Merge pull request #13672 from owen-mc/go/make-parameter-nodes-for-unused-parameters-2

Go: make `ParameterNode`s for unused parameters #2 (make a disjoint class for unused ones)

Author: owen-mc

go/ql/lib/change-notes/2023-07-05-parameter-nodes-for-unused-parameters.md

@@ -0,0 +1,4 @@
+---
+category: minorAnalysis
+---
+* Parameter nodes now exist for unused parameters as well as used parameters.

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

@@ -680,6 +680,24 @@ module Public {
     }
   }
 
+  /** A representation of a parameter initialization, defined in source via an SSA node. */
+  class UnusedParameterNode extends ParameterNode, InstructionNode {
+    override IR::InitParameterInstruction insn;
+    Parameter parm;
+
+    UnusedParameterNode() {
+      insn = IR::initParamInstruction(parm) and
+      not exists(SsaExplicitDefinition ssa | ssa.getInstruction() = insn)
+    }
+
+    /** Gets the parameter this node initializes. */
+    override Parameter asParameter() { result = parm }
+
+    override predicate isParameterOf(DataFlowCallable c, int i) {
+      parm.isParameterOf(c.asCallable().getFuncDef(), i)
+    }
+  }
+
   /** A representation of a parameter initialization, defined in source via an SSA node. */
   class SsaParameterNode extends ParameterNode, SsaNode {
     override SsaExplicitDefinition ssa;

go/ql/test/library-tests/semmle/go/dataflow/FunctionInputsAndOutputs/FunctionInput_getExitNode.expected

@@ -4,6 +4,7 @@
 | parameter 0 | reset.go:8:1:16:1 | function declaration | reset.go:8:27:8:27 | definition of r |
 | parameter 0 | tst2.go:8:1:12:1 | function declaration | tst2.go:8:12:8:15 | definition of data |
 | parameter 0 | tst.go:8:1:11:1 | function declaration | tst.go:8:12:8:17 | definition of reader |
+| parameter 0 | tst.go:13:1:13:25 | function declaration | tst.go:13:12:13:13 | initialization of xs |
 | parameter 0 | tst.go:15:1:19:1 | function declaration | tst.go:15:12:15:12 | definition of x |
 | parameter 1 | main.go:5:1:11:1 | function declaration | main.go:5:20:5:20 | definition of x |
 | parameter 1 | main.go:13:1:20:1 | function declaration | main.go:13:21:13:21 | definition of x |