add test for alias-bound shadowing, rename folder

Author: lcnr

tests/ui/traits/next-solver/normalization-shadowing/alias-bound-shadowed-by-env.rs

@@ -0,0 +1,19 @@
+//@ compile-flags: -Znext-solver
+//@ check-pass
+
+trait Super {
+    type Assoc;
+}
+trait Bound {
+    type Assoc: Super<Assoc = u32>;
+}
+trait Trait: Super {}
+
+// Elaborating the environment results in a `T::Assoc: Super` where-bound.
+// This where-bound must not prevent normalization via the `Super<Assoc = u32>`
+// item bound.
+fn heck<T: Bound<Assoc: Trait>>(x: <T::Assoc as Super>::Assoc) -> u32 {
+    x
+}
+
+fn main() {}