SI-8023 Fix symbol-completion-order type var pattern bug

Removing the `isComplete` check altogether leads to cycles in,
for instatnce, F-bound type parameters:

    trait LSO[+A, +Repr <: LSO[A, Repr]] // error: illegal cyclic reference involving type Repr

But, I believe that we can (and must) eagerly initialize the type
parameter symbols if we are typechecking a pattern.

While this appeared to regress in 2.11.x, but the problem was in fact
dormant and was merely uncovered in the fix for SI-7756, 3df1d77fc.

1 files changed, 22 insertions, 0 deletions

diff --git a/test/files/pos/t8023.scala b/test/files/pos/t8023.scala
new file mode 100644
index 0000000000..86824084ed
--- /dev/null
+++ b/test/files/pos/t8023.scala
@@ -0,0 +1,22 @@
+import language._
+
+
+object Test {
+  def foo = (null: Any) match {
+    case a: A[k] =>
+      // error: kinds of the type arguments (k) do not conform to the 
+      // expected kinds of the type parameters (type K) in class B.
+      new B[k]()
+  }
+}
+
+class A[K[L[_]]]
+
+class B[K[M[_]]]
+
+
+object Test2 {
+  def foo = (null: Any) match {
+    case a: A[k] => new B[k]() // this one worked before as the info of `A` was complete
+  }
+}