skip user-type annotations if they don't have regions

src/librustc_mir/build/expr/as_place.rs

@@ -139,17 +139,19 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
 
             ExprKind::PlaceTypeAscription { source, user_ty } => {
                 let place = unpack!(block = this.as_place(block, source));
-                this.cfg.push(
-                    block,
-                    Statement {
-                        source_info,
-                        kind: StatementKind::AscribeUserType(
-                            place.clone(),
-                            Variance::Invariant,
-                            user_ty,
-                        ),
-                    },
-                );
+                if let Some(user_ty) = user_ty {
+                    this.cfg.push(
+                        block,
+                        Statement {
+                            source_info,
+                            kind: StatementKind::AscribeUserType(
+                                place.clone(),
+                                Variance::Invariant,
+                                user_ty,
+                            ),
+                        },
+                    );
+                }
                 block.and(place)
             }
             ExprKind::ValueTypeAscription { source, user_ty } => {
@@ -157,17 +159,19 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                 let temp = unpack!(
                     block = this.as_temp(block, source.temp_lifetime, source, mutability)
                 );
-                this.cfg.push(
-                    block,
-                    Statement {
-                        source_info,
-                        kind: StatementKind::AscribeUserType(
-                            Place::Local(temp.clone()),
-                            Variance::Invariant,
-                            user_ty,
-                        ),
-                    },
-                );
+                if let Some(user_ty) = user_ty {
+                    this.cfg.push(
+                        block,
+                        Statement {
+                            source_info,
+                            kind: StatementKind::AscribeUserType(
+                                Place::Local(temp.clone()),
+                                Variance::Invariant,
+                                user_ty,
+                            ),
+                        },
+                    );
+                }
                 block.and(Place::Local(temp))
             }
 

src/librustc_mir/hair/cx/expr.rs

@@ -749,7 +749,7 @@ fn make_mirror_unadjusted<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
 
                 ExprKind::ValueTypeAscription {
                     source: cast_expr.to_ref(),
-                    user_ty: user_ty,
+                    user_ty: Some(user_ty),
                 }
             } else {
                 cast
@@ -757,15 +757,7 @@ fn make_mirror_unadjusted<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
         }
         hir::ExprKind::Type(ref source, ref ty) => {
             let user_provided_tys = cx.tables.user_provided_tys();
-            let user_ty = UserTypeAnnotation::Ty(
-                *user_provided_tys
-                    .get(ty.hir_id)
-                    .expect(&format!(
-                        "{:?} not found in user_provided_tys, source: {:?}",
-                        ty,
-                        source,
-                    ))
-            );
+            let user_ty = user_provided_tys.get(ty.hir_id).map(|&c_ty| UserTypeAnnotation::Ty(c_ty));
             if source.is_place_expr() {
                 ExprKind::PlaceTypeAscription {
                     source: source.to_ref(),

src/librustc_mir/hair/mod.rs

@@ -276,12 +276,12 @@ pub enum ExprKind<'tcx> {
     PlaceTypeAscription {
         source: ExprRef<'tcx>,
         /// Type that the user gave to this expression
-        user_ty: UserTypeAnnotation<'tcx>,
+        user_ty: Option<UserTypeAnnotation<'tcx>>,
     },
     ValueTypeAscription {
         source: ExprRef<'tcx>,
         /// Type that the user gave to this expression
-        user_ty: UserTypeAnnotation<'tcx>,
+        user_ty: Option<UserTypeAnnotation<'tcx>>,
     },
     Closure {
         closure_id: DefId,

src/librustc_typeck/check/mod.rs

@@ -2359,8 +2359,15 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
 
     pub fn to_ty_saving_user_provided_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
         let ty = self.to_ty(ast_ty);
-        let c_ty = self.infcx.canonicalize_response(&ty);
-        self.tables.borrow_mut().user_provided_tys_mut().insert(ast_ty.hir_id, c_ty);
+
+        // If the type given by the user has free regions, save it for
+        // later, since NLL would like to enforce those. Other sorts
+        // of things are already sufficiently enforced. =)
+        if ty.has_free_regions() {
+            let c_ty = self.infcx.canonicalize_response(&ty);
+            self.tables.borrow_mut().user_provided_tys_mut().insert(ast_ty.hir_id, c_ty);
+        }
+
         ty
     }
 

src/test/ui/consts/const-eval/conditional_array_execution.rs

@@ -14,7 +14,6 @@ const X: u32 = 5;
 const Y: u32 = 6;
 const FOO: u32 = [X - Y, Y - X][(X < Y) as usize];
 //~^ WARN this constant cannot be used
-//~| ERROR
 
 fn main() {
     println!("{}", FOO);

src/test/ui/consts/const-eval/conditional_array_execution.stderr

@@ -13,7 +13,7 @@ LL | #![warn(const_err)]
    |         ^^^^^^^^^
 
 error[E0080]: referenced constant has errors
-  --> $DIR/conditional_array_execution.rs:20:20
+  --> $DIR/conditional_array_execution.rs:19:20
    |
 LL | const FOO: u32 = [X - Y, Y - X][(X < Y) as usize];
    |                   ----- attempt to subtract with overflow
@@ -21,20 +21,12 @@ LL | const FOO: u32 = [X - Y, Y - X][(X < Y) as usize];
 LL |     println!("{}", FOO);
    |                    ^^^
 
-error[E0080]: could not evaluate constant
-  --> $DIR/conditional_array_execution.rs:20:20
+error[E0080]: erroneous constant used
+  --> $DIR/conditional_array_execution.rs:19:20
    |
 LL |     println!("{}", FOO);
    |                    ^^^ referenced constant has errors
 
-error[E0080]: constant evaluation error
-  --> $DIR/conditional_array_execution.rs:15:1
-   |
-LL | const FOO: u32 = [X - Y, Y - X][(X < Y) as usize];
-   | ^^^^^^^^^^^^^^^^^^-----^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |                   |
-   |                   attempt to subtract with overflow
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0080`.

src/test/ui/consts/const-eval/promoted_errors.stderr

@@ -34,12 +34,6 @@ warning: attempt to divide by zero
 LL |     println!("{}", 1/(false as u32));
    |                    ^^^^^^^^^^^^^^^^
 
-warning: this expression will panic at runtime
-  --> $DIR/promoted_errors.rs:24:20
-   |
-LL |     println!("{}", 1/(false as u32));
-   |                    ^^^^^^^^^^^^^^^^ attempt to divide by zero
-
 warning: attempt to divide by zero
   --> $DIR/promoted_errors.rs:26:14
    |