Auto merge of #57714 - matthewjasper:wellformed-unreachable, r=pnkfelix

[NLL] Clean up handling of type annotations

* Renames (Canonical)?UserTypeAnnotation -> (Canonical)?UserType so that the name CanonicalUserTypeAnnotation is free.
* Keep the inferred type associated to user type annotations in the MIR, so that it can be compared against the annotated type, even when the annotated expression gets removed from the MIR. (#54943)
* Use the inferred type to allow infallible handling of user type projections (#57531)
* Uses revisions for the tests in #56993
* Check the types of `Unevaluated` constants with no annotations (#46702)
* Some drive-by cleanup

Closes #46702
Closes #54943
Closes #57531
Closes #57731
cc #56993 leaving this open to track the underlying issue: we are not running tests with full NLL enabled on CI at the moment

r? @nikomatsakis

src/librustc/ich/impls_ty.rs

@@ -1240,16 +1240,22 @@ impl_stable_hash_for!(
     }
 );
 
-impl<'a, 'gcx> HashStable<StableHashingContext<'a>> for ty::UserTypeAnnotation<'gcx> {
+impl_stable_hash_for!(
+    struct ty::CanonicalUserTypeAnnotation<'tcx> {
+        user_ty, span, inferred_ty
+    }
+);
+
+impl<'a, 'gcx> HashStable<StableHashingContext<'a>> for ty::UserType<'gcx> {
     fn hash_stable<W: StableHasherResult>(&self,
                                           hcx: &mut StableHashingContext<'a>,
                                           hasher: &mut StableHasher<W>) {
         mem::discriminant(self).hash_stable(hcx, hasher);
         match *self {
-            ty::UserTypeAnnotation::Ty(ref ty) => {
+            ty::UserType::Ty(ref ty) => {
                 ty.hash_stable(hcx, hasher);
             }
-            ty::UserTypeAnnotation::TypeOf(ref def_id, ref substs) => {
+            ty::UserType::TypeOf(ref def_id, ref substs) => {
                 def_id.hash_stable(hcx, hasher);
                 substs.hash_stable(hcx, hasher);
             }

src/librustc/mir/mod.rs

@@ -31,7 +31,7 @@ use ty::subst::{Subst, Substs};
 use ty::layout::VariantIdx;
 use ty::{
     self, AdtDef, CanonicalUserTypeAnnotations, ClosureSubsts, GeneratorSubsts, Region, Ty, TyCtxt,
-    UserTypeAnnotationIndex, UserTypeAnnotation,
+    UserTypeAnnotationIndex,
 };
 use util::ppaux;
 

src/librustc/mir/tcx.rs

@@ -75,21 +75,20 @@ impl<'a, 'gcx, 'tcx> PlaceTy<'tcx> {
                          elem: &PlaceElem<'tcx>)
                          -> PlaceTy<'tcx>
     {
-        self.projection_ty_core(tcx, elem, |_, _, ty| -> Result<Ty<'tcx>, ()> { Ok(ty) })
-            .unwrap()
+        self.projection_ty_core(tcx, elem, |_, _, ty| ty)
     }
 
     /// `place_ty.projection_ty_core(tcx, elem, |...| { ... })`
     /// projects `place_ty` onto `elem`, returning the appropriate
     /// `Ty` or downcast variant corresponding to that projection.
     /// The `handle_field` callback must map a `Field` to its `Ty`,
     /// (which should be trivial when `T` = `Ty`).
-    pub fn projection_ty_core<V, T, E>(
+    pub fn projection_ty_core<V, T>(
         self,
         tcx: TyCtxt<'a, 'gcx, 'tcx>,
         elem: &ProjectionElem<'tcx, V, T>,
-        mut handle_field: impl FnMut(&Self, &Field, &T) -> Result<Ty<'tcx>, E>)
-        -> Result<PlaceTy<'tcx>, E>
+        mut handle_field: impl FnMut(&Self, &Field, &T) -> Ty<'tcx>)
+        -> PlaceTy<'tcx>
     where
         V: ::std::fmt::Debug, T: ::std::fmt::Debug
     {
@@ -140,10 +139,10 @@ impl<'a, 'gcx, 'tcx> PlaceTy<'tcx> {
                     }
                 },
             ProjectionElem::Field(ref f, ref fty) =>
-                PlaceTy::Ty { ty: handle_field(&self, f, fty)? },
+                PlaceTy::Ty { ty: handle_field(&self, f, fty) },
         };
         debug!("projection_ty self: {:?} elem: {:?} yields: {:?}", self, elem, answer);
-        Ok(answer)
+        answer
     }
 }
 

src/librustc/mir/visit.rs

@@ -1,7 +1,6 @@
 use hir::def_id::DefId;
-use infer::canonical::Canonical;
 use ty::subst::Substs;
-use ty::{ClosureSubsts, GeneratorSubsts, Region, Ty};
+use ty::{CanonicalUserTypeAnnotation, ClosureSubsts, GeneratorSubsts, Region, Ty};
 use mir::*;
 use syntax_pos::Span;
 
