Auto merge of #60794 - Centril:rollup-vlguvns, r=Centril

Rollup of 5 pull requests

Successful merges:

 - #60176 (Explain error when yielding a reference to a local variable)
 - #60201 (coretest: Downgrade deny to warn)
 - #60562 (Add #[doc(hidden)] attribute on compiler generated module.)
 - #60710 (Use `delay_span_bug` for error cases when checking `AnonConst` parent)
 - #60770 (add impl_trait_in_bindings to INCOMPLETE_FEATURES)

Failed merges:

r? @ghost

src/libcore/tests/lib.rs

@@ -31,7 +31,7 @@
 #![feature(slice_partition_dedup)]
 #![feature(copy_within)]
 #![feature(int_error_matching)]
-#![deny(rust_2018_idioms)]
+#![warn(rust_2018_idioms)]
 
 extern crate test;
 

src/librustc_mir/borrow_check/error_reporting.rs

@@ -826,18 +826,21 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
 
         let borrow_span = borrow_spans.var_or_use();
         if let BorrowExplanation::MustBeValidFor {
-            category: ConstraintCategory::Return,
+            category,
             span,
             ref opt_place_desc,
             from_closure: false,
             ..
         } = explanation {
-            return self.report_cannot_return_reference_to_local(
+            if let Some(diag) = self.try_report_cannot_return_reference_to_local(
                 borrow,
                 borrow_span,
                 span,
+                category,
                 opt_place_desc.as_ref(),
-            );
+            ) {
+                return diag;
+            }
         }
 
         let mut err = self.infcx.tcx.path_does_not_live_long_enough(
@@ -1015,17 +1018,20 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
         );
 
         if let BorrowExplanation::MustBeValidFor {
-            category: ConstraintCategory::Return,
+            category,
             span,
             from_closure: false,
             ..
         } = explanation {
-            return self.report_cannot_return_reference_to_local(
+            if let Some(diag) = self.try_report_cannot_return_reference_to_local(
                 borrow,
                 proper_span,
                 span,
+                category,
                 None,
-            );
+            ) {
+                return diag;
+            }
         }
 
         let tcx = self.infcx.tcx;
@@ -1064,15 +1070,22 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
         err
     }
 
-    fn report_cannot_return_reference_to_local(
+    fn try_report_cannot_return_reference_to_local(
         &self,
         borrow: &BorrowData<'tcx>,
         borrow_span: Span,
         return_span: Span,
+        category: ConstraintCategory,
         opt_place_desc: Option<&String>,
-    ) -> DiagnosticBuilder<'cx> {
+    ) -> Option<DiagnosticBuilder<'cx>> {
         let tcx = self.infcx.tcx;
 
+        let return_kind = match category {
+            ConstraintCategory::Return => "return",
+            ConstraintCategory::Yield => "yield",
+            _ => return None,
+        };
+
         // FIXME use a better heuristic than Spans
         let reference_desc = if return_span == self.mir.source_info(borrow.reserve_location).span {
             "reference to"
@@ -1110,7 +1123,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
             let local = if let Place::Base(PlaceBase::Local(local)) = *root_place {
                 local
             } else {
-                bug!("report_cannot_return_reference_to_local: not a local")
+                bug!("try_report_cannot_return_reference_to_local: not a local")
             };
             match self.mir.local_kind(local) {
                 LocalKind::ReturnPointer | LocalKind::Temp => {
@@ -1131,6 +1144,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
 
         let mut err = tcx.cannot_return_reference_to_local(
             return_span,
+            return_kind,
             reference_desc,
             &place_desc,
             Origin::Mir,
@@ -1140,7 +1154,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
             err.span_label(borrow_span, note);
         }
 
-        err
+        Some(err)
     }
 
     fn report_escaping_closure_capture(

src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs

@@ -310,9 +310,13 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
                             opt_place_desc,
                         }
                     } else {
+                        debug!("explain_why_borrow_contains_point: \
+                                Could not generate a region name");
                         BorrowExplanation::Unexplained
                     }
                 } else {
+                    debug!("explain_why_borrow_contains_point: \
+                            Could not generate an error region vid");
                     BorrowExplanation::Unexplained
                 }
             }

src/librustc_mir/borrow_check/nll/region_infer/error_reporting/region_name.rs

@@ -34,6 +34,7 @@ crate enum RegionNameSource {
     MatchedAdtAndSegment(Span),
     AnonRegionFromUpvar(Span, String),
     AnonRegionFromOutput(Span, String, String),
+    AnonRegionFromYieldTy(Span, String),
 }
 
 impl RegionName {
@@ -48,7 +49,8 @@ impl RegionName {
             RegionNameSource::MatchedHirTy(..) |
             RegionNameSource::MatchedAdtAndSegment(..) |
             RegionNameSource::AnonRegionFromUpvar(..) |
-            RegionNameSource::AnonRegionFromOutput(..) => false,
+            RegionNameSource::AnonRegionFromOutput(..) |
+            RegionNameSource::AnonRegionFromYieldTy(..) => false,
         }
     }
 
