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.

4 files changed, 48 insertions, 2 deletions

diff --git a/src/reflect/scala/reflect/internal/Definitions.scala b/src/reflect/scala/reflect/internal/Definitions.scala
index f8af4f155d..961e8e7264 100644
--- a/src/reflect/scala/reflect/internal/Definitions.scala
+++ b/src/reflect/scala/reflect/internal/Definitions.scala
@@ -658,8 +658,8 @@ trait Definitions extends api.StandardDefinitions {
 
     // These "direct" calls perform no dealiasing. They are most needed when
     // printing types when one wants to preserve the true nature of the type.
-    def isFunctionTypeDirect(tp: Type) = isFunctionSymbol(tp.typeSymbolDirect)
-    def isTupleTypeDirect(tp: Type)    = isTupleSymbol(tp.typeSymbolDirect)
+    def isFunctionTypeDirect(tp: Type) = !tp.isHigherKinded && isFunctionSymbol(tp.typeSymbolDirect)
+    def isTupleTypeDirect(tp: Type)    = !tp.isHigherKinded && isTupleSymbol(tp.typeSymbolDirect)
 
     // Note that these call .dealiasWiden and not .normalize, the latter of which
     // tends to change the course of events by forcing types.
diff --git a/test/files/run/t7876.scala b/test/files/run/t7876.scala
new file mode 100644
index 0000000000..aeec8c8cce
--- /dev/null
+++ b/test/files/run/t7876.scala
@@ -0,0 +1,26 @@
+import scala.tools.partest._
+
+// Type constructors for FunctionN and TupleN should not be considered as function type / tuple types.
+object Test extends DirectTest {
+  override def extraSettings: String = "-usejavacp"
+
+  def code = ""
+
+  def show() {
+    val global = newCompiler()
+    new global.Run()
+    import global._, definitions._
+    val function0TC = FunctionClass(0).typeConstructor
+    val tuple1TC = TupleClass(1).typeConstructor
+    FunctionClass.seq.foreach { sym =>
+      val tc = sym.typeConstructor
+      assert(!isFunctionType(tc), s"$tc")
+      assert(!isFunctionTypeDirect(tc), s"$tc (direct)")
+    }
+    TupleClass.seq.foreach { sym =>
+      val tc = sym.typeConstructor
+      assert(!isTupleType(tc), s"$sym")
+      assert(!isTupleTypeDirect(tc), s"$tc (direct)")
+    }
+  }
+}
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
+  }
+}