user annotations in patterns

src/librustc/mir/visit.rs

@@ -214,7 +214,7 @@ macro_rules! make_mir_visitor {
                 self.super_ty(ty);
             }
 
-            fn visit_canonical_ty(&mut self, ty: & $($mutability)* CanonicalTy<'tcx>) {
+            fn visit_user_ty(&mut self, ty: & $($mutability)* CanonicalTy<'tcx>) {
                 self.super_canonical_ty(ty);
             }
 
@@ -640,7 +640,7 @@ macro_rules! make_mir_visitor {
                                      c_ty: & $($mutability)* CanonicalTy<'tcx>,
                                      location: Location) {
                 self.visit_place(place, PlaceContext::Validate, location);
-                self.visit_canonical_ty(c_ty);
+                self.visit_user_ty(c_ty);
             }
 
             fn super_place(&mut self,
@@ -736,7 +736,7 @@ macro_rules! make_mir_visitor {
                     source_info: *source_info,
                 });
                 if let Some(user_ty) = user_ty {
-                    self.visit_canonical_ty(user_ty);
+                    self.visit_user_ty(user_ty);
                 }
                 self.visit_source_info(source_info);
                 self.visit_source_scope(visibility_scope);

src/librustc_mir/borrow_check/nll/renumber.rs

@@ -10,7 +10,7 @@
 
 use rustc::ty::subst::Substs;
 use rustc::ty::{self, CanonicalTy, ClosureSubsts, GeneratorSubsts, Ty, TypeFoldable};
-use rustc::mir::{BasicBlock, Location, Mir, Place, Statement, StatementKind};
+use rustc::mir::{BasicBlock, Location, Mir, Statement, StatementKind};
 use rustc::mir::visit::{MutVisitor, TyContext};
 use rustc::infer::{InferCtxt, NLLRegionVariableOrigin};
 
@@ -65,6 +65,14 @@ impl<'a, 'gcx, 'tcx> MutVisitor<'tcx> for NLLVisitor<'a, 'gcx, 'tcx> {
         debug!("visit_ty: ty={:?}", ty);
     }
 
+    fn visit_user_ty(&mut self, _ty: &mut CanonicalTy<'tcx>) {
+        // `user_ty` 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_ty: skipping renumber");
+    }
+
     fn visit_substs(&mut self, substs: &mut &'tcx Substs<'tcx>, location: Location) {
         debug!("visit_substs(substs={:?}, location={:?})", substs, location);
 
@@ -112,19 +120,6 @@ impl<'a, 'gcx, 'tcx> MutVisitor<'tcx> for NLLVisitor<'a, 'gcx, 'tcx> {
         debug!("visit_closure_substs: substs={:?}", substs);
     }
 
-    fn visit_ascribe_user_ty(
-        &mut self,
-        _place: &mut Place<'tcx>,
-        _variance: &mut ty::Variance,
-        _c_ty: &mut CanonicalTy<'tcx>,
-        _location: Location,
-    ) {
-        // User-assert-ty statements represent types that the user added explicitly.
-        // 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_assert_ty: skipping renumber");
-    }
-
     fn visit_statement(
         &mut self,
         block: BasicBlock,

src/librustc_mir/build/matches/mod.rs

@@ -1307,6 +1307,14 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
     ) {
         for ascription in ascriptions {
             let source_info = self.source_info(ascription.span);
+
+            debug!(
+                "adding user ascription at span {:?} of place {:?} and {:?}",
+                source_info.span,
+                ascription.source,
+                ascription.user_ty,
+            );
+
             self.cfg.push(
                 block,
                 Statement {

src/librustc_mir/hair/cx/expr.rs

@@ -13,6 +13,7 @@ use rustc_data_structures::indexed_vec::Idx;
 use hair::cx::Cx;
 use hair::cx::block;
 use hair::cx::to_ref::ToRef;
+use hair::util::UserAnnotatedTyHelpers;
 use rustc::hir::def::{Def, CtorKind};
 use rustc::mir::interpret::GlobalId;
 use rustc::ty::{self, AdtKind, Ty};
@@ -475,7 +476,7 @@ fn make_mirror_unadjusted<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
                                 adt_def: adt,
                                 variant_index: 0,
                                 substs,
-                                user_ty: user_annotated_ty_for_adt(cx, expr.hir_id, adt),
+                                user_ty: cx.user_substs_applied_to_adt(expr.hir_id, adt),
                                 fields: field_refs(cx, fields),
                                 base: base.as_ref().map(|base| {
                                     FruInfo {
@@ -501,7 +502,7 @@ fn make_mirror_unadjusted<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
                                         adt_def: adt,
                                         variant_index: index,
                                         substs,
-                                        user_ty: user_annotated_ty_for_adt(cx, expr.hir_id, adt),
+                                        user_ty: cx.user_substs_applied_to_adt(expr.hir_id, adt),
                                         fields: field_refs(cx, fields),
                                         base: None,
                                     }
@@ -787,48 +788,17 @@ fn user_annotated_ty_for_def(
         // user.
         Def::StructCtor(_def_id, CtorKind::Const) |
         Def::VariantCtor(_def_id, CtorKind::Const) =>
-            match &cx.tables().node_id_to_type(hir_id).sty {
-                ty::Adt(adt_def, _) => user_annotated_ty_for_adt(cx, hir_id, adt_def),
-                sty => bug!("unexpected sty: {:?}", sty),
-            },
+            cx.user_substs_applied_to_ty_of_hir_id(hir_id),
 
