Swift: remove getIdentityPreservingEnclosingPattern

The Pattern public interface doesn't really need it.

Author: d10c

swift/ql/lib/codeql/swift/dataflow/internal/DataFlowPrivate.qll

@@ -192,7 +192,11 @@ private module Cached {
     )
     or
     // flow from Pattern to an identity-preserving sub-Pattern:
-    nodeFrom.asPattern() = nodeTo.asPattern().getIdentityPreservingEnclosingPattern()
+    nodeTo.asPattern() =
+      [
+        nodeFrom.asPattern().(IsPattern).getSubPattern(),
+        nodeFrom.asPattern().(TypedPattern).getSubPattern()
+      ]
     or
     // flow through a flow summary (extension of `SummaryModelCsv`)
     FlowSummaryImpl::Private::Steps::summaryLocalStep(nodeFrom, nodeTo, true)

swift/ql/lib/codeql/swift/elements/pattern/Pattern.qll

@@ -85,16 +85,6 @@ class Pattern extends Generated::Pattern {
     result = this.getFullyUnresolved().(Pattern).getImmediateEnclosingPattern()
   }
 
-  /**
-   * Gets the parent pattern of this pattern, but only if
-   * both patterns match against the same object, which is not
-   * the case when destructuring a complex data structure,
-   * like a tuple or enum.
-   */
-  final Pattern getIdentityPreservingEnclosingPattern() {
-    result = this.getFullyUnresolved().(Pattern).getImmediateIdentityPreservingEnclosingPattern()
-  }
-
   /**
    * Gets the parent pattern of this pattern, if any.
    */
@@ -105,16 +95,6 @@ class Pattern extends Generated::Pattern {
     or
     this = result.(TuplePattern).getImmediateElement(_)
     or
-    result = this.getImmediateIdentityPreservingEnclosingPattern()
-  }
-
-  /**
-   * Gets the immediate parent pattern of this pattern, but only if
-   * both patterns match against the same object, which is not
-   * the case when destructuring a complex data structure,
-   * like a tuple or enum.
-   */
-  Pattern getImmediateIdentityPreservingEnclosingPattern() {
     this = result.(BindingPattern).getImmediateSubPattern()
     or
     this = result.(IsPattern).getImmediateSubPattern()