Reinstated shallow disallowing of maybe bounds in trait objects.

Author: Alexander Regueiro

Diff for: src/librustc_passes/ast_validation.rs

@@ -504,6 +504,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                         any_lifetime_bounds = true;
                     }
                 }
+                self.no_questions_in_bounds(bounds, "trait object types", false);
             }
             TyKind::ImplTrait(_, ref bounds) => {
                 if self.is_impl_trait_banned {

Diff for: src/test/ui/maybe-bounds.rs

@@ -1,6 +1,9 @@
-trait Tr: ?Sized {} //~ ERROR `?Trait` is not permitted in supertraits
+trait Tr: ?Sized {}
+//~^ ERROR `?Trait` is not permitted in supertraits
 
 type A1 = dyn Tr + (?Sized);
+//~^ ERROR `?Trait` is not permitted in trait object types
 type A2 = dyn for<'a> Tr + (?Sized);
+//~^ ERROR `?Trait` is not permitted in trait object types
 
 fn main() {}

Diff for: src/test/ui/maybe-bounds.stderr

@@ -6,5 +6,17 @@ LL | trait Tr: ?Sized {}
    |
    = note: traits are `?Sized` by default
 
-error: aborting due to previous error
+error: `?Trait` is not permitted in trait object types
+  --> $DIR/maybe-bounds.rs:4:20
+   |
+LL | type A1 = dyn Tr + (?Sized);
+   |                    ^^^^^^^^
+
+error: `?Trait` is not permitted in trait object types
+  --> $DIR/maybe-bounds.rs:6:28
+   |
+LL | type A2 = dyn for<'a> Tr + (?Sized);
+   |                            ^^^^^^^^
+
+error: aborting due to 3 previous errors
 

Diff for: src/test/ui/parser/trait-object-trait-parens.rs

@@ -4,7 +4,9 @@ fn f<T: (Copy) + (?Sized) + (for<'a> Trait<'a>)>() {}
 
 fn main() {
     let _: Box<(Copy) + (?Sized) + (for<'a> Trait<'a>)>;
+    //~^ ERROR `?Trait` is not permitted in trait object types
     let _: Box<(?Sized) + (for<'a> Trait<'a>) + (Copy)>;
     let _: Box<(for<'a> Trait<'a>) + (Copy) + (?Sized)>;
     //~^ ERROR use of undeclared lifetime name `'a`
+    //~| ERROR `?Trait` is not permitted in trait object types
 }

Diff for: src/test/ui/parser/trait-object-trait-parens.stderr

@@ -1,9 +1,21 @@
+error: `?Trait` is not permitted in trait object types
+  --> $DIR/trait-object-trait-parens.rs:6:25
+   |
+LL |     let _: Box<(Copy) + (?Sized) + (for<'a> Trait<'a>)>;
+   |                         ^^^^^^^^
+
+error: `?Trait` is not permitted in trait object types
+  --> $DIR/trait-object-trait-parens.rs:9:47
+   |
+LL |     let _: Box<(for<'a> Trait<'a>) + (Copy) + (?Sized)>;
+   |                                               ^^^^^^^^
+
 error[E0261]: use of undeclared lifetime name `'a`
-  --> $DIR/trait-object-trait-parens.rs:8:31
+  --> $DIR/trait-object-trait-parens.rs:9:31
    |
 LL |     let _: Box<(for<'a> Trait<'a>) + (Copy) + (?Sized)>;
    |                               ^^ undeclared lifetime
 
-error: aborting due to previous error
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0261`.

Diff for: src/test/ui/traits/wf-trait-object-maybe-bound.rs

@@ -1,15 +1,20 @@
-// compile-pass
+// compile-fail
 
 // Test that `dyn ... + ?Sized + ...` is okay (though `?Sized` has no effect in trait objects).
 
 trait Foo {}
 
 type _0 = dyn ?Sized + Foo;
+//~^ ERROR `?Trait` is not permitted in trait object types
 
 type _1 = dyn Foo + ?Sized;
+//~^ ERROR `?Trait` is not permitted in trait object types
 
 type _2 = dyn Foo + ?Sized + ?Sized;
+//~^ ERROR `?Trait` is not permitted in trait object types
+//~| ERROR `?Trait` is not permitted in trait object types
 
 type _3 = dyn ?Sized + Foo;
+//~^ ERROR `?Trait` is not permitted in trait object types
 
 fn main() {}

Diff for: src/test/ui/traits/wf-trait-object-maybe-bound.stderr

@@ -0,0 +1,32 @@
+error: `?Trait` is not permitted in trait object types
+  --> $DIR/wf-trait-object-maybe-bound.rs:7:15
+   |
+LL | type _0 = dyn ?Sized + Foo;
+   |               ^^^^^^
+
+error: `?Trait` is not permitted in trait object types
+  --> $DIR/wf-trait-object-maybe-bound.rs:10:21
+   |
+LL | type _1 = dyn Foo + ?Sized;
+   |                     ^^^^^^
+
+error: `?Trait` is not permitted in trait object types
+  --> $DIR/wf-trait-object-maybe-bound.rs:13:21
+   |
+LL | type _2 = dyn Foo + ?Sized + ?Sized;
+   |                     ^^^^^^
+
+error: `?Trait` is not permitted in trait object types
+  --> $DIR/wf-trait-object-maybe-bound.rs:13:30
+   |
+LL | type _2 = dyn Foo + ?Sized + ?Sized;
+   |                              ^^^^^^
+
+error: `?Trait` is not permitted in trait object types
+  --> $DIR/wf-trait-object-maybe-bound.rs:17:15
+   |
+LL | type _3 = dyn ?Sized + Foo;
+   |               ^^^^^^
+
+error: aborting due to 5 previous errors
+

Diff for: src/test/ui/traits/wf-trait-object-only-maybe-bound.rs

@@ -2,5 +2,6 @@
 
 type _0 = dyn ?Sized;
 //~^ ERROR at least one non-builtin trait is required for an object type [E0224]
+//~| ERROR ?Trait` is not permitted in trait object types
 
 fn main() {}

Diff for: src/test/ui/traits/wf-trait-object-only-maybe-bound.stderr

@@ -1,8 +1,14 @@
+error: `?Trait` is not permitted in trait object types
+  --> $DIR/wf-trait-object-only-maybe-bound.rs:3:15
+   |
+LL | type _0 = dyn ?Sized;
+   |               ^^^^^^
+
 error[E0224]: at least one non-builtin trait is required for an object type
   --> $DIR/wf-trait-object-only-maybe-bound.rs:3:11
    |
 LL | type _0 = dyn ?Sized;
    |           ^^^^^^^^^^
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors