Auto merge of #56032 - petrochenkov:stabecip, r=nikomatsakis

Stabilize `extern_crate_item_prelude`

Closes #55599

Author: bors

src/librustc_resolve/lib.rs

@@ -58,7 +58,6 @@ use syntax::ast::{self, Name, NodeId, Ident, FloatTy, IntTy, UintTy};
 use syntax::ext::base::SyntaxExtension;
 use syntax::ext::base::Determinacy::{self, Determined, Undetermined};
 use syntax::ext::base::MacroKind;
-use syntax::feature_gate::{emit_feature_err, GateIssue};
 use syntax::symbol::{Symbol, keywords};
 use syntax::util::lev_distance::find_best_match_for_name;
 
@@ -2115,7 +2114,7 @@ impl<'a, 'crateloader: 'a> Resolver<'a, 'crateloader> {
 
         if !module.no_implicit_prelude {
             if ns == TypeNS {
-                if let Some(binding) = self.extern_prelude_get(ident, !record_used, false) {
+                if let Some(binding) = self.extern_prelude_get(ident, !record_used) {
                     return Some(LexicalScopeBinding::Item(binding));
                 }
             }
@@ -5022,21 +5021,14 @@ impl<'a, 'crateloader: 'a> Resolver<'a, 'crateloader> {
         self.name_already_seen.insert(name, span);
     }
 
-    fn extern_prelude_get(&mut self, ident: Ident, speculative: bool, skip_feature_gate: bool)
+    fn extern_prelude_get(&mut self, ident: Ident, speculative: bool)
                           -> Option<&'a NameBinding<'a>> {
         if ident.is_path_segment_keyword() {
             // Make sure `self`, `super` etc produce an error when passed to here.
             return None;
         }
         self.extern_prelude.get(&ident.modern()).cloned().and_then(|entry| {
             if let Some(binding) = entry.extern_crate_item {
-                if !speculative && !skip_feature_gate && entry.introduced_by_item &&
-                   !self.session.features_untracked().extern_crate_item_prelude {
-                    emit_feature_err(&self.session.parse_sess, "extern_crate_item_prelude",
-                                     ident.span, GateIssue::Language,
-                                     "use of extern prelude names introduced \
-                                      with `extern crate` items is unstable");
-                }
                 Some(binding)
             } else {
                 let crate_id = if !speculative {

src/librustc_resolve/macros.rs

@@ -738,8 +738,7 @@ impl<'a, 'cl> Resolver<'a, 'cl> {
                 }
                 WhereToResolve::ExternPrelude => {
                     if use_prelude {
-                        match self.extern_prelude_get(ident, !record_used,
-                                                      innermost_result.is_some()) {
+                        match self.extern_prelude_get(ident, !record_used) {
                             Some(binding) => Ok((binding, Flags::PRELUDE)),
                             None => Err(Determinacy::determined(
                                 self.graph_root.unresolved_invocations.borrow().is_empty()
@@ -906,7 +905,7 @@ impl<'a, 'cl> Resolver<'a, 'cl> {
                 // but its `Def` should coincide with a crate passed with `--extern`
                 // (otherwise there would be ambiguity) and we can skip feature error in this case.
                 if ns != TypeNS || !use_prelude ||
-                   self.extern_prelude_get(ident, true, false).is_none() {
+                   self.extern_prelude_get(ident, true).is_none() {
                     let msg = "imports can only refer to extern crate names \
                                passed with `--extern` on stable channel";
                     let mut err = feature_err(&self.session.parse_sess, "uniform_paths",

src/librustc_resolve/resolve_imports.rs

@@ -166,8 +166,7 @@ impl<'a, 'crateloader> Resolver<'a, 'crateloader> {
                 assert!(!restricted_shadowing);
                 match uniform_root_kind {
                     UniformRootKind::ExternPrelude => {
-                        return if let Some(binding) =
-                                self.extern_prelude_get(ident, !record_used, false) {
+                        return if let Some(binding) = self.extern_prelude_get(ident, !record_used) {
                             Ok(binding)
                         } else if !self.graph_root.unresolved_invocations.borrow().is_empty() {
                             // Macro-expanded `extern crate` items can add names to extern prelude.

src/libsyntax/feature_gate.rs

@@ -499,9 +499,6 @@ declare_features! (
     // Allows `const _: TYPE = VALUE`
     (active, underscore_const_names, "1.31.0", Some(54912), None),
 
