Auto merge of #41847 - alexcrichton:less-unstable-annotations, r=eddyb

rustc: Add a new `-Z force-unstable-if-unmarked` flag

This commit adds a new `-Z` flag to the compiler for use when bootstrapping the
compiler itself. We want to be able to use crates.io crates, but we also want
the usage of such crates to be as ergonomic as possible! To that end compiler
crates are a little tricky in that the crates.io crates are not annotated as
unstable, nor do they expect to pull in unstable dependencies.

To cover all these situations it's intended that the compiler will forever now
bootstrap with `-Z force-unstable-if-unmarked`. This flags serves a dual purpose
of forcing crates.io crates to themselves be unstable while also allowing them
to use other "unstable" crates.io crates. This should mean that adding a
dependency to compiler no longer requires upstream modification with
unstable/staged_api attributes for inclusion!

src/bootstrap/bin/rustc.rs

@@ -194,6 +194,8 @@ fn main() {
                 // do that we pass a weird flag to the compiler to get it to do
                 // so. Note that this is definitely a hack, and we should likely
                 // flesh out rpath support more fully in the future.
+                //
+                // FIXME: remove condition after next stage0
                 if stage != "0" {
                     cmd.arg("-Z").arg("osx-rpath-install-name");
                 }
@@ -218,6 +220,17 @@ fn main() {
             cmd.arg("-Z").arg("unstable-options");
             cmd.arg("-C").arg("target-feature=+crt-static");
         }
+
+        // Force all crates compiled by this compiler to (a) be unstable and (b)
+        // allow the `rustc_private` feature to link to other unstable crates
+        // also in the sysroot.
+        //
+        // FIXME: remove condition after next stage0
+        if env::var_os("RUSTC_FORCE_UNSTABLE").is_some() {
+            if stage != "0" {
+                cmd.arg("-Z").arg("force-unstable-if-unmarked");
+            }
+        }
     }
 
     if verbose > 1 {

src/bootstrap/lib.rs

@@ -479,7 +479,8 @@ impl Build {
         // compiled with debuginfo.
         if mode != Mode::Tool {
              cargo.env("RUSTC_DEBUGINFO", self.config.rust_debuginfo.to_string())
-                  .env("RUSTC_DEBUGINFO_LINES", self.config.rust_debuginfo_lines.to_string());
+                  .env("RUSTC_DEBUGINFO_LINES", self.config.rust_debuginfo_lines.to_string())
+                  .env("RUSTC_FORCE_UNSTABLE", "1");
         }
 
         // Enable usage of unstable features
@@ -524,7 +525,9 @@ impl Build {
         // the comipiler, libs, and tests are stable and we don't want to make
         // their deps unstable (since this would break the first invariant
         // above).
-        if mode != Mode::Tool {
+        //
+        // FIXME: remove this after next stage0
+        if mode != Mode::Tool && stage == 0 {
             cargo.env("RUSTBUILD_UNSTABLE", "1");
         }
 

src/libarena/lib.rs

@@ -19,7 +19,7 @@
 //! objects of a single type.
 
 #![crate_name = "arena"]
-#![unstable(feature = "rustc_private", issue = "27812")]
+#![cfg_attr(stage0, unstable(feature = "rustc_private", issue = "27812"))]
 #![crate_type = "rlib"]
 #![crate_type = "dylib"]
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
@@ -32,7 +32,7 @@
 #![feature(core_intrinsics)]
 #![feature(dropck_eyepatch)]
 #![feature(generic_param_attrs)]
-#![feature(staged_api)]
+#![cfg_attr(stage0, feature(staged_api))]
 #![cfg_attr(test, feature(test))]
 
 #![allow(deprecated)]

src/libflate/lib.rs

@@ -15,7 +15,7 @@
 //! [mz]: https://code.google.com/p/miniz/
 
 #![crate_name = "flate"]
-#![unstable(feature = "rustc_private", issue = "27812")]
+#![cfg_attr(stage0, unstable(feature = "rustc_private", issue = "27812"))]
 #![crate_type = "rlib"]
 #![crate_type = "dylib"]
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
@@ -25,7 +25,7 @@
 #![deny(warnings)]
 
 #![feature(libc)]
-#![feature(staged_api)]
+#![cfg_attr(stage0, feature(staged_api))]
 #![feature(unique)]
 #![cfg_attr(test, feature(rand))]
 

src/libfmt_macros/lib.rs

@@ -15,7 +15,7 @@
 //! generated instead.
 
