QL: Add basic data flow nodes

Author: asgerf

ql/ql/src/codeql_ql/dataflow/DataFlow.qll

@@ -0,0 +1,147 @@
+private import codeql_ql.ast.Ast
+private import internal.NodesInternal
+
+/**
+ * An expression or variable in a formula, including some additional nodes
+ * that are not part of the AST.
+ */
+class Node extends TNode {
+  string toString() { none() } // overridden in subclasses
+  Location getLocation() { none() } // overridden in subclasses
+
+  /**
+   * Gets the underlying `Expr` or `VarDef` node, if this is an `AstNodeNode`.
+   */
+  AstNode asAstNode() { astNode(result) = this }
+}
+
+/**
+ * A data-flow node based an `Expr` or `VarDef` AST node.
+ */
+class AstNodeNode extends Node, MkAstNodeNode {
+  private AstNode ast;
+
+  AstNodeNode() { this = MkAstNodeNode(ast) }
+
+  override string toString() {
+    result = ast.toString()
+  }
+
+  override Location getLocation() {
+    result = ast.getLocation()
+  }
+
+  /** Gets the AST node. */
+  AstNode getAstNode() {
+    result = ast
+  }
+}
+
+/**
+ * Gets the data-flow node correspoinding to the given AST node.
+ */
+pragma[inline]
+Node astNode(AstNode node) {
+  result = MkAstNodeNode(node)
+}
+
+/**
+ * A data-flow node representing `this` within a class predicate, charpred, or newtype branch.
+ */
+class ThisNode extends Node, MkThisNode {
+  private Predicate pred;
+
+  ThisNode() { this = MkThisNode(pred) }
+
+  override string toString() {
+    result = "'this' in " + pred.getName()
+  }
+
+  override Location getLocation() {
+    result = pred.getLocation()
+  }
+
+  /** Gets the class predicate, charpred, or newtype branch whose 'this' parameter is represented by this node. */
+  Predicate getPredicate() {
+    result = pred
+  }
+}
+
+/**
+ * Gets the data-flow node representing `this` within the given class predicate, charpred, or newtype branch.
+ */
+pragma[inline]
+Node thisNode(Predicate pred) {
+  result = MkThisNode(pred)
+}
+
+/**
+ * A data-flow node representing `result` within a predicate that has a result.
+ */
+class ResultNode extends Node, MkResultNode {
+  private Predicate pred;
+
+  ResultNode() { this = MkResultNode(pred) }
+
+  override string toString() {
+    result = "'result' in " + pred.getName()
+  }
+
+  override Location getLocation() {
+    result = pred.getLocation()
+  }
+
+  /** Gets the predicate whose 'result' parameter is represented by this node. */
+  Predicate getPredicate() {
+    result = pred
+  }
+}
+
+/**
+ * Gets the data-flow node representing `result` within the given predicate.
+ */
+pragma[inline]
+Node resultNode(Predicate pred) {
+  result = MkResultNode(pred)
+}
+
+/**
+ * A data-flow node representing the view of a field in the enclosing class, as seen
+ * from a charpred or class predicate.
+ */
+class FieldNode extends Node, MkFieldNode {
+  private Predicate pred;
+  private FieldDecl fieldDecl;
+
+  FieldNode() { this = MkFieldNode(pred, fieldDecl) }
+
+  /** Gets the member predicate or charpred for which this node represents access to the field. */
+  Predicate getPredicate() {
+    result = pred
+  }
+
+  FieldDecl getFieldDeclaration() {
+    result = fieldDecl
+  }
+
+  string getFieldName() {
+    result = fieldDecl.getName()
+  }
+
+  override string toString() {
+    result = "'"  + this.getFieldName() + "' in " + pred.getName()
+  }
+
+  override Location getLocation() {
+    result = pred.getLocation()
+  }
+}
+
+/**
+ * Gets the data-flow node representing the given predicate's view of the given field
+ * in the enclosing class.
+ */
+pragma[inline]
+Node fieldNode(Predicate pred, FieldDecl fieldDecl) {
+  result = MkFieldNode(pred, fieldDecl)
+}

ql/ql/src/codeql_ql/dataflow/internal/NodesInternal.qll

@@ -0,0 +1,19 @@
+private import codeql_ql.ast.Ast
+
+newtype TNode =
+  MkAstNodeNode(AstNode node) {
+    node instanceof Expr or
+    node instanceof VarDef
+  } or
+  MkThisNode(Predicate pred) {
+    pred instanceof ClassPredicate or
+    pred instanceof CharPred or
+    pred instanceof NewTypeBranch
+  } or
+  MkResultNode(Predicate pred) { exists(pred.getReturnTypeExpr()) } or
+  MkFieldNode(Predicate pred, FieldDecl fieldDecl) {
+    // TODO: should this be omitted when the field is not referenced?
+    fieldDecl.getVarDecl() = pred.(ClassPredicate).getDeclaringType().getField(_)
+    or
+    fieldDecl.getVarDecl() = pred.(CharPred).getDeclaringType().getField(_)
+  }