { path = "../librustc_resolve" }
 tempfile = "3.0.5"

src/librustc_interface/passes.rs

@@ -29,8 +29,8 @@ use rustc_metadata::cstore;
 use rustc_mir as mir;
 use rustc_parse::{parse_crate_from_file, parse_crate_from_source_str};
 use rustc_passes::{self, ast_validation, hir_stats, layout_test};
-use rustc_plugin as plugin;
-use rustc_plugin::registry::Registry;
+use rustc_plugin_impl as plugin;
+use rustc_plugin_impl::registry::Registry;
 use rustc_privacy;
 use rustc_resolve::{Resolver, ResolverArenas};
 use rustc_traits;