 #![crate_name = "fmt_macros"]
-#![unstable(feature = "rustc_private", issue = "27812")]
+#![cfg_attr(stage0, unstable(feature = "rustc_private", issue = "27812"))]
 #![crate_type = "rlib"]
 #![crate_type = "dylib"]
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
@@ -25,7 +25,7 @@
        test(attr(deny(warnings))))]
 #![deny(warnings)]
 
-#![feature(staged_api)]
+#![cfg_attr(stage0, feature(staged_api))]
 #![feature(unicode)]
 
 pub use self::Piece::*;

src/libgetopts/lib.rs

@@ -78,9 +78,9 @@
 //! ```
 
 #![crate_name = "getopts"]
-#![unstable(feature = "rustc_private",
+#![cfg_attr(stage0, unstable(feature = "rustc_private",
             reason = "use the crates.io `getopts` library instead",
-            issue = "27812")]
+            issue = "27812"))]
 #![crate_type = "rlib"]
 #![crate_type = "dylib"]
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
@@ -91,7 +91,7 @@
 
 #![deny(missing_docs)]
 #![deny(warnings)]
-#![feature(staged_api)]
+#![cfg_attr(stage0, feature(staged_api))]
 
 use self::Name::*;
 use self::HasArg::*;

src/libgraphviz/lib.rs

@@ -284,8 +284,8 @@
 //! * [DOT language](http://www.graphviz.org/doc/info/lang.html)
 
 #![crate_name = "graphviz"]
-#![unstable(feature = "rustc_private", issue = "27812")]
-#![feature(staged_api)]
+#![cfg_attr(stage0, unstable(feature = "rustc_private", issue = "27812"))]
+#![cfg_attr(stage0, feature(staged_api))]
 #![crate_type = "rlib"]
 #![crate_type = "dylib"]
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",

src/libproc_macro_plugin/lib.rs

@@ -72,7 +72,7 @@
 //! }
 //! ```
 #![crate_name = "proc_macro_plugin"]
-#![unstable(feature = "rustc_private", issue = "27812")]
+#![cfg_attr(stage0, unstable(feature = "rustc_private", issue = "27812"))]
 #![feature(plugin_registrar)]
 #![crate_type = "dylib"]
 #![crate_type = "rlib"]
@@ -81,9 +81,9 @@
        html_root_url = "https://doc.rust-lang.org/nightly/")]
 #![deny(warnings)]
 
-#![feature(staged_api)]
+#![cfg_attr(stage0, feature(staged_api))]
 #![feature(rustc_diagnostic_macros)]
-#![feature(rustc_private)]
+#![cfg_attr(stage0, feature(rustc_private))]
 
 extern crate rustc_plugin;
 extern crate syntax;

src/librustc/lib.rs

@@ -15,7 +15,6 @@
 //! This API is completely unstable and subject to change.
 
 #![crate_name = "rustc"]
-#![unstable(feature = "rustc_private", issue = "27812")]
 #![crate_type = "dylib"]
 #![crate_type = "rlib"]
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
@@ -36,15 +35,17 @@
 #![feature(nonzero)]
 #![feature(quote)]
 #![feature(rustc_diagnostic_macros)]
-#![feature(rustc_private)]
 #![feature(slice_patterns)]
 #![feature(specialization)]
-#![feature(staged_api)]
 #![feature(unboxed_closures)]
 #![feature(discriminant_value)]
 #![feature(sort_unstable)]
 #![feature(trace_macros)]
 
+#![cfg_attr(stage0, unstable(feature = "rustc_private", issue = "27812"))]
+#![cfg_attr(stage0, feature(rustc_private))]
+#![cfg_attr(stage0, feature(staged_api))]
+
 #![recursion_limit="128"]
 
 extern crate arena;

