Add some new solver tests

tests/ui/traits/next-solver/assembly/param-env-alias-bound-conflict.rs

@@ -0,0 +1,26 @@
+//@ compile-flags: -Znext-solver
+//@ check-pass
+
+// Regression test for #119607.
+
+pub trait IntoFoo {
+    type Item;
+    type IntoIter: Foo<Item = Self::Item>;
+
+    fn into_iter(self) -> Self::IntoIter;
+}
+
+pub trait Foo {
+    type Item;
+
+    fn next(self) -> Option<Self::Item>;
+}
+
+pub fn foo<'a, Iter1, Elem1>(a: &'a Iter1)
+where
+    &'a Iter1: IntoFoo<Item = Elem1>,
+{
+    a.into_iter().next();
+}
+
+fn main() {}

tests/ui/traits/next-solver/env-shadows-impls/param-env-impl-conflict.rs

@@ -0,0 +1,23 @@
+//@ compile-flags: -Znext-solver
+//@ check-pass
+
+// Regression test for #119608.
+
+pub trait Foo {}
+
+pub trait Bar {
+    type Assoc;
+}
+
+impl<T: Foo> Bar for T {
+    type Assoc = T;
+}
+
+pub fn foo<I>(_input: <I as Bar>::Assoc)
+where
+    I: Bar,
+    <I as Bar>::Assoc: Foo,
+{
+}
+
+fn main() {}