Rollup of 10 pull requests

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -914,6 +914,7 @@ impl<'a> State<'a> {
 
     pub fn print_assoc_constraint(&mut self, constraint: &ast::AssocTyConstraint) {
         self.print_ident(constraint.ident);
+        constraint.gen_args.as_ref().map(|args| self.print_generic_args(args, false));
         self.s.space();
         match &constraint.kind {
             ast::AssocTyConstraintKind::Equality { ty } => {

compiler/rustc_error_codes/src/error_codes.rs

@@ -290,6 +290,7 @@ E0543: include_str!("./error_codes/E0543.md"),
 E0545: include_str!("./error_codes/E0545.md"),
 E0546: include_str!("./error_codes/E0546.md"),
 E0547: include_str!("./error_codes/E0547.md"),
+E0549: include_str!("./error_codes/E0549.md"),
 E0550: include_str!("./error_codes/E0550.md"),
 E0551: include_str!("./error_codes/E0551.md"),
 E0552: include_str!("./error_codes/E0552.md"),
@@ -608,9 +609,6 @@ E0781: include_str!("./error_codes/E0781.md"),
 //  E0540, // multiple rustc_deprecated attributes
     E0544, // multiple stability levels
 //  E0548, // replaced with a generic attribute input check
-    // rustc_deprecated attribute must be paired with either stable or unstable
-    // attribute
-    E0549,
     E0553, // multiple rustc_const_unstable attributes
 //  E0555, // replaced with a generic attribute input check
 //  E0558, // replaced with a generic attribute input check

compiler/rustc_error_codes/src/error_codes/E0162.md

@@ -1,6 +1,6 @@
 #### Note: this error code is no longer emitted by the compiler.
 
-An if-let pattern attempts to match the pattern, and enters the body if the
+An `if let` pattern attempts to match the pattern, and enters the body if the
 match was successful. If the match is irrefutable (when it cannot fail to
 match), use a regular `let`-binding instead. For instance:
 

compiler/rustc_error_codes/src/error_codes/E0165.md

@@ -1,6 +1,6 @@
 #### Note: this error code is no longer emitted by the compiler.
 
-A while-let pattern attempts to match the pattern, and enters the body if the
+A `while let` pattern attempts to match the pattern, and enters the body if the
 match was successful. If the match is irrefutable (when it cannot fail to
 match), use a regular `let`-binding inside a `loop` instead. For instance:
 

compiler/rustc_error_codes/src/error_codes/E0549.md

@@ -0,0 +1,37 @@
+A `rustc_deprecated` attribute wasn't paired with a `stable`/`unstable`
+attribute.
+
+Erroneous code example:
+
+```compile_fail,E0549
+#![feature(staged_api)]
+#![stable(since = "1.0.0", feature = "test")]
+
+#[rustc_deprecated(
+    since = "1.0.1",
+    reason = "explanation for deprecation"
+)] // invalid
+fn _deprecated_fn() {}
+```
+
+To fix this issue, you need to add also an attribute `stable` or `unstable`.
+Example:
+
+```
+#![feature(staged_api)]
+#![stable(since = "1.0.0", feature = "test")]
+
+#[stable(since = "1.0.0", feature = "test")]
+#[rustc_deprecated(
+    since = "1.0.1",
+    reason = "explanation for deprecation"
+)] // ok!
+fn _deprecated_fn() {}
+```
+
+See the [How Rust is Made and “Nightly Rust”][how-rust-made-nightly] appendix
+of the Book and the [Stability attributes][stability-attributes] section of the
+Rustc Dev Guide for more details.
+
+[how-rust-made-nightly]: https://doc.rust-lang.org/book/appendix-07-nightly-rust.html
+[stability-attributes]: https://rustc-dev-guide.rust-lang.org/stability.html

compiler/rustc_errors/src/emitter.rs

@@ -1713,7 +1713,18 @@ impl EmitterWriter {
         let max_line_num_len = if self.ui_testing {
             ANONYMIZED_LINE_NUM.len()
         } else {
-            self.get_max_line_num(span, children).to_string().len()
+            // Instead of using .to_string().len(), we iteratively count the
+            // number of digits to avoid allocation. This strategy has sizable
+            // performance gains over the old string strategy.
+            let mut n = self.get_max_line_num(span, children);
+            let mut num_digits = 0;
+            loop {
+                num_digits += 1;
+                n /= 10;
+                if n == 0 {
+                    break num_digits;
+                }
+            }
         };
 