src/librustc/middle/cstore.rs

@@ -233,7 +233,6 @@ pub trait CrateStore {
     fn export_macros(&self, cnum: CrateNum);
     fn lang_items(&self, cnum: CrateNum) -> Vec<(DefIndex, usize)>;
     fn missing_lang_items(&self, cnum: CrateNum) -> Vec<lang_items::LangItem>;
-    fn is_staged_api(&self, cnum: CrateNum) -> bool;
     fn is_allocator(&self, cnum: CrateNum) -> bool;
     fn is_panic_runtime(&self, cnum: CrateNum) -> bool;
     fn is_compiler_builtins(&self, cnum: CrateNum) -> bool;
@@ -356,7 +355,6 @@ impl CrateStore for DummyCrateStore {
         { bug!("lang_items") }
     fn missing_lang_items(&self, cnum: CrateNum) -> Vec<lang_items::LangItem>
         { bug!("missing_lang_items") }
-    fn is_staged_api(&self, cnum: CrateNum) -> bool { bug!("is_staged_api") }
     fn dep_kind(&self, cnum: CrateNum) -> DepKind { bug!("is_explicitly_linked") }
     fn export_macros(&self, cnum: CrateNum) { bug!("export_macros") }
     fn is_allocator(&self, cnum: CrateNum) -> bool { bug!("is_allocator") }

src/librustc/middle/stability.rs

@@ -13,12 +13,12 @@
 
 pub use self::StabilityLevel::*;
 
-use hir::map as hir_map;
 use lint;
 use hir::def::Def;
 use hir::def_id::{CrateNum, CRATE_DEF_INDEX, DefId, DefIndex, LOCAL_CRATE};
 use ty::{self, TyCtxt};
 use middle::privacy::AccessLevels;
+use session::Session;
 use syntax::symbol::Symbol;
 use syntax_pos::{Span, DUMMY_SP};
 use syntax::ast;
@@ -123,7 +123,7 @@ impl<'a, 'tcx: 'a> Annotator<'a, 'tcx> {
                    item_sp: Span, kind: AnnotationKind, visit_children: F)
         where F: FnOnce(&mut Self)
     {
-        if self.index.staged_api[&LOCAL_CRATE] && self.tcx.sess.features.borrow().staged_api {
+        if self.index.staged_api[&LOCAL_CRATE] {
             debug!("annotate(id = {:?}, attrs = {:?})", id, attrs);
             if let Some(..) = attr::find_deprecation(self.tcx.sess.diagnostic(), attrs, item_sp) {
                 self.tcx.sess.span_err(item_sp, "`#[deprecated]` cannot be used in staged api, \
@@ -390,20 +390,36 @@ impl<'a, 'tcx> Index<'tcx> {
             parent_depr: None,
             in_trait_impl: false,
         };
+
+        // If the `-Z force-unstable-if-unmarked` flag is passed then we provide
+        // a parent stability annotation which indicates that this is private
+        // with the `rustc_private` feature. This is intended for use when
+        // compiling librustc crates themselves so we can leverage crates.io
+        // while maintaining the invariant that all sysroot crates are unstable
+        // by default and are unable to be used.
+        if tcx.sess.opts.debugging_opts.force_unstable_if_unmarked {
+            let reason = "this crate is being loaded from the sysroot, and \
+                          unstable location; did you mean to load this crate \
+                          from crates.io via `Cargo.toml` instead?";
+            let stability = tcx.intern_stability(Stability {
+                level: attr::StabilityLevel::Unstable {
+                    reason: Some(Symbol::intern(reason)),
+                    issue: 27812,
+                },
+                feature: Symbol::intern("rustc_private"),
+                rustc_depr: None,
+            });
+            annotator.parent_stab = Some(stability);
+        }
+
         annotator.annotate(ast::CRATE_NODE_ID, &krate.attrs, krate.span, AnnotationKind::Required,
                            |v| intravisit::walk_crate(v, krate));
     }
 
-    pub fn new(hir_map: &hir_map::Map) -> Index<'tcx> {
-        let krate = hir_map.krate();
-
-        let mut is_staged_api = false;
-        for attr in &krate.attrs {
-            if attr.path == "stable" || attr.path == "unstable" {
-                is_staged_api = true;
-                break
-            }
-        }
+    pub fn new(sess: &Session) -> Index<'tcx> {
+        let is_staged_api =
+            sess.opts.debugging_opts.force_unstable_if_unmarked ||
+            sess.features.borrow().staged_api;
 
         let mut staged_api = FxHashMap();
         staged_api.insert(LOCAL_CRATE, is_staged_api);
@@ -496,8 +512,10 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             }
         }
 
