PS: Create an internal class to model 'Arguments'.

Author: MathiasVP

powershell/ql/lib/semmle/code/powershell/internal/Argument.qll

@@ -0,0 +1,71 @@
+private import powershell
+
+module Private {
+  /**
+   * An argument to a call.
+   *
+   * The argument may be named or positional.
+   */
+  abstract class AbstractArgument extends Expr {
+    Ast call;
+
+    /** Gets the call that this is an argumnt of. */
+    final Ast getCall() { result = call }
+
+    /** Gets the position if this is a positional argument. */
+    abstract int getPosition();
+
+    /** Gets the name if this is a keyword argument. */
+    abstract string getName();
+
+    /** Holds if this is a qualifier of a call */
+    abstract predicate isQualifier();
+  }
+
+  class CmdArgument extends AbstractArgument {
+    override Cmd call;
+
+    CmdArgument() { call.getAnArgument() = this }
+
+    override int getPosition() { call.getPositionalArgument(result) = this }
+
+    override string getName() { call.getNamedArgument(result) = this }
+
+    final override predicate isQualifier() { none() }
+  }
+
+  class InvokeArgument extends AbstractArgument {
+    override InvokeMemberExpr call;
+
+    InvokeArgument() { call.getAnArgument() = this or call.getQualifier() = this }
+
+    override int getPosition() { call.getArgument(result) = this }
+
+    override string getName() { none() }
+
+    final override predicate isQualifier() { call.getQualifier() = this }
+  }
+}
+
+private import Private
+
+module Public {
+  final class Argument = AbstractArgument;
+
+  /** A positional argument to a command. */
+  class PositionalArgument extends Argument {
+    PositionalArgument() {
+      not this instanceof NamedArgument and not this instanceof QualifierArgument
+    }
+  }
+
+  /** A named argument to a command. */
+  class NamedArgument extends Argument {
+    NamedArgument() { exists(this.getName()) }
+  }
+
+  /** An argument that is a qualifier to a method. */
+  class QualifierArgument extends Argument {
+    QualifierArgument() { this.isQualifier() }
+  }
+}

powershell/ql/lib/semmle/code/powershell/internal/Internal.qll

@@ -1,9 +1,11 @@
 module Private {
   import Parameter::Private
   import ExplicitWrite::Private
+  import Argument::Private
 }
 
 module Public {
   import Parameter::Public
   import ExplicitWrite::Public
+  import Argument::Public
 }