         match self.emit_message_default(span, message, code, level, max_line_num_len, false) {

compiler/rustc_hir/src/hir.rs

@@ -1280,7 +1280,7 @@ impl Body<'hir> {
 }
 
 /// The type of source expression that caused this generator to be created.
-#[derive(Clone, PartialEq, Eq, HashStable_Generic, Encodable, Decodable, Debug, Copy)]
+#[derive(Clone, PartialEq, Eq, Hash, HashStable_Generic, Encodable, Decodable, Debug, Copy)]
 pub enum GeneratorKind {
     /// An explicit `async` block or the body of an async function.
     Async(AsyncGeneratorKind),
@@ -1298,12 +1298,21 @@ impl fmt::Display for GeneratorKind {
     }
 }
 
+impl GeneratorKind {
+    pub fn descr(&self) -> &'static str {
+        match self {
+            GeneratorKind::Async(ask) => ask.descr(),
+            GeneratorKind::Gen => "generator",
+        }
+    }
+}
+
 /// In the case of a generator created as part of an async construct,
 /// which kind of async construct caused it to be created?
 ///
 /// This helps error messages but is also used to drive coercions in
 /// type-checking (see #60424).
-#[derive(Clone, PartialEq, Eq, HashStable_Generic, Encodable, Decodable, Debug, Copy)]
+#[derive(Clone, PartialEq, Eq, Hash, HashStable_Generic, Encodable, Decodable, Debug, Copy)]
 pub enum AsyncGeneratorKind {
     /// An explicit `async` block written by the user.
     Block,
@@ -1325,6 +1334,16 @@ impl fmt::Display for AsyncGeneratorKind {
     }
 }
 
+impl AsyncGeneratorKind {
+    pub fn descr(&self) -> &'static str {
+        match self {
+            AsyncGeneratorKind::Block => "`async` block",
+            AsyncGeneratorKind::Closure => "`async` closure body",
+            AsyncGeneratorKind::Fn => "`async fn` body",
+        }
+    }
+}
+
 #[derive(Copy, Clone, Debug)]
 pub enum BodyOwnerKind {
     /// Functions and methods.

compiler/rustc_hir/src/lang_items.rs

@@ -242,6 +242,7 @@ language_item_table! {
 
     Deref,                   sym::deref,               deref_trait,                Target::Trait;
     DerefMut,                sym::deref_mut,           deref_mut_trait,            Target::Trait;
+    DerefTarget,             sym::deref_target,        deref_target,               Target::AssocTy;
     Receiver,                sym::receiver,            receiver_trait,             Target::Trait;
 
     Fn,                      kw::Fn,                   fn_trait,                   Target::Trait;

compiler/rustc_infer/src/infer/at.rs

@@ -55,6 +55,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
 
 pub trait ToTrace<'tcx>: Relate<'tcx> + Copy {
     fn to_trace(
+        tcx: TyCtxt<'tcx>,
         cause: &ObligationCause<'tcx>,
         a_is_expected: bool,
         a: Self,
@@ -178,7 +179,7 @@ impl<'a, 'tcx> At<'a, 'tcx> {
     where
         T: ToTrace<'tcx>,
     {
-        let trace = ToTrace::to_trace(self.cause, a_is_expected, a, b);
+        let trace = ToTrace::to_trace(self.infcx.tcx, self.cause, a_is_expected, a, b);
         Trace { at: self, trace, a_is_expected }
     }
 }
@@ -251,6 +252,7 @@ impl<'a, 'tcx> Trace<'a, 'tcx> {
 
 impl<'tcx> ToTrace<'tcx> for Ty<'tcx> {
     fn to_trace(
+        _: TyCtxt<'tcx>,
         cause: &ObligationCause<'tcx>,
         a_is_expected: bool,
         a: Self,
@@ -262,6 +264,7 @@ impl<'tcx> ToTrace<'tcx> for Ty<'tcx> {
 