@@ -221,7 +220,7 @@ macro_rules! make_mir_visitor {
             fn visit_user_type_annotation(
                 &mut self,
                 index: UserTypeAnnotationIndex,
-                ty: & $($mutability)* Canonical<'tcx, UserTypeAnnotation<'tcx>>,
+                ty: & $($mutability)* CanonicalUserTypeAnnotation<'tcx>,
             ) {
                 self.super_user_type_annotation(index, ty);
             }
@@ -309,12 +308,15 @@ macro_rules! make_mir_visitor {
                     self.visit_local_decl(local, & $($mutability)* mir.local_decls[local]);
                 }
 
-                for index in mir.user_type_annotations.indices() {
-                    let (span, annotation) = & $($mutability)* mir.user_type_annotations[index];
+                macro_rules! type_annotations {
+                    (mut) => (mir.user_type_annotations.iter_enumerated_mut());
+                    () => (mir.user_type_annotations.iter_enumerated());
+                };
+
+                for (index, annotation) in type_annotations!($($mutability)*) {
                     self.visit_user_type_annotation(
                         index, annotation
                     );
-                    self.visit_span(span);
                 }
 
                 self.visit_span(&$($mutability)* mir.span);
@@ -882,8 +884,10 @@ macro_rules! make_mir_visitor {
             fn super_user_type_annotation(
                 &mut self,
                 _index: UserTypeAnnotationIndex,
-                _ty: & $($mutability)* Canonical<'tcx, UserTypeAnnotation<'tcx>>,
+                ty: & $($mutability)* CanonicalUserTypeAnnotation<'tcx>,
             ) {
+                self.visit_span(& $($mutability)* ty.span);
+                self.visit_ty(& $($mutability)* ty.inferred_ty, TyContext::UserTy(ty.span));
             }
 
             fn super_ty(&mut self, _ty: & $($mutability)* Ty<'tcx>) {
@@ -964,6 +968,9 @@ pub enum TyContext {
         source_info: SourceInfo,
     },
 
+    /// The inferred type of a user type annotation.
+    UserTy(Span),
+
     /// The return type of the function.
     ReturnTy(SourceInfo),
 

src/librustc/traits/query/type_op/ascribe_user_type.rs

@@ -1,28 +1,23 @@
 use infer::canonical::{Canonical, Canonicalized, CanonicalizedQueryResponse, QueryResponse};
 use traits::query::Fallible;
 use hir::def_id::DefId;
-use mir::ProjectionKind;
-use ty::{self, ParamEnvAnd, Ty, TyCtxt};
+use ty::{ParamEnvAnd, Ty, TyCtxt};
 use ty::subst::UserSubsts;
 
 #[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
 pub struct AscribeUserType<'tcx> {
     pub mir_ty: Ty<'tcx>,
-    pub variance: ty::Variance,
     pub def_id: DefId,
     pub user_substs: UserSubsts<'tcx>,
-    pub projs: &'tcx ty::List<ProjectionKind<'tcx>>,
 }
 
 impl<'tcx> AscribeUserType<'tcx> {
     pub fn new(
         mir_ty: Ty<'tcx>,
-        variance: ty::Variance,
         def_id: DefId,
         user_substs: UserSubsts<'tcx>,
-        projs: &'tcx ty::List<ProjectionKind<'tcx>>,
     ) -> Self {
-        Self { mir_ty, variance, def_id, user_substs, projs }
+        Self { mir_ty,  def_id, user_substs }
     }
 }
 
@@ -52,19 +47,19 @@ impl<'gcx: 'tcx, 'tcx> super::QueryTypeOp<'gcx, 'tcx> for AscribeUserType<'tcx>
 
 BraceStructTypeFoldableImpl! {
     impl<'tcx> TypeFoldable<'tcx> for AscribeUserType<'tcx> {
-        mir_ty, variance, def_id, user_substs, projs
+        mir_ty, def_id, user_substs
     }
 }
 
