Auto merge of #64127 - Centril:rollup-dfgb9h8, r=Centril

Rollup of 5 pull requests

Successful merges:

 - #64049 (Emit a single error on if expr with expectation and no else clause)
 - #64056 (Account for arbitrary self types in E0599)
 - #64058 (librustc_errors: Extract sugg/subst handling into method)
 - #64071 (use just one name when parameters and fields are the same)
 - #64104 (Emit error on intrinsic to fn ptr casts)

Failed merges:

r? @ghost

src/librustc/infer/error_reporting/mod.rs

@@ -1636,6 +1636,9 @@ impl<'tcx> ObligationCause<'tcx> {
                 TypeError::CyclicTy(ty) if ty.is_closure() || ty.is_generator() => {
                     Error0644("closure/generator type that references itself")
                 }
+                TypeError::IntrinsicCast => {
+                    Error0308("cannot coerce intrinsics to function pointers")
+                }
                 _ => Error0308("mismatched types"),
             },
         }

src/librustc/ty/context.rs

@@ -2402,6 +2402,12 @@ impl<'tcx> TyCtxt<'tcx> {
         self.mk_generic_adt(def_id, ty)
     }
 
+    #[inline]
+    pub fn mk_lang_item(self, ty: Ty<'tcx>, item: lang_items::LangItem)  -> Ty<'tcx> {
+        let def_id = self.require_lang_item(item, None);
+        self.mk_generic_adt(def_id, ty)
+    }
+
     #[inline]
     pub fn mk_maybe_uninit(self, ty: Ty<'tcx>) -> Ty<'tcx> {
         let def_id = self.require_lang_item(lang_items::MaybeUninitLangItem, None);

src/librustc/ty/error.rs

@@ -46,6 +46,8 @@ pub enum TypeError<'tcx> {
     ExistentialMismatch(ExpectedFound<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>),
 
     ConstMismatch(ExpectedFound<&'tcx ty::Const<'tcx>>),
+
+    IntrinsicCast,
 }
 
 #[derive(Clone, RustcEncodable, RustcDecodable, PartialEq, Eq, Hash, Debug, Copy)]
@@ -179,6 +181,9 @@ impl<'tcx> fmt::Display for TypeError<'tcx> {
             ConstMismatch(ref values) => {
                 write!(f, "expected `{}`, found `{}`", values.expected, values.found)
             }
+            IntrinsicCast => {
+                write!(f, "cannot coerce intrinsics to function pointers")
+            }
         }
     }
 }

src/librustc/ty/structural_impls.rs

@@ -748,6 +748,7 @@ impl<'a, 'tcx> Lift<'tcx> for ty::error::TypeError<'a> {
             Sorts(ref x) => return tcx.lift(x).map(Sorts),
             ExistentialMismatch(ref x) => return tcx.lift(x).map(ExistentialMismatch),
             ConstMismatch(ref x) => return tcx.lift(x).map(ConstMismatch),
+            IntrinsicCast => IntrinsicCast,
         })
     }
 }
@@ -1338,6 +1339,7 @@ EnumTypeFoldableImpl! {
         (ty::error::TypeError::Sorts)(x),
         (ty::error::TypeError::ExistentialMismatch)(x),
         (ty::error::TypeError::ConstMismatch)(x),
+        (ty::error::TypeError::IntrinsicCast),
     }
 }
 

src/librustc_errors/annotate_snippet_emitter_writer.rs

@@ -30,10 +30,8 @@ pub struct AnnotateSnippetEmitterWriter {
 impl Emitter for AnnotateSnippetEmitterWriter {
     /// The entry point for the diagnostics generation
     fn emit_diagnostic(&mut self, db: &DiagnosticBuilder<'_>) {
-        let primary_span = db.span.clone();
         let children = db.children.clone();
-        // FIXME(#59346): Collect suggestions (see emitter.rs)
-        let suggestions: &[_] = &[];
+        let (primary_span, suggestions) = self.primary_span_formatted(&db);
 
         // FIXME(#59346): Add `fix_multispans_in_std_macros` function from emitter.rs
 

src/librustc_errors/emitter.rs

@@ -191,16 +191,25 @@ pub trait Emitter {
     fn should_show_explain(&self) -> bool {
         true
     }
-}
 