 impl<'tcx> ToTrace<'tcx> for ty::Region<'tcx> {
     fn to_trace(
+        _: TyCtxt<'tcx>,
         cause: &ObligationCause<'tcx>,
         a_is_expected: bool,
         a: Self,
@@ -273,6 +276,7 @@ impl<'tcx> ToTrace<'tcx> for ty::Region<'tcx> {
 
 impl<'tcx> ToTrace<'tcx> for &'tcx Const<'tcx> {
     fn to_trace(
+        _: TyCtxt<'tcx>,
         cause: &ObligationCause<'tcx>,
         a_is_expected: bool,
         a: Self,
@@ -284,6 +288,7 @@ impl<'tcx> ToTrace<'tcx> for &'tcx Const<'tcx> {
 
 impl<'tcx> ToTrace<'tcx> for ty::TraitRef<'tcx> {
     fn to_trace(
+        _: TyCtxt<'tcx>,
         cause: &ObligationCause<'tcx>,
         a_is_expected: bool,
         a: Self,
@@ -298,6 +303,7 @@ impl<'tcx> ToTrace<'tcx> for ty::TraitRef<'tcx> {
 
 impl<'tcx> ToTrace<'tcx> for ty::PolyTraitRef<'tcx> {
     fn to_trace(
+        _: TyCtxt<'tcx>,
         cause: &ObligationCause<'tcx>,
         a_is_expected: bool,
         a: Self,
@@ -309,3 +315,20 @@ impl<'tcx> ToTrace<'tcx> for ty::PolyTraitRef<'tcx> {
         }
     }
 }
+
+impl<'tcx> ToTrace<'tcx> for ty::ProjectionTy<'tcx> {
+    fn to_trace(
+        tcx: TyCtxt<'tcx>,
+        cause: &ObligationCause<'tcx>,
+        a_is_expected: bool,
+        a: Self,
+        b: Self,
+    ) -> TypeTrace<'tcx> {
+        let a_ty = tcx.mk_projection(a.item_def_id, a.substs);
+        let b_ty = tcx.mk_projection(b.item_def_id, b.substs);
+        TypeTrace {
+            cause: cause.clone(),
+            values: Types(ExpectedFound::new(a_is_expected, a_ty, b_ty)),
+        }
+    }
+}

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -1509,7 +1509,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
 
         impl<'tcx> ty::fold::TypeVisitor<'tcx> for OpaqueTypesVisitor<'tcx> {
             fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
-                if let Some((kind, def_id)) = TyCategory::from_ty(t) {
+                if let Some((kind, def_id)) = TyCategory::from_ty(self.tcx, t) {
                     let span = self.tcx.def_span(def_id);
                     // Avoid cluttering the output when the "found" and error span overlap:
                     //
@@ -1582,11 +1582,11 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         };
         if let Some((expected, found)) = expected_found {
             let expected_label = match exp_found {
-                Mismatch::Variable(ef) => ef.expected.prefix_string(),
+                Mismatch::Variable(ef) => ef.expected.prefix_string(self.tcx),
                 Mismatch::Fixed(s) => s.into(),
             };
             let found_label = match exp_found {
-                Mismatch::Variable(ef) => ef.found.prefix_string(),
+                Mismatch::Variable(ef) => ef.found.prefix_string(self.tcx),
                 Mismatch::Fixed(s) => s.into(),
             };
             let exp_found = match exp_found {
@@ -2489,7 +2489,7 @@ impl<'tcx> ObligationCauseExt<'tcx> for ObligationCause<'tcx> {
 pub enum TyCategory {
     Closure,
     Opaque,
-    Generator,
+    Generator(hir::GeneratorKind),
     Foreign,
 }
 
@@ -2498,16 +2498,18 @@ impl TyCategory {
         match self {
             Self::Closure => "closure",
             Self::Opaque => "opaque type",
-            Self::Generator => "generator",
+            Self::Generator(gk) => gk.descr(),
             Self::Foreign => "foreign type",
         }
     }
 