         // `Self` is used in expression as a tuple struct constructor or an unit struct constructor
-        Def::SelfCtor(_) => {
-            let sty = &cx.tables().node_id_to_type(hir_id).sty;
-            match sty {
-                ty::FnDef(ref def_id, _) => {
-                    Some(cx.tables().user_substs(hir_id)?.unchecked_map(|user_substs| {
-                        // Here, we just pair a `DefId` with the
-                        // `user_substs`, so no new types etc are introduced.
-                        cx.tcx().mk_fn_def(*def_id, user_substs)
-                    }))
-                }
-                ty::Adt(ref adt_def, _) => {
-                    user_annotated_ty_for_adt(cx, hir_id, adt_def)
-                }
-                _ => {
-                    bug!("unexpected sty: {:?}", sty)
-                }
-            }
-        }
+        Def::SelfCtor(_) =>
+            cx.user_substs_applied_to_ty_of_hir_id(hir_id),
+
         _ =>
             bug!("user_annotated_ty_for_def: unexpected def {:?} at {:?}", def, hir_id)
     }
 }
 
-fn user_annotated_ty_for_adt(
-    cx: &mut Cx<'a, 'gcx, 'tcx>,
-    hir_id: hir::HirId,
-    adt_def: &'tcx AdtDef,
-) -> Option<CanonicalTy<'tcx>> {
-    let user_substs = cx.tables().user_substs(hir_id)?;
-    Some(user_substs.unchecked_map(|user_substs| {
-        // Here, we just pair an `AdtDef` with the
-        // `user_substs`, so no new types etc are introduced.
-        cx.tcx().mk_adt(adt_def, user_substs)
-    }))
-}
-
 fn method_callee<'a, 'gcx, 'tcx>(
     cx: &mut Cx<'a, 'gcx, 'tcx>,
     expr: &hir::Expr,
@@ -943,7 +913,7 @@ fn convert_path_expr<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
                         adt_def,
                         variant_index: adt_def.variant_index_with_id(def_id),
                         substs,
-                        user_ty: user_annotated_ty_for_adt(cx, expr.hir_id, adt_def),
+                        user_ty: cx.user_substs_applied_to_adt(expr.hir_id, adt_def),
                         fields: vec![],
                         base: None,
                     }

src/librustc_mir/hair/cx/mod.rs

@@ -15,6 +15,7 @@
 //!
 
 use hair::*;
+use hair::util::UserAnnotatedTyHelpers;
 
 use rustc_data_structures::indexed_vec::Idx;
 use rustc::hir::def_id::{DefId, LOCAL_CRATE};
@@ -272,6 +273,16 @@ impl<'a, 'gcx, 'tcx> Cx<'a, 'gcx, 'tcx> {
     }
 }
 
+impl UserAnnotatedTyHelpers<'gcx, 'tcx> for Cx<'_, 'gcx, 'tcx> {
+    fn tcx(&self) -> TyCtxt<'_, 'gcx, 'tcx> {
+        self.tcx()
+    }
+
+    fn tables(&self) -> &ty::TypeckTables<'tcx> {
+        self.tables()
+    }
+}
+
 fn lint_level_for_hir_id(tcx: TyCtxt, mut id: ast::NodeId) -> ast::NodeId {
     // Right now we insert a `with_ignore` node in the dep graph here to
     // ignore the fact that `lint_levels` below depends on the entire crate.

src/librustc_mir/hair/mod.rs

@@ -29,6 +29,8 @@ pub mod cx;
 pub mod pattern;
 pub use self::pattern::{BindingMode, Pattern, PatternKind, FieldPattern};
 
+mod util;
+
 #[derive(Copy, Clone, Debug)]
 pub enum LintLevel {
     Inherited,

src/librustc_mir/hair/pattern/mod.rs

@@ -18,6 +18,8 @@ pub(crate) use self::check_match::check_match;
 
 use const_eval::{const_field, const_variant_index};
 
+use hair::util::UserAnnotatedTyHelpers;
+
 use rustc::mir::{fmt_const_val, Field, BorrowKind, Mutability};
 use rustc::mir::interpret::{Scalar, GlobalId, ConstValue, sign_extend};
 use rustc::ty::{self, CanonicalTy, TyCtxt, AdtDef, Ty, Region};
@@ -529,8 +531,9 @@ impl<'a, 'tcx> PatternContext<'a, 'tcx> {
                                        field: Field::new(i),
                                        pattern: self.lower_pattern(field),
                                    })
-                                   .collect();
-                self.lower_variant_or_leaf(def, pat.span, ty, subpatterns)
+                    .collect();
+
+                self.lower_variant_or_leaf(def, pat.hir_id, pat.span, ty, subpatterns)
             }
 