 BraceStructLiftImpl! {
     impl<'a, 'tcx> Lift<'tcx> for AscribeUserType<'a> {
         type Lifted = AscribeUserType<'tcx>;
-        mir_ty, variance, def_id, user_substs, projs
+        mir_ty, def_id, user_substs
     }
 }
 
 impl_stable_hash_for! {
     struct AscribeUserType<'tcx> {
-        mir_ty, variance, def_id, user_substs, projs
+        mir_ty, def_id, user_substs
     }
 }

src/librustc/ty/context.rs

@@ -350,7 +350,7 @@ pub struct TypeckTables<'tcx> {
     /// canonical substitutions would include only `for<X> { Vec<X> }`.
     ///
     /// See also `AscribeUserType` statement in MIR.
-    user_provided_types: ItemLocalMap<CanonicalUserTypeAnnotation<'tcx>>,
+    user_provided_types: ItemLocalMap<CanonicalUserType<'tcx>>,
 
     /// Stores the canonicalized types provided by the user. See also
     /// `AscribeUserType` statement in MIR.
@@ -493,7 +493,7 @@ impl<'tcx> TypeckTables<'tcx> {
 
     pub fn user_provided_types(
         &self
-    ) -> LocalTableInContext<'_, CanonicalUserTypeAnnotation<'tcx>> {
+    ) -> LocalTableInContext<'_, CanonicalUserType<'tcx>> {
         LocalTableInContext {
             local_id_root: self.local_id_root,
             data: &self.user_provided_types
@@ -502,7 +502,7 @@ impl<'tcx> TypeckTables<'tcx> {
 
     pub fn user_provided_types_mut(
         &mut self
-    ) -> LocalTableInContextMut<'_, CanonicalUserTypeAnnotation<'tcx>> {
+    ) -> LocalTableInContextMut<'_, CanonicalUserType<'tcx>> {
         LocalTableInContextMut {
             local_id_root: self.local_id_root,
             data: &mut self.user_provided_types
@@ -800,25 +800,46 @@ impl<'a, 'gcx> HashStable<StableHashingContext<'a>> for TypeckTables<'gcx> {
 
 newtype_index! {
     pub struct UserTypeAnnotationIndex {
-        DEBUG_FORMAT = "UserTypeAnnotation({})",
+        DEBUG_FORMAT = "UserType({})",
         const START_INDEX = 0,
     }
 }
 
 /// Mapping of type annotation indices to canonical user type annotations.
 pub type CanonicalUserTypeAnnotations<'tcx> =
-    IndexVec<UserTypeAnnotationIndex, (Span, CanonicalUserTypeAnnotation<'tcx>)>;
+    IndexVec<UserTypeAnnotationIndex, CanonicalUserTypeAnnotation<'tcx>>;
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
+pub struct CanonicalUserTypeAnnotation<'tcx> {
+    pub user_ty: CanonicalUserType<'tcx>,
+    pub span: Span,
+    pub inferred_ty: Ty<'tcx>,
+}
+
+BraceStructTypeFoldableImpl! {
+    impl<'tcx> TypeFoldable<'tcx> for CanonicalUserTypeAnnotation<'tcx> {
+        user_ty, span, inferred_ty
+    }
+}
+
+BraceStructLiftImpl! {
+    impl<'a, 'tcx> Lift<'tcx> for CanonicalUserTypeAnnotation<'a> {
+        type Lifted = CanonicalUserTypeAnnotation<'tcx>;
+        user_ty, span, inferred_ty
+    }
+}
+
 
 /// Canonicalized user type annotation.
-pub type CanonicalUserTypeAnnotation<'gcx> = Canonical<'gcx, UserTypeAnnotation<'gcx>>;
+pub type CanonicalUserType<'gcx> = Canonical<'gcx, UserType<'gcx>>;
 
-impl CanonicalUserTypeAnnotation<'gcx> {
+impl CanonicalUserType<'gcx> {
     /// Returns `true` if this represents a substitution of the form `[?0, ?1, ?2]`,
     /// i.e. each thing is mapped to a canonical variable with the same index.
     pub fn is_identity(&self) -> bool {
         match self.value {
-            UserTypeAnnotation::Ty(_) => false,
-            UserTypeAnnotation::TypeOf(_, user_substs) => {
+            UserType::Ty(_) => false,
+            UserType::TypeOf(_, user_substs) => {
                 if user_substs.user_self_ty.is_some() {
                     return false;
                 }
@@ -853,7 +874,7 @@ impl CanonicalUserTypeAnnotation<'gcx> {
 /// from constants that are named via paths, like `Foo::<A>::new` and
 /// so forth.
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
-pub enum UserTypeAnnotation<'tcx> {
+pub enum UserType<'tcx> {
     Ty(Ty<'tcx>),
 
     /// The canonical type is the result of `type_of(def_id)` with the
@@ -862,17 +883,17 @@ pub enum UserTypeAnnotation<'tcx> {
 }
 
