small coherence cleanup

compiler/rustc_trait_selection/src/traits/coherence.rs

@@ -792,11 +792,8 @@ pub fn orphan_check_trait_ref<'tcx, E: Debug>(
     in_crate: InCrate,
     lazily_normalize_ty: impl FnMut(Ty<'tcx>) -> Result<Ty<'tcx>, E>,
 ) -> Result<Result<(), OrphanCheckErr<'tcx, Ty<'tcx>>>, E> {
-    if trait_ref.has_infer() && trait_ref.has_param() {
-        bug!(
-            "can't orphan check a trait ref with both params and inference variables {:?}",
-            trait_ref
-        );
+    if trait_ref.has_param() {
+        bug!("orphan check only expects inference variables: {trait_ref:?}");
     }
 
     let mut checker = OrphanChecker::new(in_crate, lazily_normalize_ty);

tests/ui/traits/winnowing/global-non-global-env-1.current.stderr

@@ -0,0 +1,17 @@
+error[E0308]: mismatched types
+  --> $DIR/global-non-global-env-1.rs:18:5
+   |
+LL | fn foo<T>() -> u32
+   |        -       --- expected `u32` because of return type
+   |        |
+   |        found this type parameter
+...
+LL |     impls_trait(())
+   |     ^^^^^^^^^^^^^^^ expected `u32`, found type parameter `T`
+   |
+   = note:        expected type `u32`
+           found type parameter `T`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.

tests/ui/traits/winnowing/global-non-global-env-1.rs

@@ -4,7 +4,7 @@
 //@ revisions: current next
 //@ ignore-compare-mode-next-solver (explicit revisions)
 //@[next] compile-flags: -Znext-solver
-//@ check-pass
+//@[next] check-pass
 
 trait Trait<T> {}
 impl<T> Trait<T> for () {}
@@ -16,6 +16,7 @@ where
     (): Trait<T>,
 {
     impls_trait(())
+    //[current]~^ ERROR mismatched types
 }
 
 fn main() {}

tests/ui/traits/winnowing/global-non-global-env-3.current.stderr

@@ -0,0 +1,17 @@
+error[E0308]: mismatched types
+  --> $DIR/global-non-global-env-3.rs:20:5
+   |
+LL | fn foo<T>() -> u32
+   |        -       --- expected `u32` because of return type
+   |        |
+   |        found this type parameter
+...
+LL |     impls_trait(())
+   |     ^^^^^^^^^^^^^^^ expected `u32`, found type parameter `T`
+   |
+   = note:        expected type `u32`
+           found type parameter `T`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.

tests/ui/traits/winnowing/global-non-global-env-3.rs

@@ -5,7 +5,7 @@
 //@ revisions: current next
 //@ ignore-compare-mode-next-solver (explicit revisions)
 //@[next] compile-flags: -Znext-solver
-//@ check-pass
+//@[next] check-pass
 
 trait Trait<T> {}
 impl Trait<u32> for () {}
@@ -18,6 +18,7 @@ where
     (): Trait<u32>,
 {
     impls_trait(())
+    //[current]~^ ERROR mismatched types
 }
 
 fn main() {}