             PatKind::Struct(ref qpath, ref fields, _) => {
@@ -546,7 +549,7 @@ impl<'a, 'tcx> PatternContext<'a, 'tcx> {
                           })
                           .collect();
 
-                self.lower_variant_or_leaf(def, pat.span, ty, subpatterns)
+                self.lower_variant_or_leaf(def, pat.hir_id, pat.span, ty, subpatterns)
             }
         };
 
@@ -637,12 +640,12 @@ impl<'a, 'tcx> PatternContext<'a, 'tcx> {
     fn lower_variant_or_leaf(
         &mut self,
         def: Def,
+        hir_id: hir::HirId,
         span: Span,
         ty: Ty<'tcx>,
-        subpatterns: Vec<FieldPattern<'tcx>>)
-        -> PatternKind<'tcx>
-    {
-        match def {
+        subpatterns: Vec<FieldPattern<'tcx>>,
+    ) -> PatternKind<'tcx> {
+        let mut kind = match def {
             Def::Variant(variant_id) | Def::VariantCtor(variant_id, ..) => {
                 let enum_id = self.tcx.parent_def_id(variant_id).unwrap();
                 let adt_def = self.tcx.adt_def(enum_id);
@@ -675,7 +678,24 @@ impl<'a, 'tcx> PatternContext<'a, 'tcx> {
                 self.errors.push(PatternError::NonConstPath(span));
                 PatternKind::Wild
             }
+        };
+
+        if let Some(user_ty) = self.user_substs_applied_to_ty_of_hir_id(hir_id) {
+            let subpattern = Pattern {
+                span,
+                ty,
+                kind: Box::new(kind),
+            };
+
+            debug!("pattern user_ty = {:?} for pattern at {:?}", user_ty, span);
+
+            kind = PatternKind::AscribeUserType {
+                subpattern,
+                user_ty,
+            };
         }
+
+        kind
     }
 
     /// Takes a HIR Path. If the path is a constant, evaluates it and feeds
@@ -729,7 +749,7 @@ impl<'a, 'tcx> PatternContext<'a, 'tcx> {
                     },
                 }
             }
-            _ => self.lower_variant_or_leaf(def, span, ty, vec![]),
+            _ => self.lower_variant_or_leaf(def, id, span, ty, vec![]),
         };
 
         Pattern {
@@ -894,6 +914,17 @@ impl<'a, 'tcx> PatternContext<'a, 'tcx> {
     }
 }
 
+impl UserAnnotatedTyHelpers<'tcx, 'tcx> for PatternContext<'_, 'tcx> {
+    fn tcx(&self) -> TyCtxt<'_, 'tcx, 'tcx> {
+        self.tcx
+    }
+
+    fn tables(&self) -> &ty::TypeckTables<'tcx> {
+        self.tables
+    }
+}
+
+
 pub trait PatternFoldable<'tcx> : Sized {
     fn fold_with<F: PatternFolder<'tcx>>(&self, folder: &mut F) -> Self {
         self.super_fold_with(folder)

src/librustc_mir/hair/util.rs

@@ -0,0 +1,56 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use rustc::hir;
+use rustc::ty::{self, AdtDef, CanonicalTy, TyCtxt};
+
+crate trait UserAnnotatedTyHelpers<'gcx: 'tcx, 'tcx> {
+    fn tcx(&self) -> TyCtxt<'_, 'gcx, 'tcx>;
+
+    fn tables(&self) -> &ty::TypeckTables<'tcx>;
+
+    fn user_substs_applied_to_adt(
+        &self,
+        hir_id: hir::HirId,
+        adt_def: &'tcx AdtDef,
+    ) -> Option<CanonicalTy<'tcx>> {
+        let user_substs = self.tables().user_substs(hir_id)?;
+        Some(user_substs.unchecked_map(|user_substs| {
+            // Here, we just pair an `AdtDef` with the
+            // `user_substs`, so no new types etc are introduced.
+            self.tcx().mk_adt(adt_def, user_substs)
+        }))
+    }
+
+    /// Looks up the type associated with this hir-id and applies the
+    /// user-given substitutions; the hir-id must map to a suitable
+    /// type.
+    fn user_substs_applied_to_ty_of_hir_id(&self, hir_id: hir::HirId) -> Option<CanonicalTy<'tcx>> {
+        let user_substs = self.tables().user_substs(hir_id)?;
+        match &self.tables().node_id_to_type(hir_id).sty {
+            ty::Adt(adt_def, _) => Some(user_substs.unchecked_map(|user_substs| {
+                // Ok to call `unchecked_map` because we just pair an
+                // `AdtDef` with the `user_substs`, so no new types
+                // etc are introduced.
+                self.tcx().mk_adt(adt_def, user_substs)
+            })),
+            ty::FnDef(def_id, _) => Some(user_substs.unchecked_map(|user_substs| {
+                // Here, we just pair a `DefId` with the
+                // `user_substs`, so no new types etc are introduced.
+                self.tcx().mk_fn_def(*def_id, user_substs)
+            })),
+            sty => bug!(
+                "sty: {:?} should not have user-substs {:?} recorded ",
+                sty,
+                user_substs
+            ),
+        }
+    }
+}