 EnumTypeFoldableImpl! {
-    impl<'tcx> TypeFoldable<'tcx> for UserTypeAnnotation<'tcx> {
-        (UserTypeAnnotation::Ty)(ty),
-        (UserTypeAnnotation::TypeOf)(def, substs),
+    impl<'tcx> TypeFoldable<'tcx> for UserType<'tcx> {
+        (UserType::Ty)(ty),
+        (UserType::TypeOf)(def, substs),
     }
 }
 
 EnumLiftImpl! {
-    impl<'a, 'tcx> Lift<'tcx> for UserTypeAnnotation<'a> {
-        type Lifted = UserTypeAnnotation<'tcx>;
-        (UserTypeAnnotation::Ty)(ty),
-        (UserTypeAnnotation::TypeOf)(def, substs),
+    impl<'a, 'tcx> Lift<'tcx> for UserType<'a> {
+        type Lifted = UserType<'tcx>;
+        (UserType::Ty)(ty),
+        (UserType::TypeOf)(def, substs),
     }
 }
 

src/librustc/ty/mod.rs

@@ -73,8 +73,8 @@ pub use self::binding::BindingMode::*;
 pub use self::context::{TyCtxt, FreeRegionInfo, GlobalArenas, AllArenas, tls, keep_local};
 pub use self::context::{Lift, TypeckTables, CtxtInterners};
 pub use self::context::{
-    UserTypeAnnotationIndex, UserTypeAnnotation, CanonicalUserTypeAnnotation,
-    CanonicalUserTypeAnnotations,
+    UserTypeAnnotationIndex, UserType, CanonicalUserType,
+    CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations,
 };
 
 pub use self::instance::{Instance, InstanceDef};

src/librustc_mir/borrow_check/nll/constraint_generation.rs

@@ -7,7 +7,7 @@ use rustc::infer::InferCtxt;
 use rustc::mir::visit::TyContext;
 use rustc::mir::visit::Visitor;
 use rustc::mir::{BasicBlock, BasicBlockData, Location, Mir, Place, Rvalue};
-use rustc::mir::{Statement, Terminator};
+use rustc::mir::{SourceInfo, Statement, Terminator};
 use rustc::mir::UserTypeProjection;
 use rustc::ty::fold::TypeFoldable;
 use rustc::ty::subst::Substs;
@@ -66,11 +66,12 @@ impl<'cg, 'cx, 'gcx, 'tcx> Visitor<'tcx> for ConstraintGeneration<'cg, 'cx, 'gcx
     /// call. Make them live at the location where they appear.
     fn visit_ty(&mut self, ty: &ty::Ty<'tcx>, ty_context: TyContext) {
         match ty_context {
-            TyContext::ReturnTy(source_info)
-            | TyContext::YieldTy(source_info)
-            | TyContext::LocalDecl { source_info, .. } => {
+            TyContext::ReturnTy(SourceInfo { span, .. })
+            | TyContext::YieldTy(SourceInfo { span, .. })
+            | TyContext::UserTy(span)
+            | TyContext::LocalDecl { source_info: SourceInfo { span, .. }, .. } => {
                 span_bug!(
-                    source_info.span,
+                    span,
                     "should not be visiting outside of the CFG: {:?}",
                     ty_context
                 );

src/librustc_mir/borrow_check/nll/renumber.rs

@@ -1,9 +1,5 @@
-use rustc::infer::canonical::Canonical;
 use rustc::ty::subst::Substs;
-use rustc::ty::{
-    self, ClosureSubsts, GeneratorSubsts, Ty, TypeFoldable, UserTypeAnnotation,
-    UserTypeAnnotationIndex,
-};
+use rustc::ty::{self, ClosureSubsts, GeneratorSubsts, Ty, TypeFoldable};
 use rustc::mir::{Location, Mir};
 use rustc::mir::visit::{MutVisitor, TyContext};
 use rustc::infer::{InferCtxt, NLLRegionVariableOrigin};
@@ -59,18 +55,6 @@ impl<'a, 'gcx, 'tcx> MutVisitor<'tcx> for NLLVisitor<'a, 'gcx, 'tcx> {
         debug!("visit_ty: ty={:?}", ty);
     }
 
-    fn visit_user_type_annotation(
-        &mut self,
-        _index: UserTypeAnnotationIndex,
-        _ty: &mut Canonical<'tcx, UserTypeAnnotation<'tcx>>,
-    ) {
-        // User type annotations represent the types that the user
-        // wrote in the progarm. We don't want to erase the regions
-        // from these types: rather, we want to add them as
-        // constraints at type-check time.
-        debug!("visit_user_type_annotation: skipping renumber");
-    }
-
     fn visit_substs(&mut self, substs: &mut &'tcx Substs<'tcx>, location: Location) {
         debug!("visit_substs(substs={:?}, location={:?})", substs, location);