Swift: Add a test for ExtensionDecls.

Author: geoffw0

swift/ql/test/library-tests/elements/decl/extensiondecl/extensiondecl.expected

@@ -0,0 +1,4 @@
+| extensiondecl.swift:11:1:12:1 | extension | getExtendedTypeDecl:MyClass |
+| extensiondecl.swift:14:1:15:1 | extension | getExtendedTypeDecl:MyClass, getProtocol(0):MyProtocol1, getProtocol(1):MyProtocol2 |
+| extensiondecl.swift:17:1:18:1 | extension | getExtendedTypeDecl:Int |
+| extensiondecl.swift:20:1:21:1 | extension | getExtendedTypeDecl:String |

swift/ql/test/library-tests/elements/decl/extensiondecl/extensiondecl.ql

@@ -0,0 +1,11 @@
+import swift
+
+string describe(ExtensionDecl e) {
+  result = "getExtendedTypeDecl:" + e.getExtendedTypeDecl().toString()
+  or
+  exists(int ix | result = "getProtocol(" + ix.toString() + "):" + e.getProtocol(ix).toString())
+}
+
+from ExtensionDecl e
+where not e.getFile() instanceof UnknownFile
+select e, concat(describe(e), ", ")

swift/ql/test/library-tests/elements/decl/extensiondecl/extensiondecl.swift

@@ -0,0 +1,21 @@
+
+protocol MyProtocol1 {
+}
+
+protocol MyProtocol2 {
+}
+
+class MyClass {
+}
+
+extension MyClass {
+}
+
+extension MyClass : MyProtocol1, MyProtocol2 {
+}
+
+extension Int {
+}
+
+extension String {
+}