@@ -105,6 +107,12 @@ impl RegionName {
                     format!("return type{} is {}", mir_description, type_name),
                 );
             },
+            RegionNameSource::AnonRegionFromYieldTy(span, type_name) => {
+                diag.span_label(
+                    *span,
+                    format!("yield type is {}", type_name),
+                );
+            }
             RegionNameSource::Static => {},
         }
     }
@@ -170,6 +178,11 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                 self.give_name_if_anonymous_region_appears_in_output(
                     infcx, mir, mir_def_id, fr, counter,
                 )
+            })
+            .or_else(|| {
+                self.give_name_if_anonymous_region_appears_in_yield_ty(
+                    infcx, mir, mir_def_id, fr, counter,
+                )
             });
 
         debug!("give_region_a_name: gave name {:?}", value);
@@ -676,10 +689,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             "give_name_if_anonymous_region_appears_in_output: return_ty = {:?}",
             return_ty
         );
-        if !infcx
-            .tcx
-            .any_free_region_meets(&return_ty, |r| r.to_region_vid() == fr)
-        {
+        if !tcx.any_free_region_meets(&return_ty, |r| r.to_region_vid() == fr) {
             return None;
         }
 
@@ -724,6 +734,57 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         })
     }
 
+    fn give_name_if_anonymous_region_appears_in_yield_ty(
+        &self,
+        infcx: &InferCtxt<'_, '_, 'tcx>,
+        mir: &Mir<'tcx>,
+        mir_def_id: DefId,
+        fr: RegionVid,
+        counter: &mut usize,
+    ) -> Option<RegionName> {
+        // Note: generators from `async fn` yield `()`, so we don't have to
+        // worry about them here.
+        let yield_ty = self.universal_regions.yield_ty?;
+        debug!(
+            "give_name_if_anonymous_region_appears_in_yield_ty: yield_ty = {:?}",
+            yield_ty,
+        );
+
+        let tcx = infcx.tcx;
+
+        if !tcx.any_free_region_meets(&yield_ty, |r| r.to_region_vid() == fr) {
+            return None;
+        }
+
+        let mut highlight = RegionHighlightMode::default();
+        highlight.highlighting_region_vid(fr, *counter);
+        let type_name = infcx.extract_type_name(&yield_ty, Some(highlight));
+
+        let mir_node_id = tcx.hir().as_local_node_id(mir_def_id).expect("non-local mir");
+
+        let yield_span = match tcx.hir().get(mir_node_id) {
+            hir::Node::Expr(hir::Expr {
+                node: hir::ExprKind::Closure(_, _, _, span, _),
+                ..
+            }) => (
+                tcx.sess.source_map().end_point(*span)
+            ),
+            _ => mir.span,
+        };
+
+        debug!(
+            "give_name_if_anonymous_region_appears_in_yield_ty: \
+             type_name = {:?}, yield_span = {:?}",
+            yield_span,
+            type_name,
+        );
+
+        Some(RegionName {
+            name: self.synthesize_region_name(counter),
+            source: RegionNameSource::AnonRegionFromYieldTy(yield_span, type_name),
+        })
+    }
+
     /// Creates a synthetic region named `'1`, incrementing the
     /// counter.
     fn synthesize_region_name(&self, counter: &mut usize) -> InternedString {

src/librustc_mir/util/borrowck_errors.rs

@@ -634,6 +634,7 @@ pub trait BorrowckErrors<'cx>: Sized + Copy {
     fn cannot_return_reference_to_local(
         self,
         span: Span,
+        return_kind: &str,
         reference_desc: &str,
         path_desc: &str,
         o: Origin,
@@ -642,15 +643,16 @@ pub trait BorrowckErrors<'cx>: Sized + Copy {
             self,
             span,
             E0515,
-            "cannot return {REFERENCE} {LOCAL}{OGN}",
+            "cannot {RETURN} {REFERENCE} {LOCAL}{OGN}",
+            RETURN=return_kind,
             REFERENCE=reference_desc,
             LOCAL=path_desc,
             OGN = o
         );
 
         err.span_label(
             span,
-            format!("returns a {} data owned by the current function", reference_desc),
+            format!("{}s a {} data owned by the current function", return_kind, reference_desc),
         );
 
         self.cancel_if_wrong_origin(err, o)

