Auto merge of rust-lang#55152 - nikomatsakis:nll-issue-54571-type-annot-in-constants, r=pnkfelix

support type annot in constants, casts

Fixes rust-lang#54571
Fixes rust-lang#54332
Fixes rust-lang#55183

r? @pnkfelix

Author: bors

src/librustc/ich/impls_mir.rs

@@ -597,11 +597,7 @@ impl<'a, 'gcx> HashStable<StableHashingContext<'a>> for mir::UserTypeAnnotation<
             mir::UserTypeAnnotation::Ty(ref ty) => {
                 ty.hash_stable(hcx, hasher);
             }
-            mir::UserTypeAnnotation::FnDef(ref def_id, ref substs) => {
-                def_id.hash_stable(hcx, hasher);
-                substs.hash_stable(hcx, hasher);
-            }
-            mir::UserTypeAnnotation::AdtDef(ref def_id, ref substs) => {
+            mir::UserTypeAnnotation::TypeOf(ref def_id, ref substs) => {
                 def_id.hash_stable(hcx, hasher);
                 substs.hash_stable(hcx, hasher);
             }

src/librustc/infer/canonical/query_response.rs

@@ -19,7 +19,7 @@
 
 use infer::canonical::substitute::substitute_value;
 use infer::canonical::{
-    Canonical, CanonicalVarKind, CanonicalVarValues, CanonicalizedQueryResponse, Certainty,
+    Canonical, CanonicalVarValues, CanonicalizedQueryResponse, Certainty,
     OriginalQueryValues, QueryRegionConstraint, QueryResponse,
 };
 use infer::region_constraints::{Constraint, RegionConstraintData};
@@ -262,13 +262,6 @@ impl<'cx, 'gcx, 'tcx> InferCtxt<'cx, 'gcx, 'tcx> {
     where
         R: Debug + TypeFoldable<'tcx>,
     {
-        // In an NLL query, there should be no type variables in the
-        // query, only region variables.
-        debug_assert!(query_response.variables.iter().all(|v| match v.kind {
-            CanonicalVarKind::Ty(_) => false,
-            CanonicalVarKind::Region => true,
-        }));
-
         let result_subst =
             self.query_response_substitution_guess(cause, original_values, query_response);
 

src/librustc/infer/region_constraints/mod.rs

@@ -149,7 +149,7 @@ pub struct Verify<'tcx> {
     pub bound: VerifyBound<'tcx>,
 }
 
-#[derive(Copy, Clone, PartialEq, Eq)]
+#[derive(Copy, Clone, PartialEq, Eq, Hash)]
 pub enum GenericKind<'tcx> {
     Param(ty::ParamTy),
     Projection(ty::ProjectionTy<'tcx>),

src/librustc/mir/mod.rs

@@ -2425,15 +2425,16 @@ pub struct Constant<'tcx> {
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
 pub enum UserTypeAnnotation<'tcx> {
     Ty(CanonicalTy<'tcx>),
-    FnDef(DefId, CanonicalUserSubsts<'tcx>),
-    AdtDef(&'tcx AdtDef, CanonicalUserSubsts<'tcx>),
+
+    /// The canonical type is the result of `type_of(def_id)` with the
+    /// given substitutions applied.
+    TypeOf(DefId, CanonicalUserSubsts<'tcx>),
 }
 
 EnumTypeFoldableImpl! {
     impl<'tcx> TypeFoldable<'tcx> for UserTypeAnnotation<'tcx> {
         (UserTypeAnnotation::Ty)(ty),
-        (UserTypeAnnotation::FnDef)(def, substs),
-        (UserTypeAnnotation::AdtDef)(def, substs),
+        (UserTypeAnnotation::TypeOf)(def, substs),
     }
 }
 

src/librustc_mir/borrow_check/nll/region_infer/mod.rs

@@ -25,7 +25,7 @@ use rustc::mir::{
 use rustc::ty::{self, RegionVid, Ty, TyCtxt, TypeFoldable};
 use rustc::util::common;
 use rustc_data_structures::bit_set::BitSet;
-use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::graph::scc::Sccs;
 use rustc_data_structures::indexed_vec::IndexVec;
 use rustc_errors::{Diagnostic, DiagnosticBuilder};
@@ -67,10 +67,8 @@ pub struct RegionInferenceContext<'tcx> {
     constraint_sccs: Rc<Sccs<RegionVid, ConstraintSccIndex>>,
 
     /// Map closure bounds to a `Span` that should be used for error reporting.
-    closure_bounds_mapping: FxHashMap<
-        Location,
-        FxHashMap<(RegionVid, RegionVid), (ConstraintCategory, Span)>,
-    >,
+    closure_bounds_mapping:
+        FxHashMap<Location, FxHashMap<(RegionVid, RegionVid), (ConstraintCategory, Span)>>,
 
     /// Contains the minimum universe of any variable within the same
     /// SCC. We will ensure that no SCC contains values that are not
@@ -580,6 +578,11 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     ) {
         let tcx = infcx.tcx;
 
+        // Sometimes we register equivalent type-tests that would
+        // result in basically the exact same error being reported to
+        // the user. Avoid that.
+        let mut deduplicate_errors = FxHashSet::default();
+
         for type_test in &self.type_tests {
             debug!("check_type_test: {:?}", type_test);
 
@@ -605,11 +608,31 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                 }
             }
 
-            // Oh the humanity. Obviously we will do better than this error eventually.
+            // Type-test failed. Report the error.
+
+            // Try to convert the lower-bound region into something named we can print for the user.
             let lower_bound_region = self.to_error_region(type_test.lower_bound);
+
+            // Skip duplicate-ish errors.
+            let type_test_span = type_test.locations.span(mir);
+            let erased_generic_kind = tcx.erase_regions(&type_test.generic_kind);
+            if !deduplicate_errors.insert((
+                erased_generic_kind,
+                lower_bound_region,
+                type_test.locations,
+            )) {
+                continue;
+            } else {
+                debug!(
+                    "check_type_test: reporting error for erased_generic_kind={:?}, \
+                     lower_bound_region={:?}, \
+                     type_test.locations={:?}",
+                    erased_generic_kind, lower_bound_region, type_test.locations,
+                );
+            }
+
             if let Some(lower_bound_region) = lower_bound_region {
                 let region_scope_tree = &tcx.region_scope_tree(mir_def_id);
-                let type_test_span = type_test.locations.span(mir);
                 infcx
                     .construct_generic_bound_failure(
                         region_scope_tree,
@@ -629,7 +652,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                 // to report it; we could probably handle it by
                 // iterating over the universal regions and reporting
                 // an error that multiple bounds are required.
-                let type_test_span = type_test.locations.span(mir);
                 tcx.sess
                     .struct_span_err(
                         type_test_span,

src/librustc_mir/borrow_check/nll/type_check/constraint_conversion.rs

@@ -142,6 +142,7 @@ impl<'a, 'gcx, 'tcx> ConstraintConversion<'a, 'gcx, 'tcx> {
     }
 
     fn add_type_test(&mut self, type_test: TypeTest<'tcx>) {
+        debug!("add_type_test(type_test={:?})", type_test);
         self.type_tests.push(type_test);
     }
 }