add test which reproduces the problem

idea/testData/kdoc/finder/OverriddenWithSubstitutedType.kt

@@ -0,0 +1,10 @@
+open class Foo<T>() {
+    /**
+     * Doc for method xyzzy
+     */
+    open fun xyzzy(): Int = 0
+}
+
+open class Bar(): Foo<String>() {
+    override fun xyzzy(): Int = 1
+}

idea/tests/org/jetbrains/kotlin/idea/kdoc/KDocFinderTest.kt

@@ -46,4 +46,13 @@ public class KDocFinderTest() : LightPlatformCodeInsightFixtureTestCase() {
         val doc = KDocFinder.findKDoc(overriddenFunctionDescriptor)
         Assert.assertEquals("Doc for method xyzzy", doc!!.getContent())
     }
+
+    public fun testOverriddenWithSubstitutedType() {
+        myFixture.configureByFile(getTestName(false) + ".kt")
+        val declaration = (myFixture.getFile() as JetFile).getDeclarations().single { it.getName() == "Bar" }
+        val descriptor = declaration.resolveToDescriptor() as ClassDescriptor
+        val overriddenFunctionDescriptor = descriptor.getDefaultType().getMemberScope().getFunctions(Name.identifier("xyzzy")).single()
+        val doc = KDocFinder.findKDoc(overriddenFunctionDescriptor)
+        Assert.assertEquals("Doc for method xyzzy", doc!!.getContent())
+    }
 }