Don't ICE when encountering bound var in builtin copy/clone bounds

Author: compiler-errors

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -2149,7 +2149,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             ty::Alias(..) | ty::Param(_) | ty::Placeholder(..) => None,
             ty::Infer(ty::TyVar(_)) => Ambiguous,
 
-            // We can make this an ICE if/once we actually instantiate the trait obligation.
+            // We can make this an ICE if/once we actually instantiate the trait obligation eagerly.
             ty::Bound(..) => None,
 
             ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
@@ -2257,7 +2257,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 }
             }
 
-            ty::Adt(..) | ty::Alias(..) | ty::Param(..) => {
+            ty::Adt(..) | ty::Alias(..) | ty::Param(..) | ty::Placeholder(..) => {
                 // Fallback to whatever user-defined impls exist in this case.
                 None
             }
@@ -2269,9 +2269,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 Ambiguous
             }
 
-            ty::Placeholder(..)
-            | ty::Bound(..)
-            | ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
+            // We can make this an ICE if/once we actually instantiate the trait obligation eagerly.
+            ty::Bound(..) => None,
+
+            ty::Infer(ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
                 bug!("asked to assemble builtin bounds of unexpected type: {:?}", self_ty);
             }
         }

tests/ui/traits/non_lifetime_binders/bad-copy-cond.rs

@@ -0,0 +1,9 @@
+#![feature(non_lifetime_binders)]
+//~^ WARN the feature `non_lifetime_binders` is incomplete
+
+fn foo() where for<T> T: Copy {}
+
+fn main() {
+    foo();
+    //~^ ERROR the trait bound `T: Copy` is not satisfied
+}

tests/ui/traits/non_lifetime_binders/bad-copy-cond.stderr

@@ -0,0 +1,24 @@
+warning: the feature `non_lifetime_binders` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/bad-copy-cond.rs:1:12
+   |
+LL | #![feature(non_lifetime_binders)]
+   |            ^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #108185 <https://github.com/rust-lang/rust/issues/108185> for more information
+   = note: `#[warn(incomplete_features)]` on by default
+
+error[E0277]: the trait bound `T: Copy` is not satisfied
+  --> $DIR/bad-copy-cond.rs:7:5
+   |
+LL |     foo();
+   |     ^^^ the trait `Copy` is not implemented for `T`
+   |
+note: required by a bound in `foo`
+  --> $DIR/bad-copy-cond.rs:4:26
+   |
+LL | fn foo() where for<T> T: Copy {}
+   |                          ^^^^ required by this bound in `foo`
+
+error: aborting due to previous error; 1 warning emitted
+
+For more information about this error, try `rustc --explain E0277`.