SI-7876 Scaladoc crasher due to regression in isFunctionType.

`isFunctionType` and `isTupleType` started returing true for
type constructors as of aeb73314. This led to a crash in type
printing in ScalaDoc (specfically, in ModelFactoryTypeSupport.scala)

This commit:
  - fixes those methods by guarding with !isHigherKinded
  - unit tests said methods
  - tests the reported crasher with a ScalaDoc test.

2 files changed, 20 insertions, 0 deletions

diff --git a/test/scaladoc/run/t7876.check b/test/scaladoc/run/t7876.check
new file mode 100644
index 0000000000..619c56180b
--- /dev/null
+++ b/test/scaladoc/run/t7876.check
@@ -0,0 +1 @@
+Done.
diff --git a/test/scaladoc/run/t7876.scala b/test/scaladoc/run/t7876.scala
new file mode 100644
index 0000000000..63c63f8a0c
--- /dev/null
+++ b/test/scaladoc/run/t7876.scala
@@ -0,0 +1,19 @@
+import scala.tools.nsc.doc.model._
+import scala.tools.partest.ScaladocModelTest
+
+object Test extends ScaladocModelTest {
+
+  override def code = """
+  import language.higherKinds
+  trait T[M[_]]
+  class C extends T[Function0]
+  class D extends T[Tuple1]
+                      """
+
+  def scaladocSettings = ""
+
+  def testModel(rootPackage: Package) = {
+    import access._
+    // did not crash
+  }
+}