Add tests for extracting tuples in f(g(...))

Author: owen-mc

go/ql/test/library-tests/semmle/go/IR/test.expected

@@ -4,3 +4,7 @@
 | test.go:15:2:15:20 | ... := ...[1] | test.go:15:13:15:20 | index expression | 1 | file://:0:0:0:0 | bool |
 | test.go:21:2:21:22 | ... := ...[0] | test.go:21:13:21:22 | type assertion | 0 | file://:0:0:0:0 | string |
 | test.go:21:2:21:22 | ... := ...[1] | test.go:21:13:21:22 | type assertion | 1 | file://:0:0:0:0 | bool |
+| test.go:29:2:29:7 | call to f[0] | test.go:29:4:29:6 | call to g | 0 | file://:0:0:0:0 | int |
+| test.go:29:2:29:7 | call to f[1] | test.go:29:4:29:6 | call to g | 1 | file://:0:0:0:0 | int |
+| test.go:33:2:33:7 | call to f[0] | test.go:33:4:33:6 | call to v | 0 | file://:0:0:0:0 | int |
+| test.go:33:2:33:7 | call to f[1] | test.go:33:4:33:6 | call to v | 1 | file://:0:0:0:0 | int |

go/ql/test/library-tests/semmle/go/IR/test.go

@@ -21,3 +21,14 @@ func testTypeAssert() {
 	got, ok := i.(string)
 	fmt.Printf("%v %v", got, ok)
 }
+
+func f(x, y int)    {}
+func g() (int, int) { return 0, 0 }
+
+func testNestedFunctionCalls() {
+	f(g())
+
+	// Edge case: when we call a function from a variable, `getTarget()` is not defined
+	v := g
+	f(v())
+}