Rollup of 5 pull requests

src/bootstrap/toolstate.rs

@@ -88,7 +88,7 @@ static STABLE_TOOLS: &[(&str, &str)] = &[
 static NIGHTLY_TOOLS: &[(&str, &str)] = &[
     ("miri", "src/tools/miri"),
     ("embedded-book", "src/doc/embedded-book"),
-    ("rustc-dev-guide", "src/doc/rustc-dev-guide"),
+    // ("rustc-dev-guide", "src/doc/rustc-dev-guide"),
 ];
 
 fn print_error(tool: &str, submodule: &str) {

src/ci/docker/x86_64-gnu-tools/checktools.sh

@@ -14,7 +14,6 @@ python3 "$X_PY" test --no-fail-fast \
     src/doc/rust-by-example \
     src/doc/embedded-book \
     src/doc/edition-guide \
-    src/doc/rustc-dev-guide \
     src/tools/clippy \
     src/tools/rls \
     src/tools/rustfmt \

src/librustc_ast_passes/ast_validation.rs

@@ -23,6 +23,7 @@ use rustc_session::Session;
 use rustc_span::symbol::{kw, sym};
 use rustc_span::Span;
 use std::mem;
+use std::ops::DerefMut;
 
 const MORE_EXTERN: &str =
     "for more information, visit https://doc.rust-lang.org/std/keyword.extern.html";
@@ -1113,17 +1114,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
 
         for predicate in &generics.where_clause.predicates {
             if let WherePredicate::EqPredicate(ref predicate) = *predicate {
-                self.err_handler()
-                    .struct_span_err(
-                        predicate.span,
-                        "equality constraints are not yet supported in `where` clauses",
-                    )
-                    .span_label(predicate.span, "not supported")
-                    .note(
-                        "see issue #20041 <https://github.com/rust-lang/rust/issues/20041> \
-                         for more information",
-                    )
-                    .emit();
+                deny_equality_constraints(self, predicate, generics);
             }
         }
 
@@ -1300,6 +1291,89 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
     }
 }
 
+/// When encountering an equality constraint in a `where` clause, emit an error. If the code seems
+/// like it's setting an associated type, provide an appropriate suggestion.
+fn deny_equality_constraints(
+    this: &mut AstValidator<'_>,
+    predicate: &WhereEqPredicate,
+    generics: &Generics,
+) {
+    let mut err = this.err_handler().struct_span_err(
+        predicate.span,
+        "equality constraints are not yet supported in `where` clauses",
+    );
+    err.span_label(predicate.span, "not supported");
+
+    // Given `<A as Foo>::Bar = RhsTy`, suggest `A: Foo<Bar = RhsTy>`.
+    if let TyKind::Path(Some(qself), full_path) = &predicate.lhs_ty.kind {
+        if let TyKind::Path(None, path) = &qself.ty.kind {
+            match &path.segments[..] {
+                [PathSegment { ident, args: None, .. }] => {
+                    for param in &generics.params {
+                        if param.ident == *ident {
+                            let param = ident;
+                            match &full_path.segments[qself.position..] {
+                                [PathSegment { ident, .. }] => {
+                                    // Make a new `Path` from `foo::Bar` to `Foo<Bar = RhsTy>`.
+                                    let mut assoc_path = full_path.clone();
+                                    // Remove `Bar` from `Foo::Bar`.
+                                    assoc_path.segments.pop();
+                                    let len = assoc_path.segments.len() - 1;
+                                    // Build `<Bar = RhsTy>`.
+                                    let arg = AngleBracketedArg::Constraint(AssocTyConstraint {
+                                        id: rustc_ast::node_id::DUMMY_NODE_ID,
+                                        ident: *ident,
+                                        kind: AssocTyConstraintKind::Equality {
+                                            ty: predicate.rhs_ty.clone(),
+                                        },
+                                        span: ident.span,
+                                    });
+                                    // Add `<Bar = RhsTy>` to `Foo`.
+                                    match &mut assoc_path.segments[len].args {
+                                        Some(args) => match args.deref_mut() {
+                                            GenericArgs::Parenthesized(_) => continue,
+                                            GenericArgs::AngleBracketed(args) => {
+                                                args.args.push(arg);
+                                            }
+                                        },
+                                        empty_args => {
+                                            *empty_args = AngleBracketedArgs {
+                                                span: ident.span,
+                                                args: vec![arg],
+                                            }
+                                            .into();
+                                        }
+                                    }
+                                    err.span_suggestion_verbose(
+                                        predicate.span,
+                                        &format!(
+                                            "if `{}` is an associated type you're trying to set, \
+                                            use the associated type binding syntax",
+                                            ident
+                                        ),
+                                        format!(
+                                            "{}: {}",
+                                            param,
+                                            pprust::path_to_string(&assoc_path)
+                                        ),
+                                        Applicability::MaybeIncorrect,
+                                    );
+                                }
+                                _ => {}
+                            };
+                        }
+                    }
+                }
+                _ => {}
+            }
+        }
+    }
+    err.note(
+        "see issue #20041 <https://github.com/rust-lang/rust/issues/20041> for more information",
+    );
+    err.emit();
+}
+
 pub fn check_crate(session: &Session, krate: &Crate, lints: &mut LintBuffer) -> bool {
     let mut validator = AstValidator {
         session,

