Fix bug in isPurelyFunctional, comments

src/main/scala/inox/ast/ExprOps.scala

@@ -3,10 +3,7 @@
 package inox
 package ast
 
-import utils._
-import scala.reflect._
-
-/** Provides functions to manipulate [[purescala.Expressions]].
+/** Provides functions to manipulate [[Expressions.Expr]].
   *
   * This object provides a few generic operations on Leon expressions,
   * as well as some common operations.
@@ -114,9 +111,9 @@ trait ExprOps extends GenTreeOps {
   /** Returns if this expression behaves as a purely functional construct,
     * i.e. always returns the same value (for the same environment) and has no side-effects
     */
-  def isPurelyFunctional(e: Expr): Boolean = exists {
-    case _ : Error => false
-    case _ => true
+  def isPurelyFunctional(e: Expr): Boolean = !exists {
+    case _ : Error => true
+    case _ => false
   }(e)
 
   /** Extracts the body without its specification

src/main/scala/inox/ast/Trees.scala

@@ -80,7 +80,6 @@ trait Trees extends Expressions with Extractors with Types with Definitions with
     /** Builds a fresh identifier
       *
       * @param name The name of the identifier
-      * @param tpe The type of the identifier
       * @param alwaysShowUniqueID If the unique ID should always be shown
       */
     def apply(name: String, alwaysShowUniqueID: Boolean = false) : Identifier = {
@@ -92,7 +91,7 @@ trait Trees extends Expressions with Extractors with Types with Definitions with
       *
       * @param name The name of the identifier
       * @param forceId The forced ID of the identifier
-      * @param tpe The type of the identifier
+      * @param alwaysShowUniqueID If the unique ID should always be shown
       */
     def forceId(name: String, forceId: Int, alwaysShowUniqueID: Boolean = false): Identifier =
       new Identifier(decode(name), uniqueCounter.nextGlobal, forceId, alwaysShowUniqueID)