Auto merge of #95250 - matthiaskrgr:rollup-ma4zl69, r=matthiaskrgr

Rollup of 5 pull requests

Successful merges:

 - #94249 (Better errors when a Copy impl on a Struct is not self-consistent)
 - #95069 (Fix auto traits in rustdoc)
 - #95221 (interpret/memory: simplify check_and_deref_ptr)
 - #95225 (remove `[async output]` from `impl Future` pretty-printing)
 - #95238 (Stop emitting E0026 for struct enums with underscores)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

compiler/rustc_const_eval/src/interpret/memory.rs

@@ -427,22 +427,12 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
             }
         }
 
-        // Extract from the pointer an `Option<AllocId>` and an offset, which is relative to the
-        // allocation or (if that is `None`) an absolute address.
-        let ptr_or_addr = if size.bytes() == 0 {
-            // Let's see what we can do, but don't throw errors if there's nothing there.
-            self.ptr_try_get_alloc(ptr)
-        } else {
-            // A "real" access, we insist on getting an `AllocId`.
-            Ok(self.ptr_get_alloc(ptr)?)
-        };
-        Ok(match ptr_or_addr {
+        Ok(match self.ptr_try_get_alloc(ptr) {
             Err(addr) => {
-                // No memory is actually being accessed.
-                debug_assert!(size.bytes() == 0);
-                // Must be non-null.
-                if addr == 0 {
-                    throw_ub!(DanglingIntPointer(0, msg))
+                // We couldn't get a proper allocation. This is only okay if the access size is 0,
+                // and the address is not null.
+                if size.bytes() > 0 || addr == 0 {
+                    throw_ub!(DanglingIntPointer(addr, msg));
                 }
                 // Must be aligned.
                 if let Some(align) = align {

compiler/rustc_middle/src/lib.rs

@@ -41,6 +41,7 @@
 #![feature(new_uninit)]
 #![feature(nll)]
 #![feature(once_cell)]
+#![feature(let_chains)]
 #![feature(let_else)]
 #![feature(min_specialization)]
 #![feature(trusted_len)]

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -896,44 +896,48 @@ pub trait PrettyPrinter<'tcx>:
             );
 
             if !generics.is_empty() || !assoc_items.is_empty() {
-                p!("<");
                 let mut first = true;
 
                 for ty in generics {
-                    if !first {
+                    if first {
+                        p!("<");
+                        first = false;
+                    } else {
                         p!(", ");
                     }
                     p!(print(trait_ref.rebind(*ty)));
-                    first = false;
                 }
 
                 for (assoc_item_def_id, term) in assoc_items {
-                    if !first {
+                    // Skip printing `<[generator@] as Generator<_>>::Return` from async blocks
+                    if let Some(ty) = term.skip_binder().ty() &&
+                       let ty::Projection(ty::ProjectionTy { item_def_id, .. }) = ty.kind() &&
+                       Some(*item_def_id) == self.tcx().lang_items().generator_return() {
+                        continue;
+                    }
+
+                    if first {
+                        p!("<");
+                        first = false;
+                    } else {
                         p!(", ");
                     }
+
                     p!(write("{} = ", self.tcx().associated_item(assoc_item_def_id).name));
 
                     match term.skip_binder() {
                         Term::Ty(ty) => {
-                            // Skip printing `<[generator@] as Generator<_>>::Return` from async blocks
-                            if matches!(
-                              ty.kind(), ty::Projection(ty::ProjectionTy { item_def_id, .. })
-                              if Some(*item_def_id) == self.tcx().lang_items().generator_return()
-                            ) {
-                                p!("[async output]")
-                            } else {
-                                p!(print(ty))
-                            }
+                            p!(print(ty))
                         }
                         Term::Const(c) => {
                             p!(print(c));
                         }
                     };
-
-                    first = false;
                 }
 
-                p!(">");
+                if !first {
+                    p!(">");
+                }
             }
 
             first = false;

compiler/rustc_trait_selection/src/traits/misc.rs

@@ -11,7 +11,7 @@ use crate::traits::error_reporting::InferCtxtExt;
 
 #[derive(Clone)]
 pub enum CopyImplementationError<'tcx> {
-    InfrigingFields(Vec<&'tcx ty::FieldDef>),
+    InfrigingFields(Vec<(&'tcx ty::FieldDef, Ty<'tcx>)>),
     NotAnAdt,
     HasDestructor,
 }
@@ -67,7 +67,7 @@ pub fn can_type_implement_copy<'tcx>(
                 match traits::fully_normalize(&infcx, ctx, cause, param_env, ty) {
                     Ok(ty) => {
                         if !infcx.type_is_copy_modulo_regions(param_env, ty, span) {
-                            infringing.push(field);
+                            infringing.push((field, ty));
                         }
                     }
                     Err(errors) => {

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -1270,7 +1270,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         // the master cache. Since coherence executes pretty quickly,
         // it's not worth going to more trouble to increase the
         // hit-rate, I don't think.
-        if self.intercrate {
+        if self.intercrate || self.allow_negative_impls {
             return false;
         }
 