src/librustc_typeck/collect.rs

@@ -1404,15 +1404,27 @@ pub fn checked_type_of<'a, 'tcx>(
                                     if !fail {
                                         return None;
                                     }
-                                    bug!("unexpected const parent path def {:?}", x);
+                                    tcx.sess.delay_span_bug(
+                                        DUMMY_SP,
+                                        &format!(
+                                            "unexpected const parent path def {:?}", x
+                                        ),
+                                    );
+                                    tcx.types.err
                                 }
                             }
                         }
                         x => {
                             if !fail {
                                 return None;
                             }
-                            bug!("unexpected const parent path {:?}", x);
+                            tcx.sess.delay_span_bug(
+                                DUMMY_SP,
+                                &format!(
+                                    "unexpected const parent path {:?}", x
+                                ),
+                            );
+                            tcx.types.err
                         }
                     }
                 }
@@ -1421,7 +1433,13 @@ pub fn checked_type_of<'a, 'tcx>(
                     if !fail {
                         return None;
                     }
-                    bug!("unexpected const parent in type_of_def_id(): {:?}", x);
+                    tcx.sess.delay_span_bug(
+                        DUMMY_SP,
+                        &format!(
+                            "unexpected const parent in type_of_def_id(): {:?}", x
+                        ),
+                    );
+                    tcx.types.err
                 }
             }
         }

src/libsyntax/feature_gate.rs

@@ -563,6 +563,7 @@ declare_features! (
 // unanticipated results, such as compiler crashes. We warn the user about these
 // to alert them.
 const INCOMPLETE_FEATURES: &[Symbol] = &[
+    sym::impl_trait_in_bindings,
     sym::generic_associated_types,
     sym::const_generics
 ];

src/libsyntax_ext/proc_macro_decls.rs

@@ -328,6 +328,7 @@ impl<'a> Visitor<'a> for CollectProcMacros<'a> {
 
 // Creates a new module which looks like:
 //
+//      #[doc(hidden)]
 //      mod $gensym {
 //          extern crate proc_macro;
 //
@@ -361,6 +362,10 @@ fn mk_decls(
     });
     let span = DUMMY_SP.apply_mark(mark);
 
+    let hidden = cx.meta_list_item_word(span, Symbol::intern("hidden"));
+    let doc = cx.meta_list(span, Symbol::intern("doc"), vec![hidden]);
+    let doc_hidden = cx.attribute(span, doc);
+
     let proc_macro = Ident::from_str("proc_macro");
     let krate = cx.item(span,
                         proc_macro,
@@ -425,7 +430,7 @@ fn mk_decls(
         span,
         span,
         ast::Ident::with_empty_ctxt(Symbol::gensym("decls")),
-        vec![],
+        vec![doc_hidden],
         vec![krate, decls_static],
     ).map(|mut i| {
         i.vis = respan(span, ast::VisibilityKind::Public);

src/test/run-pass/impl-trait-in-bindings.rs

@@ -1,4 +1,5 @@
 #![feature(impl_trait_in_bindings)]
+//~^ WARN the feature `impl_trait_in_bindings` is incomplete and may cause the compiler to crash
 
 use std::fmt::Debug;
 

src/test/run-pass/impl-trait-in-bindings.stderr

@@ -0,0 +1,6 @@
+warning: the feature `impl_trait_in_bindings` is incomplete and may cause the compiler to crash
+  --> $DIR/impl-trait-in-bindings.rs:1:12
+   |
+LL | #![feature(impl_trait_in_bindings)]
+   |            ^^^^^^^^^^^^^^^^^^^^^^
+

src/test/ui/const-generics/cannot-infer-type-for-const-param.rs

@@ -0,0 +1,11 @@
+#![feature(const_generics)]
+//~^ WARN the feature `const_generics` is incomplete and may cause the compiler to crash
+
+// We should probably be able to infer the types here. However, this test is checking that we don't
+// get an ICE in this case. It may be modified later to not be an error.
+
+struct Foo<const NUM_BYTES: usize>(pub [u8; NUM_BYTES]);
+
+fn main() {
+    let _ = Foo::<3>([1, 2, 3]); //~ ERROR type annotations needed
+}

src/test/ui/const-generics/cannot-infer-type-for-const-param.stderr

@@ -0,0 +1,15 @@
+warning: the feature `const_generics` is incomplete and may cause the compiler to crash
+  --> $DIR/cannot-infer-type-for-const-param.rs:1:12
+   |
+LL | #![feature(const_generics)]
+   |            ^^^^^^^^^^^^^^
+
+error[E0282]: type annotations needed
+  --> $DIR/cannot-infer-type-for-const-param.rs:10:19
+   |
+LL |     let _ = Foo::<3>([1, 2, 3]);
+   |                   ^ cannot infer type for `{integer}`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0282`.

src/test/ui/const-generics/invalid-const-arg-for-type-param.rs

@@ -0,0 +1,9 @@
+use std::convert::TryInto;
+
+struct S;
+
+fn main() {
+    let _: u32 = 5i32.try_into::<32>().unwrap(); //~ ERROR wrong number of const arguments
+    S.f::<0>(); //~ ERROR no method named `f`
+    S::<0>; //~ ERROR  wrong number of const arguments
+}