C#: Include parameters and their defaults in the CFG

Author: hvitved

csharp/ql/lib/semmle/code/csharp/ExprOrStmtParent.qll

@@ -13,7 +13,7 @@ private import internal.Location
  * An element that can have a child statement or expression.
  */
 class ExprOrStmtParent extends Element, @exprorstmt_parent {
-  final override ControlFlowElement getChild(int i) {
+  override ControlFlowElement getChild(int i) {
     result = this.getChildExpr(i) or
     result = this.getChildStmt(i)
   }
@@ -42,14 +42,8 @@ class ExprOrStmtParent extends Element, @exprorstmt_parent {
  *
  * An element that can have a child top-level expression.
  */
-class TopLevelExprParent extends Element, @top_level_expr_parent {
+class TopLevelExprParent extends ExprOrStmtParent, @top_level_expr_parent {
   final override Expr getChild(int i) { result = this.getChildExpr(i) }
-
-  /** Gets the `i`th child expression of this element (zero-based). */
-  final Expr getChildExpr(int i) { expr_parent_top_level_adjusted(result, i, this) }
-
-  /** Gets a child expression of this element, if any. */
-  final Expr getAChildExpr() { result = this.getChildExpr(_) }
 }
 
 /** INTERNAL: Do not use. */

csharp/ql/lib/semmle/code/csharp/PrintAst.qll

@@ -299,7 +299,9 @@ class ControlFlowElementNode extends ElementNode {
     not isNotNeeded(element.getParent+()) and
     // LambdaExpr is both a Callable and a ControlFlowElement,
     // print it with the more specific CallableNode
-    not element instanceof Callable
+    not element instanceof Callable and
+    // Handled in `ParameterNode`
+    not element instanceof Parameter
   }
 
   override PrintAstNode getChild(int childIndex) {

csharp/ql/lib/semmle/code/csharp/Variable.qll

@@ -87,7 +87,9 @@ class LocalScopeVariable extends Variable, @local_scope_variable {
  * }
  * ```
  */
-class Parameter extends LocalScopeVariable, Attributable, TopLevelExprParent, @parameter {
+class Parameter extends LocalScopeVariable, Attributable, TopLevelExprParent, ControlFlowElement,
+  @parameter
+{
   /** Gets the raw position of this parameter, including the `this` parameter at index 0. */
   final int getRawPosition() { this = this.getDeclaringElement().getRawParameter(result) }
 

csharp/ql/lib/semmle/code/csharp/controlflow/ControlFlowGraph.qll

@@ -73,9 +73,16 @@ private module Ast implements AstSig<Location> {
   private AstNode getParent(AstNode n) { n = getChild(result, _) }
 
   Callable getEnclosingCallable(AstNode node) {
-    result = node.(ControlFlowElement).getEnclosingCallable() or
-    result.(ObjectInitMethod).initializes(getParent*(node)) or
+    result = node.(ControlFlowElement).getEnclosingCallable()
+    or
+    result.(ObjectInitMethod).initializes(getParent*(node))
+    or
     Initializers::staticMemberInitializer(result, getParent*(node))
+    or
+    result = node.(Parameter).getCallable()
+    or
+    not skipControlFlow(node) and
+    getParent*(node) = any(Parameter p | result = p.getCallable()).getDefaultValue()
   }
 
   class Callable = CS::Callable;
@@ -85,6 +92,17 @@ private module Ast implements AstSig<Location> {
     result = c.getBody()
   }
 
+  final private class ParameterFinal = CS::Parameter;
+
+  class Parameter extends ParameterFinal {
+    Expr getDefaultValue() {
+      result = super.getDefaultValue() and
+      getCompilation(result.getFile()) = getCompilation(this.getFile())
+    }
+  }
+
+  Parameter callableGetParameter(Callable c, int i) { result = c.getParameter(i) }
+
   class Stmt = CS::Stmt;
 
   class Expr = CS::Expr;
@@ -415,10 +433,10 @@ private module Input implements InputSig1, InputSig2 {
     l = TLblGoto(n.(LabelStmt).getLabel())
   }
 
-  class CallableBodyPartContext = CompilationExt;
+  class CallableContext = CompilationExt;
 
   pragma[nomagic]
-  Ast::AstNode callableGetBodyPart(Callable c, CallableBodyPartContext ctx, int index) {
+  Ast::AstNode callableGetBodyPart(Callable c, CallableContext ctx, int index) {
     not Ast::skipControlFlow(result) and
     ctx = getCompilation(result.getFile()) and
     (
@@ -437,9 +455,19 @@ private module Input implements InputSig1, InputSig2 {
         or
         i = 2 and result = ctor.getBody()
       )
+      or
+      not c instanceof Constructor and
+      result = c.getBody() and
+      index = 0
     )
   }
 
+  pragma[nomagic]
+  Ast::Parameter callableGetParameter(Callable c, CallableContext ctx, int index) {
+    result = Ast::callableGetParameter(c, index) and
+    ctx = getCompilation(result.getFile())
+  }
+
   private Expr getQualifier(QualifiableExpr qe) {
     result = qe.getQualifier() or
     result = qe.(ExtensionMethodCall).getArgument(0)

csharp/ql/lib/semmlecode.csharp.dbscheme

@@ -1362,7 +1362,7 @@ compiler_generated(unique int id: @element ref);
 
 /** CONTROL/DATA FLOW **/
 
-@control_flow_element = @stmt | @expr;
+@control_flow_element = @stmt | @expr | @parameter;
 
 /* XML Files */