-    pub fn from_ty(ty: Ty<'_>) -> Option<(Self, DefId)> {
+    pub fn from_ty(tcx: TyCtxt<'_>, ty: Ty<'_>) -> Option<(Self, DefId)> {
         match *ty.kind() {
             ty::Closure(def_id, _) => Some((Self::Closure, def_id)),
             ty::Opaque(def_id, _) => Some((Self::Opaque, def_id)),
-            ty::Generator(def_id, ..) => Some((Self::Generator, def_id)),
+            ty::Generator(def_id, ..) => {
+                Some((Self::Generator(tcx.generator_kind(def_id).unwrap()), def_id))
+            }
             ty::Foreign(def_id) => Some((Self::Foreign, def_id)),
             _ => None,
         }

compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs

@@ -383,7 +383,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                 InferenceDiagnosticsData {
                     name: s,
                     span: None,
-                    kind: UnderspecifiedArgKind::Type { prefix: ty.prefix_string() },
+                    kind: UnderspecifiedArgKind::Type { prefix: ty.prefix_string(self.tcx) },
                     parent: None,
                 }
             }

compiler/rustc_lint_defs/src/builtin.rs

@@ -1815,7 +1815,7 @@ declare_lint! {
 
 declare_lint! {
     /// The `irrefutable_let_patterns` lint detects detects [irrefutable
-    /// patterns] in [if-let] and [while-let] statements.
+    /// patterns] in [`if let`] and [`while let`] statements.
     ///
     ///
     ///
@@ -1832,7 +1832,7 @@ declare_lint! {
     /// ### Explanation
     ///
     /// There usually isn't a reason to have an irrefutable pattern in an
-    /// if-let or while-let statement, because the pattern will always match
+    /// `if let` or `while let` statement, because the pattern will always match
     /// successfully. A [`let`] or [`loop`] statement will suffice. However,
     /// when generating code with a macro, forbidding irrefutable patterns
     /// would require awkward workarounds in situations where the macro
@@ -1843,14 +1843,14 @@ declare_lint! {
     /// See [RFC 2086] for more details.
     ///
     /// [irrefutable patterns]: https://doc.rust-lang.org/reference/patterns.html#refutability
-    /// [if-let]: https://doc.rust-lang.org/reference/expressions/if-expr.html#if-let-expressions
-    /// [while-let]: https://doc.rust-lang.org/reference/expressions/loop-expr.html#predicate-pattern-loops
+    /// [`if let`]: https://doc.rust-lang.org/reference/expressions/if-expr.html#if-let-expressions
+    /// [`while let`]: https://doc.rust-lang.org/reference/expressions/loop-expr.html#predicate-pattern-loops
     /// [`let`]: https://doc.rust-lang.org/reference/statements.html#let-statements
     /// [`loop`]: https://doc.rust-lang.org/reference/expressions/loop-expr.html#infinite-loops
     /// [RFC 2086]: https://github.com/rust-lang/rfcs/blob/master/text/2086-allow-if-let-irrefutables.md
     pub IRREFUTABLE_LET_PATTERNS,
     Warn,
-    "detects irrefutable patterns in if-let and while-let statements"
+    "detects irrefutable patterns in `if let` and `while let` statements"
 }
 
 declare_lint! {

compiler/rustc_middle/src/ty/diagnostics.rs

@@ -75,6 +75,36 @@ impl<'tcx> TyS<'tcx> {
     }
 }
 
+pub fn suggest_arbitrary_trait_bound(
+    generics: &hir::Generics<'_>,
+    err: &mut DiagnosticBuilder<'_>,
+    param_name: &str,
+    constraint: &str,
+) -> bool {
+    let param = generics.params.iter().find(|p| p.name.ident().as_str() == param_name);
+    match (param, param_name) {
+        (Some(_), "Self") => return false,
+        _ => {}
+    }
+    // Suggest a where clause bound for a non-type paremeter.
+    let (action, prefix) = if generics.where_clause.predicates.is_empty() {
+        ("introducing a", " where ")
+    } else {
+        ("extending the", ", ")
+    };
+    err.span_suggestion_verbose(
+        generics.where_clause.tail_span_for_suggestion(),
+        &format!(
+            "consider {} `where` bound, but there might be an alternative better way to express \
+             this requirement",
+            action,
+        ),
+        format!("{}{}: {}", prefix, param_name, constraint),
+        Applicability::MaybeIncorrect,
+    );
+    true
+}
+
 /// Suggest restricting a type param with a new bound.
 pub fn suggest_constraining_type_param(
     tcx: TyCtxt<'_>,