Swift: AST and CFG tests for nil coalescing

Author: rdmarsh2

swift/ql/test/library-tests/ast/PrintAst.expected

@@ -3300,6 +3300,21 @@ cfg.swift:
 #  526|     Type = Int
 #  533| [ConcreteVarDecl] i
 #  533|     Type = Int
+#  538| [NamedFunction] testNilCoalescing(x:)
+#  538|     InterfaceType = (Int?) -> Int
+#  538|   getParam(0): [ParamDecl] x
+#  538|       Type = Int?
+#  538|   getBody(): [BraceStmt] { ... }
+#  539|     getElement(0): [ReturnStmt] return ...
+#  539|       getResult(): [BinaryExpr] ... ??(_:_:) ...
+#  539|         getFunction(): [DeclRefExpr] ??(_:_:)
+#  539|         getArgument(0): [Argument] : x
+#  539|           getExpr(): [DeclRefExpr] x
+#  539|         getArgument(1): [Argument] : { ... }
+#  539|           getExpr(): [AutoClosureExpr] { ... }
+#  539|             getBody(): [BraceStmt] { ... }
+#  539|               getElement(0): [ReturnStmt] return ...
+#  539|                 getResult(): [IntegerLiteralExpr] 0
 declarations.swift:
 #    1| [StructDecl] Foo
 #    2|   getMember(0): [PatternBindingDecl] var ... = ...

swift/ql/test/library-tests/ast/cfg.swift

@@ -534,3 +534,7 @@ func testAsyncFor () async {
         print(i)
     }
 }
+
+func testNilCoalescing(x: Int?) -> Int {
+  return x ?? 0
+}

swift/ql/test/library-tests/controlflow/graph/Cfg.expected

@@ -6180,3 +6180,36 @@ cfg.swift:
 
 #  534| i
 #-----|  -> (Any) ...
+
+#  538| enter testNilCoalescing(x:)
+#-----|  -> testNilCoalescing(x:)
+
+#  538| exit testNilCoalescing(x:)
+
+#  538| exit testNilCoalescing(x:) (abnormal)
+#-----|  -> exit testNilCoalescing(x:)
+
+#  538| exit testNilCoalescing(x:) (normal)
+#-----|  -> exit testNilCoalescing(x:)
+
+#  538| testNilCoalescing(x:)
+#-----|  -> x
+
+#  538| x
+#-----|  -> ??(_:_:)
+
+#  539| return ...
+#-----| return -> exit testNilCoalescing(x:) (normal)
+
+#  539| x
+#-----|  -> { ... }
+
+#  539| ... ??(_:_:) ...
+#-----| exception -> exit testNilCoalescing(x:) (abnormal)
+#-----|  -> return ...
+
+#  539| ??(_:_:)
+#-----|  -> x
+
+#  539| { ... }
+#-----|  -> ... ??(_:_:) ...

swift/ql/test/library-tests/controlflow/graph/cfg.swift

@@ -534,3 +534,7 @@ func testAsyncFor () async {
         print(i)
     }
 }
+
+func testNilCoalescing(x: Int?) -> Int {
+  return x ?? 0
+}