Cleanup bunch of small issues in JdepsGetExtension.kt (#819)

- Remove explicit casts unneeded because of smart casts.
- Remove `collectSuperTypes` parameter as it is always `true`.
- Remove the mention of Remapper from the comment - its use was removed in 71246c9
- Typo fixes.

src/main/kotlin/io/bazel/kotlin/plugin/jdeps/JdepsGenExtension.kt

@@ -52,16 +52,15 @@ import java.nio.file.Paths
 /**
  * Kotlin compiler extension that tracks classes (and corresponding classpath jars) needed to
  * compile current kotlin target. Tracked data should include all classes whose changes could
- * affect target's compilation out : direct class dependencies (i.e external classes directly
+ * affect target's compilation out : direct class dependencies (i.e. external classes directly
  * used), but also their superclass, interfaces, etc.
  * The primary use of this extension is to improve Kotlin module compilation avoidance in build
  * systems (like Buck).
  *
- * Tracking of classes is done with a Remapper, which exposes all object types used by the class
- * bytecode being generated. Tracking of the ancestor classes is done via modules and class
+ * Tracking of classes and their ancestors is done via modules and class
  * descriptors that got generated during analysis/resolve phase of Kotlin compilation.
  *
- * Note: annotation processors dependencies may need to be tracked separatly (and may not need
+ * Note: annotation processors dependencies may need to be tracked separately (and may not need
  * per-class ABI change tracking)
  *
  * @param project the current compilation project
@@ -130,10 +129,10 @@ class JdepsGenExtension(
     ) {
       when (val resultingDescriptor = resolvedCall.resultingDescriptor) {
         is FunctionImportedFromObject -> {
-          collectTypeReferences((resolvedCall.resultingDescriptor as FunctionImportedFromObject).containingObject.defaultType)
+          collectTypeReferences(resultingDescriptor.containingObject.defaultType)
         }
         is PropertyImportedFromObject -> {
-          collectTypeReferences((resolvedCall.resultingDescriptor as PropertyImportedFromObject).containingObject.defaultType)
+          collectTypeReferences(resultingDescriptor.containingObject.defaultType)
         }
         is JavaMethodDescriptor -> {
           getClassCanonicalPath((resultingDescriptor.containingDeclaration as ClassDescriptor).typeConstructor)?.let { explicitClassesCanonicalPaths.add(it) }
@@ -223,26 +222,23 @@ class JdepsGenExtension(
      * types.
      */
     private fun collectTypeReferences(kotlinType: KotlinType,
-                                      isExplicit: Boolean = true,
-                                      collectSuperTypes: Boolean = true) {
+                                      isExplicit: Boolean = true) {
       if (isExplicit) {
         addExplicitDep(kotlinType)
       } else {
         addImplicitDep(kotlinType)
       }
 
-      if (collectSuperTypes) {
-        kotlinType.supertypes().forEach {
-          addImplicitDep(it)
-        }
+      kotlinType.supertypes().forEach {
+        addImplicitDep(it)
       }
 
       collectTypeArguments(kotlinType, isExplicit)
     }
 
-    fun collectTypeArguments(kotlinType: KotlinType,
-                             isExplicit: Boolean,
-                             visitedKotlinTypes: MutableSet<KotlinType> = mutableSetOf()) {
+    private fun collectTypeArguments(kotlinType: KotlinType,
+                                     isExplicit: Boolean,
+                                     visitedKotlinTypes: MutableSet<KotlinType> = mutableSetOf()) {
       visitedKotlinTypes.add(kotlinType)
       kotlinType.arguments.map { it.type }.forEach { typeArgument ->
         if (isExplicit) {