Swift: Move NominalType.getABaseType() implementation out from NominalType (inconsistent, difficult to find) to Type.

Author: geoffw0

swift/ql/lib/codeql/swift/elements/type/NominalType.qll

@@ -1,12 +1,6 @@
 private import codeql.swift.generated.type.NominalType
-private import codeql.swift.elements.decl.NominalTypeDecl
-private import codeql.swift.elements.type.Type
 
 /**
  * A class, struct, enum or protocol.
  */
-class NominalType extends Generated::NominalType {
-  override Type getABaseType() { result = this.getDeclaration().(NominalTypeDecl).getABaseType() }
-
-  NominalType getADerivedType() { result.getABaseType() = this }
-}
+class NominalType extends Generated::NominalType { }

swift/ql/lib/codeql/swift/elements/type/Type.qll

@@ -1,4 +1,5 @@
 private import codeql.swift.generated.type.Type
+private import codeql.swift.elements.type.AnyGenericType
 
 /**
  * A Swift type.
@@ -53,5 +54,7 @@ class Type extends Generated::Type {
    * typealias B_alias = B
    * ```
    */
-  Type getABaseType() { none() }
+  Type getABaseType() { result = this.(AnyGenericType).getDeclaration().getABaseType() }
+
+  Type getADerivedType() { result.getABaseType() = this }
 }