Avoid using getTarget() as it may not exist

Author: owen-mc

go/ql/lib/semmle/go/controlflow/IR.qll

@@ -744,7 +744,7 @@ module IR {
 
     override Type getResultType() {
       exists(CallExpr c | this.getBase() = evalExprInstruction(c) |
-        result = c.getTarget().getResultType(i)
+        result = c.getCalleeType().getResultType(i)
       )
       or
       exists(Expr e | this.getBase() = evalExprInstruction(e) |

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

@@ -439,8 +439,8 @@ module Public {
     CallNode getCallNode() { result = call }
 
     override Type getType() {
-      exists(Function f | f = call.getTarget() |
-        result = f.getParameterType(f.getNumParameter() - 1)
+      exists(SignatureType t | t = call.getCall().getCalleeType() |
+        result = t.getParameterType(t.getNumParameter() - 1)
       )
     }