Add tests for #20071 and #20136

Both observe different behaviours match type reductions
depending on whether they are compiled together or separately.
They both compile only with separate compilation.

Author: EugeneFlesselle

tests/neg/i20071.scala renamed to tests/neg/i20071a.scala

@@ -0,0 +1,13 @@
+
+trait Scope
+object Scope:
+  given i: Int = ???
+
+type ReferencesScope[S] >: Int <: Int
+
+type ScopeToInt[Why] = Why match
+  case Scope => Int
+
+def foo[T](using d: ReferencesScope[T]): Any = ???
+
+def bar[T](using d: ScopeToInt[T]): Any = ???

tests/neg/i20071b/A_1.scala

@@ -0,0 +1,8 @@
+
+def test: Unit =
+  foo[Scope] // ok
+  bar[Scope] // error
+
+  import Scope.i
+  bar[Scope] // ok
+

tests/neg/i20071b/B_2.scala

@@ -0,0 +1,14 @@
+
+trait Expr:
+  type Value
+object Expr:
+  type Of[V] = Expr { type Value = V }
+  type ExtractValue[E <: Expr] = E match
+    case Expr.Of[v] => v
+
+trait TC[E <: Expr]:
+  type Elem = Expr.ExtractValue[E]
+class BIExpr extends Expr:
+  type Value = BigInt
+class Foo extends TC[BIExpr]:
+  val v: Elem = 0

tests/pos/i20136a.scala

@@ -0,0 +1,8 @@
+package a
+
+trait Expr:
+  type Value
+object Expr:
+  type Of[V] = Expr { type Value = V }
+  type ExtractValue[E <: Expr] = E match
+    case Expr.Of[v] => v

tests/pos/i20136b/A_1.scala

@@ -0,0 +1,8 @@
+package a
+
+trait TC[E <: Expr]:
+  type Elem = Expr.ExtractValue[E]
+class BIExpr extends Expr:
+  type Value = BigInt
+class Foo extends TC[BIExpr]:
+  val v: Elem = 0