src/librustc_hir/hir.rs

@@ -2626,8 +2626,42 @@ impl Node<'_> {
         match self {
             Node::TraitItem(TraitItem { generics, .. })
             | Node::ImplItem(ImplItem { generics, .. })
-            | Node::Item(Item { kind: ItemKind::Fn(_, generics, _), .. }) => Some(generics),
+            | Node::Item(Item {
+                kind:
+                    ItemKind::Trait(_, _, generics, ..)
+                    | ItemKind::Impl { generics, .. }
+                    | ItemKind::Fn(_, generics, _),
+                ..
+            }) => Some(generics),
             _ => None,
         }
     }
+
+    pub fn hir_id(&self) -> Option<HirId> {
+        match self {
+            Node::Item(Item { hir_id, .. })
+            | Node::ForeignItem(ForeignItem { hir_id, .. })
+            | Node::TraitItem(TraitItem { hir_id, .. })
+            | Node::ImplItem(ImplItem { hir_id, .. })
+            | Node::Field(StructField { hir_id, .. })
+            | Node::AnonConst(AnonConst { hir_id, .. })
+            | Node::Expr(Expr { hir_id, .. })
+            | Node::Stmt(Stmt { hir_id, .. })
+            | Node::Ty(Ty { hir_id, .. })
+            | Node::Binding(Pat { hir_id, .. })
+            | Node::Pat(Pat { hir_id, .. })
+            | Node::Arm(Arm { hir_id, .. })
+            | Node::Block(Block { hir_id, .. })
+            | Node::Local(Local { hir_id, .. })
+            | Node::MacroDef(MacroDef { hir_id, .. })
+            | Node::Lifetime(Lifetime { hir_id, .. })
+            | Node::Param(Param { hir_id, .. })
+            | Node::GenericParam(GenericParam { hir_id, .. }) => Some(*hir_id),
+            Node::TraitRef(TraitRef { hir_ref_id, .. }) => Some(*hir_ref_id),
+            Node::PathSegment(PathSegment { hir_id, .. }) => *hir_id,
+            Node::Variant(Variant { id, .. }) => Some(*id),
+            Node::Ctor(variant) => variant.ctor_hir_id(),
+            Node::Crate(_) | Node::Visibility(_) => None,
+        }
+    }
 }

src/librustc_middle/mir/interpret/error.rs

@@ -3,8 +3,7 @@ use super::{AllocId, Pointer, RawConst, ScalarMaybeUndef};
 use crate::mir::interpret::ConstValue;
 use crate::ty::layout::LayoutError;
 use crate::ty::query::TyCtxtAt;
-use crate::ty::tls;
-use crate::ty::{self, layout, Ty};
+use crate::ty::{self, layout, tls, FnSig, Ty};
 
 use rustc_data_structures::sync::Lock;
 use rustc_errors::{struct_span_err, DiagnosticBuilder, ErrorReported};
@@ -329,7 +328,7 @@ impl fmt::Display for CheckInAllocMsg {
 }
 
 /// Error information for when the program caused Undefined Behavior.
-pub enum UndefinedBehaviorInfo {
+pub enum UndefinedBehaviorInfo<'tcx> {
     /// Free-form case. Only for errors that are never caught!
     Ub(String),
     /// Unreachable code was executed.
@@ -347,6 +346,8 @@ pub enum UndefinedBehaviorInfo {
     PointerArithOverflow,
     /// Invalid metadata in a wide pointer (using `str` to avoid allocations).
     InvalidMeta(&'static str),
+    /// Invalid drop function in vtable.
+    InvalidDropFn(FnSig<'tcx>),
     /// Reading a C string that does not end within its allocation.
     UnterminatedCString(Pointer),
     /// Dereferencing a dangling pointer after it got freed.
@@ -380,6 +381,8 @@ pub enum UndefinedBehaviorInfo {
     InvalidDiscriminant(ScalarMaybeUndef),
     /// Using a pointer-not-to-a-function as function pointer.
     InvalidFunctionPointer(Pointer),
+    /// Using a string that is not valid UTF-8,
+    InvalidStr(std::str::Utf8Error),
     /// Using uninitialized data where it is not allowed.
     InvalidUndefBytes(Option<Pointer>),
     /// Working with a local that is not currently live.
@@ -391,7 +394,7 @@ pub enum UndefinedBehaviorInfo {
     },
 }
 
-impl fmt::Display for UndefinedBehaviorInfo {
+impl fmt::Display for UndefinedBehaviorInfo<'_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         use UndefinedBehaviorInfo::*;
         match self {
@@ -404,6 +407,11 @@ impl fmt::Display for UndefinedBehaviorInfo {
             RemainderByZero => write!(f, "calculating the remainder with a divisor of zero"),
             PointerArithOverflow => write!(f, "overflowing in-bounds pointer arithmetic"),
             InvalidMeta(msg) => write!(f, "invalid metadata in wide pointer: {}", msg),
+            InvalidDropFn(sig) => write!(
+                f,
+                "invalid drop function signature: got {}, expected exactly one argument which must be a pointer type",
+                sig
+            ),
             UnterminatedCString(p) => write!(
                 f,
                 "reading a null-terminated string starting at {} with no null found before end of allocation",
@@ -446,6 +454,7 @@ impl fmt::Display for UndefinedBehaviorInfo {
             InvalidFunctionPointer(p) => {
                 write!(f, "using {} as function pointer but it does not point to a function", p)
             }
+            InvalidStr(err) => write!(f, "this string is not valid UTF-8: {}", err),
             InvalidUndefBytes(Some(p)) => write!(
                 f,
                 "reading uninitialized memory at {}, but this operation requires initialized memory",
@@ -549,7 +558,7 @@ impl dyn MachineStopType {
 
 pub enum InterpError<'tcx> {
     /// The program caused undefined behavior.
-    UndefinedBehavior(UndefinedBehaviorInfo),
+    UndefinedBehavior(UndefinedBehaviorInfo<'tcx>),
     /// The program did something the interpreter does not support (some of these *might* be UB
     /// but the interpreter is not sure).
     Unsupported(UnsupportedOpInfo),