[HACK] don't require T: Trait for type Foo<T> = <T as Trait>::Assoc;

Author: eddyb

src/librustc_typeck/check/wfcheck.rs

@@ -135,7 +135,8 @@ pub fn check_item_well_formed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: Def
             let generics = tcx.generics_of(def_id);
             let used_params = super::check_params_are_used(tcx, &generics, item_ty);
             for_item(tcx, item).with_fcx(|fcx, _this| {
-                let item_ty = fcx.normalize_associated_types_in(item.span, &item_ty);
+                // HACK(eddyb) Commented out to not require trait bounds for projections.
+                // let item_ty = fcx.normalize_associated_types_in(item.span, &item_ty);
 
                 // Check the user-declared bounds, assuming the type is WF.
                 // This ensures that by checking the WF of the aliased type, where
@@ -172,7 +173,8 @@ pub fn check_item_well_formed<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: Def
                     }));
                 }
 
-                vec![item_ty]
+                // HACK(eddyb) Commented out to not require trait bounds for projections.
+                vec![/*item_ty*/]
             });
         }
         hir::ItemKind::Struct(ref struct_def, ref ast_generics) => {

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

@@ -1,22 +1,22 @@
-warning: attempt to subtract with overflow
-  --> $DIR/pub_const_err.rs:19:22
+warning: this constant cannot be used
+  --> $DIR/pub_const_err.rs:16:1
    |
-LL | pub type Foo = [i32; 0 - 1];
-   |                      ^^^^^
+LL | pub const Z: u32 = 0 - 1;
+   | ^^^^^^^^^^^^^^^^^^^-----^
+   |                    |
+   |                    attempt to subtract with overflow
    |
 note: lint level defined here
   --> $DIR/pub_const_err.rs:12:9
    |
 LL | #![warn(const_err)]
    |         ^^^^^^^^^
 
-warning: this constant cannot be used
-  --> $DIR/pub_const_err.rs:16:1
+warning: attempt to subtract with overflow
+  --> $DIR/pub_const_err.rs:19:22
    |
-LL | pub const Z: u32 = 0 - 1;
-   | ^^^^^^^^^^^^^^^^^^^-----^
-   |                    |
-   |                    attempt to subtract with overflow
+LL | pub type Foo = [i32; 0 - 1];
+   |                      ^^^^^
 
 warning: this array length cannot be used
   --> $DIR/pub_const_err.rs:19:22

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

@@ -1,22 +1,22 @@
-warning: attempt to subtract with overflow
-  --> $DIR/pub_const_err_bin.rs:17:22
+warning: this constant cannot be used
+  --> $DIR/pub_const_err_bin.rs:14:1
    |
-LL | pub type Foo = [i32; 0 - 1];
-   |                      ^^^^^
+LL | pub const Z: u32 = 0 - 1;
+   | ^^^^^^^^^^^^^^^^^^^-----^
+   |                    |
+   |                    attempt to subtract with overflow
    |
 note: lint level defined here
   --> $DIR/pub_const_err_bin.rs:12:9
    |
 LL | #![warn(const_err)]
    |         ^^^^^^^^^
 
-warning: this constant cannot be used
-  --> $DIR/pub_const_err_bin.rs:14:1
+warning: attempt to subtract with overflow
+  --> $DIR/pub_const_err_bin.rs:17:22
    |
-LL | pub const Z: u32 = 0 - 1;
-   | ^^^^^^^^^^^^^^^^^^^-----^
-   |                    |
-   |                    attempt to subtract with overflow
+LL | pub type Foo = [i32; 0 - 1];
+   |                      ^^^^^
 
 warning: this array length cannot be used
   --> $DIR/pub_const_err_bin.rs:17:22

src/test/ui/type/type-alias-bounds-err.rs

@@ -19,9 +19,6 @@ type S2Vec<T> where T: Send = Vec<T>;
 //~^ ERROR `T` cannot be sent between threads safely
 
 trait Bound { type Assoc; }
-type T4<U> = <U as Bound>::Assoc;
-//~^ ERROR the trait bound `U: Bound` is not satisfied
-//~| ERROR the size for values of type `U` cannot be known at compilation time
 
 type T6<U: Bound> = ::std::vec::Vec<U>;
 //~^ ERROR the trait bound `U: Bound` is not satisfied

src/test/ui/type/type-alias-bounds-err.stderr

@@ -17,31 +17,13 @@ LL | type S2Vec<T> where T: Send = Vec<T>;
    = help: consider adding a `where T: std::marker::Send` bound
 
 error[E0277]: the trait bound `U: Bound` is not satisfied
-  --> $DIR/type-alias-bounds-err.rs:22:1
-   |
-LL | type T4<U> = <U as Bound>::Assoc;
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Bound` is not implemented for `U`
-   |
-   = help: consider adding a `where U: Bound` bound
-
-error[E0277]: the size for values of type `U` cannot be known at compilation time
-  --> $DIR/type-alias-bounds-err.rs:22:1
-   |
-LL | type T4<U> = <U as Bound>::Assoc;
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
-   |
-   = help: the trait `std::marker::Sized` is not implemented for `U`
-   = note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
-   = help: consider adding a `where U: std::marker::Sized` bound
-
-error[E0277]: the trait bound `U: Bound` is not satisfied
-  --> $DIR/type-alias-bounds-err.rs:26:1
+  --> $DIR/type-alias-bounds-err.rs:23:1
    |
 LL | type T6<U: Bound> = ::std::vec::Vec<U>;
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Bound` is not implemented for `U`
    |
    = help: consider adding a `where U: Bound` bound
 
-error: aborting due to 5 previous errors
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0277`.

src/test/ui/type/type-alias-bounds.rs

@@ -59,7 +59,7 @@ type T2<U> where U: Bound + ?Sized = U::Assoc;  //~ WARN not enforced in type al
 // This errors
 // type T3<U> = U::Assoc;
 // Do this instead
-// type T4<U: ?Sized> = <U as Bound>::Assoc; // NOTE(eddyb) moved to `type-alias-bounds-err.rs`
+type T4<U> = <U as Bound>::Assoc;
 
 // Make sure the help about associatd types is not shown incorrectly
 type T5<U: Bound + ?Sized> = <U as Bound>::Assoc;  //~ WARN not enforced in type aliases