-impl Emitter for EmitterWriter {
-    fn emit_diagnostic(&mut self, db: &DiagnosticBuilder<'_>) {
+    /// Formats the substitutions of the primary_span
+    ///
+    /// The are a lot of conditions to this method, but in short:
+    ///
+    /// * If the current `Diagnostic` has only one visible `CodeSuggestion`,
+    ///   we format the `help` suggestion depending on the content of the
+    ///   substitutions. In that case, we return the modified span only.
+    ///
+    /// * If the current `Diagnostic` has multiple suggestions,
+    ///   we return the original `primary_span` and the original suggestions.
+    fn primary_span_formatted<'a>(
+        &mut self,
+        db: &'a DiagnosticBuilder<'_>
+    ) -> (MultiSpan, &'a [CodeSuggestion]) {
         let mut primary_span = db.span.clone();
-        let mut children = db.children.clone();
-        let mut suggestions: &[_] = &[];
-
         if let Some((sugg, rest)) = db.suggestions.split_first() {
             if rest.is_empty() &&
+               // ^ if there is only one suggestion
                // don't display multi-suggestions as labels
                sugg.substitutions.len() == 1 &&
                // don't display multipart suggestions as labels
@@ -216,21 +225,34 @@ impl Emitter for EmitterWriter {
             {
                 let substitution = &sugg.substitutions[0].parts[0].snippet.trim();
                 let msg = if substitution.len() == 0 || sugg.style.hide_inline() {
-                    // This substitution is only removal or we explicitly don't want to show the
-                    // code inline, don't show it
+                    // This substitution is only removal OR we explicitly don't want to show the
+                    // code inline (`hide_inline`). Therefore, we don't show the substitution.
                     format!("help: {}", sugg.msg)
                 } else {
+                    // Show the default suggestion text with the substitution
                     format!("help: {}: `{}`", sugg.msg, substitution)
                 };
                 primary_span.push_span_label(sugg.substitutions[0].parts[0].span, msg);
+
+                // We return only the modified primary_span
+                (primary_span, &[])
             } else {
                 // if there are multiple suggestions, print them all in full
                 // to be consistent. We could try to figure out if we can
                 // make one (or the first one) inline, but that would give
                 // undue importance to a semi-random suggestion
-                suggestions = &db.suggestions;
+                (primary_span, &db.suggestions)
             }
+        } else {
+            (primary_span, &db.suggestions)
         }
+    }
+}
+
+impl Emitter for EmitterWriter {
+    fn emit_diagnostic(&mut self, db: &DiagnosticBuilder<'_>) {
+        let mut children = db.children.clone();
+        let (mut primary_span, suggestions) = self.primary_span_formatted(&db);
 
         self.fix_multispans_in_std_macros(&mut primary_span,
                                           &mut children,

src/librustc_typeck/check/_match.rs

@@ -112,19 +112,26 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
 
             self.diverges.set(pats_diverge);
-            let arm_ty = self.check_expr_with_expectation(&arm.body, expected);
+            let arm_ty = if source_if && if_no_else && i != 0 && self.if_fallback_coercion(
+                expr.span,
+                &arms[0].body,
+                &mut coercion,
+            ) {
+                tcx.types.err
+            } else {
+                // Only call this if this is not an `if` expr with an expected type and no `else`
+                // clause to avoid duplicated type errors. (#60254)
+                self.check_expr_with_expectation(&arm.body, expected)
+            };
             all_arms_diverge &= self.diverges.get();
-
-            let span = expr.span;
-
             if source_if {
                 let then_expr = &arms[0].body;
                 match (i, if_no_else) {
-                    (0, _) => coercion.coerce(self, &self.misc(span), &arm.body, arm_ty),
-                    (_, true) => self.if_fallback_coercion(span, then_expr, &mut coercion),
+                    (0, _) => coercion.coerce(self, &self.misc(expr.span), &arm.body, arm_ty),
+                    (_, true) => {} // Handled above to avoid duplicated type errors (#60254).
                     (_, _) => {
                         let then_ty = prior_arm_ty.unwrap();
-                        let cause = self.if_cause(span, then_expr, &arm.body, then_ty, arm_ty);
+                        let cause = self.if_cause(expr.span, then_expr, &arm.body, then_ty, arm_ty);
                         coercion.coerce(self, &cause, &arm.body, arm_ty);
                     }
                 }
@@ -139,7 +146,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     // The reason for the first arm to fail is not that the match arms diverge,
                     // but rather that there's a prior obligation that doesn't hold.
                     0 => (arm_span, ObligationCauseCode::BlockTailExpression(arm.body.hir_id)),
-                    _ => (span, ObligationCauseCode::MatchExpressionArm {
+                    _ => (expr.span, ObligationCauseCode::MatchExpressionArm {
                         arm_span,
                         source: match_src,
                         prior_arms: other_arms.clone(),
@@ -180,16 +187,19 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     }
 
     /// Handle the fallback arm of a desugared if(-let) like a missing else.
+    ///
+    /// Returns `true` if there was an error forcing the coercion to the `()` type.
     fn if_fallback_coercion(
         &self,
         span: Span,
         then_expr: &'tcx hir::Expr,
         coercion: &mut CoerceMany<'tcx, '_, rustc::hir::Arm>,
-    ) {
+    ) -> bool {
         // If this `if` expr is the parent's function return expr,
         // the cause of the type coercion is the return type, point at it. (#25228)
         let ret_reason = self.maybe_get_coercion_reason(then_expr.hir_id, span);
         let cause = self.cause(span, ObligationCauseCode::IfExpressionWithNoElse);
+        let mut error = false;
         coercion.coerce_forced_unit(self, &cause, &mut |err| {
             if let Some((span, msg)) = &ret_reason {
                 err.span_label(*span, msg.as_str());
@@ -200,7 +210,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
             err.note("`if` expressions without `else` evaluate to `()`");
             err.help("consider adding an `else` block that evaluates to the expected type");
+            error = true;
         }, ret_reason.is_none());
+        error
     }
 
     fn maybe_get_coercion_reason(&self, hir_id: hir::HirId, span: Span) -> Option<(Span, String)> {

src/librustc_typeck/check/cast.rs

@@ -40,6 +40,7 @@ use rustc::ty::{self, Ty, TypeFoldable, TypeAndMut};
 use rustc::ty::subst::SubstsRef;
 use rustc::ty::adjustment::AllowTwoPhase;
 use rustc::ty::cast::{CastKind, CastTy};
+use rustc::ty::error::TypeError;
 use rustc::middle::lang_items;
 use syntax::ast;
 use syntax_pos::Span;
@@ -461,6 +462,9 @@ impl<'a, 'tcx> CastCheck<'tcx> {
                                              self.expr_ty,
                                              fcx.tcx.mk_fn_ptr(f),
                                              AllowTwoPhase::No);
+                    if let Err(TypeError::IntrinsicCast) = res {
+                        return Err(CastError::IllegalCast);
+                    }
                     if res.is_err() {
                         return Err(CastError::NonScalar);
                     }

src/librustc_typeck/check/coercion.rs

@@ -70,6 +70,7 @@ use std::ops::Deref;
 use syntax::feature_gate;
 use syntax::symbol::sym;
 use syntax_pos;
+use rustc_target::spec::abi::Abi;
 
 struct Coerce<'a, 'tcx> {
     fcx: &'a FnCtxt<'a, 'tcx>,
@@ -689,6 +690,11 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
         match b.sty {
             ty::FnPtr(_) => {
                 let a_sig = a.fn_sig(self.tcx);
+                // Intrinsics are not coercible to function pointers
+                if a_sig.abi() == Abi::RustIntrinsic ||
+                   a_sig.abi() == Abi::PlatformIntrinsic {
+                   return Err(TypeError::IntrinsicCast);
+                }
                 let InferOk { value: a_sig, mut obligations } =
                     self.normalize_associated_types_in_as_infer_ok(self.cause.span, &a_sig);
 

src/librustc_typeck/check/expr.rs

@@ -12,7 +12,7 @@ use crate::check::fatally_break_rust;
 use crate::check::report_unexpected_variant_res;
 use crate::check::Needs;
 use crate::check::TupleArgumentsFlag::DontTupleArguments;
-use crate::check::method::SelfSource;
+use crate::check::method::{probe, SelfSource, MethodError};
 use crate::util::common::ErrorReported;
 use crate::util::nodemap::FxHashMap;
 use crate::astconv::AstConv as _;
@@ -29,6 +29,7 @@ use rustc::hir::def::{CtorKind, Res, DefKind};
 use rustc::hir::ptr::P;
 use rustc::infer;
 use rustc::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
+use rustc::middle::lang_items;
 use rustc::mir::interpret::GlobalId;
 use rustc::ty;
 use rustc::ty::adjustment::{
@@ -775,35 +776,80 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // no need to check for bot/err -- callee does that
         let rcvr_t = self.structurally_resolved_type(args[0].span, rcvr_t);
 