-        let is_staged_api = *self.stability.borrow_mut().staged_api.entry(def_id.krate)
-            .or_insert_with(|| self.sess.cstore.is_staged_api(def_id.krate));
+        let is_staged_api = self.lookup_stability(DefId {
+            index: CRATE_DEF_INDEX,
+            ..def_id
+        }).is_some();
         if !is_staged_api {
             return;
         }
@@ -530,15 +548,32 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
 
         match stability {
             Some(&Stability { level: attr::Unstable {ref reason, issue}, ref feature, .. }) => {
-                if !self.stability.borrow().active_features.contains(feature) {
-                    let msg = match *reason {
-                        Some(ref r) => format!("use of unstable library feature '{}': {}",
-                                               feature.as_str(), &r),
-                        None => format!("use of unstable library feature '{}'", &feature)
-                    };
-                    emit_feature_err(&self.sess.parse_sess, &feature.as_str(), span,
-                                     GateIssue::Library(Some(issue)), &msg);
+                if self.stability.borrow().active_features.contains(feature) {
+                    return
                 }
+
+                // When we're compiling the compiler itself we may pull in
+                // crates from crates.io, but those crates may depend on other
+                // crates also pulled in from crates.io. We want to ideally be
+                // able to compile everything without requiring upstream
+                // modifications, so in the case that this looks like a
+                // rustc_private crate (e.g. a compiler crate) and we also have
+                // the `-Z force-unstable-if-unmarked` flag present (we're
+                // compiling a compiler crate), then let this missing feature
+                // annotation slide.
+                if *feature == "rustc_private" && issue == 27812 {
+                    if self.sess.opts.debugging_opts.force_unstable_if_unmarked {
+                        return
+                    }
+                }
+
+                let msg = match *reason {
+                    Some(ref r) => format!("use of unstable library feature '{}': {}",
+                                           feature.as_str(), &r),
+                    None => format!("use of unstable library feature '{}'", &feature)
+                };
+                emit_feature_err(&self.sess.parse_sess, &feature.as_str(), span,
+                                 GateIssue::Library(Some(issue)), &msg);
             }
             Some(_) => {
                 // Stable APIs are always ok to call and deprecated APIs are
@@ -658,7 +693,7 @@ pub fn check_unused_or_stable_features<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
 
     let access_levels = &tcx.privacy_access_levels(LOCAL_CRATE);
 
-    if tcx.stability.borrow().staged_api[&LOCAL_CRATE] && tcx.sess.features.borrow().staged_api {
+    if tcx.stability.borrow().staged_api[&LOCAL_CRATE] {
         let krate = tcx.hir.krate();
         let mut missing = MissingStabilityAnnotations {
             tcx: tcx,

src/librustc/session/config.rs

@@ -1027,6 +1027,8 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "add a source pattern to the file path remapping config"),
     remap_path_prefix_to: Vec<String> = (vec![], parse_string_push, [TRACKED],
         "add a mapping target to the file path remapping config"),
+    force_unstable_if_unmarked: bool = (false, parse_bool, [TRACKED],
+        "force all crates to be `rustc_private` unstable"),
 }
 
 pub fn default_lib_output() -> CrateType {

src/librustc_back/lib.rs

@@ -22,7 +22,6 @@
 //! build speedups.
 
 #![crate_name = "rustc_back"]
-#![unstable(feature = "rustc_private", issue = "27812")]
 #![crate_type = "dylib"]
 #![crate_type = "rlib"]
 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
@@ -34,10 +33,12 @@
 #![feature(const_fn)]
 #![feature(libc)]
 #![feature(rand)]
-#![feature(rustc_private)]
-#![feature(staged_api)]
 #![cfg_attr(test, feature(rand))]
 
+#![cfg_attr(stage0, unstable(feature = "rustc_private", issue = "27812"))]
+#![cfg_attr(stage0, feature(rustc_private))]
+#![cfg_attr(stage0, feature(staged_api))]
+
 extern crate syntax;
 extern crate libc;
 extern crate serialize;

src/librustc_bitflags/lib.rs

@@ -11,11 +11,11 @@
 
 #![crate_name = "rustc_bitflags"]
 #![feature(associated_consts)]
-#![feature(staged_api)]
 #![crate_type = "rlib"]
 #![no_std]
-#![unstable(feature = "rustc_private", issue = "27812")]
 #![deny(warnings)]
+#![cfg_attr(stage0, unstable(feature = "rustc_private", issue = "27812"))]
+#![cfg_attr(stage0, feature(staged_api))]
 
 //! A typesafe bitmask flag generator.