Fix result node and remove SPURIOUS test result

Author: owen-mc

go/ql/lib/semmle/go/dataflow/internal/DataFlowNodes.qll

@@ -932,6 +932,10 @@ module Public {
 
     ResultNode() {
       exists(FuncDef fd |
+        // When a function has any (named) result variables, then the
+        // `ReadResultInstruction`s at the end of the function are the correct
+        // result nodes.
+        not exists(fd.getAResultVar()) and
         exists(IR::ReturnInstruction ret | ret.getRoot() = fd | insn = ret.getResult(i))
         or
         insn.(IR::ReadResultInstruction).reads(fd.getResultVar(i))

go/ql/test/library-tests/semmle/go/dataflow/Nodes/ResultNode.expected

@@ -6,4 +6,3 @@
 | resultParameters.go:13:9:13:9 | 3 | Result node with index 0 |
 | resultParameters.go:16:26:16:26 | implicit read of r | Result node with index 0 |
 | resultParameters.go:21:38:21:38 | implicit read of r | Result node with index 0 |
-| resultParameters.go:24:10:24:10 | 1 | Result node with index 0 |

go/ql/test/library-tests/semmle/go/dataflow/Nodes/resultParameters.go

@@ -21,7 +21,7 @@ func resultParameter1() (r int) { // $ Alert[result-node] // implicit reads of r
 func resultParameter2(selector int) (r int) { // $ Alert[result-node] // implicit reads of result parameters are located at the result parameter declaration
 	r = 0
 	if selector == 1 {
-		return 1 // $ SPURIOUS: Alert[result-node]
+		return 1
 	}
 	return
 }