PS: Fix the scope of parameters.

Author: MathiasVP

powershell/ql/lib/semmle/code/powershell/Function.qll

@@ -1,4 +1,5 @@
 import powershell
+import semmle.code.powershell.controlflow.BasicBlocks
 
 abstract private class AbstractFunction extends Ast {
   abstract string getName();
@@ -20,6 +21,8 @@ abstract private class AbstractFunction extends Ast {
   }
 
   final Parameter getAParameter() { result = this.getParameter(_) }
+
+  EntryBasicBlock getEntryBasicBlock() { result.getScope() = this.getBody() }
 }
 
 class NonMemberFunction extends @function_definition, Stmt, AbstractFunction {

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

@@ -2,10 +2,40 @@ private import powershell
 private import semmle.code.powershell.controlflow.internal.Scope
 private import internal.Internal as Internal
 
+private predicate isFunctionParameterImpl(Internal::Parameter p, Function f, int i) {
+  function_definition_parameter(f, i, p)
+  or
+  function_member_parameter(f, i, p)
+}
+
+private predicate hasParameterBlockImpl(Internal::Parameter p, ParamBlock block, int i) {
+  param_block_parameter(block, i, p)
+}
+
+/**
+ * Gets the enclosing scope of `p`.
+ * 
+ * For a function parameter, this is the function body. For a parameter from a
+ * parameter block, this is the enclosing scope of the parameter block.
+ * 
+ * In both of the above cases, the enclosing scope is the function body.
+ */
+private Scope getEnclosingScopeImpl(Internal::Parameter p) {
+  exists(Function f |
+    isFunctionParameterImpl(p, f, _) and
+    result = f.getBody()
+  )
+  or
+  exists(ParamBlock b |
+    hasParameterBlockImpl(p, b, _) and
+    result = b.getEnclosingScope()
+  )
+}
+
 bindingset[scope]
 pragma[inline_late]
 private predicate isParameterImpl(string name, Scope scope) {
-  exists(Internal::Parameter p | p.getName() = name and p.getEnclosingScope() = scope)
+  exists(Internal::Parameter p | p.getName() = name and getEnclosingScopeImpl(p) = scope)
   or
   name = "_"
 }
@@ -47,17 +77,13 @@ private class InternalParameter extends ParameterImpl, TInternalParameter {
 
   override string getName() { result = p.getName() }
 
-  final override Scope getEnclosingScope() { result = p.getEnclosingScope() }
+  final override Scope getEnclosingScope() { result = getEnclosingScopeImpl(p) }
 
   override predicate hasParameterBlock(ParamBlock block, int i) {
-    param_block_parameter(block, i, p)
+    hasParameterBlockImpl(p, block, i)
   }
 
-  override predicate isFunctionParameter(Function f, int i) {
-    function_definition_parameter(f, i, p)
-    or
-    function_member_parameter(f, i, p)
-  }
+  override predicate isFunctionParameter(Function f, int i) { isFunctionParameterImpl(p, f, i) }
 
   override Expr getDefaultValue() { result = p.getDefaultValue() }
 }
@@ -161,4 +187,6 @@ class Parameter extends AbstractLocalScopeVariable, TParameter {
   predicate hasDefaultValue() { exists(this.getDefaultValue()) }
 
   int getIndex() { this.isFunctionParameter(_, result) }
+
+  Function getFunction() { result.getBody() = this.getDeclaringScope() }
 }