@@ -1287,7 +1287,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         // mode, so don't do any caching. In particular, we might
         // re-use the same `InferCtxt` with both an intercrate
         // and non-intercrate `SelectionContext`
-        if self.intercrate {
+        if self.intercrate || self.allow_negative_impls {
             return None;
         }
         let tcx = self.tcx();

compiler/rustc_typeck/src/check/pat.rs

@@ -17,7 +17,7 @@ use rustc_session::lint::builtin::NON_EXHAUSTIVE_OMITTED_PATTERNS;
 use rustc_span::hygiene::DesugaringKind;
 use rustc_span::lev_distance::find_best_match_for_name;
 use rustc_span::source_map::{Span, Spanned};
-use rustc_span::symbol::{sym, Ident};
+use rustc_span::symbol::{kw, sym, Ident};
 use rustc_span::{BytePos, MultiSpan, DUMMY_SP};
 use rustc_trait_selection::autoderef::Autoderef;
 use rustc_trait_selection::traits::{ObligationCause, Pattern};
@@ -1275,7 +1275,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             .filter(|(_, ident)| !used_fields.contains_key(ident))
             .collect::<Vec<_>>();
 
-        let inexistent_fields_err = if !(inexistent_fields.is_empty() || variant.is_recovered()) {
+        let inexistent_fields_err = if !(inexistent_fields.is_empty() || variant.is_recovered())
+            && !inexistent_fields.iter().any(|field| field.name == kw::Underscore)
+        {
             Some(self.error_inexistent_fields(
                 adt.variant_descr(),
                 &inexistent_fields,

compiler/rustc_typeck/src/coherence/builtin.rs

@@ -91,8 +91,40 @@ fn visit_implementation_of_copy(tcx: TyCtxt<'_>, impl_did: LocalDefId) {
                 E0204,
                 "the trait `Copy` may not be implemented for this type"
             );
-            for span in fields.iter().map(|f| tcx.def_span(f.did)) {
-                err.span_label(span, "this field does not implement `Copy`");
+            for (field, ty) in fields {
+                let field_span = tcx.def_span(field.did);
+                err.span_label(field_span, "this field does not implement `Copy`");
+                // Spin up a new FulfillmentContext, so we can get the _precise_ reason
+                // why this field does not implement Copy. This is useful because sometimes
+                // it is not immediately clear why Copy is not implemented for a field, since
+                // all we point at is the field itself.
+                tcx.infer_ctxt().enter(|infcx| {
+                    let mut fulfill_cx = traits::FulfillmentContext::new_ignoring_regions();
+                    fulfill_cx.register_bound(
+                        &infcx,
+                        param_env,
+                        ty,
+                        tcx.lang_items().copy_trait().unwrap(),
+                        traits::ObligationCause::dummy_with_span(field_span),
+                    );
+                    for error in fulfill_cx.select_all_or_error(&infcx) {
+                        let error_predicate = error.obligation.predicate;
+                        // Only note if it's not the root obligation, otherwise it's trivial and
+                        // should be self-explanatory (i.e. a field literally doesn't implement Copy).
+
+                        // FIXME: This error could be more descriptive, especially if the error_predicate
+                        // contains a foreign type or if it's a deeply nested type...
+                        if error_predicate != error.root_obligation.predicate {
+                            err.span_note(
+                                error.obligation.cause.span,
+                                &format!(
+                                    "the `Copy` impl for `{}` requires that `{}`",
+                                    ty, error_predicate
+                                ),
+                            );
+                        }
+                    }
+                });
             }
             err.emit();
         }

src/test/rustdoc/auto-trait-not-send.rs

@@ -0,0 +1,8 @@
+#![crate_name = "foo"]
+
+// @has 'foo/struct.Foo.html'
+// @has - '//*[@id="impl-Send"]' 'impl !Send for Foo'
+// @has - '//*[@id="impl-Sync"]' 'impl !Sync for Foo'
+pub struct Foo(*const i8);
+pub trait Whatever: Send {}
+impl<T: Send + ?Sized> Whatever for T {}

src/test/ui/async-await/async-block-control-flow-static-semantics.rs

@@ -24,7 +24,7 @@ async fn return_targets_async_block_not_async_fn() -> u8 {
         return 0u8;
     };
     let _: &dyn Future<Output = ()> = &block;
-    //~^ ERROR type mismatch resolving `<impl Future<Output = [async output]> as Future>::Output == ()`
+    //~^ ERROR type mismatch resolving `<impl Future as Future>::Output == ()`
 }
 
 fn no_break_in_async_block() {

src/test/ui/async-await/async-block-control-flow-static-semantics.stderr

@@ -31,7 +31,7 @@ LL | |
 LL | | }
    | |_^ expected `u8`, found `()`
 
-error[E0271]: type mismatch resolving `<impl Future<Output = [async output]> as Future>::Output == ()`
+error[E0271]: type mismatch resolving `<impl Future as Future>::Output == ()`
   --> $DIR/async-block-control-flow-static-semantics.rs:26:39
    |
 LL |     let _: &dyn Future<Output = ()> = &block;
@@ -47,7 +47,7 @@ LL | fn return_targets_async_block_not_fn() -> u8 {
    |    |
    |    implicitly returns `()` as its body has no tail or `return` expression
 
-error[E0271]: type mismatch resolving `<impl Future<Output = [async output]> as Future>::Output == ()`
+error[E0271]: type mismatch resolving `<impl Future as Future>::Output == ()`
   --> $DIR/async-block-control-flow-static-semantics.rs:17:39
    |
 LL |     let _: &dyn Future<Output = ()> = &block;