rustc_typeck: make "global" WF requirements hard errors, in type aliases.

Author: eddyb

src/librustc_typeck/check/wfcheck.rs

@@ -136,9 +136,25 @@ pub fn check_item_well_formed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: Def
 
                 let def_id = fcx.tcx.hir.local_def_id(item.id);
                 let ty = fcx.tcx.type_of(def_id);
-                let item_ty = fcx.inh.normalize_associated_types_in(cause, fcx.param_env, &ty);
+                let item_ty = fcx.inh.normalize_associated_types_in(
+                    cause.clone(),
+                    fcx.param_env,
+                    &ty,
+                );
+
+                let wf_obligations = ty::wf::obligations(fcx,
+                                                         fcx.param_env,
+                                                         &cause,
+                                                         item_ty)
+                    .unwrap_or(vec![]);
 
-                fcx.register_wf_obligation(item_ty, hir_ty.span, code.clone());
+                for mut obligation in wf_obligations {
+                    // Produce hard errors for monomorphic/"global" obligations.
+                    if obligation.predicate.is_global() {
+                        obligation.cause.code = ObligationCauseCode::MiscObligation;
+                    }
+                    fcx.register_predicate(obligation);
+                }
 
                 check_where_clauses(tcx, fcx, item.span, def_id, None, code);
 

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

@@ -6,17 +6,14 @@ LL | pub type Foo = [i32; 0 - 1];
    |
    = note: #[deny(const_err)] on by default
 
-error: could not evaluate constant expression
+error[E0080]: could not evaluate constant expression
   --> $DIR/pub_const_err.rs:13:16
    |
 LL | pub type Foo = [i32; 0 - 1];
    |                ^^^^^^-----^
    |                      |
    |                      attempt to subtract with overflow
-   |
-   = note: #[deny(type_alias_missing_bounds)] on by default
-   = help: missing bounds in type aliases were previously allowed
-   = help: this is a hard error in Rust 2018
 
 error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0080`.

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

@@ -6,17 +6,14 @@ LL | pub type Foo = [i32; 0 - 1];
    |
    = note: #[deny(const_err)] on by default
 
-error: could not evaluate constant expression
+error[E0080]: could not evaluate constant expression
   --> $DIR/pub_const_err_bin.rs:11:16
    |
 LL | pub type Foo = [i32; 0 - 1];
    |                ^^^^^^-----^
    |                      |
    |                      attempt to subtract with overflow
-   |
-   = note: #[deny(type_alias_missing_bounds)] on by default
-   = help: missing bounds in type aliases were previously allowed
-   = help: this is a hard error in Rust 2018
 
 error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0080`.

src/test/ui/resolve/issue-3907-2.stderr

@@ -5,8 +5,6 @@ LL | type Foo = issue_3907::Foo+'static;
    |            ^^^^^^^^^^^^^^^^^^^^^^^ the trait `issue_3907::Foo` cannot be made into an object
    |
    = note: method `bar` has no receiver
-   = help: missing bounds in type aliases were previously allowed
-   = help: this is a hard error in Rust 2018
 
 error[E0038]: the trait `issue_3907::Foo` cannot be made into an object
   --> $DIR/issue-3907-2.rs:21:1

src/test/ui/structs/struct-path-alias-bounds.stderr

@@ -1,12 +1,9 @@
-error: the trait bound `NoClone: std::clone::Clone` is not satisfied
+error[E0277]: the trait bound `NoClone: std::clone::Clone` is not satisfied
   --> $DIR/struct-path-alias-bounds.rs:16:10
    |
 LL | type A = S<NoClone>;
    |          ^^^^^^^^^^ the trait `std::clone::Clone` is not implemented for `NoClone`
-   |
-   = note: #[deny(type_alias_missing_bounds)] on by default
-   = help: missing bounds in type aliases were previously allowed
-   = help: this is a hard error in Rust 2018
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0277`.