-    // `extern crate foo as bar;` puts `bar` into extern prelude.
-    (active, extern_crate_item_prelude, "1.31.0", Some(55599), None),
-
     // `reason = ` in lint attributes and `expect` lint attribute
     (active, lint_reasons, "1.31.0", Some(54503), None),
 );
@@ -691,6 +688,8 @@ declare_features! (
     // impl<I:Iterator> Iterator for &mut Iterator
     // impl Debug for Foo<'_>
     (accepted, impl_header_lifetime_elision, "1.31.0", Some(15872), None),
+    // `extern crate foo as bar;` puts `bar` into extern prelude.
+    (accepted, extern_crate_item_prelude, "1.31.0", Some(55599), None),
 );
 
 // If you change this, please modify src/doc/unstable-book as well. You must

src/test/ui-fulldeps/proc-macro/extern-prelude-extern-crate-proc-macro.rs

@@ -1,8 +1,6 @@
 // compile-pass
 // edition:2018
 
-#![feature(extern_crate_item_prelude)]
-
 extern crate proc_macro;
 use proc_macro::TokenStream; // OK
 

src/test/ui/feature-gates/feature-gate-extern_crate_item_prelude.rs

@@ -1,8 +1,6 @@
 // compile-pass
 // edition:2018
 
-#![feature(extern_crate_item_prelude)]
-
 macro_rules! define_iso { () => {
     extern crate std as iso;
 }}

src/test/ui/feature-gates/feature-gate-extern_crate_item_prelude.stderr

@@ -1,7 +1,6 @@
 // compile-pass
 // compile-flags:--cfg my_feature
 
-#![feature(extern_crate_item_prelude)]
 #![no_std]
 
 #[cfg(my_feature)]

src/test/ui/imports/extern-prelude-extern-crate-absolute-expanded.rs

@@ -1,8 +1,6 @@
 // compile-pass
 // aux-build:two_macros.rs
 
-#![feature(extern_crate_item_prelude)]
-
 extern crate two_macros;
 
 mod m {

src/test/ui/imports/extern-prelude-extern-crate-cfg.rs

@@ -1,7 +1,5 @@
 // aux-build:two_macros.rs
 
-#![feature(extern_crate_item_prelude)]
-
 macro_rules! define_vec {
     () => {
         extern crate std as Vec;
@@ -16,4 +14,13 @@ mod m {
     }
 }
 
+macro_rules! define_other_core {
+    () => {
+        extern crate std as core;
+        //~^ ERROR macro-expanded `extern crate` items cannot shadow names passed with `--extern`
+    }
+}
+
+define_other_core!();
+
 fn main() {}

src/test/ui/imports/extern-prelude-extern-crate-pass.rs

@@ -1,19 +1,28 @@
+error: macro-expanded `extern crate` items cannot shadow names passed with `--extern`
+  --> $DIR/extern-prelude-extern-crate-restricted-shadowing.rs:19:9
+   |
+LL |         extern crate std as core;
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^
+...
+LL | define_other_core!();
+   | --------------------- in this macro invocation
+
 error[E0659]: `Vec` is ambiguous (macro-expanded name vs less macro-expanded name from outer scope during import/macro resolution)
-  --> $DIR/extern-prelude-extern-crate-restricted-shadowing.rs:15:9
+  --> $DIR/extern-prelude-extern-crate-restricted-shadowing.rs:13:9
    |
 LL |         Vec::panic!(); //~ ERROR `Vec` is ambiguous
    |         ^^^ ambiguous name
    |
    = note: `Vec` could refer to a struct from prelude
 note: `Vec` could also refer to the extern crate imported here
-  --> $DIR/extern-prelude-extern-crate-restricted-shadowing.rs:7:9
+  --> $DIR/extern-prelude-extern-crate-restricted-shadowing.rs:5:9
    |
 LL |         extern crate std as Vec;
    |         ^^^^^^^^^^^^^^^^^^^^^^^^
 ...
 LL | define_vec!();
    | -------------- in this macro invocation
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0659`.

src/test/ui/imports/extern-prelude-extern-crate-restricted-shadowing.rs

@@ -0,0 +1,12 @@
+// compile-pass
+// aux-build:two_macros.rs
+
+extern crate two_macros as core;
+
+mod m {
+    fn check() {
+        core::m!(); // OK
+    }
+}
+
+fn main() {}