-        let method = match self.lookup_method(rcvr_t,
-                                              segment,
-                                              span,
-                                              expr,
-                                              rcvr) {
+        let method = match self.lookup_method(rcvr_t, segment, span, expr, rcvr) {
             Ok(method) => {
                 self.write_method_call(expr.hir_id, method);
                 Ok(method)
             }
             Err(error) => {
                 if segment.ident.name != kw::Invalid {
-                    self.report_method_error(span,
-                                             rcvr_t,
-                                             segment.ident,
-                                             SelfSource::MethodCall(rcvr),
-                                             error,
-                                             Some(args));
+                    self.report_extended_method_error(segment, span, args, rcvr_t, error);
                 }
                 Err(())
             }
         };
 
         // Call the generic checker.
-        self.check_method_argument_types(span,
-                                         expr.span,
-                                         method,
-                                         &args[1..],
-                                         DontTupleArguments,
-                                         expected)
+        self.check_method_argument_types(
+            span,
+            expr.span,
+            method,
+            &args[1..],
+            DontTupleArguments,
+            expected,
+        )
+    }
+
+    fn report_extended_method_error(
+        &self,
+        segment: &hir::PathSegment,
+        span: Span,
+        args: &'tcx [hir::Expr],
+        rcvr_t: Ty<'tcx>,
+        error: MethodError<'tcx>
+    ) {
+        let rcvr = &args[0];
+        let try_alt_rcvr = |err: &mut DiagnosticBuilder<'_>, new_rcvr_t| {
+            if let Ok(pick) = self.lookup_probe(
+                span,
+                segment.ident,
+                new_rcvr_t,
+                rcvr,
+                probe::ProbeScope::AllTraits,
+            ) {
+                err.span_label(
+                    pick.item.ident.span,
+                    &format!("the method is available for `{}` here", new_rcvr_t),
+                );
+            }
+        };
+
+        if let Some(mut err) = self.report_method_error(
+            span,
+            rcvr_t,
+            segment.ident,
+            SelfSource::MethodCall(rcvr),
+            error,
+            Some(args),
+        ) {
+            if let ty::Adt(..) = rcvr_t.sty {
+                // Try alternative arbitrary self types that could fulfill this call.
+                // FIXME: probe for all types that *could* be arbitrary self-types, not
+                // just this whitelist.
+                let box_rcvr_t = self.tcx.mk_box(rcvr_t);
+                try_alt_rcvr(&mut err, box_rcvr_t);
+                let pin_rcvr_t = self.tcx.mk_lang_item(
+                    rcvr_t,
+                    lang_items::PinTypeLangItem,
+                );
+                try_alt_rcvr(&mut err, pin_rcvr_t);
+                let arc_rcvr_t = self.tcx.mk_lang_item(rcvr_t, lang_items::Arc);
+                try_alt_rcvr(&mut err, arc_rcvr_t);
+                let rc_rcvr_t = self.tcx.mk_lang_item(rcvr_t, lang_items::Rc);
+                try_alt_rcvr(&mut err, rc_rcvr_t);
+            }
+            err.emit();
+        }
     }
 
     fn check_expr_cast(
@@ -1466,8 +1512,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let struct_variant_def = def.non_enum_variant();
             let field_names = self.available_field_names(struct_variant_def);
             if !field_names.is_empty() {
-                err.note(&format!("available fields are: {}",
-                                    self.name_series_display(field_names)));
+                err.note(&format!(
+                    "available fields are: {}",
+                    self.name_series_display(field_names),
+                ));
             }
         }
     }

src/librustc_typeck/check/method/mod.rs

@@ -245,7 +245,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         Ok(result.callee)
     }
 
-    fn lookup_probe(
+    pub fn lookup_probe(
         &self,
         span: Span,
         method_name: ast::Ident,