C++: Go back to abstract classes.

Author: MathiasVP

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/DebugPrinting.qll

@@ -8,14 +8,12 @@ private import codeql.util.Unit
 private import Node0ToStringSig
 private import DataFlowUtil
 
-private module DebugNode0ToString implements Node0ToStringSig {
-  string instructionToString(Instruction i) { result = i.getDumpString() }
+class DebugNode0ToString extends Node0ToString {
+  override string instructionToString(Instruction i) { result = i.getDumpString() }
 
-  string operandToString(Operand op) {
+  override string operandToString(Operand op) {
     result = op.getDumpString() + " @ " + op.getUse().getResultId()
   }
 
-  string toExprString(Node n) { none() }
+  override string toExprString(Node n) { none() }
 }
-
-import DebugNode0ToString

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/Node0ToString.qll

@@ -5,4 +5,5 @@
  * one can import `DebugPrinting.qll` to better correlate the dataflow nodes with their underlying instructions and operands.
  */
 
+import Node0ToStringSig
 import NormalNode0ToString

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/Node0ToStringSig.qll

@@ -7,19 +7,27 @@ private import codeql.util.Unit
 private import DataFlowUtil
 
 /** A signature for a module to control the behavior of `Node.toString`. */
-signature module Node0ToStringSig {
+abstract class Node0ToString extends Unit {
   /**
    * Gets the string that should be used by `OperandNode.toString`.
    */
-  string operandToString(Operand op);
+  abstract string operandToString(Operand op);
 
   /**
    * Gets the string that should be used by `InstructionNode.toString`.
    */
-  string instructionToString(Instruction i);
+  abstract string instructionToString(Instruction i);
 
   /**
    * Gets the string representation of the `Expr` associated with `n`, if any.
    */
-  string toExprString(Node n);
+  abstract string toExprString(Node n);
 }
+
+string operandToString(Operand op) { result = any(Node0ToString s).operandToString(op) }
+
+string instructionToString(Instruction instr) {
+  result = any(Node0ToString s).instructionToString(instr)
+}
+
+string toExprString(Node n) { result = any(Node0ToString s).toExprString(n) }

cpp/ql/lib/semmle/code/cpp/ir/dataflow/internal/NormalNode0ToString.qll

@@ -9,25 +9,23 @@ private import Node0ToStringSig
 private import DataFlowUtil
 private import DataFlowPrivate
 
-private module NormalNode0ToStringImpl implements Node0ToStringSig {
-  string instructionToString(Instruction i) {
+class NormalNode0ToStringImpl extends Node0ToString {
+  override string instructionToString(Instruction i) {
     if i.(InitializeParameterInstruction).getIRVariable() instanceof IRThisVariable
     then result = "this"
     else result = i.getAst().toString()
   }
 
-  string operandToString(Operand op) {
+  override string operandToString(Operand op) {
     if op.getDef().(InitializeParameterInstruction).getIRVariable() instanceof IRThisVariable
     then result = "this"
     else result = op.getDef().getAst().toString()
   }
 
-  string toExprString(Node n) {
+  override string toExprString(Node n) {
     result = n.asExpr(0).toString()
     or
     not exists(n.asExpr()) and
     result = stars(n) + n.asIndirectExpr(0, 1).toString()
   }
 }
-
-import NormalNode0ToStringImpl